Bobgram 25 Jan

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 25 Jan 2026
An accumulated rain map for New Zealand for the past week is available
courtesy of MetService.com.
Its purple rain areas had several flooded areas and devasting landslips.
Some rain gauges got over 300mm rain.

The averaged isobars for last week show low pressure over Coral Sea and High
pressures south of Tasmania and southeast of Tahiti. Courtesy of the NOAA
map room.
This pattern collects moist air between Tahiti and New Zealand and feeds it
directly onshore in the northeast winds and smack onto the mountains of
northeastern North Island.

A trajectory analysis during this rain event shows where the air had come
from for a 3x3 matrix of spots around New Zealand (back tracking 5 days).
Courtesy of the Air Resources Laboratory at
https://www.ready.noaa.gov/index.php
Cold air from the south is shown to mingle with the moist air from the
east to produce this deluge.


TROPICS
• Minimal Tropical Storm Nokaen remained just offshore of the central
Philippines but brought locally heavy rainfall to some coastal areas of
Luzon.
• Cyclone Dudzai skirted the remote Indian Ocean island of Rodrigues as a
tropical storm before dissipating to the south of Réunion and Mauritius.
• Cyclone Luana made landfall over northwest Australia.


WEATHER ZONES

Rain accumulation this week from Windy.com above shows a well-defined
monsoonal trough where the South Pacific convergence zone usually sits.
There are NW winds on the northern side of this trough and southeast winds
on the south side.
Wind accumulation from windy.com above shows bursts of wind associated with
the three tropical lows.
Highs and LOWS
Tonight and on Monday and Tuesday, a deep low L1 south of Chatham Islands is
bringing a south to Southwest flow to NZ,
with showery westerly winds over the northern third.
This is followed on Wednesday with a passing High H1, and then a series of
fronts for a few days
and then another High H2 travelling east along 40S and crossing Tasmania on
Friday.
There are three main tropical lows this week. L2 is expected to bring wind
and rain to southern cooks especially around local Thursday and Friday.
L3 is havering around Vanuatu for a few days and then may move towards Fiji
and Tonga late this week/early next week.
And L4 is the remains of Luana, staying as a monsoonal low over central
Australia.

A moderate heat wave is expected to remain over southeastern 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.
>>>>>>>>>>>>>>>>

Bobgram 18 Jan

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 18 Jan 2026

This weekend we had damaging "flash flood" in Sydney and another around
Whangarei

Here are some Key Findings on Hail Trends from The European Severe Storms
Laboratory at essl.org
. Fewer, Bigger Hailstones: Climate change creates stronger updrafts
and more moisture, allowing hailstones to grow larger, even as overall hail
frequency might decrease in some regions, notes a study in Nature Climate
and Atmospheric Science.
. Increased Damage: Rising losses are due to a mix of bigger hail and
more buildings/infrastructure in vulnerable areas (e.g., US, Australia),
making them more susceptible to damage.
. Regional Differences: Europe shows the strongest increase in very
large hail frequency, while some Southern Hemisphere areas see declines
. Record-Breaking Events: The US has seen record-breaking reports of
large hail in recent years (2023, 2024), exceeding previous highs
significantly.
What's Driving These Changes?
. Atmospheric Moisture: More humidity near the surface fuels stronger
thunderstorms, increasing hail size.
. Temperature & Instability: Warmer air supports powerful updrafts
that keep hail suspended longer, allowing it to grow.
. Socio-Economic Factors: More development in hail-prone zones (like
coastal Australia) significantly increases potential losses, even more than
just the weather changes.
What Does This Mean for the Future?
. Expect more powerful, damaging hailstorms in some areas, with
significant economic impacts.
. Insurance, building codes, and urban planning will need to adapt to
this growing risk.


TROPICS

. Australia's northern Queensland coast was drenched with some of the
heaviest rain since 1916 from Tropical Storm Koji and its remnants.
. Cyclone Dudzai, which briefly reached Category-4 strength, formed over the
central Indian Ocean. Cyclone Nokean is hovering east of the Philippines.
A new tropical depression name with token name 94P has been picked up by the
computer models expected to travel steadily to southeast reaching Northland,
New Zealand on Thursday.


WEATHER ZONES

Rain accumulation this week from Windy.com above shows well defined tracks
of rain associated with a few Lows L1 and L2 described below.

Wind accumulation from windy.com above shows tracks of wind associated with
Lows L1 and L2. Northern NZ seems to be a place to AVOID this week .
Highs and LOWS
The Low L1 to east of Northland tonight which was responsible with
yesterday's deluge near Whangarei is expected to travel east until Wednesday
and then stall and maybe travel to SW if caught in the circulation around
L1.
The Tropical depression L2 tonight in the Coral Sea may well earn a Cyclone
name soon and is expected to travel southeast reaching northern NZ on
Thursday. Avoid.

Another low over inland Australia is expected to travel slowly east this
week.

The subtropical ridge is this week well south of its normal position. Highs
are travelling east along around 45S. High H1 is expected to squeeze past
southern NZ on Monday to Wednesday/ High H2 should spread east into the
Sussie Bight reaching Tasmania on Friday.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
>>>>>>>>>>>>>>>>

Bobgram 11 Dec

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 11 Jan 2026
Last year's New Zealand weather.
Illustrated version has a time-latitude plot of the air temperature measured
over a north-south slice of Aotearoa/ NZ as it travelled through 2025.

The land silhouette is provided to help relate the latitude axis to your
place. It clearly shows temperature is cooler further south and during
winter. This time section makes a "bar-code" graph which reveals the annual
trend and the daily variation. It gives a rough indication of the extremes
and provides a visual image for quick comparison with any another year to
see seasonal variations.
Here below is what we had in 2024.
Compared with 2024, 2025 was cooler with some blue getting to the far north
in winter.

Looking at a similar diagram for the barometric air pressure provides a
graph that combines all the daily weather maps into one image. This produces
a more random looking barcode. The yellow and red lines correspond to
passing HIGHS on the weather map, and the blues show the LOWS or
depressions/storms. The scale is in Pascals, divide this by 100 to get
hectoPascals/millibar.

This has more red in it than last year, with the months from April to August
being mostly marked with passing Highs on the weather map.
The rain image below is probably the most interesting as it highlights the
dry periods in Northland last February to April, wetness from May to October
and dry from October to mid-December, then a wet Christmas/New year.

Bob McDavitt
TROPICS

Tropical Cyclone GRANT, after crossing almost the entire Southern Indian
Ocean , faded on approach to Madagascar.
Iggy and Jenna formed south of Java and faded quickly. Dudzai is currently
in South Indian Ocea,
Also KOJI formed yesterday and is now fading after making landfall in
Queensland,

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 above shows well defined
monsoonal trough where the South Pacific convergence zone usually sits.
There are NW winds on the northern side of this trough and northerly winds
across the equator as far east as 180. If these winds get further east then
they may disrupt the cooler than normal surface water that marks the current
weak La Nina.


Wind accumulation from windy.com shows bursts of wind associated with the
three tropical lows and another well to east-southeast of New Zealand..

Highs and LOWS
A trough is crossing New Zealand tonight/early Monday, followed by High H1
with a few days of dry weather. Then High H1 travels steadily off to the
east along around 40S.
Three tropical lows are expected to form along the SPCZ/Monsoonal trough
this week. L1 affecting Tonga, L2 affecting Vanuatu and New Caledonia
(maybe travelling south next week), and L3 the remains of TC KOJI settling
in as a heat trough over central Oz..

A heat wave is expected to continue over Australia, with the peak heat
travelling to NW to north parts of WA between Broome and Karratha by end of
the week.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
>>>>>>>>>>>>>>>>

Bobgram 4 Jan 2026

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 4 Jan 2026
A review of last month's weather
Here is a link to a YouTube clip giving an animated loop of the isobars and
streamlines
For the month of December youtu.be/GoVdw1VqSZk

Australia had several heatwaves during December 2025. In New Zealand a cold
pool entered the Tasman Sea a few days before Christmas and then fed intense
thunderstorms over the country until a few days after New yea . Intense
winds on 30 Dec produced widespread damage around my place but none in my
village

The 500hPa heights and anomalies shows that prolonged upper low over Tasman
sea late in the month
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 show
that the La Nina cool waters are relaxing. The intense warm pool that was
from Coral sea to New Zealand has shifted east and weakened a little.

Average isobars for past month (below)
From http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html show that the
subtropical ridge in the Southern hemisphere has weakened and turned trough
over New Zealand. The low pressure band over the Aleutian Islands has
weakened.


Pressure anomalies for past month (below)
From https://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html show that the
anomaly pressure pattern for December shows the large low breeding area
over New Zealand. The 1010 line has shifted north from Dunedin to
Auckland.


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 Cyclone GRANT spent last week crossing the South Indian Ocean.
There is increasing potential for a cyclone to forma around the north coast
of Australia.

WEATHER ZONES

Rain accumulation this week from Windy.com above shows well defined
monsoonal trough over north end of Australia and a track of rain southeast
from Fiji due to a couple of lows. Wet over the Southern Alps due to passing
fronts and mainly dry in the High over north Tasman Sea and North island.
Wind accumulation from windy.com above shows windy areas associated with
low pressures over northern Australia with monsoonal NW winds getting as far
as Solomon Islands and SE winds over the Coral Sea.

Highs and LOWS
Low L1 left New Zealand today and is expected to travel off to the east.
Low L2 is tropical feature that was over Fiji today and is expected to go
southeast. It may deepen between 30 and 40S late in the week.
High H1 now over Chathams is expected to travel off to the east /northeast
at a steady rate.
High H2 now in the Tasman Sea is expected to take its time travelling east
across North Island this week.
A wet and windy monsoonal trough is sitting over north end of Australia and
expected to brew tropical lows L3 over Gulf of Carpentaria and L4 over NW
Australia late this week. 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.
>>>>>>>>>>>>>>>>