Bob Blog 6 Dec

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.

Compiled Sun 06 Dec 2020

 

REVIEW OF THE LAST MONTH (November 2020)

La NINA (the cool eastern equatorial Pacific) is well marked, and there are warmer-than-normal seas over the Southwest Pacific. This means the cyclone season is likely to more active near the dateline.

The sub-tropical ridge in the southern hemisphere has weakened and the westerly isobars of the Southern Ocean have widened, deepened and shifted north.

Zooming into the NZ area, and comparing monthly anomalies from last month with now, the sub-tropical ridge has weakened - the 1015 isobar has drifted from 45/50S to 30S over Australia and New Zealand.

 

The Tropics

Things are quiet for now with no cyclones around but some potential areas for formation around Philippines/Indonesia/Northern Australia

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is in its normal position from Solomon Islands to Samoa to Southern Cooks.

A passing trough is expected over Southern Cooks area early in the week, and another over New Caledonia mid-week and again another over the weekend.

According to the GFS model, a tropical low is likely over northern Vanuatu from late in the week,,,, worth watching out for.

 

Subtropical ridge (STR)

HIGH 1018-1022 over northern NZ is expected to travel off to east along 30S.

Next HIGH is expected to enter Tasman Sea mid-week and travel east along 35S reaching northern NZ late in the week

 

NZ/Tasman troughs

LOW has deepened to 965 at 50S south of Tasmania and is expected to move off to southeast by Tuesday with associated troughs crossing South Island.

Low is expected to form off Sydney on local Monday and travel east southeast across the Tasman Sea reaching central New Zealand by mid-week 1002 hPa.

Another Low is expected to form in central Tasman Sea around the end of the week and move over South Island early next week.

 

Fiji/Tonga to NZ:

Looks Ok to head off this week, but need to reach NZ by Sun 20 Dec.

 

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