Bob Blog 11 Feb 2018

WEATHERGRAM

YOTREPS

Compiled Sun 11 Feb 2018

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.

TROPICS

This MJO period of expected extra convection which has been visiting the South pacific over last few weeks is now reaching its peak.

Over Samoa on Saturday UTC, after a week of heavy convective rain, Topical Cyclone GITA brought even more intense rain along with some damaging winds. GITA is still developing in intensity and size and is now heading for southern Tonga, then southern Lau group in Fiji.

GITA is disrupting the South Pacific Convergence zone and may take some of its energy off to the south. Later this week it is expected to  turn south into the Tasman Sea and weaken, and  its remnants may reach New Zealand some stage after Friday…progress may be much slower than the models are showing at present—they are not to be trusted this far out.

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From www.tropicstidbits.com

There is a Tropical Low 997hPa this evening located to south of French Polynesia and moving off to the southeast, Associated convergence zone is likely to bring squally showers to Tahiti until mid-week, with strong northerly winds especially on Tuesday UTC.

There is another minor tropical depression located in the SPCZ at present to NW of GITA, and this system is expected to fade in a few days.

Tropical Storm 02W or TWO has developed in the NW Pacific and is heading west and expected to visit the Philippine Islands in a few days. And there is a tropical low in the south Indian Ocean.

Looking at the weekly rain maps from last week and the week before, we can see that the South Pacific Convergence zone has been the site of the most intense train on the planet for the past week, especially in a zone form Samoa to western parts of French Polynesia.

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See trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

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Weather Zones (see text) as expected on Wednesday (EC and GFS model) showing isobars, winds, sea (magenta), and current. STR, and SPCZ. Pink area = lightning likely (CAPE)

SPCZ=South Pacific Convergence zone.

The SPCZ is active across the whole region mainly from Solomons to Tuvalu to Samoa to parts if the Southern Cooks and parts of French Polynesia. TC GITA is likely to take some of the energy of the SPCZ off to the west then SW/S/SE around that quasi-stationary HIGH located NE of NZ.

Tropical Cyclones act as safety values and remove extra heat from the sea. disturbing that energy as wind and rain over a wide area. Let’s hope GITA does this job without doing much more damage.

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Accumulated rainfall for next week from windyty.com

Subtropical ridge (STR)

HIGH to east of NZ at around 160W is supported by conditions aloft to be quasi-stationary. It is expected to start the week near 40S and to track to 35S then a new cell should bring its centre of pressure back to 40S. It is a major factor in moulding the track of GITA.

A weak High is expected to travel east across mainly southern NZ on Wednesday, making that and Thursday the driest days of the week for NZ.

Around Tasman Sea

A week to avoid the Tasman Sea or travelling to NZ, because of GITA.

Panama to Galapagos

I’ll be adding this zone to my weekly outlooks for the next few months.

If you are ready now to do this strip, then the next two weeks are looking OK with N to NE winds as far as 5N and a weak convergence zone the light winds to Galapagos.

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

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