Bobgram 4 August

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 4 August 2024

A review of last month's weather
Here is a link to a YouTube clip giving an animated loop of the isobars and streamlines in the South Pacific for the last month at youtu.be/alCjq_vMeqM
An interesting period of weather occurred when a LOW was blocked in the Tasman Sea from 14 to 24 July under a closed low aloft. As in June there was a dose of rapid cyclogenesis between 19 and 20 July.

The tropics in the South Pacific were quiet.

Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
The Kuroshio current has spread out into the north Pacific. The equatorial Atlantic remains warmer than normal. The cool seas of an El Nino are spreading westwards from Galapagos to the dateline along the equator. A buildup of cold water - melted ice is showing around the Aleutians.

Average isobars for past month as at www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html
During July the Monsoon spread east across Asia and the subtropical ridge in northern hemisphere intensifies.

Pressure anomalies for past month (below)
The anomaly pressure pattern for July shows a relaxing away of the negative anomalies that were over North America and Australia. South America has built up large positive anomalies.
Around Suth Pacific : Not much change, but the low anomalies in the Tasman have faded.

TROPICS
Typhoon Gaemi weakened to a tropical storm as it made landfall on South China's Fujian coast. Even as a weakened storm, Gaemi's remnants had enough power to kill 22 people in disastrous flooding and mudslides across a wide area of China and parts of North Korea. In total, Typhoon Gaemi was responsible for at least 77 deaths over a two-week period. * Tropical Storm Bud formed briefly

Tonight we have DANIEL and CARLOTTA in the NE Pacific plus two tropical depressions. In the North Atlantic DEBBY is heading for Florida's panhandle.

WEATHER ZONES
The South Pacific Convergence zone is sitting over the northern Coral Sea and extends to Tuvalu and Tokelau to Suwarrow. There is a passing tough travelling east from Tonga to Southern Cooks this week, and maybe a squash zone of strong SE winds near Niue from 10 to 15 August.

HIGHS and LOWS
Low L1 was just north of Northland tonight and is expected to travel east along around 33S this week, with its northern extension bringing a slack passing trough to the zone between Tonga and Tahiti.

HIGH H1 is rather weak and expected to move southeast across NZ on Wednesday then fade away.

Low L2 is expected to form in mid-Taman by Tuesday and cross NZ area as a broad trough on Thursday and Friday.

HIGH H2 is expected to build in the Tasman Sea along 35S later in the week and poke a tongue of high pressure along 30S east of the dateline next week, causing a squash zone further north between 10 and 15 August. Avoid.

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