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

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.

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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.

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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.

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

10 September 2017

Bob Blog 10 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 10 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.

TROPICS

CAT 4 IRMA is damaging parts of Florida as I write this:

Some good news about Cyclone JOSE is that it is expected to do a loop and then stay offshore as it goes north.

KATIA has gone inland, and may end up off the west coast of central America.

Meanwhile over in Northwest pacific, TC TALIM is heading for Taiwan.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

This week, a thin SPCZ is expected to remain across the Coral Sea.  Part of it may visit Vanuatu/ Southern Fiji and Southern Tonga tonight, and then weaken.  A smaller convergence zone may form near 8 to 10S to north and east of Samoa.

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

Another passing trough may reach New Caledonia area around Monday 18  Sep local.

 

Subtropical ridge (STR)

HIGH around 1022hPa is expected to move into North Tasman Sea on Monday and then spread east along around 25 to 30S this week reaching south of French Polynesia by end of week.

Another HIGH around 1024hPa is expected to spread from Australia into northern Tasman Sea on Friday.

And then spread along 25 to 30S over next few days.

These High should maintain reasonable trade winds for sailing across the South pacific this week

French Polynesia to the west:

The main obstacle this week is that travelling trough over Niue on local Monday and Rarotonga on local Wednesday.

 Apart from that this should be a god settled week with reasonably steady winds for sailing.

Between  NZ and the tropics:

On Monday and Tuesday, the SW winds and associated large swells over NZ around a LOW to east of the South Island should slowly ease as the Low moves away.

Next front from the Tasman Sea is likely to pass across NZ on Friday,

and then a deep Low may cross southern NZ on Mon/Tue 18/19 Sep.

 

There may be some gaps between these passing fronts with OK departure for arrival/departure.

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,

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03 September 2017

Bob Blog 3 Sep 2017

WEATHERGRAM

YOTREPS

Compiled Sun 3 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.

 

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.

And there is still a warm river appearing along east coast of South America.

The eddies of cooler than normal water along the Eastern Equatorial Pacific looks like symptom of LA NINA, but the surrounding warmer than normal seas dilute this.

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

 

In August, the subtropical ridge in the southern hemisphere lay in its normal seasonal latitudes between Fiji and NZ, with a disturbed westerly flow as far north as Bass strait to North Cape, somewhat further north than normal. Looking at the anomalies, we can see that wave 3 has been dominating proceedings, with HIGHS lingering in 3 places: South Atlantic and South Indian Oceans, and to SE of French Polynesia, and LOWS lingering in 3 places: over Chile, well south of South Africa, and over the Tasman Sea. Cyclonic northerly winds for NZ have been bringing a wet winter.

 

The wetter than normal conditions over northern NZ also show in the monthly rain map—but this map shows that peak anomaly has been to NE of NZ, and, when averaged over the whole month, is surprisingly near neutral over the NZ mainland.

 

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

The monthly rain map shows heaviest rainfall along equatorial area from Indian Ocean to Indonesia, with some heavy rain over India, Nepal and Bangladesh, and a spot of heavy rain over Houston, Texas… (Three days of epic rainfall looks minor when averaged over a month).  The anomaly map shows that the ITCZ is further north than normal--- this is a LA NINA trait, but it’s a real LOCAL La Nina.

 

TROPICS

Deluging rain from HARVEY brought damaging flooding to Houston.

The intensity of the rain in HARVEY was so much that NWS had to add a new colour to their rain map…

see www.youtube.com/watch?v=x28AcE5bxIo

And the intense monsoon continued in southeast Asia with a death toll of around 1,200 people, see www.theguardian.com/world/2017/aug/30/mumbai-paralysed-by-floods-as-india-and-region-hit-by-worst-monsoon-rains-in-years

 

This week, TC IRMA is in the Atlantic Ocean and model’s, at this stage, are suggesting that it might make landfall on North Carolina later this week.

And on the US west coast, TC LIDIA is expected to remain over the ocean put travel almost parallel to the coast.

And in the NW Pacific, remains of TC SANVU is fading as it approaches the Korean Peninsula, and a depression (MAWAR) is expected to make land fall to north of Hong Kong.

 

Last week’s rain map from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif shows enhancements in the rain over SE Asia, along the equatorial Indian Ocean, about the south of Japan (due to SANVU), over Eastern Pacific in the ITCZ, and a hotspot near Houston.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

This week, the SPCZ is expected to remain near Solomon Islands to Tuvalu and occasionally affect Tokelau.

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

Another passing trough may reach New Caledonia area around Saturday9 Sep local.

 

Subtropical ridge (STR)

HIGH over 1034hPa is travelling east along 40S for the next few days well south of French Polynesia, and as it moves away the winds over French Polynesia should weaken and turn easterly then Northeasterly.

 

Another HIGH, around 1022hPa, in northern Tasman Sea on Monday is expected to travel east along 25 to 30S this week across the South Pacific. it should help maintain moderate SE trade winds.

 

French Polynesia to the west:

The main obstacle this week is that travelling trough over Niue on local Sunday and Rarotonga on local Tuesday.

 

Departing northern NZ to the north or east for the tropics:

On Monday, a low travelling off to east of NZ should bring SW flow to the northern north Island.

On Tuesday, there should be a passing ridge with lighter winds.

On Wednesday, the forecast is for an increasing NW winds ahead of an approaching trough.

On Thursday and Friday, expect squally west to WSW winds, and rough seas.

By Saturday night, a Low around 1002hpa is expected to travel across northern N., followed on Sunday and Monday by showery SW/S winds.

SO maybe this isn’t the week to come or go, unless you can time departure on Tuesday or arrival on early Saturday.

 

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

 

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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,

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27 August 2017

Bob Blog 27 Aug 2017

WEATHERGRAM

YOTREPS

Compiled Sun 27 Aug 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.

 

LISA BLAIR arrived back in Sydney yesterday—the first woman to circumnavigate Antarctica solo in a yacht.

For a VIDEO OF S/v CLIMATE ACTION NOW closing in on Sydney heads see tinyurl.com/y8zytx6h

I have been helping Lisa with some weather information during this fantastic adventure.

 

TROPICS

Both HARVEY (Texas) and PAKHAR (Hong Kong) have moved inland and turned into wet tropical depressions.

There are two tropical depressions at present, one is east of PAKHAR and is forecast to go north and stay east of Japan. T’other is in the Atlantic and is forecast to go N/NE and may sideswipe the Eastern seaboard of United States with some northerly winds on its western side.

We can see these track possibilities at ruc.noaa.gov/

 

Last week’s rain map, compared with the week before, shows the most intense rain is still around Southeast Asia in the monsoon. This is affecting 41 million people, and there have been 1200 recent deaths, see www.aljazeera.com/news/2017/08/floods-kill-1200-india-nepal-bangladesh-170826230610924.html.

 

In the tropical South Pacific, the rain map at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif shows a general decrease in activity.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put his week and linger across east Solomon Islands and Tuvalu slowly spread southwards towards Fiji and Samoa this week.

A trough is travelling east off NZ tonight and is expected to travel east and is expected to affect the region between NZ and south of Tonga during the next few days.

Another trough is expected to travel east across the Society Islands and Tahiti from mid-to-late week, but since this region is at the northern end of this trough, its impact is minor.

 

Subtropical ridge (STR)

HIGH 1033hPa east of NZ is expected to travel east along 40S and build to 1036hPa during Monday/Tuesday/Wednesday and then slowly ease and travel off to the southeast. Although this is 25degrees of latitude away from the tropics, this HIGH is expected to squeeze the isobars near 15S closer together forming a squash zone of strong trade winds and swells rising to 3 to 4 metres mid-week between Borabora and Samoa. Avoid.

One of my quotes applies "When the HIGH is over 1030 it's going to get dirty"

 

French Polynesia, going to the west:

Not this week. We should wait a while until after this squash zone.

 

Between NZ and the tropics:

A Low is expected to travel east across North island on Wednesday UTC and another on Friday UTC.

If in NZ, may as well stay put this week.

If travelling to NZ, arrange arrival after Sat 2 Sep.

 

Between Australia and the tropics:

Weak subtropical ridge is expected to linger over northern Tasman Sea between Queensland and south of New Caledonia. Southwest winds are likely south of 30S.

 

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.

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20 August 2017

Bob Blog 20 Aug 2017

WEATHERGRAM
YOTREPS
Compiled Sun 20 Aug 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
The Atmosphere:
El Nino and La Nina the opposite ends of an identifiable tropical influence on our seasonal weather: the La Nina shifts the subtropical ridge away from the equator and the El Nino 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 data from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the weather pattern over the South Pacific as 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 at present we are on the La Nina side of zero, but that has peaked so I think we are still in some more unsteady swings over the next few months, with the SOI basically hovering around zero. This means the subtropical ridge may wander a little north or south of its seasonal normal position, but not hover away from its norm long enough for us to change our cruising plans. Just keep an eye on that subtropical ridge.

An unsteady SOI 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 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 near zero or neutral state. .

Neutral territory as seen at ww.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

The International Research Institute of the Climate Prediction Centre compile data from several ENSO prediction models. The overall trend is towards little change later this year, with most all of the models within -0.5 and +0.5.

For CPC/IRI predictions see iri.columbia.edu/our-expertise/climate/forecasts/#ENSO_Forecasts

One seasonal prediction that can be made is that the number of tropical cyclones forming in the North Pacific Ocean over the next few months. This is likely to be more than normal, due to warmer than normal seas. It is too early at this stage to comment on the incoming South Pacific cyclone season starting later this year..... but the early indication is that, because of warmer than normal seas, there may be an increased risk.

For Sea surface temperatures across the Pacific on 17 Aug see www.ospo.noaa.gov/data/sst/anomaly/2017/anomp.8.17.2017.gif

TROPICS
At present tropical cyclone HARVEY is travelling west onto central america and KENNETH tavelling northwest off the west Mexican coas. There is a depression heading west into the China Sea and another on the Atlantic west of Africa that may travel west to Florida. We can see these tracks at ruc.noaa.gov/

Last week's rain map, compared with the week before, shows a shift of intense rain from Myanmar to Indonesia, and an easing of rain in the NW Pacific. In the tropical South Pacific, the rain map shows a passing intense trough during the past week; as mentioned in last week's weathergram. And there are continuing hotspots of intensity around Panama and Sierra Leone.
A link to the devastating mudslides in Sierra Leone is at
www.independent.co.uk/news/world/africa/sierra-leone-mudslides-latest-fears-1000-people-dead-bodies-a7902806.html

Rain for the past week is at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is expected to slowly spread southwards towards Fiji and Samoa this week.
Also a passing trough is expected to bring some rain to the Tonga and Niue area early this week and then fade away. Accumulated rainfall may be seen at from windyty.com

Generically speaking, a passing trough in the South Pacific islands is preceded by a period of weakening northerly winds, accompanied by variable winds and showers and then followed by a period of S then SE winds. Satellite imagery shows that these troughs travel eastwards, and that may appear confusing at first to someone on the ground considering these wind changes. However, if we look at a time/height diagram of the wind flow over, say, Nuku'alofa, we can see there are lots more westerly winds aloft than easterly winds at the surface, and THAT is what explains the eastward travel of these passing troughs.


For Time/height diagram over Nuku'alofa, see windyty.com, type in nukualofa as the search box then select airgram. (This diagram has the wind barbs on wrong side of arrow shaft, treating them as northern hemisphere winds).

Subtropical ridge (STR)
High is expected to build in the North Tasman sea on Monday and then travel onto northern NZ by Wednesday and then travel slowly to east of the North Island by the end of the week building to around 1029hpa. This should help maintain SE trade winds between French Polynesia and Tonga.

Between NZ and the tropics:
Low near Chatham Islands tonight is travelling off to the east. The southerly flow and swell on the backside of this low should weaken over northern NZ on Monday and Tuesday, then the outlook over northern NZ is for light winds on Wednesday to Friday, then we expect strengthening NE winds ahead of an approaching trough on Sat and Sunday.
So, the best days for getting off to the north are Monday and Tuesday, and a departure on Wednesday may be OK as well.

Between Australia and the tropics:
A trough is expected to travel off the eastern seaboard and into Tasman sea on Tuesday and then travel east across the Tasman Sea and deepen into a low on Wednesday that should reach the South Island early next week, with associated trough reaching New Caledonia around Sunday and North Island around Monday 28 August.
Any travel form Australia to tropics should be on back side of that trough, and any travel from New Caledonia to Australia this week will need to encounter this trough.

French Polynesia to the West:
There is a passing rough over tonga tonight that is travelling east and expected to fade south of Niue during Monday UTC.
After that a slow-moving and not-very-intense High /subtropical ridge along 30 to 35S should ensure moderate trade winds and swells, good for sailing westwards.
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

13 August 2017

Bob Blog 13 Aug 2017

WEATHERGRAM
YOTREPS
Compiled Sun 13 Aug 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.

TROPICS
At present tropical cyclone JOVA is travelling ESE (a strange direction) off the west Mexican coast and a tropical depression is expected to take a clockwise path around the Atlantic Ocean.
Meanwhile TC BANYAN is in the Northwest Pacific and is expected to go north and then northeast - its remains may reach Alaska, perhaps.
We can see these tracks at ruc.noaa.gov/tracks/

Last week's rain map, compared with the week before, shows continuing high rainfall around the NW Pacific, and the equatorial Indian Ocean, and the equatorial Atlantic Ocean. It has been very wet around Bangladesh, and there is a build-up of activity along the South Pacific Convergence zone.

Rain for the past week is from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is expected to shrink and shift to the north this week. The build-up of shower activity that occurred last week is expected to be gathered by a tropical trough and conducted south-southeastwards across Tonga /Niue area on Wednesday 16 Aug UTC.

Subtropical ridge (STR)
High to northeast of NZ is expected to travel east along 30 to 35s this week and build to a peak of over 1035 on Thursday 17 Aug UTC. This is expected to produce a squash zone of enhanced trade winds on the north side of this High on 17 to 19 Aug UTC-this should mainly affect French Polynesia.
New High is expected to move off eastern Australia into North Tasman Sea on Monday, and to travel along 20 to 30S past northern NZ on wed/thu UTC. This high is taking the typical path of a winter anticyclone.


Between Australia /NZ and the tropics:
Light winds in the subtropics between 20 and 30s with the incoming high.
South of 30s the pattern is a typical winter of disturbed westerlies, made stronger and squally by a deep Southern Ocean low travelling east along 45 to 55S, 960hpa, in Aussie Bight by Tuesday and south of the Taman Sea by Friday. SW swells up to 5+ metres with a period over 10 seconds in Tasman sea by this weekend.

French Polynesia to the west:
The trough that is expected to travel south-southeast over the Tonga/Niue area on Wed 16 Aug is likely to dominate the landscape this week for any vessels hoping to travel westwards towards Tonga.
It is likely to be an active trough because it is taking away (southwards) the build-up of extra energy from the SPCZ. Also, as this extra warmth comes south it is likely to encounter the colder denser airmass which crossed North Island tonight showing itself as an upper trough with lots of thunder and lightning.
I'll assume that it may be better to wait for this trough to make its way south-southeast, and so delay that trip toward Tonga until later this week or early next week.
The trough should bring a brief period of strong NE winds to Niue on Wednesday morning local or Rarotonga around Friday morning local.
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

06 August 2017

Bob Blog 6 Aug 2017

WEATHERGRAM
YOTREPS
Compiled Sun 6 Aug 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.

TROPICS
NORU is still going and is expected to visit Japan this week, and NALGAR is over the open ocean further east. There are two tropical depressions on the Atlantic Ocean that may develop further during the coming week. We can see these at ruc.noaa.gov/tracks/

Last week's rain map, compared with the week before, shows continuing high rainfall around Japan, the equatorial Indian Ocean, and possibly the equatorial Atlantic ocean, and decreasing amounts elsewhere.

Rain for the past fortnight from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ starts this week draped from Solomon Islands to Tuvalu and Tokelau Islands to Northern Cooks. An MJO event is moving into the western Pacific this week and that should help activate the SPCZ.
A convergence zone /trough is expected to travel east across the Society Islands on local Monday. Better to stay put for that and depart local Tuesday.
Next trough from the west is expected to reach New Caledonia on local Wednesday and Tonga area on local Friday, it's a minor trough but worthy of consideration.

Subtropical ridge (STR)
High east of NZ is expected to travel east along 30s until Thursday and then weaken as a High from further south builds around 160W.
New High is expected to move off eastern Australia into North Tasman Sea on Thursday, and travel along 28S past norther NZ by Saturday 12 Aug.

Between Australia /NZ and the tropics:
Low is expected to travel east along 40S from Monday to Wednesday across Southern Tasman sea. Moving southeast across central NZ on Thursday.

French Polynesia to the west:
A trough/convergence zone that is expected to be crossing the Society Islands on local Monday UTC. Wait until TUESDAY and its should be ok to go west from Society islands.
The SPCZ is expected to be mainly confined to the Solomon Islands to Tokelau Islands area, but may extend to Suwarrow by end of the week.

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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

30 July 2017

Bob Blog 30 July

WEATHERGRAM
YOTREPS
Compiled Sun 30 July 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
The Atmosphere:
You may have heard about El Nino and its opposite, La Nina. They are tropical influences on the weather: the La Nina shifts the subtropical ridge away from the equator and the El Nino 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.
A month or so ago we were on the brink of a possible El Nino, but latest data shows things are "unsteady".
The main data from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the weather pattern over the South Pacific as one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words the placement of the 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.
For most of the period from May 2015 to May 2016 we had an extreme El Nino. Then there was a weak La Nina in October 2016, and since then we have had several fluctuations, plus then minus, each lasting around a month. For want of a better word, I'll describe this as "UNSTEADY". The latest SOI, last week, is plus .5 (or plus 5 in the units used in the farmonline site), and shows a continuing of this "unsteady" trend.
An unsteady SOI is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

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 a warm period so far in 2017. This warmth is getting less over last few weeks. It seems that the trend in towards a neutral state.
Neutral territory is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

The International Research Institute of the Climate Prediction Centre compile data from several ENSO prediction models. The overall trend is towards little change later this year, with most of the models on the side of a weak El Nino.
CPC/IRI predictions are at
iri.columbia.edu/our-expertise/climate/forecasts/#ENSO_Forecasts
One seasonal prediction that can be made is that the number of tropical cyclones forming in the North Pacific Ocean over the next few months is likely to be more than normal, due to warmers than normal seas. It is too early at this stage to comment on the incoming South Pacific cyclone season starting later this year.

EVIDENCE OF CLIMATE CHANGE:
People have been noting warmer summer temperatures in the Northern Hemisphere, and Dr. Hanen and two colleagues have been extracting some bell curves for various decades to compare with the 1951-1980 epoch. See www.pnas.org/content/109/37/E2415.full or /www.nytimes.com/interactive/2017/07/28/climate/more-frequent-extreme-summer-heat.html?mcubz=1
-- the New York Times doesn't explain much about the methods used, but the PNAS paper gives a full account.

TROPICS
This is the peak of the heat for the Northern summer, and, sure enough , it's busy with cyclones as we can see from ruc.noaa.gov/tracks/, showing 5 cyclones = HILARY and IRWIN east of Hawaii, and NORU, HAITANG, and NESAT between Hawaii and China. Also an "invest" area. These storms are mostly oceanic, but for NESAT heading for Taiwan with HAITANG on its heels.

Last week's rain map, from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif, compared with the week before, shows continuing high rainfall over parts of India and across SE Asia to the Philippines and an increase in rain around Solomon Islands. The path of cyclone NORU stands out.


WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ starts this week draped from Solomon Islands to Tuvalu and Tokelau Islands, and slowly increasing in intensity.
A convergence zone /trough tonight stretches from Vanuatu to Fiji to Tonga containing variable winds and a few squalls. This is expected to travel southeast and deepen into a low near 30S on Tuesday UTC, that may then bomb (rapid deepening) to 972 hPa at 40S 40E by Thursday. Too far away to bother anyone, but may generate southerly swells to over 4 metres for the Gambier Islands by the weekend. Long period swells that are loved by surfers. Accompanying convergence zone is expected to pass to east of Rarotonga on Tue UTC and then stall and then return to south across Rarotonga on Sat 5 Aug UTC.


Subtropical ridge (STR)
High over NZ tonight is expected to travel northeast to 30S then eastwards at around 1020 hPa- not strong enough to enhance the southeast trade winds on its northern side.
Next High is expected to form over south Tasman sea on Tuesday and travel around the south end of NZ and then along 50S to 170W by the weekend.

Between Australia /NZ and the tropics:
Low is expected to deepen in Tasman Sea off New South Wales on Monday and then travel east across Northland on local Thursday and then travel east along 33S to east of NZ to the end of the week. It may be followed by another low deepening off the New South Wales coast on local Thursday. Avoid these lows/.

French Polynesia to the west:
The main challenge for going west this week is the trough/convergence zone that is expected to be crossing the Tongan area on Monday UTC. This zone is expected to continue southeast past Rarotonga on Tue/wed UTC and then stall and travel back southwards across Rarotonga around Sat UTC. Avoid.
This zone is not expected to have much impact any further north-a trip via Palmerston Island is likely to be mostly unaffected.
The SPCZ is expected to be confined to the Solomon Islands to Tokelau Islands area.
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.
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23 July 2017

Bon blog for 23 July

WEATHERGRAM
YOTREPS
Compiled Sun 23 July 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.

CONGRATULATIONS
Bravo to Lisa Blair for being the first woman to sail solo around Antarctica below 45 South (with one stop due to a dismasting). Lisa crossed her outgoing track on Friday 21 July at 9:48pm local time. Inspirational.
I have been emailing daily weather ideas to Lisa throughout this trip, but that's just idea- sharing and does not affect her claim to have sailed this adventure solo and unassisted (but for the stop at Cape Town for a new mast). Lisa has had knock downs, giant waves, winds over 80 knots, snow, hail, bumped into a container ship, encountered an easterly gale, and wallowed in large wind holes. Her blogs are at lisablairsailstheworld.com/blog/

If you feel inspired by this accomplishment, please buy one of her beanies to help out, while they are still available. See lisablairsailstheworld.com/shop

TROPICS
This is the peak of the heat for the Northern summer, sometimes called 'the Dog Days' - named for the appearance just before dawn of Sirius, the Dog star and brightest star in the sky, from around 19 July. Sure enough, it's busy with cyclones as we can see from ruc.noaa.gov/tracks/, showing 5 cyclones = Fernanda and Greg east of Hawaii, and Kolup, Noru and Roke between Hawaii and China.
Also 3 depressions and 3 "invest" areas. These storms are mostly oceanic, but Roke seems to be heading for Hong Kong, and the remains of a faded Fernanda may bring some rain to a dry Hawai'i, if they are lucky.

Last week's rain map, compared with the week before, shows a decrease in rain around the South Pacific, and an enhancement in the rain over India, SE Asia and Indonesia.
Rain for the past week may be seen at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ starts this week draped from Solomon Islands to Tuvalu and Tokelau Islands, and is having a weak week further east.
A passing trough, associated with a front in the Southern Ocean, is expected to go east across southern cooks on local Tuesday, and another may reach New Caledonia area on local Thursday and then move onto the Tongan area by local Sunday. These troughs are preceded by NE winds and followed by south or southeast winds.

Subtropical ridge (STR)
From Monday to Wednesday UTC a HIGH is expected to travel east across northern Tasman sea along 27S, and the further east to east of NZ along 30s from Thursday to Sunday UTC. There may be a squash zone of enhanced SE trade winds near 10 to 15S on the north side of this High.
From Friday to Monday UTC, another High is expected to travel east across northern Tasman sea along 30S.

Between NZ and the tropics:
Avoid the trough that is expected to be crossing northern NZ on Wed/Thu and early Friday.

French Polynesia to the west:
This looks to be a good week to go west. The SPCZ is still weak and expected to be confined to the Solomon Islands to Tokelau Islands area. However, there may be a squash zone of enhanced trade winds between Tahiti and Niue between Friday and Sunday local.
Also, a weak passing trough is expected to affect southern cooks on local Tuesday, and another may affect New Caledonia on local Thursday.
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

16 July 2017

Bob blog 16 July 2017

WEATHERGRAM
YOTREPS
Compiled Sun 16 July 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.

TROPICS
Tonight HURRICANE FERNANDA is travelling west-northwards away from the Mexican west coast. And it is being followed by a tropical depression.
It is vaguely heading towards Hawaii, but at its current pace will not reach those longitudes until 24 July and is likely to fade away by then.
And there is TALAS in the China Sea. The models are picking it may travel west across SE Asia , but will probably fade away inland. Cyclone tracks may be seen at https://ruc.noaa.gov/tracks/

Last week's rain map, compared with the week before, from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif, shows an enhancement in the rain in Solomon islands, and relaxing rain along the ITCZ.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ starts this week reasonably active around Solomon Islands, and is expected to slowly weaken during the week.
A passing trough, associated with a front in the Southern Ocean, is expected to go east across New Caledonia area on local Thursday and then move onto the Tongan area on local Saturday preceded by NE winds and followed by southerlies.

Subtropical ridge (STR)
HIGH located over Northern NZ tonight is expected to travel east along 33s to east of NZ this week. It may build to over 1040 when it gets east of 140W after Friday and the should have a squash zone strong SE winds and over 3m swell on its northern side, around the Gambier Islands.

Australia to New Caledonia:
A trough is expected is to travel east across the eastern seaboard on Tuesday night local, followed by strong SW winds and large swells on Wednesday. It should be ok to depart on Thursday but the voyage will need to go ese at first and allow for ESE wind after 158E.

Departing northern NZ to the north or east for the tropics:
North to NW winds over northern NZ until a cold front crosses the area on Wednesday/Thursday. It may be ok for departure on Friday if you don't mind SW winds and 3 metres swells. Otherwise better to wait until Saturday.

French Polynesia to the west:
This looks to be a good week to go west. The SPCZ is weak and the subtropical ridge is not expected to produce much of a squash zone on this path - however you may get swell over 3 metres on Thursday UTC.
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

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