Bobgram

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 15 Mar 2026
Outlook for April
The internet is abuzz with several commentators reporting that there may be
a switch to an extreme El Nino later this year. For now, relax.
Indications are that, during April and into May, the Tasman Sea /New Zealand
area weather is likely to be close to normal.

Our friends at tropical tidbits.com mainly watch tropical cyclones. They
also give access to some climate models which show outlooks for the month of
April based on current trends.
These are called anomalies and they indicate how this April may vary from
normal.

The map has isobars which show the averaged weather forecast for April. In
April, on average, the west-southwest winds of winter reach as far north as
Cook strait, and a High centred near the Australian Bight noses a ridge of
relatively light winds onto the Bay of Islands. Daily weather pattern
shuffle around this idea.
The anomalies show expected difference from a normal April. Papua New
Guinea is above normal --- but only by small amounts. And between Solomons
and Tonga are below normal. Since these are over a low-pressure area (the
South Pacific convergence zone) and this is expected to be accentuated in
April.

Indeed, when we look at the forecast rain anomalies for April:
New Guina highlands are pointing to extremely dry condition. And from the
Solomon Islands to Tonga there is an accentuated South Pacific convergence
zone. A dry zone over Tasman Sea and New Zealand indicates this area may
have light winds and sunny skies that linger in autumnal anticyclones (an
Indian summer).





TROPICS

It has been a quiet week with no named storms.
There OLR trend shows that, for the south Pacific, the next few weeks may be
sunnier than normal (yellow) and so the risk of cyclone formation may be
lower than normal.


WEATHER ZONES
For the New Zealand area: On Monday and Tuesday High H1 travels across
central areas. On Tuesday, Low L1 is expected to form on a trough crossing
Tasmania and then travel southeast on Wednesday past southern New Zealand.
From Wednesday to Saturday Low L2 is expected to deepen over the Kermadecs
and then travel off to the SE sideswiping east coast of North Island. After
Saturday the next High from the Australian Bight is expected to travel
across central New Zealand.


In tropical areas, the SPCZ os expected to be active between the Solomon
Islands and to south of Fiji.
A tropical low L3 may form on Thursday in the Coral Sea and then travel
west into the Gulf of Carpentaria.
Another low L4 may form off west Australian coast and fade as it goes
south.


In my illustrated edition is a diagram that shows a week of rain
accumulation around the equator.

Normally the ITCZ sits between 3N and 10N, but during March another
convergence zone forms south of the equator. I call this a mirror ITCZ. I
think it forms because during March these of the latitudes of the direct
overhead Sun. This month the sun will be directly overhead the equator at
Friday 20 March at 14:46 UTC (early Saturday for Fiji and New Zealand).

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