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

02 October 2016

Bob Blog 2 Oct 2016

WEATHERGRAM
YOTREPS
Compiled 2 October2016

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.

SEPTEMBER was an interesting month.
September averaged isobars may be seen at
www.esrl.noaa.gov/psd/map/images/fnl/slp_30.fnl.anim.html
Pressure anomalies seen at
www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html show that
for much of September HIGHS lingered south and east of NZ.
A time-longitude cross section of the blocking index shows this blocking was
strongest between 6 and 11 September.
See
www.cpc.ncep.noaa.gov/products/precip/CWlink/blocking/real_time_sh/real_time_ind
ex_nrm.shtml

The lingering highs in this area led to more NE winds onto eastern parts of the
North Island, so that by the end of the month some parts of Coromandel had an
accumulated rainfall around a metre --- an amount more typical of Fjordland.
Topsy-turvy weather.

The Tropics
Tonight TC MATTHEW is Cat 5 as it moves to the Jamaica /Haiti/ Cuba area.
May be seen at ruc.noaa.gov/tracks/
And in the NW Pacific TC CHABA is moving towards Japan.

Rain for the past fortnight may be seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
Rain accumulation maps show an increase in convection over Indonesia and
Philippines and along the Intertropical Convergence zone across the central
Pacific, and to north of South America. Also a decline in activity in the North
Atlantic and Tasman Sea. The front that knocked the power out over South
Australia last Thursday shows up well.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to remain much the same in the Solomon Islands to
Tokelau area, with another finger covering northern Vanuatu and the sea between
Vanuatu and Fiji. Another branch of the SPCZ may cover the zone from Niue to
Gamier Islands in a loose and scattered manner.
A tropical LOW is expected to form in the Vanuatu to Fiji area on Sun 9/Mon 10
Oct and then MAY go SE across Fiji on Fiji day holiday on Mon 10 Oct-to Thu 13
Oct, consider avoiding.

Subtropical ridge (STR)
This is expected to remain weak and further north than normal along round 25S
between Australian coast and south of French Polynesia. It is likely to get
wider and stronger from this weekend and stretch to 30S.

Travel from Tahiti to Tonga:
Light winds over Tahiti area until local Tuesday. Then winds may be Ok for
getting as far west as Niue. As for Tonga, well, a passing trough associated
with the Fiji Low is expected around Mon 10/Tue 11 Oct local. Avoid.

Travel between the Tropics and NZ:
A trough is expected to bring strong winds and showers to northern NZ on Tuesday
night and another more intense trough is expected to bring strong winds to
northern NZ on Thursday /Friday followed by SW swells from the Southern Ocean
over 4 metres reaching as far north as 22S on Friday might/Saturday NZ time.
Peak swells are likely to be over 8 metres near northern NZ on Thu night/Fri 7
Oct. Avoid.

Travel between New Caledonia and Brisbane area:
A ridge is expected to travel along 25/30S across Tasman Sea from Thu night 6
Oct and to get east of NZ from Mon 10 Oct. This should provide good conditions
for sailing from Fiji to New Caledonia or from New Caledonia to Brisbane, but
NOT for going east.
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See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website www.metbob.com for information on tailor-made voyage forecasts
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2 comments:

Mariana Daubine said...
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alexandra mollet said...
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