Bobgram 25 Jan

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 25 Jan 2026
An accumulated rain map for New Zealand for the past week is available
courtesy of MetService.com.
Its purple rain areas had several flooded areas and devasting landslips.
Some rain gauges got over 300mm rain.

The averaged isobars for last week show low pressure over Coral Sea and High
pressures south of Tasmania and southeast of Tahiti. Courtesy of the NOAA
map room.
This pattern collects moist air between Tahiti and New Zealand and feeds it
directly onshore in the northeast winds and smack onto the mountains of
northeastern North Island.

A trajectory analysis during this rain event shows where the air had come
from for a 3x3 matrix of spots around New Zealand (back tracking 5 days).
Courtesy of the Air Resources Laboratory at
https://www.ready.noaa.gov/index.php
Cold air from the south is shown to mingle with the moist air from the
east to produce this deluge.


TROPICS
• Minimal Tropical Storm Nokaen remained just offshore of the central
Philippines but brought locally heavy rainfall to some coastal areas of
Luzon.
• Cyclone Dudzai skirted the remote Indian Ocean island of Rodrigues as a
tropical storm before dissipating to the south of Réunion and Mauritius.
• Cyclone Luana made landfall over northwest Australia.


WEATHER ZONES

Rain accumulation this week from Windy.com above shows a well-defined
monsoonal trough where the South Pacific convergence zone usually sits.
There are NW winds on the northern side of this trough and southeast winds
on the south side.
Wind accumulation from windy.com above shows bursts of wind associated with
the three tropical lows.
Highs and LOWS
Tonight and on Monday and Tuesday, a deep low L1 south of Chatham Islands is
bringing a south to Southwest flow to NZ,
with showery westerly winds over the northern third.
This is followed on Wednesday with a passing High H1, and then a series of
fronts for a few days
and then another High H2 travelling east along 40S and crossing Tasmania on
Friday.
There are three main tropical lows this week. L2 is expected to bring wind
and rain to southern cooks especially around local Thursday and Friday.
L3 is havering around Vanuatu for a few days and then may move towards Fiji
and Tonga late this week/early next week.
And L4 is the remains of Luana, staying as a monsoonal low over central
Australia.

A moderate heat wave is expected to remain over southeastern Australia.


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