Bob Blog

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 05 Apr 2026

A review of last month's weather

Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines
For last month is at youtu.be/f7fN5sa53pQ

Lows affected NZ on 13, 19, 26 and 30 March
Tropical cyclone Narelle formed of Saint Patricks day and deepened by 19
March:
The 500hPa heights and anomalies shows that prolonged upper low  over Tasman
sea late in the month

Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
The waters over eastern equatorial Pacific remain near normal.
The warm patch between Tonga and New Zealand continues to relax.
The cool (dry) zone around NW Australia is shrinking.

Average isobars for past month show that
The subtropical ridge in the southern hemisphere has intensified and shifted
north.
The HIGH over Siberia has intensified at a time of the year it  usually
weakens.

Pressure anomalies for past two months show that
The anomaly pressure pattern for last month shows a low breeding area around
Hawaii… they had a particularly stormy March.   The southern subtropical
ridge intensification also stands out.
The 1015 isobar has shifted north over Australia to Brisbane

TROPICS
Our cyclone season nominally finishes at the end of April, and indeed we
still have a few more cyclones and tropical lows to come. Three are around
this evening .31P and INDUSA are caught in upper NW winds.  MAILA is likely
to be steered east then south then southwest across the Coral Sea.

WEATHER ZONES
MAILA may not start moving southwest until after Wednesday.
31P might earn a name on Monday and is expected to affect Fiji on Tuesday
night/Wednesday and maybe eastern North island of NZ from Friday.
There is an active part of the South Pacific convergence zone mostly over
Southern Cooks to Austral Islands until mid-week, then expected to travel
across Tahiti area this weekend. Avoid.
A trough covers the eastern Tasman Sea this evening and is expected to move
onto NZ on Monday/Tuesday, fading as it moves… Northland and Coromandel take
the brunt of this trough, but it is followed by a cold southerly over
eastern South Island.
HIGH H1 remains quasi-stationary east of New Zealand.
HIGH H2 is expected to bud off eastern Australia by Wednesday and then
travel southeast across the South Island on Friday.
Lows L2 and L3 south of Australia are expected to travel east or southeast.

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