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

28 June 2015

BobBlog issued 28 June 2015

WEATHERGRAM

YOTREPS

Issued 28 June 2015

 

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 Brisbane to Noumea 2015 Yacht race started on Saturday 20 June and, as luck would have it, was undertaken in a near perfect weather pattern:  Almost a beam reach the whole way but wind gets forward of the beam near New Caledonia.  Winning yacht was Beau Geste taking 2 days 43 minutes and six seconds – a new race record.

See www.sailnoumea.com for all the info.

 

In The Atmosphere:

The Southern Oscillation Index SOI sums up the weather pattern over the South Pacific in one number and is based on the standardized difference in the barometer readings between Tahiti and Darwin (30 day running mean). The weekly update was lower than -10 for four weeks in May, enough to start a moderate El Nino episode. A couple of weeks ago the index went positive, and last week it was negative again. Possibly these fluctuations can be explained away as due to passing troughs over Tahiti.

 

SOI is shown at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

 

TROPICAL TOPICS

 

No Tropical Cyclones at present but a very interesting thing is happening along the equator near Papua New Guinea . It is called “equatorial westerlies”. This burst of wind started off from the Asian monsoon and is best seen at the 5000ft level (lower cloud level) to clearly show how it is producing eddies, helping create tropical lows—three in the Northern Hemisphere just north of 5N and one in the Southern hemisphere just south of 5S. Equatorial westerlies may be  seen at on Windyty.com

 

The tropical depression in the southern Hemisphere already has the name TD17F and seems to have  a very good chance of being a named tropical cyclone over the next few days, Its central parts may track across western parts of Solomons on Tuesday, but the main damaging winds are in a ring about 50 to 100 miles from the centre and are likely to visit all of Solomons. BRACE FOR SQUALLY GALES, HEAVY RAIN (150-250mm/day) AND HIGH SEAS especially Tuesday and Wednesday.

 

 

The Indian Monsoon has been progressing stronger (in wind) than normal over past week, but the clouds stalled for a time so that there was a heat wave up to 44C over Karachi (peak temperature on 22 June), with over 1200 related human deaths.

 

Monsoon progress may be seen at http://apdrc.soest.hawaii.edu/projects/monsoon/realtime-monidx.html

 

The weekly rain maps over the past two weeks show the monsoon rain moving onto Burma/Myanmar and intense rains already inTD17F to northeast of Solomons.

These weekly rain signatures may be seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

 

SPCZ=South Pacific Convergence zone.

SPCZ section that is over Solomons is expected to drift into Coral Sea from Wednesday. The section over the Southern Cooks is expected to form a LOW that travels SE to south of the Austral Islands and deepens further as it turns south over the weekend.

 

STR= Sub-tropical Ridge

STR is expected to remain strong this week along about 30S. However there is a weak spot between NZ and Fiji. The computer models have been trying to produce a trough in this region. Note that there is a squash zone of strong enhanced trade winds from near west of Fiji to Coral Sea between SPCZ and STR.

 

Mid latitudes

Intense trough is expected to move across NZ from Tasman Sea on Thursday and Friday, preceded by strong NE winds, accompanied by wind change and rain, and followed by strong SW flow and bug swells on Saturday and maybe on Sunday 5 July. Then another trough is expected over northern NZ on Tue 7 to Thu 9 July.

 

Departing from Australia to the tropics this week:

After the great weather pattern for the Brisbane Noumea 2015, the way from Brisbane to Noumea has been blocked by too many headwinds, and so shall be the case until Wednesday. There may be an opportunity after the Thursday SW winds in the Tasman Sea ease.

 

Departing from Northern NZ going north.

It looks OK to depart Mon/Tue but I think these departure will need to negotiate NE winds by Thursday and a passing front on Friday. These negotiations may be at 30 to 25S where the front is expected to be tame, so these voyages may be OK--- but not the best. At this stage weather pattern for a departure on Sun 5 July is looking more comfortable.

 

>>>>>>

 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

 

See my website www.metbob.com for information on tailor-made voyage forecasts–

Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

 

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.

 

 

21 June 2015

Bobgram

WEATHERGRAM

YOTREPS

Issued 21 June 2015

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.

As you read this give yourself a pinch and punch– not for the first of the month but the turn of the year, the Solstice is at 21 1648UTC, that’s when the sun’s declination stops going north and starts coming south, hooray. 

And the quote of the week goes to Pope Francis in his encyclical on Our Common Home saying “The biblical texts tell us to "till and keep" the garden of the world (Gen 2:15). "Tilling" refers to cultivating, ploughing or working, while "keeping" means caring, protecting, overseeing and preserving. This implies a relationship of mutual responsibility between human beings and nature.”

  I somehow think that cruising yachts, of necessity, appreciate the relationship between humans and nature.

Now, what is nature up to???

The Atmosphere:

The Southern Oscillation Index SOI is based on the standardized difference in the barometer readings between Tahiti and Darwin (30 day running mean) and thus sums up the weather pattern over the South Pacific in one number. The weekly update was lower than -10 for four weeks in May, enough to convince the meteorological community that we are now having an EL NINO episode. And in the past week it has gone slightly positive.   This may possibly show that the current El Nino is fickle – or that troughs around Tahiti are variable.

SOI is shown at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

 

The Ocean

The amount of heat that is being stored in the sea in the Eastern Equatorial pacific has been above normal since late 2014, as measured by the NINO3.4index, and is currently well over the EL NINO threshold.

NINO3.4 is shown at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi, confirming an El Nino.

 

El Nino’s impact:  During an El Nino episode, weather patterns tend to be drawn closer to the equator. The South Pacific Convergence zone tends to be tugged north and east of its normal position and there tend to be more troughs over Tahiti.  The subtropical ridge in the southern hemisphere tends to be north of its normal position and this weakens the trade winds overall, but doesn’t stop the squash zones that can be found on the north side of the migratory HIGHS.

El Nino encourage the disturbed westerlies of the Southern ocean to be very active, especially in the southern spring (September to November).  It raises the planet’s atmospheric temperature overall but places like New Zealand have cooler air and sea temperatures.

 

TROPICAL TOPICS

During the past week, between my blogs. TC BILL came and went along east coast of USA.

A rather subdued TC KUJURA is about to make landfall on south China coast to west of Hong Kong.

The rain map for the last two weeks shows the Indian monsoon at its height and extreme rain to left and right of Solomons. The one-week-average over Tasman Sea looks climatologically tame but fell fast enough to swamp Whanganui, Western North Island, New Zealand.  Weekly rain signatures for past two weeks, may be  seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

 

SPCZ=South Pacific Convergence zone.

SPCZ starts this week in normal El Nino position STTT= Solomons Tuvalu Tokelau Tahiti and by mid-week should have lifted south to Samoa.  The section over French Polynesia is expected to spread out and diversify, spreading light wind and odd squalls across much of the Tuamotu Islands. So if you are there then wait until late in the week for more steady winds. Tahitian troughs are an El Nino trait.

 

STR= Sub-tropical Ridge

STR has weakened since that 1-38hPa whopper last week.

The High entering the Tasman Sea today should take its time and fade and spread northeast to be between Fiji and NZ by Sun 28 June UTC. 

There should be strong squash zones on north side of his HIGH and another one travelling east along 45S to south of Tahiti.

 

Mid latitudes

Cold southerly is spreading north and likely to trigger the development of a low near Minerva on Monday UTC. Associate trough should travel east across Fiji on Monday, Tonga on Tuesday and reach Tahiti on Sunday UTC.

 

Departing from Australia to the tropics this week:

High crossing the Tasman Sea makes it too difficult. Maybe OK after trough moves off New South Wales on Thursday.

 

Departing from Northern NZ going north.

Low near Minerva is likely to result is a squash zone with strong winds and heavy swells at first.  Best to delay departure until at least Thursday.

 

See my yotpak at boatbooks.co.nz/weather.html for terms used.  See my website at www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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 this email send a reply email saying LEAVE.

14 June 2015

Bob's Blog

WEATHERGRAM

YOTREPS

Issued 14 June 2015

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 Atmosphere:

The Southern Oscillation Index SOI sums up the weather pattern over the South Pacific as one number and is based on the standardized difference in the barometer readings between Tahiti and Darwin (30 day running mean).  The weekly update has been lower than -10 for four weeks and now is relaxing.

 SOI is shown at http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

 

TROPICAL TOPICS

TC CARLOS is following the lead of BLANCO onto the Mexican west coast.

 The Indian Monsoon arrived in Kolkata/Calcutta on Thursday with a bang—a thunderstorm

  This can be seen at http://www.timeandtide.com/

And in the South Pacific the Highs have been HIGHER than normal,  with a 1038 hPa HIGH visiting New South Wales for much of the last few days:

The Sydney Barometer for past week, may be  seen at http://www.wunderground.com

The rain map for the last two weeks shows BLANCA and CARLOS off the west Mexican coast, and also a burst of intensity over Solomons, and a build-up in intensity along the South Pacific Convergence zone. The weekly rain signature may be  seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

  Galapagos to Marquesas:

Best winds for departing are on local Sunday/Monday/Tuesday. There is still signs of a good west-going current along around 6S from 115 W to 125W.

 

SPCZ=South Pacific Convergence zone.

SPCZ has been strong over the Solomons and is building in intensity from Solomons to Samoa and then to the southeast. A trough is expected to cross Samoa/Tonga by Wednesday UTC and then move onto Tahiti by Sat 20 UTC, followed by a squash zone.

 

STR= Sub-tropical Ridge

STR is along its normal latitudes for this time of the year.  The HIGH that has been intense over New South Wales over last few days is expected to weaken as it skirts around northern NZ on Wednesday, with a squash zone of enhanced trade winds on its northern side along 20S,  and then re-intensify to over 1030hPa as it travels east along 30/35S to east of NZ. 

Next HIGH is expected to travel east across Tasmania on Sat 20 June.

 

Tasman Sea /NZ area:

Disturbed SW flow on Monday easing on Tuesday and a High is expected to skirt northern NZ on Wednesday.  LOW is expected to deepen off New South Wales by Wednesday 17 June and then travel SE across southern NZ by Friday, with associated front moving across Tasman Sea and onto Northern NZ by Saturday, preceded by strong to gale northerly winds on Friday.

Low may deepen between NZ and Fiji early next week on 22/23 June.

 

Departing from Australia to the tropics this week:

There may be some good weather for departing after the LOW, perhaps on Friday 19 June.

 

Departing from Northern NZ going north.

OK to depart with Monday’s SW winds, but that will give a rough start.   The light winds on Tuesday and Wednesday get replaced by northerly winds on Thursday, strong to gale on Friday and then a passing front on Saturday, followed by a southerly/SE flow.

If a low does form between Northland and Fiji on Mon/Tue 22/23 June then it is likely to be worth avoiding.

 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

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.  My website is at metbob.com – Feedback to bob@metbob.com To unsubscribe send a reply email saying LEAVE.

 

 

07 June 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 7 June 2015
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 Atmosphere:
The Southern Oscillation Index SOI sums up the weather pattern over the
South Pacific as one number and is based on the standardized difference in
the barometer readings between Tahiti and Darwin (30 day running mean). The
weekly update has been lower than -10 for four week now, so that means we
are now having a full blown El Nino affecting both Atmosphere and Ocean.
SOI is shown at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekl
y
In an El Nino the normal weather zone get pulled closer to the Equator, and
we can see this in the pressure anomaly map for the past month. The
subtropical ridge in the Pacific is over New Caledonia/Fiji/Tonga. There
are higher than normal pressures over Darwin and lower than normal over
Tahiti. As seen at
http://www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html
This trend allows some Meteorological companies to extrapolate it a month
ahead and produce wind anomaly maps such as seen at
http://www.extendweather.com/seasonalforecast/GLOBAL/E3201505/windspeed-anom
aly

TROPICAL TOPICS
TC BLANCA is not following ANDRES (of last week) into the Pacific, instead
it is expected to make landfall over Baja California on our Monday (local
Sunday).
In the Arabian Sea, west of India, there is a tropical depression. However
there is no sign yet of anything forming in the Atlantic, nor in the NW
Pacific during the following week. Strange.
In an El Nino year the Indian monsoon is usually late, slow, and not-so-wet.
And indeed, this year's Indian Monsoon has struggled to keep to its normal
sequence and is now about 5 days BEHIND schedule. Its failure to bring
ocean-moistened air into the heart of India has led to extremely high
temperature to inland India:

Advance of Northern limit of Monsoon may be seen at
www.imd.gov.in/section/nhac/dynamic/Monsoon_frame.htm, extending the
pre-monsoonal heat wave over central India.

The rain map for the last two weeks shows ANDRES and BLANCA off the west
Mexican coast, and also a burst of intensity with the South Pacific
Convergence zo is seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

Galapagos to Marquesas:
Best winds for departing are on Monday/Tuesday or Wednesday local.
There is still signs of a good west-going current along around 5 to 6S near
100W but it is now weakening.

SPCZ=South Pacific Convergence zone.
SPCZ has been strong over the Solomons and is expected to be moderate this
week between Solomons and Samoa with a stretch of activity across Northern
Cooks. A trough is expected to cross French Polynesia late in the week and
develop a low near 30S 140W by Thursday UTC (local Wednesday) that should
then move SE.

STR= Sub-tropical Ridge
STR remains north of normal-an El Nino trait. One HIGH is expected to move
east along 30/35S from North Tasman Sea to 150W during this week, with a
squash zone of enhanced trade winds along 25S on its northern side. There
is a large 1030 hPa high over SE Australia: It is expected to move along
35/40S from Australian Bight to Eastern Australia from Wednesday to Friday
and then to eastern Tasman Sea this weekend 13/14 June and hover over
northern NZ early next week.

Tasman Sea /NZ area:
Trough over southern Tasman Sea and southern NZ by Tuesday should cross
central NZ on Wednesday and North Island on Thursday.

Departing from Australia to the tropics this week:
Avoid the squash zone of strong SE winds in the Coral Sea and northern
Tasman Sea from Monday to Saturday- These are on the north side of the large
1030 HIGH over SE Australia.

Departing from Northern NZ going north.
OK to depart on Monday if you are quick enough, otherwise there are nosy
head winds ahead of that incoming trough on Wednesday and strong winds on
Thursday. May be Ok to depart for the north again on Friday or Saturday.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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.
My website is at metbob.com - Feedback to bob@metbob.com To unsubscribe send
a reply email saying LEAVE.

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