Bob blog 17 Oct

Bob McDavitt: 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 17 October 2021

South Pacific coming Cyclone season Nov 2021 to April 2022.

During the past week NIWA and MetService of New Zealand, along with BoM from
Australia, issued a combined news release giving their outlook for the
coming South Pacific Cyclone season.

For details see tinyurl.com/SouthPacificOutlook2022

In summary, the agencies say there is a good chance that we will be having a
LA NINA episode during next six months. NOAA have already declared this to
have developed along with an 87% to continue into February 2022 (see
tinyurl.com/NCEPENSO).

Combine this with recent Sea surface temperature anomolies across the South
Pacific, and it is logical to forecast that the South Pacific Convergence
zone SPCZ is likely to be south and west of its normal position , enhancing
the cyclone risk for western countries and reducing the risk east of the
dateline.

From around 50 years of data, 6 analogue years with similar La Nina and Sea
surface temperature coupling were picked, Showing the first cyclones may
form around New Caledonia and Queensland coast, and later in the season the
zone from Queensland coast across the Coral Sea to between Vanuatu and Fiji
may be favoured.

Looking at atmospheric dynamics combining several models shows the outlook
for isobar anomolies from Jan to Mar 2022 Indicates lows are likely to
develop or deepen between New Caledonia and New Zealand.

And the forecast rain map for January to March shows the South Pacific
Convergence zone from Coral Sea to northern Tonga, with a finger towards
northern New Zealand.

In summary, the expected number of cyclones over the South Pacific is
between 9 and 12, slightly above normal:

A passing MJO (Madden Julian Oscillation = burst of tropical convection that
travels eastwards from Indian Ocean to Pacific Ocean around once a month) is
likely to provide us with times when risk of cyclone formation may peak.

TROPICS
NAMTHEUN is weakening over the open ocean in the far north Pacific.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ stretches from PNG to Tuvalu to Samoa and may visit Tahiti this
week.
Active trough over southern Cooks is expected to linger near Tahiti from
mid-week and form L2 that should go off to the SE
Active trough is expected to form over New Caledonia from Mid-week and
develop L4 near 40S/New Zealand.

HIGHS and LOWS
L1 about southern NZ tonight and associated trough over North Island
travelling off to the southeast followed by a west to southwest flow.
High1 east of NZ is expected to travel off to the east along 40S by
mid-week.
L3 is expected to travel northeast out of the Southern Ocean to 35S in the
wake of H1.
High2 should reach South Tasman Sea by Wednesday and travel east along 45S
to be near Chathams by the weekend.
After Wednesday, L4 complicates trans-Tasman travel, and L4 and H2 should
produce a NE flow between Fiji and NZ.
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If you would like more detail for your voyage, then check metbob.com to see
what I offer.
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at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or txt 64277762212
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