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

19 March 2017

Bob Blog 19 March 2017

WEATHERGRAM
YOTREPS
Compiled Sun 19 March 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 passing a great meteorologist.
Dev Raj Sikka died of a cardiac arrest yesterday (18 March) at the age of 85. He leaves a great legacy, linking the behaviour of the Asian Monsoon to El Nino back in 1982. He has been involved in the preparation of more than 200 scientific papers on meteorology from India, over the last 60 years. He has earned the name "Monsoon Man"
Last December he received the prestigious 'lifetime achievement award' from IMS (the Indian Meteorological Society). And back in 2010 he was the recipient of the Sir Gilbert Walker Gold Medal. (Sir Gilbert Walker was a statistician who applied lag-correlation techniques when appointed as Director-General of the Indian Meteorological Department in 1904 resulting in the Yule-Walker equations and the Southern Oscillation Index).

For more reading: projecteuclid.org/download/pdf_1/euclid.ss/1023799000

The Equinox
The sun is directly over the equator at 10:28UTC on 20 March. This marks a natural "corner" in the orbit of the earth around the sun, and indeed is marked as a turning point in the seasonal weather patterns.
It is interesting that, over the eastern equatorial pacific, the arrival of warmer-than-normal sea along the coast recently has, over the last few days, triggered downpours that are bringing floods and mudslides - the worst in 20 years. This has already been called "El Nino Rain" at www.thestar.com/news/world/2017/03/17/peru-floods-caused-by-el-nino-rain-kill-at-least-67.html


The Tropics.
There are some tropical depressions around and some active convergence zones, but we have gone thru another quiet week as far as tropical cyclones are concerned.
The rain map from last week, when compared with previous week, as seen at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif shows continuing heavy rain around northern and eastern Australia and across Peru, the Amazon, and the equatorial Atlantic. The convergence zone between Galapagos and Marquesas is one that tends to occur around this time of the year, and is starting to show signs of weakening.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ has been very active over Fiji for last few days. A small tropical depression is expected to travel along the SPCZ across Tonga on Monday/Tuesday and then off to the SE. After that the SPCZ is expected to drift north and be very active this week across the Coral Sea and the Northern Vanuatu /Wallis and Futuna/and Samoa to Niue area.
The "near equatorial convergence zone" is expected to hang around for a few weeks.

Subtropical ridge (STR)
Much like last week, another "dry High" is in the Tasman Sea tonight and expected to travel across northern North Island from Monday to Thursday. Next HIGH over NZ is expected around 27/28 March.

Tasman Sea troughs.
The Low between two highs is expected in Tasman Sea/NZ area on Fri 24 to Sun 26 March. Avoid.

Mexico to Marquesas:
There is expected to be a Tehuantepec NE blast of wind near 95W until local Wednesday to avoid. The ITCZ is still rather weak and can be expected to bring some squalls between 10N and 5N. There may also be some squalls near 5S. Should be a tail wind to 6N, mostly 10 to 15 knots, then light winds.

Panama to Galapagos
Looks good for departure until 28 March with northerly winds for starters. After that winds are lighter and may be southerly. Main convection is likely between 5N and 2N.
Prepare for light winds south of 4N, maybe head for 4N 83deg30minsW as a waypoint for best wind and tail current.

Galapagos to Marquesas
There is now a river of east-going current between 2 and 6S west of Galapagos, hard to avoid.
Maybe go to waypoints 5S 93W and then 10S 110W then direct. This will get into the trade winds and south of the squalls in the near equatorial convergence zone.
The pattern is changing and may well be different in a week or so, so get updates.

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