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 16 March 2025

How goes our Modoki La Nina
Looking at the ocean...
Modoki is a Japanese word loosely translated to "similar, but
different" or in New Zealand slang "Yeah, nah". Professor Toshio
Yamagata and a colleague named the phenomenon while investigating the
causes of Japan's hot summer in 2004.
This occurs when the Sea surface temperature SST in the central
equatorial Pacific cools, while the SST in the western and eastern
parts warm.
This differs from the regular La Nina where the cool zone is in the
eastern equatorial Pacific near the Galapagos.
A recent time section of SST anomalies near the equator and across the
Pacific, shows the cool zone of this La Nina is edging towards the 180
longitude. See psl.noaa.gov/map/clim/sst.shtml

The ENSO trend is followed by forecasting the SST for region NINO 3.4,
with values less than 0.5 needed for a La Nina event..
The combo of forecasts as calculated by IRI shows that
The Dynamic average forecast (red) stays below the La Nina threshold
(neutral)
and the Static model average (green) stays just over the La Nina
threshold until December this year.
I suppose we are somewhere in between.

Looking at the atmosphere...
The SOI index over the past month has been positive but trending to
zero.


TROPICS
There are no named cyclones around at present

In the past week Category-1
. Cyclone Jude killed at least six people when it roared onto
Mozambique's northeastern coast with winds of up to 75 mph, causing
significant flooding and extensive damage.
. Cyclone Ivone churned the open waters of the central Indian Ocean.

At present the MJO is poised to bring a new boost of energy onto
northern Australia over next few weeks and then into the Pacific by
early April
As seen at
www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/forca.shtml

WEATHER ZONES

The wind accumulation shows that the windy signature around the lows
and convergence zones.

The South Pacific Convergence zone SPCZ and tropical convergence is
very active over northern Australia. There was an active convergence
zone over Fiji /Samoa last week and it has travelled south and can be
seen going SE in the wind and rain accumulation forecasts.

This week is looking relatively quiet in the South Pacific tropics.

LOWS and HIGHS
An active Low and Front labelled L1 south of Tahiti is expected to go
off to the SSE.
The HIGH H1 now east of the North Island and with a ridge over
northern NZ, is expected to move off to the SE.
The Low labelled L2 east of Tasmania and its associated front is
expected to travel over NZ on Monday/Tuesday followed by a southerly
flow on Wednesday.
HIGH H2 now in Australian Bight is expected to follow L2 and cross NZ
on Thursday and Friday.
L3 is expected to travel east so that associated front reaches NZ on
Sat/Sunday.

In Gulf of Panama: Useful NE winds for starters but they may be over
20kt between Tuesday and Saturday.
From Panama to Galapagos.. SW swells 1 to 2m. Tail currents and mostly
a tail wind.
May be showery between 4 and 1N

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