Bob Blog

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 23 July 2023

Waves: Height(m) x Height (m) x period (Sec) = Power (in KW/m)
This is a simple approximation for estimating wave power.
So a 2m wave with period 7 sec has power of 28 kW/m
And a 4m wave with a period 7sec has Power 112 kW/m (four times more)
This is based on some lecture notes in a training video at
www.youtube.com/watch?v=2ODs5lxqRdw


TROPICS
TALIM uprooted trees in South China, remnants of CALVIN skirted around
southern Hawaiian Islands, DON went across the north Atlantic and DOKSURI
spun up east of Philippines.
The MJO, a burst of extra energy in the tropics, is on the move and expected
to visit the Indonesian longitudes in the next week or so and reach west
Pacific early August.

WEATHER ZONES
The South Pacific Convergence zone is expected to extend from Coral Sea to
Vanuatu and Samoa.
Low L1 near Niue is moving off to the southeast and associated convergence
zone is expected to travel east and cross southern cooks late this week.
HIGH H1 well east of NZ and at 45S is quasi -stationary and drifting east,
blocking the lows on its western shoulder.
Low L2 near Chatham Islands tonight is being steered southwards around H1,
maintaining a cold snap and a southerly flow over New Zealand.
In this southerly flow a second cold burst crosses NZ on Wed and then turns
into low L3 off North Island that curves to the SE. This is followed by a
third cold burst and then low over northern NZ next weekend.
After that HIGH H2 might finally have a chance to cross the northern Tasman
Sea early next week.
The southerly flow over NZ this week is likely to reach as far as Minerva,
and the swells may be over 3m at times.

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