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Bob McDavitt's ideas for sailing weather around the South pacific

03 July 2022

Bob Blog 3 July

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 03 July 2022

There has been an interesting write up of my article on SUCKERS AND PUFFERS
in the July edition of at issuu.com/downunderrally/docs/ahoy-july_22/58 and
on SHAKERS AND BREAKERS in the July edition of Tell Tales at
opuacruisingclub.co.nz/wp-content/uploads/2022/06/Web-TT-0722-.pdf

REVIEW OF THE LAST MONTH (June2022)

MetService issue a tropical analysis of the South Pacific with isobars and
streamlines, it is NOT available from their home page but from their severe
weather page (which can sometimes be otherwise empty) of the AHOY magazine
at www.metservice.com/warnings/tropical-cyclone-activity

I am now saving one image a day from this page and here is an animation of
last month's weather https://youtu.be/Z-5-sgVSlPc

It shows a slow-moving complex Low over Tasman/NZ until mid month and a Low
between NZ and Tonga 20-23June, so there really was only one good
opportunity for sailing from NZ to Fiji last month and it was well picked by
many sailors.

Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
shows a relaxation of the cool zone that makes up La Nina. The surrounding
C shaped ring of warm water has intensified over the North Pacific and is
strong from New Guinea to south of Tahiti. The Águilas current extends all
the way east to south of NZ. The NW passage is almost open, and the Med is
having a marine heatwave. Tasman Sea heat wave seems to have relaxed thanks
to the June thunderstorms but a warm patch is still off Sydney, and is the
source of the flooding there tonight.

The averaged isobar map shows that the subtropical ridge in the north
Atlantic has intensified. The subtropical ridge in the Southern Hemisphere
has weakened a little.
The anomaly map shows that the lows that were bothering Australia ln May
shifted onto the Tasman/NZ area in June, and there was a similar shift from
South Africa to Indian Ocean

Zooming into the NZ area shows that the subtropical ridge around NZ has
shifted north, and pressures have relaxed around the equator, relaxing the
trade winds.

TROPICS
Things are heating up after the northern summer solstice with two cyclones
in the Atlantic BONNIE and COLIN, and two around east Asia CHABA and AERE.
BONNIE turned in a cyclone just north of Colon in Panama and has travelled
east to west along the Costa Rica/Nicaragua border.

WEATHER ZONES
The SPCZ seems to be having a holiday this week and is replaced by separated
convergence zones. One of these is Travelling east and pulling south and
expected to clear Rarotonga on local Tuesday and another is lingering in the
Coral Sea and finally expected to reach New Caledonia on local Saturday. A
weaker zone may stretch west to east from Vanuatu to Fiji to Samoa from
mid-week.

HIGHS and LOWS
High H1 expected to move east along 35S crossing NZ on Monday and reaching
south of Tahiti by mid-week.
L1 is the low off Sydney tonight bringing flood. Its associated trough is
expected to follow Hi and cross NZ on Tuesday/Wednesday and then off to the
east.
L2 is expected to form well SE of Rarotonga next few days throwing some
swell northwards.
Low L1 is expected to form in the trough that crossed NZ on Saturday and
travel SE on western side of H1.
Low L2 is expected to form on the northwest side of a trough crossing South
Island on Monday.
By mid-week another low L3 is expected to form near Lord Howe Island as High
H3 arrives over Tasmania from Aussie Bight. H3 is expected to rotate around
L3 slowing L3 in the Tasman so that H3 may cross NZ on Thursday and L3 may
cross NZ on Friday and Sat when at its peak, followed by a cold southerly
and maybe a secondary low on Sunday/Monday.

1. Not Ok to depart NZ for the tropics in northerly flow between H1 and l2
or with L2.
2. Should be Ok to depart Aus for points east late in the week after L2.
3. If wanting to get to Aus from Noumea, maybe wait until next week.

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If you would like more detail for your voyage, then check metbob.com to see
what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe
at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or txt 64277762212
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