BobBlog

WEATHERGRAM

YOTREPS

Issued 25 May 2014

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 of weather maps, so please fine-tune to your place. Dates are in UTC unless otherwise stated.

Scott Donaldson has had made good progress in the past week kayaking across the Tasman Sea. Tonight he is in 4 to 5 metres swells and 20 knot winds from the SW, and managing to make way to the southeast.

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Scott Donaldson’s track as at doubleditch.co.nz/tracking. He is doing this to raise funds for Asthma Foundation, see http://doubleditch.co.nz/donate

The Ocean: The warmer the sea the quicker it evaporates, tossing water vapour into the air, where is rises and cools into cloud. The equatorial Pacific region hosts the warmest sea on the planet. Thus its sea surface temperatures SST is a factor in the running of planetary weather engine. An index for this is NINO3.4 and its abnormalities tend to influence changes in clouds along the equator and thus tweak the latitude zones of weather around the planet. Recently a lot of extra heat has been stored in the upper depths of the equatorial Pacific Ocean and some of this is now reaching the surface near the Galapagos.

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Sea temperatures along the equatorial Pacific as shown at http://www.farmonlineweather.com.au/climate, showing a warming trend.

TROPICAL TOPICS—

The new hurricane season in northern hemisphere is meant to start at the end of this month and already HURRICANE AMANDA has started off the west coast of Mexico:

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Hurricane AMANDA as seen at http://www.tropicaltidbits.com/storminfo/

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Weekly rain signatures for past two weeks, as seen at http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

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Weather Zones (see text) as expected mid-week at 0000UTC on Wednesday (GFS model) showing isobars, Lows and Highs, wind, waves, rain, current, SPCZ and STR . Purple lines are upper flow.

SPCZ= South Pacific Convergence Zone

South end of SPCZ is expected to visit Fiji on Monday 26 May UTC, Tonga on Monday/Tuesday, Niue on Wednesday and Southern Cooks on Thursday/Friday UTC.

Another part of the SPCZ is likely to spread south onto Tonga again around Sat 31 May UTC.

STR= Sub-tropical Ridge

The STR is north of its normal position for this time of the year in Australia, and mainly at its normal position between 30 and 35S across the Pacific.

Tonight a high has budded off from the Antarctic ice shelf and travelled NE into the South Tasman Sea/, shoveling ice-chilled SSW wind flow onto Southern NZ. This cold high is expected to travel NE cross the Tasman Sea on Monday and northern NZ on Tuesday and then travel east along 30/35S into the Pacific.

The next HIGH is expected to move off Australian coast into central Tasman on weekend of 31 May/1 June

Departing from NZ to the tropics

A cold southerly/SW flow over northern NZ on Monday is good for going north,

Light winds over northern NZ on Tuesday with passing HIGH, not so good for sailing.

Then a large and intense trough is expected to approach North Island on Wednesday, with increasing NW winds, and cross the Island on Thursday with a period of squally showers. Not good for departure.

The decreasing SW flow on Friday may offer a good weather pattern for departure – but such a departure might encounter a new trough over the Tongan area the following week, too far away to tell at this stage. A Friday departure might work ok.

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

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