Bobgram 19 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 19 January 2025

New Zealand weather review 2024
In a time-latitude plot of the air temperature measured over a
north-south slice of Aotearoa/ NZ as it travelled through 2024.

It clearly shows temperature is cooler further south and during
winter.

This time section makes a "bar-code" graph which reveals the annual
trend and the daily variation. It gives a rough indication of the
extremes and provides a visual image for quick comparison with any
another year to see seasonal variations. The land silhouette is
provided to help relate the latitude axis to your place.

Looking at a similar diagram for the barometric air pressure provides
a graph that combines all the daily weather maps into one image.

This produces a more random looking barcode. The yellow and red lines
correspond to passing HIGHS on the weather map, and the blues show the
LOWS or depressions/storms. Th "HIGH JULY" stands out (see
https://blog.metservice.com/node/1192)

There is a notable swing to blue low pressure that started from 20
December. This continued into January 2025.

The rain image is probably the most interesting as it highlights the
dry periods in Northland last February, April and late November to
early December

TROPICS

The MJO is now in the Indian ocean and moving onto the NW end of
Australia.
Tropical cyclone Sean is travelling out to sea from the Karratha
region.

WEATHER ZONES
TC Sean's forecast stands out in the wind and rain accumulation maps.

The South Pacific Convergence zone SPCZ is expected to have a routine
week and mainly be between Solomon Islands and Tokelau, north of
Samoa.

LOWS and HIGHS

The High which has been lingering well to southeast of Tahiti for past
ten days is expected to move off to Southeast this week.

The Low which has been lingering near Chatham Islands for past 10 days
is also expected to now move quickly off to the Southeast. This allows
the High that is currently around southern NZ to also move off to the
east following that Low/

A multi-centred complex low L1 in the Tasman Sea to NW o Auckland is
expected to travel southeast across Northland on Tuesday then weaken.

An active front is expected to reach Tasmania on Tuesday night and
then cross NZ on Thursday and Friday and weaken.

That Low is expected to be following by a High H2, and that front is
expected to be followed by a High H3 starting in the Aussie Bight.

These highs should combine in the Tasman Sea and then cross NZ on
Friday/Saturday.

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Contact is bob@metbob.com or text 64277762212.
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