Bobgram 6 June 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 6 July 2025

FNMOC is no more….

On June 25, 2025, the Trump administration issued a service change
notice announcing that the Defense Meteorological Satellite Program,
DMSP, and the Navy's Fleet Numerical Meteorology and Oceanography
Center would terminate data collection, processing and distribution of
all DMSP data no later than June 30. The data termination was
postponed until July 31 following a request from the head of NASA's
Earth Science Division.

The 2025 Atlantic hurricane season, which runs from June 1 to Nov. 30,
is forecast to be above average, with six to 10 hurricanes. The most
active part of the season runs from the middle of August to the middle
of October, after the DMSP satellite data is set to be turned off.
Hurricane forecasters will continue to use all available tools,
including satellite, radar, weather balloon and dropsonde data, to
monitor the tropics and issue hurricane forecasts. But the loss of
satellite data, along with other cuts to data, funding and staffing,
will make the forecasting harder.

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/y5BpNdbsX0E
Lows crossed NZ on 4-5, 12-13,20-21 and 27-28 June…. A weekly cycle
The Low on 27-28 brough heavy flowing to Tasman/Nelson/Marlborough
area and wind and rain damage to Taranaki.

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 as at 30 May
from psl.noaa.gov/map/clim/sst.shtml
The build up of heat east of Japan an in the north Atlantic is
concerning.
The cooling /upwelling off Peru is interesting.

The monthly pressure pattern and anomalies are
from http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html

During June the sub-tropical ridge in southern hemisphere has widened
and shifted north. The heat low over Asia has intensified and
pressures have fallen over Siberia.

Pressure anomalies for past month Shows lows forming around south
Australia. Also, higher than normal pressures around Indonesia.  
The 1020 isobar has disappeared off NZ and shifted north (and shrunk)
over Australia.
The isobars are closer together over the Southern Ocean in June than
they were in May .

TROPICS

The latest cyclone activity report

Barry was a tropical storm for only about 12 hours after it formed in
Mexico's Bay of Campeche. It brought moderate rain to northeastern
Mexico.
• Hurricane Flossie intensified rapidly off Mexico's Pacific coast as
Typhoon Mun and Dunas formed near Japan.

WEATHER ZONES

Rain accumulation this week from Windy.com shows well defined SPCZ
between Solomon Islands and Samoa.  Also a passing trough south of
French Polynesia .

The wind accumulation shows NO squash zones in the tropics, but there
is a windy passing trough east of New Caledonia and south of Fiji.
Also, a windy zone associated with the passing trough south of Tahiti.

LOWS and HIGHS

HIGH H1 is taking a southern route from South of NZ along 45S.

Low L1 is an amalgam of several smaller lows all under one large upper
trough.  Some of these are the remains of the East coast low that
thrashed Sydney last Thursday.  It gets onto the western side of the
upper trough and thus is steered NE towards 25S before then turning
south again mid-week.  This is likely to bring a few days of northerly
then westerly winds to islands in Southern Cooks… not nice.

Not shown on that Wednesday map is a weak east coast low forming off
Sydney tonight then fading in Tasman Sea on Tuesday but associated
front and westerly winds bring strong winds to Tasman Sea south of
30S.

L1 is followed by H2 from central Australia but H2 fades away in north
Tasman Sea.

The reverse is expected further south, with L2 from the Australian
bight moving south of Tasmania by mid-week and forming a secondary L3
on its NW shoulder/ L3 then deepens in 3 days and travels across NZ
next Friday and weekend, keeping with the weekly pattern.

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