Translator

Bob McDavitt's ideas for sailing weather around the South pacific

10 December 2017

Bob blog 10 Dec 2017

WEATHERGRAM

YOTREPS

Compiled Sun 10 December 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

The state of ENSO – We are having a LA NINA—but for how long?

El Nino and La Nina are opposite ends of an identifiable tropical influence on our weather. La Nina comes with cooler than normal seas along the equatorial eastern pacific, and is associated with stronger than normal trade winds and shifts the subtropical ridge (and its jetstream) away from the equator. El Nino has weaker than normal trade winds and warmer than normal seas draws the subtropical ridge closer to the equator. So, they are like opposite tilts of a seesaw. Their comings and goings can last several months, maybe over a year, and so their status can be used to forecast the weather for the next month or so.

 

BoM, Australia, has now declared this to be a LA NINA.

The central to eastern tropical Pacific Ocean has cooled steadily over last few months and are now at the La NiƱa thresholds (0.8 °C below average). See www.bom.gov.au/climate/enso/

However, the BoM have pointed out that this La Nina may be weak and short-lived—weaker than the last one in 2010-2012. It looks stronger than the La Nina we had around a year ago.

 

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino, or becomes cooler than normal during a La Nina. This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see that since August there has been a cool trend for NONO3.4, and a few weeks ago the seas were over 1-degree cooler than normal.

Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

 

Atmosphere

The parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words the placement of isobars on the weather map. When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

Since August the SOI has been more than 0.5, and for two weeks in October and one week (so far) in December it was over the +1 threshold.

This all ties in with “early start to summer” experienced in NZ, with anticyclones lingering over the Tasman Sea and New Zealand mainland, bringing periods of sunny weather and light winds. After New year, these HIGHS may shrink, but still stay near central NZ, so that there may be periods of strong easterly winds over Northland. In the South Pacific, convergence zones should be further south than normal, allowing tropical lows to form near 15South latitude rather than 10S.

La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10= 1 standard deviation)

 

The Models

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models. The mid-November edition shows the the cluster of data from the models for NINO3.4 temperature may have bottomed out in DJF (Dec Jan feb) and start rising a little in JFM 2018, and more so in FMA.

CPC/IRI predictions are at iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

TROPICS

No cyclones around at present.

There continues to be a burst of equatorail westerly winds from east of Malaysia to north of Papua New Guinea.

Looking at the weekly rain maps from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif and comparing last week and the week before, we can see pockets of intense convection around Thailand and Indonesia, but weaker than last week. This cluster of extra convection is expected to make its way eastwards and start appearing in the Coral Sea area ovr next few weeks. This is called an MJO (Madden Julian Oscillation).

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is hovering over the Coral Sea to south of Solomon Islands to Samoa to Southern Cooks. The low that is tonight at the end of the SPCZ and south of the Southern Cooks is expected to travel slowly south and deepen.

By mid-week a new convergence zone and Low is expected to form in the Coral sea, and by next weekend this Low may deepen as it travels from Vanuatu to Fiji, with SPCZ over Tonga. Avoid these developments.

 

Subtropical ridge (STR)

HIGH H1 is expected to travel east along 40S from south of Southern cooks tonight to south of Pitcairn island by end of this week.

HIGH H2 is forming in South Tasman Sea by Tuesday, and expected to travel onto southern NZ on Wednesday and stretch from North Tasman Sea across central NZ to south of Chathams by Friday. Then it may stall for a few days, or perhaps weaken away.

 

Tasman Sea/NZ

I think the sailors are now resting. If you would like more detail for your voyage, then check metbob.com to see what I offer.

>>>>>>>>>>>>>>>>>>>>>>>> 

“I think my whole life has been one of sort of daring,

and sort of sailing against the wind instead of just going with the wind.”

John Lewis

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Click FOLLOW at bottom right.

To unsubscribe send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

03 December 2017

Bob Blog 3 Dec 2017b

WEATHERGRAM

YOTREPS

Compiled Sun 3 December 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

The November weather.

Sea Surface temperature anomalies may be seen at www.ospo.noaa.gov/data/sst/anomaly/2017/anomg.11.30.2017.gif

The SST anomaly image is that of a typical LA NINA, with cooler than normal sea along the eastern Pacific equator linked to stronger than normal trade winds that spread further away from the equator, so that the subtropical ridge (in both hemispheres) is further than normal away from the equator.

There appears to be a warmer than normal zone between Tasmania and the South Island—it may take a few weeks, but this can activate troughs to produce more rain.

 

To see how the annual weather cycle and the seasons are working out, take a quick look at the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

During November the 1015hP isobar has spread from middle NZ to south of NZ 

—that’s a large jump for the subtropical ridge.

This is a strong regional change and, examining the details, there have been some similarly significant pattern changes in the northern hemisphere too. However, there hasn’t been as strong a change over South America or South Africa. So, the impact of this LA NINA has its peculiarities

 

Last 30 days of rainfall, and its anomaly, may be seen at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

We can see one of the typical impacts of this La Nina by looking at the Intertropical convergence zone ITCZ on the monthly total rainfall total and its anomaly maps. This shows the latitude of the ITCZ has been knocked to the north across the Pacific, further away from the equator, and its normal latitude is now a yellow zone of dry anomalies. But this impact is regional,  and a reversal of it is seen in the Atlantic Ocean.

 

TROPICS

TC OCKHI is currently in the North Indian Ocean heading toward NW India. It is expected to weaken before it makes landfall around Wednesday. See www.tropicaltidbits.com/storminfo/

The South Pacific Cyclone season has opened with TD 01S DAHLIA off to the NW of Australia .

This is just a tropical depression (doesn’t have a ring of gales around its centre) and is likely to fade in a few days, but does get the season-count rolling.

Models are picking that there may be another tropical depression forming in the Coral Sea this week, but it should fade as it moves towards New Caledonia.

There are some bursts or equatorial westerly winds across the Timor Sea and to north of Papua New Guinea.

 

Looking at the weekly rain maps from last week and the week before,  at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif,   we can see an increase in convection in the equatorial Indian Ocean. This cluster of extra convection is expected to make its way eastwards and start appearing in the Coral Sea area around mid-December. This is called an MJO oscillation

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is hovering from Coral Sea to northern Vanuatu to Tonga to Southern cooks, with a reasonably clear gap over Fiji. Small lows are expected to form along 25South, to south of the SPCZ during mid-week. These are formed by a passing upper trough.

 

Subtropical ridge (STR)

HIGH H1 is expected to linger along 30 to 40S to east of NZ for the whole week.

Then another HIGH H2 is expected to cross Tasmania on Tuesday and southern NZ on Wednesday and then build to east of South Island from Thursday.

 

Between Tropics and NZ

A Low is expected to form between Fiji and NZ near 28S on Wednesday and fade away to the east on Thursday. This  feature is the  surface reflection of a passing upper trough  and may be reasonably easily avoided.

As H2 travels to east of NZ there should be a NE flow over northern NZ until Mon 11 Dec, providing a reasonable opportunity for getting to NZ.

After that the models differ wildly, so may be better to wait for a more solid favourable forecast.

 

Between tropics and Australia

Looks ok: The trough that is along and offshore the east coast of Australia is the one that flooded parts of Victoria over the weekend. It should fade and go off to the south by Thursday.

>>>>>>>>>>>>>>>>>>>>

“Sailing is just the bottom line, like adding up the score in bridge.

My real interest is in the tremendous game of life.”

- Dennis Conner

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Click FOLLOW at bottom right.

To unsubscribe send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

26 November 2017

Bobgram issued 26 Nov

WEATHERGRAM

YOTREPS

Compiled Sun 26 November 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Pattern and Chaos

At my talk to the All Points Rally last Friday, Peter Mott of Northland Radio commented that two vessels about 100 n miles apart had completely different wind speed—one ESE 18 knots and t’other 34 to 38 knots from SE. The computer models at that time was forecasting much the same conditions for both around 20 to 30 knots from ESE.

A scatterometer satellite (measuring the wind speed over the surface of the sea by using microwaves to measure the sea foam, helps to show what was happening. The computer model averages things out and thus produce a smooth image showing the weather pattern. However, actually, the stronger winds lay across the sea in filaments, with avenues of weaker wind around them.  This can be seen at manati.star.nesdis.noaa.gov/datasets/WindSATData.php 

This is a good example for anyone using grib data. Weather is a mix of pattern and chaos. The computers can only give us a pattern, but the real world always has elements of chaos- sailor are on the receiving world of the real world, and thus notice the chaos more than the pattern, The lesson is to take the grid data with a “grain of salt” and allow a +/- of around 10% even when the data is given to the nearest 0.1 of a knot.

 

CANANZ

As well as running MetBob, I am also President of a club called Cruising and Navigation Association of New Zealand, www.cananz.org.nz This is a small club that, as it name implies, aims at organising events for a group of Auckland-based yachts– some interested in cruising around the Hauraki Gulf and some interested in the navigation and meteorology of sailing. We welcome cruising yachts visiting Auckland from overseas. We may be able to help as local liaison and answer questions such as

· Where to shop/bank/get things fixed

· Local knowledge for anchoring

· Visiting Yacht clubs

If you are visiting Auckland and have a query then let me know at bobmcdavitt@hotmail.com or info@cananz.org.nz and I’ll see what can be arranged.

 

TROPICS

There are no named cyclones around at present, but there are two small tropical depressions south of the equator in the Indian Ocean, and that means we may be in for a visit from a MJO.

MJO is the name given to a equatorial weather feature; its full name is Madden Julian Oscillation , named after two meteorologists who wrote a paper describing it back in 1971. See en.wikipedia.org/wiki/Madden%E2%80%93Julian_oscillation

An MJO occurs when a conglomerate of tropical convection forms in the Indian equatorial Ocean, and then this slowly moves eastward across the Indo-Australian zone into the western equatorial Pacific. It may take 30 to 50 days. The arrival of an MJO and it increased cloud/rain and convection in the equatorial western Pacific may help trigger tropical cyclones, so this is a feature worth watching .

There is a conglomerate of convection forming in the Indian Ocean this week, and it shows itself in the first map below as a zone of blue. The following maps are forecasts of that extra convection showing where it is expected in 5, 10, and 15 days time. It may reach the Papua New Guinea area around mid December. (In these maps OLR = Outgoing radiation). See www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

 

Looking at the weekly rain maps from last week and the week before, we can see an increase in convection in the equatorial Indian Ocean. See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is hovering from Coral Sea to northern Vanuatu to Samoa to Southern cooks. It is expected to shift south onto Fiji/Tonga from Tuesday to Friday, and then move off to the southeast as a trough/Low.

 

Subtropical ridge (STR)

HIGH H1 to southeast of NZ tonight is expected to slowly travel NE and then east along 40S this week.

Weak trough should cover inland NZ from Tuesday to Thursday (with inland showers).

Then another HIGH H2 is expected to form Se of NZ by Thursday and then slowly follow or merge with H1.

 

Between Tropics and NZ

With isobars around 1020+ over Northland and around 1010 to 1005 around Fiji, the wind flow between tropics and NZ is mainly easterly (and over 20gust30 knots in places).

Next week, a trough/warm front is likely to make its way across the Tasman Sea – at this stage its arrival in northern NZ is anticipated to be around Sat 9/Sun 10 December, but that may change.

 

>>>>>>>>>>>>>>>>>>>>

“The Sea, once it casts its spell, holds us in its net of wonder forever.” –

Jacques Yves Cousteau, Oceanographer.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Click FOLLOW at bottom right.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

 

 

19 November 2017

Bob Blog issued 19 nov 2017

WEATHERGRAM

YOTREPS

Compiled Sun 19 November 2017

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

For those of you who may be interested:  I’ve been invited to speak for an hour or so at 3pm Friday 24 Nov at the All Point Rally 2017 seminar being held by ICA in Opua.  I wonder what I should talk about-----

 

Some interesting photos of this month’s weather:

On Tuesday 7 November Bundaberg was hit by a passing heat trough with thunderstorms This visit was unusually windy, with wind gusts reaching 68 knots (image at metbob.wordpress.com courtesy of John Hembrow from the Downunder rally).

 

And I received an image from a yacht I’m forecasting for on its way across the equator towards Hawaii (Courtesy of Jono Wishart), taken at 11S 170W of a Brooks and Gatehouse monitor showing sea temperature of 35.3C where weather global model was forecasting sea temperature of 30C.   He says he has seem 35.8 since.

 

 

I’ve compiled a 3min 25sec video using windyty.com to show the development of that Low on Friday 17 November --- the one I referred to last week as “Something to avoid” and if you have access to good Internet you can view this at website  youtu.be/6_U-IRXZCVI

 

TROPICS

It has been busy around Vietnam recently, and Tropical Sytem KIROGI  is currently heading west across the South China Sea onto South East Asia, but should soon fade.

  

Looking at the weekly rain maps from last week trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif, and the week before, we can see some interesting bursts of rain in the Northern Hemisphere particularly in Bengal Sea, in North Pacific west of Hawaii, and from Cuba to central North Atlantic. There is also an increase in rain in the South Pacific Convergence Zone, especially from Coral Sea to Fiji/Tonga.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is hovering from Coral Sea to northern Vanuatu to northern Fiji at present, and is expected this week to drift south onto all of Vanuatu and Fiji and maybe onto parts of Tonga. These areas can expect some random squally downpours.   Another convergence zone, a continuation of the main zone, is expected to be draped from Tuvalu to south of Samoa to parts of Tahiti. 

 

Subtropical ridge (STR)

HIGH H1 in the south Tasman sea on Monday is expected to move towards central NZ by Wednesday and off to the east of NZ on Friday.   It may be a useful HIGH for anyway intending to cross the Tasman Sea

 Weak trough should cross southern NZ on Thursday/Friday and deepen into a Low and it travels off to the south on Sunday. Then another HIGH H2 is expected to travel northeast from the southern Tasman Sea onto central NZ by Tuesday 28 Nov.   These are good conditions from anyone planning to ail west-wards across Northern Tasman Sea.

 

Between Tropics and NZ

The Low to NE of NZ is already moving away, and today’s data shows it is followed by a week or more with High pressures dominating over NZ and thus easterly wind from tropics to NZ, so if anyone is still waiting to come south then this week is looking OK.

Winds may be variable near northern NZ from Fri 24 to Mon 27 Nov due to a passing trough.

Note that there may be a squash zone of strong SE winds on the northern side of the High over NZ from Tuesday to Thursday, near 20S.

>>>>>>>>>>>>>>>>>>>>

The Sea is the last free place on earth

- Humphrey Bogart

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Click FOLLOW at bottom right.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

12 November 2017

Bob Blog 12 Nov 2017

WEATHERGRAM

YOTREPS

Compiled Sun 12 November 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

Correction to my Facebook entry last week: Tonga is NOT having Summer time this year .

 

The state of the ENSO = La Nina trend now showing

El Nino and La Nina are opposite ends of an identifiable tropical influence on our seasonal weather. La Nina brings cooler than normal seas along the equatorial eastern pacific, is associated with stronger than normal trade winds and shifts the subtropical ridge (and its jetstream) away from the equator. El Nino with its weaker than normal trade winds and warmer than normal seas draws the subtropical ridge closer to the equator. Their comings and goings can last several months, maybe over a year, and so their status can be used to forecast the weather for the coming season.

 

NOAA have declared this to now be a (weak) LA NINA event with a good chance of lasting next 3 to 6 months. See www.cleveland.com/weather/blog/index.ssf/2017/11/noaa_la_nina_underway_with_a_6.html

Bureau of Met, Australia, is on a LA NINA watch and says the La Nina remains possible, but the effect on Australia’s climate may be less than recent events.

Implications for NZ area in the next 6 weeks is that we should have an early start to summer, with anticyclones crossing the Tasman Sea and New Zealand mainland bringing periods of sunny weather and light winds. After New year, there may be periods of strong easterly winds over Northland. In the South Pacific, convergence zones should be further south than normal, and trade winds may be stronger than normal, especially along the equator.

 

The Atmosphere:

The main parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words the placement of isobars on the weather map. When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

Since August the SOI has been more than 0.5, and two weeks ago it was over the +1 threshold. In the past week it has relaxed a little. Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10= 1 standard deviation).

 

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino, or becomes cooler than normal during a La Nina. This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see that since August there has been a cool trend for NONO3.4, and a few weeks ago the seas were almost 1-degree cooler than normal.

Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

 

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models. The mid-October edition shows NINO3.4 temperature may keep dropping (a little) until JFM (Jan Feb Marc) 2018.   CPC/IRI predictions are at  iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

TROPICS

It has been busy around Vietnam recently, and Tropical Storm HAIKUI is currently heading west across the South china Sea after visiting the Philippines, but should soon fade.

Looking at the weekly rain maps at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif from last week and the week before, we can see a burst of heavy rain travelling east along the Indian ocean equatorial region towards Indonesia, and a burst of rain about Cuba (passing cyclone).

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay from Solomon Islands to northern Vanuatu to Fiji. A Low is expected to form on this zone by Thursday between Vanuatu and Fiji by Thursday. This low is expected to deepen to around 1000 hPa near 27S 174E by Friday.

A secondary convergence zone is expected to hover from Samoa to Southern cooks.

Any voyage from Tahiti to Tonga will need to sail/motor thru this secondary zone —it has several weak spots, so this may be worthwhile with a little guidance.

 

Subtropical ridge (STR)

HIGH H1 in the south Tasman sea on Monday is expected to move towards central NZ by Thursday and off to the east of NZ on Friday. It may be a useful HIGH for anyway intending to cross the Tasman Sea

Weak trough should cross southern NZ on Thursday, followed by another HIGH H2 spreading slowly into South Tasman Sea from Friday to Sunday (19 Nov). This may be a useful pattern for anyone intending to cross the Tasman Sea next week.

 

Between Tropics and NZ

Models are picking LOW to form between Fiji and NZ and deepen on Friday with strong, maybe gale, easterly winds near 30 to 33S (a squash zone with H1). Something to avoid.

The Low is expected to move off to the east/southeast on Sat/Sun 18/19 Nov, or maybe early next week--- its future depends on sneaking in-between H1 and H2.

 

Between New Caledonia and Australia

H1 allows a good voyages from New Caledonia to Australia this week and H2 next week.

>>>>>>>>>>>>>>>>>>>>

It is the set of the sails, not the direction of the wind, that determine which way we will go

- Jim Robin

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Click FOLLOW at bottom right.

To unsubscribe  send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

05 November 2017

Bob Blog 5 Nov 2017

Bob Blog 5 Nov 2017

Posted on November 5, 2017

WEATHERGRAM

YOTREPS

Compiled Sun 05 November 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

SOUTH PACIFIC TROPICAL CYCLONE SEASON STARTED last WEDNESDAY

Now that season has started, New Caledonia Meteo are producing probability maps of TC Genesis /formation.

To see the latest go to

www.meteo.nc/nouvelle-caledonie/cyclone/coin-des-experts

and click on the diagrams under the words

“Cliquez ci-dessous pour afficher les graphes “

and the maps open as a pop-up (will need a browser that allows pop ups).

 

 

OCTOBER IN REVIEW

Sea Surface temperature anomalies may be seen at www.ospo.noaa.gov/data/sst/anomaly/2017/anomg.11.2.2017.gif

 

There continues to be more yellow than blue, more area covered by warm anomalies than by cool anomalies, but the blue is getting darker where it matters – along the eastern Equatorial Pacific, and things are on track for us to have a brief La Nina around the turn of the year, ). And there is still a warm river appearing along east coast of South America. Out to South Atlantic.

 

To see how the annual weather cycle and the seasons are working out, here is a quick look at the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

In October the isobars drifted southwards across New Zealand, pushing the SW winds and fronts of spring away, so that October was more like a regular November. This is consistent with the impact of a La Nina pattern, allowing the subtropical ridge to drift further south than its normal position. The anomaly map shows this has been happening in the South Pacific but not over South America or South Africa, so it’s a regional seasonal thing.

The anomaly rain map shows that the ITCZ is, in parts, further north than normal—this is a LA NINA trait.

 

Last 30 days of rainfall, and its anomaly, is seen at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

 

TROPICS

After a busy October, cyclone activity is finally slowing, with just TC DAMREY fading away over Asia.

 

Looking at the weekly rain maps from last week and the week before, we can see a burst of heavy rain in the past week around Indonesia and the China Sea, and around Solomon islands and between Niue and South Cooks.

See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay from Solomon Islands to northern Vanuatu to northern Fiji, and hover around Samoa. The more active portion which has been lingering between Niue and Southern cooks is expected to travel onto French Polynesia late in the week.

Any voyage from Tahiti to Tonga will need to sail/motor thru the SPCZ and it is likely to breed several squally showers this week. So take care with this.

 

Subtropical ridge (STR)

The remains of last week’s bfh (big fat high) are travelling off to the east f NZ along 30S. They are being followed by a trough moving off to east of NZ on Monday. Also, on Monday a high briefly crosses the Tasman sea and northern NZ.

The NEXT High is expected to be a slow-moving one, taking its time from Friday 10 to wed 15 Nov to cross the central Tasman Sea and central NZ area. This HIGH should be useful for anyone planning a voyage crossing the Tasman Sea.

 

Between Tropics and NZ

A trough is expected to cross New Caledonia on Wednesday and then form a low east of Norfolk Island on Thursday that is expected to deepen as it travels SE across northern NZ on Friday 10/Sat 11 Nov.

Those planning a voyage to NZ should arrange to avoid that Low as it has the potential to deliver gale winds and rough seas. Maybe. SO, delay getting south of 30S until around Mon 13 or Tues 14 Nov, +/-.

 

Between New Caledonia and Australia

On Monday a Low is expected to deepen off New South wales to SW of Lord Howe. Then on Tuesday and Wednesday this low is expected to travel across the South Island bring wind, rain and cold to southern NZ.

Conditions in the central Tasman Sea should ease from Wednesday, but the low forming near Norfolk Island may delay a good voyage from Noumea until Thursday or Friday.

From Friday 10 Nov onwards there should be some good voyages from Noumea to Australia around that slow-moving High in the Tasman Sea.

 

Any fool can carry on, but a wise man knows how to shorten sail in time.

– Joseph Conrad

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

 

 

29 October 2017

Bob Blog 29 Oct 2017

WEATHERGRAM

YOTREPS

Compiled Sun 29 October 2017

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

SOUTH PACIFIC TROPICAL CYCLONE SEASON STARTS on WEDNESDAY

Another good website for watching out for Tropical disturbances is www.tropicaltidbits.com/storminfo/

This site combines information from a number of websites dedicated to watching tropical disturbances.  When using it, remember that your insurance companies will mainly be interested in if you heed information that comes from the OFFICAL warning agencies, and in our part of the world that’s Fiji Met Service or NZ MetService (websites given in last weathergram) and, around Australia , the Bureau of Meteorology.

See www.bom.gov.au/qld/forecasts/cyclone.shtml  for the Coral Sea region.

 

TROPICS

TC PHILIPPE formed over Cuba in the past day or so and is now heading northeast where it is likely to follow the Gulf Stream.  This system may re-intensity into a mid-latitude system in a few days, thus have a stronger spin of wind around it and get deflected to the northwest and inland near New York.   If so it has the potential to deepen to 970hPa and bring a northwest gale to Lake Ontario. Reminds me of  Gordon Lightfoot’s ‘Wreck of the Edmund Fitzgerald “(in Lake Superior, 10 Nov 1975)) with lyrics: “When the gales of November come early” see www.youtube.com/watch?v=9vST6hVRj2A

In the NW Pacific TC SAOLA is forming over Micronesia near Guam and is expected to travel NW then N towards Japan.

 

Looking at the weekly rain maps at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif from last week and the week before, we can see a burst of heavy rain in the past week around central America and Guam., and another near the central Pacific to the north of Hawaii.  Intensity seems to be easing around India, in the ITCZ across the North Pacific and in the SPCZ across the South Pacific.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay where it is, from Solomon Islands to northern Vanuatu to northern Fiji to between Samoa and northern Tonga to between Niue and Southern Cooks.  Any voyage from Tahiti to Tonga will need to sail/motor thru the SPCZ and it is likely to breed several squally showers this week.  Avoid.

 

Subtropical ridge (STR)

There is a Big Fat High (BFH) HIGH east of NZ from Monday to Thursday.  This is being supported by a break in the normal upper level Jet Stream pattern, and is indicated by the mid atmosphere (500hPa level) wind map showing the shape of the Greek Capital Letter Omega, but upside down in the Southern Hemisphere.

The left and right hooks of the OMEGA are associated with surface lows.  

So, this BFH is expected to BLOCK the troughs in the Tasman Sea this week and redirect them AROUND New Zealand rather than onto NZ.

For more about the Omega pattern see en.wikipedia.org/wiki/Block_(meteorology)

And for a blocking index in the Southern hemisphere see

www.cpc.ncep.noaa.gov/products/precip/CWlink/blocking/real_time_sh/real_time_index_nrm.shtml

(This site doesn’t show this block yet as it is still forming.)

 

From Friday this block is expected to weaken, and the surface high should relax and move off to the northeast, allowing a new HIGH to travel east across Tasmania into the Tasman Sea from Saturday.

 

Between Tropics and NZ

There is a squash zone of strong east to NE winds between the BFH and the tropics.

Those departing from Fiji or New Caledonia to NZ should arrange their voyage so that they do not get near NZ until after Thursday.

This squash zone is expected to visit the Minerva/ South Tongan area from Tuesday to Thursday, so stay put for that. Should be able to depart Tonga or Minerva from Friday, but may need to try and time your departure taking into account south to southwest winds near NZ. 

The next trough to reach northern NZ is likely around 5 to 6 November. 

 

Between New Caledonia and Australia

Looks ok for departure Noumea any day this week.

The trough crossing Brisbane on Monday is expected to deepen into a low in central Tasman Sea by Tuesday, but the BFH should push that off to the south so it just fades away on the Noumea  to Brisbane route.

Next intense thundery trough is expected to reach Brisbane/Bundaberg area around late Mon 6 November or Tuesday7 November, so avoid that as arrival date.

 

“I can't control the wind but I can adjust the sail.”

― Ricky Skaggs

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

22 October 2017

Bob Blog 22 oct 2017

WEATHERGRAM

YOTREPS

Compiled Sun 22 October 2017

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

TROPICAL CYCLONE SEASON

Now that the tropical cyclone season is almost upon us, here are some links for you to check the latest. The Fiji Met Service watch for disturbances between equator and 25S from 160E to 120W. Even if you have no Internet access, and only email, you can get the latest tropical disturbance advisory by sending an email to query@saildocs.com,

no subject needed, with the message

SEND http://www.met.gov.fj/aifs_prods/20032.txt

Or, for the tropical discussion use

SEND http://www.met.gov.fj/aifs_prods/20036.txt

(wait until after 1 November)

 

Those with access to the Internet can study proceedings from the NZ MetService Tropical page at www.metservice.com/warnings/tropical-cyclone-activity

This page offers a streamline analysis And specially coloured satellite imagery for watching for rotating cloud tops

 

Tropics

TC LAN is bringing wind and rain to eastern Japan tonight, in time for a snap election.

And this is being followed bu tropical depression TD27W which may intensify later this week and head for Japan.

see www.tropicaltidbits.com/storminfo/

 

Looking at the weekly rain maps from last week and the week before, we can see a burst of heavy rain in the past week with cyclones between Guam and Japan, also intense rain on the Intertropical convergence zine just south of Hawaii. The South Pacific Convergence zone also shows an intensification in the past week. The Madden Julian Oscillation MJO is in phase with the Western Pacific this coming week, and that suggests we can expect more intensification along the ITCZ in the North Pacific this week.

See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to remain lingering in place this week from Solomon Islands to Tuvalu/Tokelau area. It may drift south onto Fiji/Samoa and northern Tonga/Niue next week or around the end of the month.

A passing trough is expected to visit northern NZ to New Caledonia on Monday and South Fiji to Minerva area on Tuesday and Wednesday then fade away. It may contain a few squalls.  Tropical accumulated rainfall for next week can ve seen at windyty.com

 

Subtropical ridge (STR)

HIGH is expected to travel east along 30S across the Tasman sea from Monday to Thursday reaching to east of northern NZ on Friday.

Another HIGH is expected to travel across the South Tasman Sea along 40S from Wednesday to Friday, then it may build to east of NZ over the weekend and next week (but models differ on this).

 

Between Tropics and NZ

The High crossing the Tasman Sea/northern NZ area this week offers a reasonable period of settled weather for getting to NZ. The trough that follows this High is expected to reach northern NZ on Wednesday 1-2 November so try and not arrive on those dates.

If this means arriving a few days later, that’s OK, we can arrange to sail thru the passing trough around 30S where its weak.

The next trough to reach northern NZ is likely around 5 to 6 November.

 

Between New Caledonia and Australia

Stay put on Monday and let a passing trough get across New Caledonia. Should be OK to depart from Tuesday, but departures on Tuesday to Friday will likely encounter a period of light winds from a passing ridge.

Try and avoid arriving on Queensland coast on late Monday 30 Oct/Tuesday 31 Oct due to a possible passing trough.

Note that New Caledonia and French Polynesia have a public holiday on Wed 1 November.

 

 

“The pessimist complains about the wind,

the optimist expects it to change soon,

and the realist adjusts the sails”

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe from WordPress: click the “unsubscribe” link on the bottom of the email.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

15 October 2017

Bob Blog 15 oct 2017

WEATHERGRAM

YOTREPS

Compiled Sun 15 October 2017

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

TROPICAL CYCLONE SEASON OUTLOOK

The South Pacific/Australian tropical cyclone season is nominally from 1 Nov to 30 April.   A weak to briefly moderate LA NINA is expected to affect the tropical Pacific Ocean over the next six months. This tends to nudge the South pacific convergence zone to the south and west of its normal position, increasing the cyclone risk around Australia and Coral Sea, and perhaps reducing this risk in places east of the dateline.

The Bureau of Meteorology have considered this and say that the cyclone risk over Northern Australia is increased. The average number of cyclones per season across the entire region is 11.  Chances of more this season are 56%.

 

From www.bom.gov.au/climate/cyclones/australia/ note this image remains copyright to BoM, repeated here for educational purposes only.

Looking at the behaviour of the sea surface temperature over the past year, NIWA has searched the database for analogue years that may point the way as to how this season may develop. The top analogues are 1970/71, 1978/9, 1995/96, 2005/6, and 2007/8, and using this data they have compiled some cyclone risk maps.

In summary, NIWA and MetService is anticipating 8 to 10 named storms this coming season (compared to an average of 10.4), a normal to above normal risk for New Zealand, New Caledonia, and Papua New Guinea (mainly late in the season),  and a below normal risk for the southern Cook Islands, the Marquesas, and French Polynesia.

For more details see www.scoop.co.nz/stories/SC1710/S00022.htm

 

Addendum to last week’s comment on Fleet code:

Chuck and Linda on JACARANDA say that :Once we open the email from saildocs we <Right> click the data.  A window opens up with some choices and we choose <export> The next window asks us where we want to export the data.  We have a folder already created called "Fleet Code".  We then just click <save> We also use OpenCPN as we like to see the data on an easier identified chart of the SP.  But we have also used Physplot in the past with good results.

 

Tropics

During the past week a suprising development occurred in the mid North Atlantic ocean:  TC OPHELIA, the strongest such system this far east in the North Atlantic. Warmer seas are the most likely explanation for this. And its heading for Ireland on local Monday.  Reminds us of  “The Great Storm” 30 years ago in October 1987, but  this one is likely to bring warm dry gusty winds to southern UK.

 And over in the China Sea we have TC KHANUN heading for South China.

 see  www.tropicaltidbits.com/storminfo/

Looking at the weekly rain maps from last week and the week before, we can see a shift of heaviest rain from equatorial Indian Ocean to The Vietnam/Philippines region, and an easing of the rain over central America. There is also a stretching-southeastwards of the rain in the South Pacific.

See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ has been lingering in place this week from Solomon Islands to Tuvalu/Tokelau area and is expected to spread onto Fiji/Samoa and norther Tonga later this week.

An upper trough that is over the Niue area for the next few days is expected to descend and form a surface Low near 35S 165W by Thursday UTC.  This low is then expected to deepen as it travels south into the Southern Ocean, leaving a trough over the Niue/Southern Cooks area by the end of the week.

 

Subtropical ridge (STR)

HIGH  is in the central Tasman Sea tonight is expected to build to over 1032hpa by Wednesday and then slowly weaken and travel east along 30S this weekend to east of the dateline next week.   There is expected to be a squash zone of enhanced trade winds and rough seas on the north side of this High, mainly between 20 and 25S from 175E to the Queensland coastline on Wednesday/Thursday.

 

French Polynesia to the west:

Be mindful of the trough that is in the Niue to Southern Cooks area this week.

 

From tropics to NZ or Australia

The Island Cruising Association are supporting the All Points Rally, from all major parts of South Pacific to Opua ending in ten days of activities 15 to 25 November in Opua. Boats joining the rally are assisted with weather info, resources and planning tools to help make the passage to NZ as easy as possible. See www.bayofislandsmarina.co.nz/all-points-rally/  to register.

Further west there is the GO WEST Rally.  From New Caledonia to Australia, culminating with Welcome week events in Bundaberg, 6-12 November.  It’s NOT too late to join the rally and enjoy a tailored voyage. See www.downunderrally.com. Registration includes standard Australian clearance fees, and these can be around $A400.

 

Between Tropics and NZ

The High crossing the Tasman Sea is expected to bring lots of southerly winds south of 30S until Wednesday and then the squash zone associated with High may bring some strong SE winds near 25 to 30S on Thursday.   The High is expected to be followed by a FRONT reaching northern NZ on Sun 22 Oct, so avoid landing then.  That should be followed by OK conditions for arriving in northern NZ from Mon 23 to Thursday 26 Oct, and then a FRONT to avoid on Friday 27 Oct.   Note that Mon 23 Oct is a public holiday.

 

Between New Caledonia and Australia

There is expected to be a convergence zone along the Queensland coast on Monday and Tuesday. Avoid.

The squash zone associated with the Tasman High is expected o bring strong SE winds and rough seas between 20and 25S from 175E to the Australian coast on Wed and Thursday (crudely speaking), so wait until after this squash zone.

After the squash zone there is expected to be a ridge with light winds across the route from Sun22 to Wed 25 Oct, and then a prefrontal NW flow.

 

NZ Coastal Classic

This RACE departs Auckland on Friday for Bay of Island. Expect SW winds, fading at times, especially around Cape Brett.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

08 October 2017

Bob Blog 8 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 08 October 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Its Palolo season this week: On the last quarter moon there is an overnight full tide, the first since the equinox, and that’s the trigger for a spawning of a coral worm called Palolo. They drop off their tails or pod; jade for female and brown for male and these mix together in the swirling tide, with each having a light-sensitive spot that directs them all to the moon a sit sinks in the west. At dawn the pods dissolve allowing eggs and sperm to get together and start a new generation. The rising is only on the turn of that one tide, taking place in a few hours.

If you get the chance ask locals in Vanuatu/Fiji/Samoa/Tonga for more.

 

FLEET CODE (my annual mention)

FLEET CODE was established to allow a weather map to be sent to the whole Fleet all at once via Morse code transmitted over Shortwave. Fiji Met Service are still manually converting their analysis map into fleet code and, thanks to Mike Harris of Pangolin and the people at saildocs these maps can be downloaded as email and drawn on your own computer as you travel around the South Pacific.

They have an advantage over GRIB files in that they contain convergence zones, as seen by Fiji Met Service meteorologists using satellite imagery to fine tune placements.

To download the latest Nadi Fleet code send an email to query@saildocs.com, no subject needed, saying SEND nadi-fleetcode.

When you receive the reply email, use something such as notepad to save the data as a text file and store this, say, on your desktop, as, e.g. fleet.txt

Mike Harris’ PANGOLIN website contains a page which allows you to save a beta version of PhysPlot. Go to www.pangolin.co.nz/physplot . This is a windows program physplot.exe (now called a desktop ap) which can open that file fleet.txt and turn it into a weather map for you.

I don’t use OPENCPN, but apparently you can download the fleet code plug in from opencpn.org website and this gives better viewing of the overall area.

 

Topics

TC NATE developed over central America and deepened as it travelled north across Gulf of Mexico , and made landfall tonight over Alabama, and is weakening as it goes inland.

 

Looking at the weekly rain maps from last week and the week before, we can see that there is an increase in area of rain activity in the South Pacific, and in the area and intensity of rain across the equatorial part of the Indian Ocean.

See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif for weekly rain maps.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ has been lingering in place this week from Solomon Islands to Tuvalu/Tokelau area. Its eastern flank may shift south and visit Samoa later this week and extend southeast Southern Cooks next week.

There is likely to be a squash zone of enhance SE winds and south to southeast swells over 3 metres across the French Polynesian area from Wednesday to Saturday (UTC). May as well stay put for this.

Tropical accumulated rainfall for next week can be seen at from windyty.com

 

Subtropical ridge (STR)

HIGH 1 is expected to travel east along 45 to 40S from east of NZ on Monday to south of French Polynesia by end of the week. It is this high which is forecast to be responsible for the squash zone over FP late this week.

HIGH2 is expected to spread into the central Tasman Sea on Wednesday and then travel northeast across northern NZ on Friday and to east of NZ along 35S from Saturday.

 

French Polynesia to the west:

Be mindful of that squash zone and increased swells near French Polynesia from Wednesday to Saturday (UTC). May as well stay put for that.

 

From tropics to NZ or Australia

The Island Cruising Association are supporting the All Points Rally, from all major parts of South Pacific to Opua ending in a ten days of activities 15 to 25 November in Opua. Boats joining the rally are assisted with weather info, resources and planning tools to help make the passage to NZ as easy as possible. See www.bayofislandsmarina.co.nz/all-points-rally/ to register.

Further west there is the GO WEST Rally. From New Caledonia to Australia, culminating with Welcome week events in Bundaberg, 6-12 November. It’s NOT too late to join the rally and enjoy a tailored voyage. See www.downunderrally.com. Registration includes standard Australian clearance fees, and these are around $A400.

In deciding upon a departure date, it’s as simple as 1.2.3:

1.The first factor to consider is the local weather: the SPCZ South Pacific Convergence Zone as it sometimes brings squalls, but is well to the north this week.

Some like to use Minerva reef as an extra staging post since it is 1.5 to 2 days sail south of Tonga, and just out of the tropics (so marine insurance that may be void in the tropics may work in Minerva). But it only shelters you from the waves (so long as they don’t topple over the reef) and not from the wind or rain. It has a passing trough on Monday, and no strong winds this week. .

2.The second factor to watch is the STR, or subtropical ridge, where the HIGHS travel, that zone between the trade winds of the tropics and the disturbed westerlies of the roaring 40s. This zone is usually near 30S, and if there is a big high then on its northern side there is usually an accompanying are of enhanced trade winds, what I call a SQUASH ZONE. This week there is a squash zone expected near French Polynesia later this week.

3.The third factor is weather for arrival. Try to avoid bursts of strong southerly winds and heavy swells during the trip or upon arrival. These come from the Southern Ocean and occur on a different pattern to the passing troughs in the tropics. Sometimes a southerly burst inter-reacts with a tropical trough and things get nasty. Not this week. You can use windyty.com to see expected weather features at your arrival point for the next week, and aim to arrive “in-between active features”, but remember that these outlooks are just ideas, and real world does its own thing.

 

Let’s apply this 1,2,3 rule to some popular destinations:

Between Tropic and NZ

1 and 2 are OK but 3 has problems. Avoid the SW winds near NZ on Tuesday and Wednesday. Winds are Ok for arrival on Thursday to Sunday, then NOT OK on Mon/16 to Sat 21 Oct next week.

If it takes you around 8 days to get to NZ then consider delaying departure to sometime later next week, or contending with some southerly winds.

 

Between New Caledonia and Australia

1and 2 are OK this week. 2 and 3 may have problems this or next week depending on your desired port of entry.

A Trough is expected to reach Sydney and fade near Coffs on Tuesday. A stronger trough should reach Sydney on Wednesday and fade near Coffs /Brisbane by Friday.

The HIGH that is expected to be crossing south Tasman sea on 15 to 20 Oct may cause a squash zone of strong easterly winds near 25S near Australian Coast. Avoid arriving there then.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

 

01 October 2017

Bob Blog 1 Oct 2017

WEATHERGRAM

YOTREPS

Compiled Sun 01 October 2017

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Last month

Sea Surface temperature anomalies may be seen at www.ospo.noaa.gov/data/sst/anomaly/2017/anomnight.8.31.2017.gif

There continues to be more yellow than blue, more area covered by warm anomalies than by cool anomalies, but the blue is getting darker where it matters - along the eastern Equatorial Pacific (a possible LA NINA signal). And there is still a warm river appearing along east coast of South America.

To see how the annual weather cycle and the seasons are working out, take a quick look at the average isobar maps from  www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

In September, the subtropical ridge in the southern hemisphere shifted slightly north of its August position, with the disturbed westerly flow as far north as Bass strait to north of North Cape, somewhat further north than normal.  A large anomalous LOW remains over South Australia/South Tasman Sea and explains the seasonal variations in the region: the hot NW winds for NE Australia, and the wet westerlies for North island and wet NE winds for eastern South Island.  

There is a purple anomaly from Caribbean to Eastern USA -  That’s IRMA MARIA and their associates. 

The anomaly map shows that the ITCZ is further north than normal---this is a LA NINA trait.

The Atlantic hurricanes also show in the monthly rain map at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

 

Topics

Remains of TC MARIA have travelled more than half way across the North Atlantic, and may affect UK in a few days. Otherwise, things seem to be quietening down for now. Then again, a new tropical system is expected to form off the Mexican west coast later this week.

Rainfall for the past week compared with last week, shows the paths of IRMA and MARIA with a peak over Puerto Rica.  Also a build-up of rain near 5S in the Indian Ocean.  See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

 

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay in place this week from Solomon Islands to Tuvalu/Tokelau area.   Its eastern flank may shift south towards Samoa by this weekend.

The Trough that is travelling to east of NZ tonight is expected to continue east and fade well to the south of the tropics on Tue/Wed UTC.  It is followed by a day or so of 3 metres + southerly swells from the Southern Ocean reaching as far north as 20S for Tuesday.  These swells are gentle giants with a period of 12 seconds, so very well spaced apart.

 Another trough is expected to travel east across Southern Cooks and French Polynesia late this week, and this may form a LOW further south.

 

Subtropical ridge (STR)

HIGH 1 is expected to move across Tasman Sea along 30S on Monday and Tuesday and then fade over northern NZ on Thursday and Friday. HIGH 2 is expected to spread into the South Tasman Sea on Thursday and then travel east across South Island and rebuild east of New Zealand on Friday and Saturday.

French Polynesia to the west:

There may be some strong SE winds near Bora Bora on local Sunday and Monday.

The next obstacle to consider appears from around the end of the week  -- and is a travelling trough over Southern Cooks / French Polynesia. 

If tossing up between going to Samoa or Tonga, then pick Tonga and avoid the SPCZ.

 

Between NZ and the tropics:

Avoid the strong W/SW winds and rough seas near NZ on Monday, these should ease away on Tuesday.

Then there should be a window of opportunity for getting to northern NZ from Tue 3 to Sat 7 October thanks to passing Highs. 

 There is expected to be a trough near northern NZ around Sun/Mon 8/9 Oct with strong NE winds and some rain. 

 Then there should be another period of acceptable weather to get to northern NZ until the next trough arrives around sat 14 Oct.

 

Between New Caledonia and Australia

It’s Ok to go to Bundaberg or Brisbane, BUT avoid arriving there on Thursday 5 October, for that is when there may be a venting of the heat trough. This trough is expected to travel east across the eastern seaboard of Australia on Thursday, and deepen into a Tasman Low offshore on Friday.  This Low should then travel east to northern NZ by 9/10 October.

The trough may bring squalls and lightning to Bundaberg and Brisbane ion Thursday, followed by a brief period of SW winds, so avoid. 

 Apart from that,  the Tasman low is NOT expected to have much impact on the New Caledonia to Bundaberg or Brisbane route.

 

Vanuatu Volcano

And, for the goodness of your health, stay away from Ambae Island and its active volcano, Manaro Voul.

This island, east of Espiritu Santo, inspired James Michener’s mythical Bali Hai.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Click FOLLOW at bottom right to subscribe.

To unsubscribe: send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

24 September 2017

Bob Blog 24 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 24 September 2017

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

The equinox was Friday 22 Sep at 22:02 UTC and so several nations around the South Pacific are switching from ST/ Standard Time to DT/ Daylight time over the next few weeks as follows:

 

Sep 24 (today)

 

NZST (UTC +12) switches to NZDT (UTC +13)

 

Samoa (UTC+13) switches to Samoa DT (UTC+14)

 

 

 

1 October (next Sunday)

 

AEST = UTC+10 switches to AEDT= UTC+11

 

Lord Howe ST = UTC+11 switches to Lord Howe DT = UTC +12

 

 

 

5 November

 

Fiji ST = UTC+12 switches to Fiji DT = UTC+13

 

Tonga ST = UTC+13 switches to Tonga DT = UTC +14

 

====================================

 

When calculating your departure from the Islands to Australia /NZ be mindful of the public holidays:

 

 

Tonga: Monday Nov 6 Constitution.

 

 

 

Fiji: Tues Oct 10 = Fiji Day, Thursday Oct 19 = Diwali

 

 

 

New Caledonia:

 

National Day : Sep 24th, All saints Day 1 November, Armistice Day 11 November

 

 

 

New Zealand: Labour Day Monday 23 October.

 

 

 

Australia: On Mon 2 October Queensland observes Queens Birthday  (NSW/ACT/Sa observe Labour day the same day).

======================

 

Topics

 

TC MARIA has done its dash in the Caribbean, and is expected to stay offshore from now on, but may sideswipe Bermuda.

LEE is also still going but further east

PILAR is affecting Mexican west coast

And there are a couple of tropical depressions in the NW Pacific.

 

Rainfall for the past week   as seen at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif, shows the path of the Atlantic cyclones, with a peak over Puerto Rica.

 

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ starts this week from Solomon Islands to Tuvalu/Tokelau area.

A weak upper trough is fading between Tonga and Niue on Monday UTC.

Another trough is expected to travel east across Tonga and Niue on Thurs/Fri UTC reaching the Rarotonga area on Sun/Mon 1/2 Oct UTC, preceded by NE/N winds, accompanied by variable winds and showers, and followed by SW/S/SE winds.

 

 

Subtropical ridge (STR)

HIGH moving off to east of NE New Zealand on Monday is expected to intensify to over 1032 near 35S 150W by Friday, and this may increase the trade winds between French Polynesia and the Cook Islands to around 20 gusting 30 knots. This is a slow-moving High, so the winds on its western side—over NZ are expected to be intensified on Monday and Tuesday.

Another HIGH is expected to move off eastern Australia on Tuesday and slowly move to between NZ and New Caledonia/Fiji by Thursday and then linger there until early next week..

 

French Polynesia to the west:

The main obstacle this week is that travelling trough over Tonga/Niue on Thursday/Friday UTC, but it may Ok to sail thru this trough. It is looking to be a fading feature after it travels east past Niue.

 

Between NZ and the tropics:

Very strong NW winds over the North island on Monday and Tuesday, and then a passing trough on Wednesday. Thursday, with a passing ridge, is the best day of the week for arrival/departure. Then there is likely to be another trough on Friday followed by another on late Saturday and decreasing SW winds on Sunday.

Best date to depart/arrive is either Wednesday 27 or Monday/Tuesday 2/3 Oct.

With that High lingering between New Zealand and New Caledonia/Fiji from Thursday, the voyage is likely to face a few days of light winds.

 

Between New Caledonia and Australia

This week the wind between New Caledonia and the Brisbane area are likely to be mainly northerly. A southerly change is likely for Sun 1 to Tuesday 3 October.

Further South, in the central Tasman sea, a trough is expected to be travelling east on Monday and Tuesday, followed by light winds with a passing ridge on Wednesday and the another trough with NW winds on Thursday and variable/southwest winds on Friday/Saturday.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage,

then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

17 September 2017

Bob Blog 17 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 17 September 2017

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

The state of the ENSO = weak La Nina trend now showing

The Atmosphere:

El Nino and La Nina are opposite ends of an identifiable tropical influence on our seasonal weather:  the La Nina, caused by cooler than normal seas along the equatorial eastern pacific. shifts the subtropical ridge away from the equator, and the El Nino, with warmer than normal seas, draws the subtropical ridge closer to the equator.  Their comings and goings can last several months, maybe over a year, and so their status can be used to forecast the weather for the coming season. 

The main parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words the placement of isobars on the weather map.  When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

So far this year there have been an unsteady swings either way, and in Aug/Sep the SOI has settled around plus 0.5 (or 5 units in the graph shown here), in the zone which some call a weak La Nina.  So, this is a hint that the subtropical ridge line may shift southwards faster than normal over the next three months.  The warming of spring/summer should reach Australia and NZ faster than normal.   Maybe this also means the tropical wet season may start earlier than normal.

Weak La Nina may be seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10= 1 standard deviation)

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino, or becomes cooler than normal during a La Nina.  This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see the trend in the sea surface temperature in the NINO3.4 area. The diagram shows the weekly temperature anomalies since Jan 2014, with the El Nino of 2015 looking like a hump on a camel. Since then there has been a cool period late 2016/early2017, and then a warm period until July 2017.  We are now in a cool period again. But only around half a degree below the old "normal"( maybe 1 degree below the new normal).

Weak La Nina is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models.  The early September probabilistic forecasts show the chance of La Nina is as high as 60% over next few months, dropping below 50% again early next year. CPC/IRI predictions from iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

The sea surface temperature anomaly map has been showing MOSTLY WARMER THAN NORMAL on planet earth for months now, so that climate change is beginning to warp out the seasonal influences. The warmer than normal seas in the Atlantic has been breeding stronger than normal cyclones, but it seem that HARVEY has managed to stir the Gulf waters so they are now cooler than normal.  Reminds us that tropical cyclones are one way this planet gets rid of excess energy. Without them, worse would happen.

Latest SST anomaly map shows the wonderful cooler eddies along the equator of a typical La Nina, but the ENSO values involved are only half a degree and so it’s only half-a-La-Nina, and not being called as such yet.  I’m wondering that if we could remove the climate change trend for the data, then maybe it’d exceed the La Nina threshold. 

Sea surface temperatures are at www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

TROPICS

IRMA has done its damage and JOSE is staying offshore,

LEE is Fading away,

Next in line is MARIA in the Caribbean,

And NORMA off Baja California,

and to west of NORMA is OTIS.

Meanwhile over in Northwest pacific, TC TALIM has turned away from Taiwan  and is now affecting Japan.

See www.livemint.com/Politics/s0eTyRYVnX3ZdpXLua5weJ/Typhoon-Talim-slams-Japan-hundreds-of-flights-grounded.html

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ starts this week from Solomon Islands to Samoa area, and is expected to drift South so as to visit Fiji and maybe northern Tonga this weekend sat/sun/mon 23/24/25 Sep.

A passing, mainly upper, trough, is expected to travel eastwards across Niue on local Monday night and Southern Cooks on local Tuesday/Wednesday, preceded by NE/N winds, accompanied by variable winds and showers, and followed by SW/S/SE winds.

Tropical accumulated rainfall for next week may be seen at windyty.com

 

Subtropical ridge (STR)

HIGH moving off eastern Australia tonight is expected is expected to move northeast across the North Tasman Sea next few days, fading near the date line after Thursday.

Another HIGH is expected to move off eastern Australia on Thursday and travel across Northern NZ on Sunday 24 Sep and remain above 1022 and it travels east along 30S to east of NZ next week.

When these Highs are in the Northern Tasman Sea we can expect a weak squash zone in the Coral sea.

 

French Polynesia to the west:

The main obstacle this week is that travelling trough over Niue on local Monday and Rarotonga on local Wednesday. This trough may bring a day or two of variable winds south of 18S, but not much disturbance to the surface winds further north. Take into account that Tonga may receive some tropical showers early next week ( 25/26 Sep Local) from a visit from South Pacific Convergence zone.

Between NZ and the tropics:

LOW#1 is travelling Northeast across eastern NZ on Monday/Tuesday followed by strong squally SW winds and a burst of SW swell over 4 metres as far north as 28S. Avoid.

Low#2 is expected to travel northeast across central NZ on Thursday and Friday followed by a period of strong SW winds and a burst of SW swell over 4 metres as far north as 30S. Conditions easing Friday night/Saturday morning.

Best dates to depart/arrive is either Wednesday or Sunday 24 Sep.

 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

See my website http://www.metbob.com for more information

Feedback to bob@metbob.com or txt 6427 7762212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com,

Click FOLLOW at bottom right to subscribe.

To unsubscribe, send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

Blog Archive