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
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 20 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 20 February 2022
TC DOVI passed over Waikato to Gisborne on Sunday20 Feb
The storm brought waves to 7m as measured by a MetOcean buoy off Taranaki
See
metocean.co.nz/news/2022/2/15/drifting-wave-buoy-rides-the-waves-of-cyclone-
dovi
TROPICS
We have had a "quiet" time in the tropics since TC DOVI and indeed are now
"between MJO episodes".
In 1971 Roland Madden and Paul Julian discovered a pulse of extra energy
that forms in the Indian Ocean and then travels eastwards along the tropics
across Indonesia/Northern Australia to the Pacific Ocean, fading away near
180 degrees longitude. It is a regional scale coupling between atmospheric
circulation and tropical convection. Now called an MJO/Madden Julian
Oscillation, it is known to increase the risk of cyclone formation and can
be tracked by watching cloud and rain patterns, taking a week or two to
transit each area. So, each MJO lasts around 30 to 60 days.
A good site to see its extrapolated trend is
www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml, scroll down
to Ensemble map of the OLR (outgoing long wave radiation) anomolies for the
next 15 days in 5-day steps. Here, blue is bubbly and yellow is mellow. At
present the next MJO is building in the Indian Ocean and expected to reach
Papua New Guinea in around 15 days near 8 March.

So, with some hand-waving, this shows that the next two weeks across the
South Pacific is likely to remain "quiet" and then by around mid-March the
risk of cyclone formation is likely to rise. The next two weeks is likely
to be a good time for those who are planning to do some Island hoping,
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

The Indian Ocean continues to bubble up cyclones and the latest is EMANATI
following two recent cyclones to Madagascar. ANA and BASTRATI.
A tropical low L1 s expected to form over Fiji/Tonga mid-week and then
deepen as it moves southeast out of the tropics by end of the week.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is less active than last week relaxing after a few heated weeks. m
Vanuatu/New Caledonia to Fiji. A trough forming over southern cooks and
south of there by mod-week is expected to drift westwards later in the week.

HIGHS and LOWS
High H1 moving across NZ on Monday and then east along 45S.
Low L2 in South Tasman Sea on Monday going southeast, and its associated
trough should cross NZ on Tuesday and Wednesday.
Then HIGH H2 is expected to travel east from South Australia along 45S to
reach the South Island this weekend.
Subtropical ridge is strong along 40 to 45S with trade winds north of 35S
making Trans-Tasman travel OK this week.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 13 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 13 February 2022

Where to put your AIS Antenna?
Here's an article update from Peter Mott of Passage Guardian about this
topic.
passageguardian.nz/pages/best-practice-ais-for-bluewater-sailing-yachts
Conclusion
A radar arch or stern post mounted antenna should deliver reliable satellite
reception, whilst permitting detection of cargo ships out to at least 20nm.
I have experience tracking vessels conducting circumnavigations that have
experienced knock downs and have lost everything on the mast head. The AIS
antenna mounted on the radar arch continued to operate normally.

Tropical Cyclone DOVI
DOVI's steering field around and above it took it south and then southeast.
Windy.com is a good resource for viewing this.
Here is link to animation of wind flow around DOVI as it crossed NZ. :
t.co/G9J3IbWHuz Watch this and see how the southerly gale wind arrives in in
Cook Strait BEFORE the Low made landfall. Hence the saying "It isn't so much
Wellington that blows, it's also Auckland that sucks"
And in the illustrated edition of this blog is a MetService manual analysis
of the situation at local 6am Sunday. showing detailed isobars around DOVI.

When I was at MetService in the days before automatic weather stations, it
was this dawn analysis (when the lighthouse keepers started the day) that
was the most important map of the day and we would spend up to an hour
drawing and watching it. Where the isobars bunch together the winds blow
stronger, so isobar=spacing matters. Also note the orographic trough leeward
of the Alps-Aotearoa.

TROPICS
DOVI formed in the Coral Sea and moved east onto Vanuatu then south past Nee
Caledonia into the Tasman Sea then southeast across North Island.
There is a zone of high potential for formation this week to northwest of
Australia.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is less active than last week relaxing after a few heated weeks. m
Vanuatu/New Caledonia to Fiji. A trough forming over southern cooks and
south of there by mod-week is expected to drift westwards later in the week.

HIGHS and LOWS
The remains of DOVI are tonight east of North Island and travelling fast
eastwards and fading.
High H1 should remain slow-moving to southeast of French Polynesia this
week.
LOW L1 is expected to form in a tropical trough south of Southern Cooks by
mid-week and then go southeast.
High H2 tonight in the Tasman Sea is expected to travel east along40S
crossing central NZ on Thursday.
Another trough should cross NZ this weekend.

With H2 it is OK to travel from NZ to Australia this week, but difficult to
go the other way.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 6 Feb. 2022

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 06 February 2022

REVIEW OF THE LAST MONTH (January2022)
Sea surface temperature continues cool around the eastern equatorial
Pacific, showing us the LA NINA. This is surrounding by a warm C shaped
zone across the central North Pacific to PNG to Tasman Sea to central South
pacific. Marine heat waves are triggering a squid bloom off the Origan Coast


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

Average isobars for past month (below)
In the north there is a weak subtropical ridge and a strong Siberian winter
High
The southern subtropical ridge is well south of its normal latitude.
The anomaly map shows deeper than normal lows over the Aleutian Islands.


TROPICS
BATSIRAI crossed Madagascar yesterday brining widespread damage. CLIFF is
in the mid-south Indian Ocean going SW. There is a zone of high potential
for formation across the Coral Sea to Fiji.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is more active than last week especially from Vanuatu/New Caledonia
to Fiji. A tropical Low L2 is expected to move from Coral Sea to New
Caledonia area by mid-week and then go south.
HIGHS and LOWS
High1 to east of NZ is expected to travel east along 35S maintaining a good
SE flow over Tahiti that curls to a NE flow over Samoa and Tonga.
Low1 in north Tasma Sea with a rain band over the North Island early in the
week is moving off to southwest/south.
High H2 starts the week south of Tasmania then travels east around South
Island then northeast.
Low2 in Coral Sea may deepen inti a tropical cyclone over southern
Vanuatu/New Caledonia area by mid-week and then go south towards Northland.
These Lows make trans-Tasman voyages risky this week.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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