Bob Blog 11June

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 11 June 23

STANDING BY for EL NINO
The Bureau of Meteorology Australia have shifted their ENSO status to EL
NINO ALERT indicating that there is now a 70% chance of El Niño forming this
year. Central and eastern Pacific sea-surface temperatures (SSTs) have
warmed to El Niño thresholds. Some atmospheric indicators such as the
Southern Oscillation Index (SOI) have shifted towards El Niño thresholds,
but wind, cloud and broad-scale pressure patterns indicate that Ocean and
atmosphere are not yet in sync. It looks that this El Nino episode may start
by September and peak around the end of 2023.

May trade winds were close to normal in the central equatorial Pacific, but
a relaxation of trades in early and late June will enable further warming of
sea surface temperatures.

NIWA (NZ Climate institute) comment that the persistence of warmth in the
West Pacific is still encouraging low pressure systems to blossom in the
Tasman Sea area, and this may lengthen the transition window from La Niña
toward El Niño. Due to this lag they are forecasting an augmented La Nina
like rain pattern over the South Pacific with a DRY ZONE roughly near 15S
from Tuvalu to the Tuamotu Islands.


This pattern suggests the main rain from the SPCZ may stay well north of
normal, and the rain from passing troughs in the mid latites may mainly
affect 20 to 25S in the South Pacific.

From this forecast it appears that those sailing from Tahiti to Tonga in the
next months should, on average, look at a northern route via Suwarrow,
rather than a southern route via 20-25S

TROPICS
Cyclone GUCHOL is moving NE across the southern Japan offshore islands and
BIPARJOY os in the Arabian Sea.
The MJO, a burst of extra energy in the tropics, is now rebuilding in the
Indian Ocean, so that

WEATHER ZONES
South Pacific Convergence Zone

The South Pacific Convergence zone is expected to stretch from northern
Coral Sea to northern Tonga to Southern Cooks. A convergence zone near 12S
is likely from northern Cooks to midway between Marquesas and Tuamotu
Islands.

HIGHS and LOWS
Low L1 has been east of NZ all last week. It is now rotating clockwise to
the SW around a dance partner L2 east of Gisborne which is deepening
tonight. L2 should take the dance off to the east this week.
High H1 in the central Tasman Se is expected to cover NZ on Wednesday and
Thursday and then fade into a ridge east of the country.
Low L3 is expected to reach mid Tasman Sea by mid-week and then cross
northern NZ this weekend. Avoid.
The gulf of Panama = Not recommended due convergence zone and SW winds.

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