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 04 April

REVIEW OF THE LAST MONTH (March 2021)
Sea Surface temperature anomalies as at
www.weatherzone.com.au/climate/indicator_sst.jsp?lt=global&lc=global&c=ssta
Early April (below)

The eastern equatorial Pacific is now near normal so La Nina has faded.
Also, the warm blob south of Tahiti and east of NZ is easing. Everything
else is much the same as last month.
To see how the annual weather cycle and the seasons are working out, we can
check the average isobar maps for past 30 days and their anomaly from
https://psl.noaa.gov/map/clim/glbcir.quick.shtml

The Aleutian Low and North Atlantic low have weakened. The Siberian HIGH
continues to weaken. The subtropical ridges have intensified. The doldrums
low has shifted north over Philippines/Australia/Indian Ocean, retreated
westwards across the Pacific, and retreated eastwards across Indian Ocean.
The Antarctic High has strengthened. The seasons they are a changing

Arctic has changed from above normal to below normal pressure. the South
Indian ocean has changed from a mixed pattern to lower than normal
pressures. The lower-than-normal pressures over Australia and the Tasman
sea and along 30S across the South Pacific Ocean have weakened.
Zooming into the NZ area, (note that isobars colours have changed) the 1015
isobar has expanded northwards. The Antarctic High has strengthened. This
maybe in response to a switch of SAM from negative to positive and enhances
westerly winds in the polar vortex.

Madden-Julian Oscillation
The MJO is a pulse of upward motion that travels eastwards around the
tropics from Indian Ocean to Pacific Ocea.
It is now active over northern Australian as can be seen as the blue area of
the graphic from
https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml

The Tropics
The latest cyclone activity report is at tropic.ssec.wisc.edu and Tropical
Cyclone Potential is from
www.ssd.noaa.gov/PS/TROP/TCFP/index.html
It is another quiet weekend with no active cyclones. However, there are
areas of medium to high potential for tropical cyclone formation around
norther Australia. A reminder that, even though we have switched from
Summertime back to standard time, and the tropics have been quiet for past
few weeks, the month of April is still part of the Southern Hemisphere
Cyclone Season.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to be a well-defined and rather intense zone from Papua New
Guinea to Solomons to northern Vanuatu to north of Fiji to Samoa.
Low is Coral Sea is expected to travel SSE into central Tasman Sea.
Low is expected to form south of Niue on local Sunday and travel off to
south.
Low south of Gambier Islands is expected to travel slowly E/SE.

Rain Accumulation next five days from windy.com
Subtropical ridge (STR)
Easter egg of a HIGH over northern Tasman Sea should fade by Tuesday.
HIGH is moving over Tasmania and expected to skirt around South Island on
local Wednesday then travel east along 40 South.

Aussie/Tasman/NZ troughs
Low in central Tasman sea by Wednesday expected to cross central NZ on Sat
10 April, followed by another low over NZ on Sunday/Monday then strong
southerly next week, avoid.

Panama to Galapagos/Marquesas
Moderate northerly winds at Panama but for light variable winds from Tues 6
to Tue 13 April. Light winds around Galapagos.
Good current to south-southwest between Panama and Galapagos. Path to take
to Marquesas this week is much the same north of south of Galapagos.
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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 6427 7762212
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