Bobgram 2 Feb 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 2 February 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/iXd4tg4toU8

During January the climate modellers agreed the Pacific is in ENSO neutral territory and have given up on the idea a La NINA trending in. The MJO built over Indian Ocean and has moved onto northern Australia., with several tropical systems now around Australia.

The 500hPa heights and anomalies shows last month's trough fading then a series of large HIGHs south and east of NZ for a few weeks in January


For much of the month a HIGH straddled southern and eastern NZ as seen here on 21Jan.


Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml

show a fading blue tongue along the central Pacific so we are now in ENSO neutral territory.

Average isobars for past month (below)

From http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html

show that The Aleutian low has relaxed, and the Greenland low has deepened.
The subtropical ridge in the Southern hemisphere is still weak but has recovered a little from its December extreme.

The anomaly pressure pattern highlights these differences.
The 1010 trough-anomaly has sifted east off NZ.
The 1015 line south of Australia has shrunk.

TROPICS
There are no named storms around at present, but there are 4 tropical depressions being watched and a fifth in Gulf of Carpentaria too close (at present) to land to be able to spin-up however is bringing flooding rains to the eastern Qld coast. The MJO is active around Australia.

WEATHER ZONES

Rain accumulation this week from Windy.com shows an intense SPCZ and the heavy rain especially with the tropical low near New Caledonia and about eastern Qld coast.

The wind accumulation shows trails of wind mapped out by tropical lows L1 and L2.

LOWS and HIGHS

Low L1 now near Raoul Island is expected to deepen a lot as it travels southeast.

Tropical Low L2 near New Caledonia is also expected to deepen and bring heavy rain to Loyalty islands then move slowly southeast towards Minerva reef, so is mostly south of Fiji/Tonga.

Tropical Low L3 is expected to stay slow-moving over inland Australia, like a monsoonal low, feeding flooding rains onto Qld east coast.

High H1 in Tasman Sea is Quasi stationary. It may fade away on Thursday/Waitangi Day, as a brief passing front brings a southerly wind change to NZ East Coast, then H1 may reform.

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