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 31 August 2025
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
www.youtube.com/watch?v=DQheG_B2I24
Lows crossed NZ on1,8,17 and 27 August, with healthy Highs in-between ..
The Low on 27 August was especially squally and thundery:
A back trajectory analysis shows that the air then arriving over NZ was a
clash between air from the north and air from the south:
The 500hPa heights and anomalies shows three healthy HIGHS crossing NZ in
August.
From http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_sh_anim.shtml
Sea Surface temperature anomalies from psl.noaa.gov/map/clim/sst.shtml
North Pacific just continues to war. North Atlantic has cooled. And there
seems to be some strong cooling along the southern polar circle.
There is now a NEGATIVE IOD (Indian Ocean Dipole) (west cool/east warm).
this may bring some rain to central/southern AUSTRALIA.
Also, the SAM/AAO index has gone negative over last few days , consistent
with a burst of polar air onto NZ. However, this is NOT expected to last
long.
The monthly pressure pattern and anomalies are
from http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html
During August the Subtropical ridge in both hemispheres weakened in
intensity. However, it resumed over the Tasman Sea after lower-than-normal
isobars there in July.
The monsoon is moving steadily east across Asia.
Pressure anomalies for past month
Shows a major zone of Higher isobars over NZ and lower isobars east of NZ.
with strong cold SW winds in-between.
And a zoom in on the SW Pacific
There is a new 1020 isobar over Australia and NZ , but the 1025 isobar has
faded away.
The 1015 isobar is drifting NORTH over north Australia.
TROPICS
. At least three people perished as Typhoon Kajiki battered northern and
central Vietnam with fierce winds and torrential rainfall that collapsed
homes, felled trees and turned streets in the capital of Hanoi into rivers.
. Tropical Storm Fernand formed over the North Atlantic, while Juliette
passed well off Baja California.
WEATHER ZONES
Rain accumulation this week from Windy.com below shows well defined SPCZ
between Solomon Islands and Tulavu (north of Samoa).Also a convergence zone
around the Niue area.
Wind accumulation from windy.com below shows squash zones in the tropics one
to north of Fiji and one from Tonga to the Southern Cooks. These are
associated with the passage of HIGH H1 from 35 to 30S after Wednesday.
LOWS and HIGHS
LOW L1 crossed central NZ today and is travelling quickly off to the
southeast.
HIGH H1 is expected to cross the Tasman Sea on Monday and Tuesday and NZ on
Wednesday, then travel from 35S to 30S when east of NZ. This should produce
squash zones of enhanced Se winds further north. between Tonga and Southern
Cooks late in the week. Be aware.
A Low L2 should travel quickly along 50S mid-week.
Another Low L3 is expected to form west pf H1 and then the trough of L3
should cross NZ on Friday, followed by High H2 coming from central
Australia.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>
31 August 2025
24 August 2025
Bobgram
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 24 August 2025
NASA Extends PREFIRE Mission to 2026
NASA's PREFIRE (Polar Radiant Energy in the Far-InfraRed Experiment)
mission uses two CubeSats spectrophotometers, each no larger than a
The satellites are in what's called an asynchronous near-polar orbit,
traveling near the poles with each pass but hours apart from one
another. This provides two snapshots of the same area over time,
enabling the mission to capture phenomena that occur on short
timescales, such as cloud cover's temporary effects on the temperature
of the area beneath it.
While the tropics take in the greatest share of the Sun's energy,
winds, storms, and ocean currents carry much of that heat toward the
colder polar regions, which receive far less sunlight. Ice, snow, and
clouds in these regions then release some of the heat into space,
primarily as far-infrared radiation. The difference between the heat
absorbed in the tropics and the heat radiated out at the poles
strongly influences global temperatures and helps drive Earth's
climate and weather systems.
The global energy budget is interesting….
Note there is incoming of 341.3 W/m2 and outgoing of
101.9+238.5W/m2=340.4 .
The data collected gives new details about the changing glow found in
processes such as the melting and freezing of surface ice, seasonal
snow changes, and variations in cloud cover.
"The PREFIRE satellites show that at these longer wavelengths, the
amount of radiation going into space can differ from one type of ice
to another by as much as 5%," said Brian Drouin, PREFIRE's project
scientist at JPL. "Measurements that look at the same areas but with
shorter wavelengths do not show this difference."
"We have the capacity to collect data for the whole world, not just
the poles. What we'll be able to do is look at the size of ice
particles in clouds that affect energy exchange between Earth and
space," said PREFIRE's principal investigator, Tristan L'Ecuyer of the
University of Wisconsin–Madison. "We'll be able to incorporate the
data into weather prediction models to improve forecasts and improve
our understanding of how moisture circulates, which affects where
storms form and how precipitation moves around the world."
TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is
from www.ospo.noaa.gov/products/ocean/tropical/tcfp/
• Hurricane ERIN underwent one of the most rapid intensifications of
any Atlantic basin storm in history, exploding in force from a
tropical storm to a Category5 hurricane in just 25 hours.
• Tropical Storm Lingling drenched southern Japan's Kyushu Island and
nearby smaller islands.
WEATHER ZONES
Weather Zones Mid-week GFS model showing isobars, winds, waves
(purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge),
SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)
Rain accumulation this week from Windy.com below shows well defined
SPCZ between Solomon Islands and Fiji and a passing trough south of
Fiji and another south of French Polynesia. Also, a large dry zone
over Australia.
Wind accumulation from windy.com below shows generally OK ailing winds
in the tropics. And the roaring forties extending north almost to
Noumea at times .
LOWS and HIGHS
HIGH H1 centred east of NZ tonight is now moving off to the east or
northeast leaving a ridge over central NZ and a squash zone of East to
NE winds between Northland and New Caledonia.
Low L1 is tonight between Lord Howe and Noumea, and by Wednesday is
expected to be north of Northland with Front crossing Fiji. Front
reaching Tonga area on Thursday. Avoid.
Later in the week it should travel off to the southeast of NZ,
followed by a westerly flow.
Then L2 from the Aussie Bight is expected to cross Tasmania by Friday
and NZ on Friday /Saturday
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are
from the patterned world.
Compiled 24 August 2025
NASA Extends PREFIRE Mission to 2026
NASA's PREFIRE (Polar Radiant Energy in the Far-InfraRed Experiment)
mission uses two CubeSats spectrophotometers, each no larger than a
The satellites are in what's called an asynchronous near-polar orbit,
traveling near the poles with each pass but hours apart from one
another. This provides two snapshots of the same area over time,
enabling the mission to capture phenomena that occur on short
timescales, such as cloud cover's temporary effects on the temperature
of the area beneath it.
While the tropics take in the greatest share of the Sun's energy,
winds, storms, and ocean currents carry much of that heat toward the
colder polar regions, which receive far less sunlight. Ice, snow, and
clouds in these regions then release some of the heat into space,
primarily as far-infrared radiation. The difference between the heat
absorbed in the tropics and the heat radiated out at the poles
strongly influences global temperatures and helps drive Earth's
climate and weather systems.
The global energy budget is interesting….
Note there is incoming of 341.3 W/m2 and outgoing of
101.9+238.5W/m2=340.4 .
The data collected gives new details about the changing glow found in
processes such as the melting and freezing of surface ice, seasonal
snow changes, and variations in cloud cover.
"The PREFIRE satellites show that at these longer wavelengths, the
amount of radiation going into space can differ from one type of ice
to another by as much as 5%," said Brian Drouin, PREFIRE's project
scientist at JPL. "Measurements that look at the same areas but with
shorter wavelengths do not show this difference."
"We have the capacity to collect data for the whole world, not just
the poles. What we'll be able to do is look at the size of ice
particles in clouds that affect energy exchange between Earth and
space," said PREFIRE's principal investigator, Tristan L'Ecuyer of the
University of Wisconsin–Madison. "We'll be able to incorporate the
data into weather prediction models to improve forecasts and improve
our understanding of how moisture circulates, which affects where
storms form and how precipitation moves around the world."
TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is
from www.ospo.noaa.gov/products/ocean/tropical/tcfp/
• Hurricane ERIN underwent one of the most rapid intensifications of
any Atlantic basin storm in history, exploding in force from a
tropical storm to a Category5 hurricane in just 25 hours.
• Tropical Storm Lingling drenched southern Japan's Kyushu Island and
nearby smaller islands.
WEATHER ZONES
Weather Zones Mid-week GFS model showing isobars, winds, waves
(purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge),
SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)
Rain accumulation this week from Windy.com below shows well defined
SPCZ between Solomon Islands and Fiji and a passing trough south of
Fiji and another south of French Polynesia. Also, a large dry zone
over Australia.
Wind accumulation from windy.com below shows generally OK ailing winds
in the tropics. And the roaring forties extending north almost to
Noumea at times .
LOWS and HIGHS
HIGH H1 centred east of NZ tonight is now moving off to the east or
northeast leaving a ridge over central NZ and a squash zone of East to
NE winds between Northland and New Caledonia.
Low L1 is tonight between Lord Howe and Noumea, and by Wednesday is
expected to be north of Northland with Front crossing Fiji. Front
reaching Tonga area on Thursday. Avoid.
Later in the week it should travel off to the southeast of NZ,
followed by a westerly flow.
Then L2 from the Aussie Bight is expected to cross Tasmania by Friday
and NZ on Friday /Saturday
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
17 August 2025
Bobgram
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 17 August 2025
Are the Oceans now struggling to store extra earth heating?
See climatereanalyzer.org/clim/sst_daily/
Since July 2023 it is as if the global averaged sea temperature has
jumped into a new regime. We still cannot tell if this is a
fundamental change that may adversely energise further weather events.
In the first half of August the rise in daily global has been
extremely rapid.
Until now, 90 per cent of the excess heat created by greenhouse gas
emissions has been drawn down into the ocean. Under this new regime it
seems that this capacity for heat absorption is being lost. SO where
will the extra heat now get stored?
The Cape Reinga region over Far North New Zealand is having a winter
heatwave. However, Hauraki Gulf is just slightly above normal
See www.moanaproject.org/marine-heatwave-forecast
The rain accumulation for year to date shows that it has been wetter
than normal in northern NZ --- with the "wetter" kicking in around 21
April, and % excess much more in Auckland than around Kerikeri.
See Visual crossing data
TROPICS
. Southern Taiwan was lashed by Category-2 Typhoon Podul, which
weakened over the island before striking China's Fujian and Guangdong
provinces.
. Mexico's central Pacific coast was brushed by passing Tropical Storm
Ivo.
. Tropical Storm Awo formed briefly near Seychelles.
. Hurricane Erin is strengthening to Category-3 force north of Puerto
Rico.
WEATHER ZONES
Rain accumulation this week from Windy.com below shows well defined
SPCZ between Solomon Islands and Samo/Niue and a passing trough over
French Polynesia. Also, an area of rain along eastern seaboard of
Australia in onshore winds.
Wind accumulation from windy.com below shows a burst of strong
southerly winds over NZ in the wake of L1. Also, generally OK ailing
winds in the tropics.
LOWS and HIGHS
Low L1 is moving off to the east of New Zealand.
H1 starts off in Australian Bight and travel east along 45S across
South Tasman Sea mid-week and onto NZ next weekend.
L2 is expected to follow H1
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are
from the patterned world.
Compiled 17 August 2025
Are the Oceans now struggling to store extra earth heating?
See climatereanalyzer.org/clim/sst_daily/
Since July 2023 it is as if the global averaged sea temperature has
jumped into a new regime. We still cannot tell if this is a
fundamental change that may adversely energise further weather events.
In the first half of August the rise in daily global has been
extremely rapid.
Until now, 90 per cent of the excess heat created by greenhouse gas
emissions has been drawn down into the ocean. Under this new regime it
seems that this capacity for heat absorption is being lost. SO where
will the extra heat now get stored?
The Cape Reinga region over Far North New Zealand is having a winter
heatwave. However, Hauraki Gulf is just slightly above normal
See www.moanaproject.org/marine-heatwave-forecast
The rain accumulation for year to date shows that it has been wetter
than normal in northern NZ --- with the "wetter" kicking in around 21
April, and % excess much more in Auckland than around Kerikeri.
See Visual crossing data
TROPICS
. Southern Taiwan was lashed by Category-2 Typhoon Podul, which
weakened over the island before striking China's Fujian and Guangdong
provinces.
. Mexico's central Pacific coast was brushed by passing Tropical Storm
Ivo.
. Tropical Storm Awo formed briefly near Seychelles.
. Hurricane Erin is strengthening to Category-3 force north of Puerto
Rico.
WEATHER ZONES
Rain accumulation this week from Windy.com below shows well defined
SPCZ between Solomon Islands and Samo/Niue and a passing trough over
French Polynesia. Also, an area of rain along eastern seaboard of
Australia in onshore winds.
Wind accumulation from windy.com below shows a burst of strong
southerly winds over NZ in the wake of L1. Also, generally OK ailing
winds in the tropics.
LOWS and HIGHS
Low L1 is moving off to the east of New Zealand.
H1 starts off in Australian Bight and travel east along 45S across
South Tasman Sea mid-week and onto NZ next weekend.
L2 is expected to follow H1
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
10 August 2025
Bobgram 10 Aug
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 10 August 2025
TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is from
http://www.ospo.noaa.gov/products/ocean/tropical/tcfp/
Tropical storm development across the Northern Hemisphere increased,
with Typhoon Krosa and Tropical Storm Bailu churning the western
Pacific.
. Hurricane Gil formed off Mexico, while Tropical Storm Henriette
passed northeast of Hawaii.
. Tropical Storm Dexter spun up over the Atlantic.
WEATHER ZONES
Weather Zones Mid-week GFS model showing isobars, winds, waves
(purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge),
SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)
Rain accumulation this week from Windy.com shows well defined SPCZ
between Solomon Islands and Tuvalu. Also, heavy rain along 25S from
175E to Rarotonga (avoid).
Wind accumulation from windy.com shows zones of strong wind around L1.
There are also bursts of wind expected south of New Caledonia and off
Sydney later in the week. (avoid).
LOWS and HIGHS
Low L1 is deepening near New Caledonia tonight and expected to travel
slowly to East-southeast reaching 29S 175W by mid-week.
Another Low is expected to form between New Caledonia and Norfolk by
Friday and trave to Tonga 16/17 August (avoid).
HIGH H1 is expected to travel steadily east along 35 to 40S, starting
this week west of Perth, reaching Adelaide by Mid-week and crossing NZ
on Friday 15 Aug.
By then there may be a squash zone of strong easterly winds around 30S
between the High over NZ and the new Low then near Fiji. Avoid.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are
from the patterned world.
Compiled 10 August 2025
TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is from
http://www.ospo.noaa.gov/products/ocean/tropical/tcfp/
Tropical storm development across the Northern Hemisphere increased,
with Typhoon Krosa and Tropical Storm Bailu churning the western
Pacific.
. Hurricane Gil formed off Mexico, while Tropical Storm Henriette
passed northeast of Hawaii.
. Tropical Storm Dexter spun up over the Atlantic.
WEATHER ZONES
Weather Zones Mid-week GFS model showing isobars, winds, waves
(purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge),
SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)
Rain accumulation this week from Windy.com shows well defined SPCZ
between Solomon Islands and Tuvalu. Also, heavy rain along 25S from
175E to Rarotonga (avoid).
Wind accumulation from windy.com shows zones of strong wind around L1.
There are also bursts of wind expected south of New Caledonia and off
Sydney later in the week. (avoid).
LOWS and HIGHS
Low L1 is deepening near New Caledonia tonight and expected to travel
slowly to East-southeast reaching 29S 175W by mid-week.
Another Low is expected to form between New Caledonia and Norfolk by
Friday and trave to Tonga 16/17 August (avoid).
HIGH H1 is expected to travel steadily east along 35 to 40S, starting
this week west of Perth, reaching Adelaide by Mid-week and crossing NZ
on Friday 15 Aug.
By then there may be a squash zone of strong easterly winds around 30S
between the High over NZ and the new Low then near Fiji. Avoid.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
03 August 2025
Bobgram 3 Aug 2025
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 3 August 2025
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
youtu.be/gjWlhQmSeTs
Lows crossed NZ on 4-5, 11, 17 and 29-31 July …. Almost continuing a
weekly cycle, but also a blocking HIGH between 20 and 29 July.
The Low on 29-31 brought heavy rain to Tasman/Nelson/Marlborough area
and Bay of Plenty area.
The 500hPa heights and anomalies shows last month's typical ridge
/trough pattern,
From http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_sh_anim.
shtml
Sea Surface temperature anomalies
from psl.noaa.gov/map/clim/sst.shtml
The build-up of heat east of Japan an in the north Atlantic is
continuing.
The cooling /upwelling off Peru has finished.
The Sothern Annual Mode /AAO spent first half of July positive,
accentuating the polar vortex.
The monthly pressure pattern and anomalies are
from http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html
During July the roaring 40s in the southern hemisphere moved north.
The Subtropical ridge across the south Indian ocean intensified.
Pressure anomalies for past month Shows the pressure rise in south
Indian ocean to be part of a roller coast with lows over Australia and
larger Highs SE of NZ. Deeper lows over Asia.
The 1015 isobar has shifted north to cover the south half of Tasman
Sea.
A 1025 Isobar has formed in the Indian Ocean.
TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is
from http://www.ospo.noaa.gov/products/ocean/tropical/tcfp/
After lashing the far northern Philippines as a Category-1 cyclone,
Tropical Storm Co-May drenched Okinawa before bringing heavy rain and
gales to the Chinese coast around Shanghai.
• Typhoon Krosa skirted the Japanese coast near Tokyo as a tropical
storm.
• Hurricane Iona and Tropical Storm Keli churned the open Pacific
Ocean, well to the south of Hawaii.
WEATHER ZONES
Weather Zones Mid-week GFS model showing isobars, winds, waves
(purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge),
SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)
Rain accumulation this week from Windy.com shows well defined SPCZ
between Solomon Islands and Tuvalu. Also, a frontal zone from Tonga
to Austral Islands (avoid).
Wind accumulation from windy.com shows zones of strong wind around L1
and L2 and a frontal zone along 20S (avoid).
LOWS and HIGHS
Low L1 near 40S 160E, well south of Tahiti is moving off to the
southeast but leaving behind lots of southerly swell getting as far as
20S.
HIGH H1 has been travelling across New Zealand last few days and
should continue a steady eastward migration along 45S
Low 2 is the one that affected the third rugby test Wallabies beating
the British and Irish Lions in Stadium Australia, Sydney … a game
delayed by lightning and influenced by rain. This Low is being
steered east along 28S… an uncommon path for a low. So, there is a
squash zone between it and H1 with strong easterly winds and large
swells at 30S. Avoid.
Further west over Australia several troughs should travel southeast
across Tasmania and the South Tasman Sea reaching southern NZ by end
of the week and a large High H2 moves into the Aussie Bight and then
follows those troughs.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If you would like more details about your voyage, check metbob.com
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Disclaimer: Weather is a mix of pattern and chaos; these ideas are
from the patterned world.
Compiled 3 August 2025
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
youtu.be/gjWlhQmSeTs
Lows crossed NZ on 4-5, 11, 17 and 29-31 July …. Almost continuing a
weekly cycle, but also a blocking HIGH between 20 and 29 July.
The Low on 29-31 brought heavy rain to Tasman/Nelson/Marlborough area
and Bay of Plenty area.
The 500hPa heights and anomalies shows last month's typical ridge
/trough pattern,
From http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_sh_anim.
shtml
Sea Surface temperature anomalies
from psl.noaa.gov/map/clim/sst.shtml
The build-up of heat east of Japan an in the north Atlantic is
continuing.
The cooling /upwelling off Peru has finished.
The Sothern Annual Mode /AAO spent first half of July positive,
accentuating the polar vortex.
The monthly pressure pattern and anomalies are
from http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html
During July the roaring 40s in the southern hemisphere moved north.
The Subtropical ridge across the south Indian ocean intensified.
Pressure anomalies for past month Shows the pressure rise in south
Indian ocean to be part of a roller coast with lows over Australia and
larger Highs SE of NZ. Deeper lows over Asia.
The 1015 isobar has shifted north to cover the south half of Tasman
Sea.
A 1025 Isobar has formed in the Indian Ocean.
TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is
from http://www.ospo.noaa.gov/products/ocean/tropical/tcfp/
After lashing the far northern Philippines as a Category-1 cyclone,
Tropical Storm Co-May drenched Okinawa before bringing heavy rain and
gales to the Chinese coast around Shanghai.
• Typhoon Krosa skirted the Japanese coast near Tokyo as a tropical
storm.
• Hurricane Iona and Tropical Storm Keli churned the open Pacific
Ocean, well to the south of Hawaii.
WEATHER ZONES
Weather Zones Mid-week GFS model showing isobars, winds, waves
(purple), rain (red), MT (Monsoonal trough), STR (Subtropical Ridge),
SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone)
Rain accumulation this week from Windy.com shows well defined SPCZ
between Solomon Islands and Tuvalu. Also, a frontal zone from Tonga
to Austral Islands (avoid).
Wind accumulation from windy.com shows zones of strong wind around L1
and L2 and a frontal zone along 20S (avoid).
LOWS and HIGHS
Low L1 near 40S 160E, well south of Tahiti is moving off to the
southeast but leaving behind lots of southerly swell getting as far as
20S.
HIGH H1 has been travelling across New Zealand last few days and
should continue a steady eastward migration along 45S
Low 2 is the one that affected the third rugby test Wallabies beating
the British and Irish Lions in Stadium Australia, Sydney … a game
delayed by lightning and influenced by rain. This Low is being
steered east along 28S… an uncommon path for a low. So, there is a
squash zone between it and H1 with strong easterly winds and large
swells at 30S. Avoid.
Further west over Australia several troughs should travel southeast
across Tasmania and the South Tasman Sea reaching southern NZ by end
of the week and a large High H2 moves into the Aussie Bight and then
follows those troughs.
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If you would like more details about your voyage, check metbob.com
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.
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