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

14 February 2016

Bob Blog 14 feb 2016

WEATHERGRAM

YOTREPS

Issued 14 February 2016

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.

 

Panama to Galapagos:

The best time of the year to do his trip is during the next month.

Looking at the monthly averaged scatterometer maps from the SCOW website at

http://numbat.coas.oregonstate.edu/scow/wind_speed_dir.html

for February, March and April shows that over much of the Pacific nothing seems to change during these months,

BUT the finer details shows a significant change in the averaged winds between Panama and Galapagos.

During February and early March there are regular period of NE winds over the Panama end of this trip,

with light SE winds around Galapagos.

 

Well, after the equinox (21 March) the likelihood of those useful NE bursts of wind around Panama dropdown significantly,

so that they are replaced by just light winds in the April average map.

Also across most of the route to the equator there are head winds from the south or southwest. Not so good.

 

Note that these averaged out maps are a OK guide for date-planning purposes,

but treat them as not being from the real world- the daily weather patterns are much more variable.

 

As for the influence of the current El Nino: This episode seems to have reached its peak,

and models are expecting the parameters we use to measure it to return to normal levels by May or June.

The extra heat that has been stored in the sea seems now to be going into the atmosphere,

and so is available for stronger weather events around the planet during the next 6 weeks or so,

but it is unlikely that anything severe will appear in the Panama to Galapagos region.

 

As for departing this week--- Looks mostly good, with convection showers between 2 and 6N mostly keeping well away

to west of 87W or along Colombian coast. However the forecast is for some strong (and thus uncomfortable) NE winds near 8N to 6N

on Monday or Friday UTC.

 

Tropical Cyclones

TC URIAH is in the Indian Ocean:as seen at http://www.bom.gov.au/products/IDW60281.shtml

 

TC TATIANA was in the Coral Sea travelling south but has been disrupted by strong winds aloft and is now downgraded to a tropical low.

 

TC WINSTON started in the middle of last week between Vanuatu and Fiji and has been drifting south and then sliding east. It was managed to miss out from being decapitated by the jetstream and now seems likely to be deflected to the northeast so that it might visit Tonga later this week. The more reliable EC model has it visiting Fiji. Worth watching and avoiding.

see http://www.met.gov.fj/aifs_prods/65648.html

Looking at the upper winds WINSTON is embedded in a SW flow and keeping away from the jetstream-

see http://squall.sfsu.edu/gif/jetstream_sohem_00.gif

 

Rainfall in the tropics over the past week has been most active in central Indian Ocean, in the Coral Sea and between Vanuatu and Fiji.

All these areas are now places where tropical cyclones are active.

Rain for the past week may be seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ now stretches all the way across the south pacific and is intense. At the beginning of the week it extends from Solomons across Vanuatu to WINSTON, and then arcs from WINSTON across Tonga and Niue to Southern Cooks. As WINSTON travels to northeast the SPCZ will travel with it.

There is a possibility that another tropical depression may form near Southern Cooks by Tuesday UTC/local Monday, and then travel off to the southeast.

 

STR= Sub-tropical Ridge

HIGH east of NZ on Monday is expected to remain quasi-stationary at around 45S.

Next HIGH is expected to cross Tasmania around Friday and then move northeast across the Tasman and reach central NZ around Tue 23 Feb.

 

For NZ and Tasman Sea

Trough in the central Tasman Sea by Tuesday is expected to cross NZ on Wednesday and Thursday.

May be wetter than last week’s trough, as it may entrain some tropical moisture from the remains of TATIANA.

This trough is likely to be followed by a cooler southerly flow on Friday to Sunday.

>>>>>> 

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.

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

 

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