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

17 April 2016

Bob Blog

WEATHERGRAM

YOTREPS

Issued 17 April 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.

 

How is El Nino doing?

The Southern Oscillation average for the last 30 days on 14 April was minus 0.98 compared with a reading of minus 2.4 in mid-March

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

 

Over the past month, the data shows that trade winds close to the equator have actually been slightly STRONGER than normal. The trade winds in the southern Pacific Ocean have been reaching as far as 3S. However there has been a convergence zone between Galapagos and Marquesas. There has also been a puddle of calm between Panama and Galapagos.

Wind averages and anomaly for past month from www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30b.fnl.html

 

The TOA data for yesterday does show a slight westerly anomaly along the equator—but only from 180 to 160W and not enough to cancel out the trade winds. See www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30b.fnl.html

 

The Tropics:

Cyclone FANTALA has an eye and is re-curving off the northeast end of Madagascar, so is expected to track to the southeast and weaken.

Track can be seen at www.tropicaltidbits.com

 

A tropical depression TD17F is travelling southeast tonight across Fiji, and brought them heavy rain over the past few days. Models have different tracks for it, and it seems likely to linger in the Fiji area this week and may do a counter-clockwise loop to north and then northwest of Fiji and then travel east and then southeast. Avoid.

 

Rain maps for the past fortnight show that the extra convergence zone that has been located between Galapagos and Marquesas is showing signs of weakening. See  trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

Panama to Galapagos:

There may be northerly winds to assist departure until local Wednesday, then SW headwinds are expected to reach Las Perlas.

South of 6N there are expected to be SW winds all week.

 

Travelling to Marquesas:

This looks like a good week to take off, with SE winds 8 to 10 knots locally around Galapagos and with that convergence zone in-between Galapagos and Marquesas clearing east of 110W.  A good idea to go via 7S or 8S at 110W so as to avoid squalls.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week very active between Samoa and Tahiti

 

STR= Sub-tropical Ridge

High is expected to spread from Tasman Sea across central NZ from Monday to Wednesday.

There is expected to be a squash zone of enhanced easterly winds on the north side of this feature on Wednesday

Another High is expected to travel over southern NZ / Chatham Islands from Wednesday to Friday.

 

For NZ and Tasman Sea

First week of the school holidays is looking good. Next trough is expected to reach South Island on Friday and bring a southwest change to remainder of NZ on Saturday.

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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

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