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 2 March 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 at
youtu.be/R1DQQPwkNYE

During February the climate modellers agreed the Pacific is in ENSO
neutral territory. The MJO travelled across the South Pacific during
the month activating the South Pacific Convergence zone and forming a
series of 7 tropical lows with 3 of them becoming cyclones in the last
week.


The 500hPa heights and anomalies shows last month's typical ridge
/trough pattern, after a troughy January.

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 fading blue tongue along the central Pacific shows we are in ENSO
neutral territory.

Average isobars for past month (below)

From http://www.psl.noaa.gov/map/images/fnl/slp_30b.fnl.html


The Aleutian low and Greenland low have deepened.

The subtropical ridge in the Southern hemisphere has recovered after
its December extreme.

Pressure anomalies for past month (below)


The anomaly pressure pattern highlights these differences.


The 1015 isobar has expanded to cover NZ.

Ridge axis seems to have moved north of Tasmania.

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/


Cyclone RAE caused some crop damage in Fiji.

Cyclone SERU went over mainly open water between Vanuatu and Fiji.

ALFRED is a slow mover currently going south and MIGHT go inland near
Brisbane mid-week.

Cyclone BIANCA formed off northwestern Australia. Cyclone Garance
started near Réunion as Cyclone Honde threatened southern Madagascar.

WEATHER ZONES
Rain accumulation this week from Windy.com shows heavy rain from Tonga
to Niue and with ALFRED.
Wind accumulation this week from Windy.com
The wind accumulation shows trails of wind mapped out by ALFRED and L1

LOWS and HIGHS

Low L1 now near Fiji is the remains of SERU and is moving slowly east
.

ALFRED is moving slowly south and MIGHT go inland late in the week
near Brisbane.

HIGH H1 now over North Island is moving off to the ESE.

This allows an active cold front to travel NE over NZ on Monday and
Tuesday and then form a Low L2 near Chathams on Wednesday with a
strong SE flow over NZ.

That should be followed by H2 now in Australian Bight and travelling
east across South Tasman mid-week then onto NZ for the weekend.

Low L3 should form near Bass Strait on Wednesday, followed another
HIGH H3.

Low l4 should remain slow-moving over inland Australia, but the
monsoonal trough is rather dry this week.

Gulf of Panama: A useful NE flow for starters

Galapagos: A low has formed to the SW and there is a CONVERGENCE ZONE
with squalls over the group and another between 6 and 9S from 95W to
106W

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