Bob Blog 29 Oct

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 29 Oct 2023

LOLA's rejuvenation

An outbreak of cold air from the Southern Ocean washed over NZ during the
past week and then, over the weekend, met with the remains of LOLA in the
north Tasman Sea

The central pressure of the system dropped from 1008 to 994 in 24 hours, a
drop of 14 hPa near 30S.
This was caused by the extreme temperature/density difference between the
air for the north and the air from the South. The process is called rapid
cyclogenesis. This is why one of the rules for sailing from Fiji to New
Zealand is "Do not go south with a falling barometer."

TROPICS
TAMMY is now in the North Atlantic after soaking the NE Caribbean, and the
depression 19-E is off the west of Mexico.
Last week LOLA was briefly Cat5 near Pentecost Island. OTIS was briefly Cat
5 near Acapulco. HARMOON caused a quarter of million people to evacuate
into shelters in southern Bangladesh. NORMA is near Baja California and
TAMMY is near the Caribbean. TEJ I flooded pasts of Yemen.

Meteorologists were slammed in the media for the jump to Category 5 by OTIS
See tinyurl.com/CycloneOtis
This idea of shooting the messenger in the media and slamming forecasters
seems to be becoming a trend. MetService issued a review of its performance
in a few major events in NZ last summer see tinyurl.com/MetServiceGabrielle
. One thing the media have not been reporting is that although the computer
models sometimes behave poorly, manual forecasters manage to add value by
issuing warnings that work in saving lives. Insurance companies have noted
that even though the amount of weather damage they have to pay out for is
rising with climate change, the death toll from weather is falling.

WEATHER ZONES

The South Pacific Convergence zone is expected to stay from Solomons to
Samoa. A trough is expected to cross the Minerva area on local Tuesday
followed by a lull.
HIGHS and LOWS
HIGH H1 crossing southern NZ tonight is moving off to the east along 40S.
LOW L1 is travelling southeast and sideswiping the northeast of North Island
on Monday then fading away, leaving behind a lull.
There is a strong squash zone between H1 and L1. Avoid.
LOW L2 is expected to form in central Tasman Sea by mid-week and then fade
across central NZ by the weekend, followed by a SW flow.
The scene is set for southerly winds over northern NZ from 6 to 9 Nov
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about 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 text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 22 Oct

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 22 Oct 2023

LOLA's origins

Last week we looked at the Australian and South Pacific Cyclone outlooks for
the coming season. In my "what to avoid" summary I concluded that "Low L3
is expected to deepen over northern Vanuatu next week and maybe travel SW
into Coral Sea. Avoid this next week."

Well "Low 3" has now been named LOLA


and is the first cyclone of the new season that nominally starts on
1November.
LOLA was named ten days before season start. Why so early?
Looking at the satellite imagery, It seems that LOLA follows the normal
recipe for cyclone cooking.

1. Heat the sea to over 26C

2. Add lots of moisture a gang of tropical squally thunderstorms

3. And spin. As the gang of thunderstorms tumble together, they create
an area where air is vented up and outwards faster than it can be drawn in
from the fringes.
4. The central pressure drops, making more isobars on the weather map,
making a faster spin. This continues as long as the system has warm sea
and moist air to feed on.


Looking at the streamlines ...


.. It seems that the centre of action that has allowed LOLA to form is
related to the warm water over the central Pacific. Prior to its formation
there was a zone of equatorial westerlies all by itself near the dateline.
not an extension of the Asian monsoon. LOLA formed with an equatorial twin
thanks to those equatorial westerlies. So, it formed around 5S, very close
to the equator, an unusual spot for a South Pacific Cyclone -- these
usually form on the South Pacific Convergence zone. This may be related to
El Nino. It is associated with a shift of the Walker cell into the central
Pacific, especially when combined with a positive Indian Dipole.



See https://tinyurl.com/hadleywalker

So, 2023 is an El Nino year with an active zone near the equator. The same
pattern happened in 1972 and helped form TC BEBE 19th-29th October. It also
formed near 5S.


TROPICS
NORMA is near Baja California and TAMMY is near the Caribbean .TEJ is making
landfall over Yemen And LOLA is deepening as it approaches Vanuatu..

WEATHER ZONES
A lot to avoid this week.
The South Pacific Convergence zone is expected to stay from Solomons to
LOLA. Another branch is expected to linger north of Fiji to Samoa. A trough
should linger from Southern Cooks to south of Tahiti. LOLA is expected to
deepen as it moves slowly south near Vanuatu and peak at category 3 by
Wednesday then travel south or southeast maybe towards NZ next weekend.
Avoid.
HIGHS and LOWS
Low L1 east of NZ is expected to travel east.
HIGH H1 over NZ is expected to follow L1.
Trough is expected to roll northeastwards across the Tasman Sea followed by
strong SE winds and southerly swells up to 5m. Should reach from Bundaberg
to Northland by Friday. Avoid.
This is followed by a HIGH that stretches from central Tasman Sea to South
Island by next weekend.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about 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 text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 15 Oct

Bob Blog 15 Oct
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 15 Oct 2023

The Cyclone Outlook for the coming season:

Gilbert Walker was an applied mathematician at the University of Cambridge
when he became director-general of observatories in India in 1904. While
there, he studied the characteristics of the Indian Ocean monsoon, the
failure of whose rains had brought severe famine to the country in 1899.
Analysing vast amounts of weather data from India and the rest of the world,
over the next fifteen years he published the first descriptions of the great
seesaw oscillation of atmospheric pressure between the Indian and Pacific
Ocean, and its correlation to temperature and rainfall patterns across much
of the Earth's tropical regions, including India. One of his identified
oscillations has been named the Southern Oscillation and Walker worked with
the Indian Meteorological Department studying the link between the monsoon
and Southern Oscillation phenomenon. He was made a Companion of the Order of
the Star of India in 1911.


Image shows a normal Walker circulation as a conceptual zone of rising air
over Australia and sinking air over Peru. aloo shows a reversed Walker as it
is now during an El Nino event with sinking air over Australia (dry) (see
Oceanreview.com))

The Walker circulation over the Indian ocean is known as the Indian Ocean
Diopole. This is having a positive phase at present, also bringing sinking
dry air over Australia. (from study iq.com).

Thanks to the combination of an El Nino and a positive Indian Dipole,
Australia is being dealt dry sinking air from both the Pacific and the
Indian Oceans. Australia's Bureau of Met have issued their Cyclone outlook
for the coming season with the summary:

Below average number of tropical cyclones is likely for Australia in 2023-24

And in New Zealand the combined resources of NIWA and MetService have issued
a map of expected cyclone numbers:

Using analogue years 73/73,83/83,02/03,04/05, and09/10 and going for reduced
risk near Australia, normal to elevated risk between Tuvalu and Tahiti, and
elevated risk for Vanuatu, Fiji and Northern Cooks.
See://niwa.co.nz/sites/niwa.co.nz/files/tc_outlook_2023-24.pdf

TROPICS

SEAN is travelling to the northwest across he North Atlantic.

WEATHER ZONES
The South Pacific Convergence zone is expected to stay north from Solomons
to northern Vanuatu to Tuvalu. There is expected to be a passing trough over
Southern Cooks and Tahiti around mid-week helping Island -hopping from
Tahiti to Tuamotu Islands.

HIGHS and LOWS
HIGH H1 east of NZ is expected to travel slowly eastwards along 35 to 40S.

LOW L1 is expected to roll in from SW of Tasmania and go NE and deepen in
the Tasman Sea on Tuesday. Associated warm front should stall around
northern NZ on Wednesday and Thursday with strong NE to E winds. Low is then
expected to weaken into a trough reaching Fiji and Tonga over the weekend.

Low L3 is expected to deepen over northern Vanuatu next week and maybe
travel SW into Coral Sea. Avoid this next week

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about 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 text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 8 Oct 23

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 8 Oct 2023

Island Climate Update

NIWA have issued their October edition of the Island Climate Update
available online as a pdf at niwa.co.nz/climate/island-climate-update.
Now that we are having El Nino this page gives us a look at what that may
mean for rainfall and drought/water stress over the next few months.

On this page there is also access to a selection of maps for various
locations the recent conditions, and Outlooks for various periods.

Amongst these I found the following to be most interesting:

During the past month there was less than 40mm of rain over Tonga ,, and
this has resulted in an area of severe water stress there as shown in the
recent water stress map.

Interestingly this region is expected to quickly recover during October:

The prospects for rain between now and December show only a narrow zone of
"near normal", a very wet equatorial zone and a tendency for dryness away
from the equator.

The "normal" pattern needs to be considered along with this map to turn it
into a rainfall map. However, this map gives an indication to what is
physically different. the Hadley cell is being distorted by an extra boost
of upward motion mainly along equator near the dateline and as this air
lifts to the top f the troposphere it is deflected away from the equator and
descends/dries out until it find =s the surface again around 25 north or
south.

TROPICS

KOINU (Japanese for "puppy") produced a measured wind of 213mph and then
destroyed the anemometer at Lanyu Island - that's the third highest
land-based measured wind gust. BOLAVEN is expected to stay out to sea east
of Japan. LIDIA and 16E are fading.

WEATHER ZONES
The South Pacific Convergence zone is expected to stay north from Solomons
to northern Vanuatu to Samoa/Northern Tonga. There is expected to be a
passing trough over Southern Cooks and Austral Islands after mid-week.

HIGHS and LOWS
LOW L1 east of NZ has some large southerly swells as far north as Fiji on
Monday. It is expected to move off to the SE allowing HIGH H1 to spread
slowly into Tasman Sea and then along 30S past the north of NZ on Friday
13th This HIGH has brought a squash zone in the Coral Sea for a few days and
is bringing good conditions for sailing from tropics to NZ or Aus this week.

The next Low following H1 is expected to bring a warm front and northerly
winds to Northland early next week and then to travel east along 30S
followed by a burst of large southerly swells mid next week. Avoid arriving
in Northland around 18/19 Oct.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about 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 text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Bob Blog 1 Oct

Bob Blog 1 October
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 1 Oct 2023

A review of last month's weather

Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines in the South Pacific for the last month at youtu.be/ryMmaz_BxdY

September was a month with several spring fronts across the Tasman Sea.
These fronts were more mobile than in July and August so brought no
lingering damage. Mobile HIGHS are now on the weather map crossing the north
Tasman Sea. In the last week of the month meteorologists conformed that
parameters are now at El Nino level, also a positive Indian Ocean Dipole (El
Nino's Indian Ocean cousin). These events combine to deprive rain over
Australia, especially SE Australia. This has already led to two brief heat
waves over SE Australia.
Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml

In the Sea temperature anomalies, there is a build -p of high temps south of
Tahiti. And the warm conditions that were near the west coast of North
America have shifted westwards.

In the Northern Hemisphere winter HIGH over northern Europe has built
quickly indicating strong autumn conditions. In the Southern Hemisphere, the
subtropical ridges are slowly

Isobars are getting higher over Australia /NE/and further east. There is
also higher pressure building over eastern Canada. Lower pressures over
southern Indian ocean.

There is a widening of the subtropical ridge over NZ. A slight southward
shift. Slightly more westerly gradient over NZ,

TROPICS
Storm surge for weakening OPHELIA flooded parts of North Carolina. NIGEL
faded on its way to Europe and is followed by PHILLIPE and RINA. KOINUI is
skirting past north of Philippines.

The MJO, a burst of extra energy in the tropics, is weakly crossing New
Guinea

WEATHER ZONES
The South Pacific Convergence zone is expected to stay north from Solomons
to northern Vanuatu to Samoa/Northern Tonga. There is expected to be a
passing trough over Southern Cooks and Austral Islands after mid-week. Be
Aware.

HIGH H1 north of NZ tonight is moving steadily along 30S with a small squash
zone and a burst of southerly swell on its northern side.

Trough associated with Low L1 is crossing NZ on Monday followed by cold
Southerly winds on Tuesday.

HIGH H2 is expected to travel NE across the Tasman Sea and linger around
northern NZ on Thursday and Friday.

Trough associated t=with L2 is expected to reach from New Caledonia to New
Zealand by Saturday, affecting anyone sailing across North Tasman Sea this
week.

Tropics to NZ: avoid arriving in NZ on Sun 8 October.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about 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 text 64277762212.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>