Bob Gram 17 Sep

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 Sunday 17Sep 2023

The incoming El Nino is starting to show its colours.

El Nino is the name given to the period when sea surface temperature SST
over the eastern equatorial Pacific is above normal. (La Nina is the name
given when sea temperature are cooler).

In the atmosphere we monitor ENSO = El Nino/Southern Oscillation and its
impact on the weather map by using. the Southern Oscillation Index SOI (30
day running mean). This is based on the standardized difference in the
barometer readings between Tahiti and Darwin, in other words it counts the
average number of isobars between them on the weather map. When the index
stays below -10 (on the scale shown here) for more than a month we call it
an EL NINO event.

And recent data is showing we are now in El Nino territory.

The Ocean:
The parameter used from the ocean is based on the sea surface temperatures
in the equatorial eastern Pacific and called the NINO 3.4 SST anomaly.
International research Institute IRI have compiled the predictions for all
the models as shown here from iri.columbia.edu. The consensus is that
NINO3.4 will peak during NDJ= November, December, January. A strong El Nino
for the coming Summer.

Expected impact in the South Pacific
An El Nino is associated with weaker trade winds, and this tends to shift
the subtropical ridge north allowing for stronger westerly winds south of
40S. The peak cyclone prone area shifts from Vanuatu towards the dateline.
In New Zealand the stronger westerly winds from the Tasman Sea arrive cool
and moist onto the western side of the main divide. They are deflected
upwards dropping their ample rains and filling up the hydro lakes. These
winds then descend across the plains on the east coast hot and dry due to
the foehn effect. In seems likely that by the end of the year eastern New
Zealand (and lots of SE Australia) will be ripe for bush fires.

However, each El Nino event is different and even a strong El Nino only
explains around 20% of the observed weather variance.

I asked Chat Gpt to turn that into a poem and it came up with the following:

Amidst New Zealand's land of pristine grace,
El Niño's touch, a climatic dance we trace.
From Tasman Sea, cool, moist winds do rise,
To fill our lakes, a watery, sweet surprise.
They sweep o'er mountains, their path deflects,
As foehn effect, along the east, reflects.
Hot, dry winds now kiss the coastal land,
In El Niño's sway, a shifting, arid brand.
Yet, in this struggle with the altered wind,
New Zealand's spirit, strong, will not rescind,
For though El Niño tests our land anew,
Our hearts and hope endure, forever true.

Hmm, somewhat flowery and disjointed I think.

TROPICS
Central Japan was drenched by slow-moving Tropical Storm Yun-yeung.
Hurricane Lee faded away as Hurricane MARGOT and NIGEL churned the central
Atlantic.
Depression TWELVE-E is moving west across central north Pacific.

WEATHER ZONES
The South Pacific Convergence zone is well north of normal from Solomons to
Tuvalu and there is an extension zone lingering across roughly from Suwarrow
to Tahiti.

HIGHS and LOWS:
HIGH H1 Is intense and moving slowly along 30 to 40S crossing northern NZ on
Tuesday and Wednesday. It has an intense SQUASH ZONE on its norther side
between the Cooks and Fiji from 25S to 12S and along 22S from south of Fiji
to east of New Caledonia. Avoid.
When H1 moves off to the east later this week there should be an easing of
the SE winds in he Coral Sea.
There is disturbed westerly flow over TSMAN SEA /NZ area south of around
38S. This doesn't interfere much with arrivals in Northland, except for
maybe some strong northerly winds there on Saturday 23 Sep with a passing
front.

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