Bob Blog 14 April

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 14 April 2024

A review of the cyclone season

This time-map shows the cyclones that affected the Australian and South pacific regions during the cyclone season that started on 1 November 2023 and ends on 30 April 2024.

Australia

South Pacific

VANUATU had a hard time in 2023 with three severe storms: Judy and Kevin in March, then Lola in October. Then in November Mal brought some minor damage to Fiji.

During this cyclone season none bothered New Zealand (unlike last season). The main damaging cyclones this season were around Australia. This was an El Nino year, and such years are sometimes “below par” for tropical cyclones in NZ.

It is interesting to compare these cyclone clusters and damaging cyclones with the passing MJO (Madden Julian Oscillation) pulses, shown here as blue zones in the OLR (outgoing longwave radiation) anomalies, from http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf.

Basically, the denser the tropical clouds, the lesser is the satellite measured OLR. We had four MJO pulses is the past cyclone season.

When a MJO pulse arrives in our part of the world, there is a higher tendency for tropical cyclones to be triggered. It is just a tendency – it doesn’t always work–and cyclones can form without the MJO –, but it is a useful indicator, as shown in the MJO’s we had this season and the main cyclones that affected Australia.

TROPICS

The latest cyclone activity report is at zoom.earth and tropic.ssec.wisc.edu and Tropical Cyclone Potential is from www.ssd.noaa.gov/PS/TROP/TCFP/index.html

Cyclone Olga attained Category-4 force over the Eastern Indian Ocean. • Tropical Storm Paul spun up briefing in the Coral Sea.

WEATHER ZONES

Weather Zones Mid-week GFS model showing isobars, winds, waves (purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge), SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)

Rain Accumulation next five days from windy.com

The South Pacific Convergence zone is being rebuilt in the Coral Sea to north of Fiji and has an active zone across central areas of French Polynesia until mid-week. Avoid.

HIGHS and LOWS

The low that travelled over central NZ last few days is now moving off to the east and by mid-week a new low L1 is expected to form well south of Niue and then move off the southeast following the former Low.

Part of HIGH H1 is travelling east along 30 to 35S past the north of NZ next few days and weakening. Later this week it is expected to be followed by the remainder of H1.

A trough is expected to form along East Australian coast on Thursday and then cross the Tasman Sea and NZ on Friday followed by strong SW flow on Saturday.

Then, High H2 is expected to travel from Australian bight into the Tasman Sea by end of the week.

Panama to Marquesas:

Some good northerly winds for starters until mid-week, then just light winds until Friday 26 April. Doldrums between 5N and equator, occasionally squally west of 100W and between 7N and 3N.

Also, west of 100W as far as 125W is a mirror ITCZ between 3S and 8S.

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Contact is bob@metbob.com or text 64277762212.

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