Bob Blog 27 Feb

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 27 February 2022

From tomorrow, Monday 28 Feb, NZ is reopening its borders to fully
vaccinated kiwis flying in from Australia, with no more MIQ for them, but
need to self-isolate for 10 days. Unvaccinated arrivals still have to attend
MIQ. NZ is going thru its peak of the Omicron wave over the next few weeks
with the highest effective spread rate in the world, so best to avoid any
contact with the locals anyway for more than next ten days.
The Australian border is now open to fully vaccinated arrivals. The
unvaccinated are subject to State health regulations. This applies to
arrivals by air or by sea, And BUNDABERG has reopened as a port of entry.


La Nina is expected to weaken this autumn
The annual cycle is soon ticking from summer to autumn in the Southern
Hemisphere, and this is usually the time when the El Nino/ La Nina swing
tends to occur.
You've probably heard about La Nina and how this tropical weather feature is
modifying our seasonal weather. To recap: It is the name given to the
period when sea surface temperature over the eastern equatorial Pacific
drops below normal. As the trade winds increase, they drag the sun-warmed
surface water away to the west and this helps the upwelling of cooler water
at the north-end of the Humboldt current.

This encourages the subtropical ridge to shift south over New Zealand
especially in summer
The illustrated edition of this blog at metbob.com shows the daily averaged
isobars over the NZ Longitudes. Passing HIGHS show up as occurring mainly
crossing New Zealand.

We monitor ENSO = El Nino/Southern Oscillation and its impact on the weather
map by using. the Southern Oscillation Index SOI (30 day running mean) This
is based on the standardized difference in the barometer readings between
Tahiti and Darwin, in other words it counts the average number of isobars
between them on the weather map. When the SOI is more than plus one
(standard deviation from its mean) for more than a month we call it a LA
NINA event, and when it stays more than minus one, we call it an EL NINO
event.
There was a La Nina that peaked in Jan 2021, and then this La Nina episode
started last August and hasn't been as strong as the last but is still here.
SOI can be seen at
www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

The parameter used from the ocean is based on the sea surface temperatures
in the equatorial eastern Pacific and is called the Oceanic Nino Index ONI.
This was also in La Nina territory in 2021 and again in summer 2022. ONI
chart and Sea temperature anomaly can be seen at
www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-sta
tus-fcsts-web.pdf
According to the International Research Institute of the Climate Prediction
Centre,
at iri.columbia.edu/our-expertise/climate/forecasts/enso/current/, reviewing
many different models that forecast the future of this La Nina, it is
expected to weaken and fade away by May.

TROPICS
As explained last week, a new MJO cycle is now making its way across
northern Australia.
This extra energy has activated a very active coastal trough along the
eastern seaboard, resulting in damaging rains for southeast Queensland see
www.theguardian.com/australia-news/2022/feb/27/south-east-queensland-floods-
whats-happened-and-which-areas-could-be-hit-next
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
EMNATI moved onto Madagascar: the fifth event for them in six weeks, see
go.nasa.gov/33IWJQw
VERNON has formed in the Indian Ocean and ANIKA is moving along the NW
Australia coast.

WEATHER ZONES
SPCZ is expected to be active from Solomons to Vanuatu to southern Fiji
Topical low L1 over Vanuatu is moving south over New Caledonia om Mon/Tue
then off to the southeast and east towards south-of-Niue.
Active trough over Brisbane area is expected to go southeast towards Lord
Howe with a low L2 over Sydney by Thursday.
HIGHS and LOWS
Low L3 near Chatham Islands is expected to travel northeast and then
southeast.
Low L4 at 30S to south of Niue is expected to go southeast, followed by L3.
Next week L1 should follow the southeast path made by L3 and L4
HIGH H1 in south Tasman Sea is expected to travel slowly onto NZ this week
and act as a blocking high. There is expected to be a squash zone between it
and L1 that moves onto northern NZ around Thu/Fri. AVOID
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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 64277762212
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