Bobgram 5 Jan 2025

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 5 January 2025

A review of last month's weather
Here is a link to a YouTube clip giving an animated loop of the
isobars and streamlines in the South Pacific for the last month at
youtu.be/VwQ10R1FMR0
December had an MJO period over North Australia and into the South
Pacific between 20 and 30 December. An unnamed and minimal tropical
storm skirted Australia's remote Cocos Islands territory, in the
eastern Indian Ocean. And some small tropical depressions formed
between Vanuatu and northern Tonga, drenching Fiji.
Next MJO may be in late January.

The 500hPa heights and anomalies show interesting upper troughs
spreading from the north onto NZ during that MJO.

This led to a series of Lows mainly east of NZ, for example on
Christmas Day


Sea Surface temperature anomalies as at
psl.noaa.gov/map/clim/sst.shtml
show a fading blue tongue along the central Pacific shows that the
trend to a La Nina is stalling.

Average isobars for past month
show that the Aleutian low has deepened.
The subtropical ridge in the Southern hemisphere has weakened, and
around NZ has been replaced by a trough.

Pressure anomalies for past month highlights these differences.
The 1020 over New Zealand has dropped to between 1000 and 1010hPa.
It snowed on the Dessert Road today, gulp.

TROPICS

There are no named storms around at present.

WEATHER ZONES
Rain accumulation this week from Windy.com shows an intense SPCZ over
Solomon Islands to Samoa/northern Tonga.
The wind accumulation shows that the Low east of NZ, L1 is surrounded
by lots of wind.
LOWS and HIGHS
The Low L1 east of NZ is expected to become a slow-moving complex.
Avoid.
A Low L2 is expected to form on the SPCZ near norther Tonga and go SE
towards Southern Cooks
then south and join the L1 complex. Avoid
High H1 now in Australian Bight is expected to move around south side
of Tasmania on Tuesday
then around south side of NZ late in the week and expand over whole of
at end of the week to early next week.
Low L3 over inland Australia is associated with a heatwave and
expected to move slowly to Victoria by end of the week.
It may deepen in Tasman Sea next week.
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