nz-weathergram
Date: Sun, 13 Sep 2026 23:22:09 +1200
Subject: Weathergram
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 13 September 2026
The PDO and how it mitigates a strong El Nino.
Ask the salmon. they know about climate cycles. Salmon are cold water fish.
When the sea is cold (<14C) they grow well, and when the sea is warm they
get underweight. Also, they are also anadromous, meaning they spawn in fresh
water
In NW America people depending on salmon have over the year observed
several patterns in the good years and the bad years. (Sadly, salmon
populations there have plummeted this century). The strong El Nino in
1957-58 triggered a symposium that linked a bad-salmon year to the weather
and sea-surface temperature. Then years later Bjerknes published the first
description on ENSO.
El Nino favours a warmer and drier winter in the Pacific NW along with
warmer ocean near the coast, so is bad news for their salmon with coastal SE
winds.
La Nina, with a NW coastal wind, is usually good news for their salmon.
Cooler and wetter spring/winters are best for Californian Salmon.
But there was NOT a good correlation between ENSO and Californian rainfall.
When Steven Hare was investigating the good-year/bad-year patterns in the
1990s he came across a paper plotting pink salmon catches in the Gulf of
Alaska with air and sea temperature measurements from 1925 to 1985. The
three timeseries rose and fell together - high until the mid-40s, then low
to mid 70s, then high again.
This hinted to another climate pattern sometimes mitigating and sometimes
reinforcing the ENSO. Some warm or cold phases of this pattern are lasting
20 to 30 years.
Steven joined forces with others (Mantua and Zhang)
and coined the term Pacific Decadal Oscillation or PDO in a paper that
appeared in 1997.
Now in September2026 the current El Nino is strong and getting stronger.
However, we are having a NEGATIVE PDO. This is mitigating the resulting
weather around California.
However, the Walker circulation is clearly located now over the central
Pacific, produced many low-pressure centres near the equator. The
MetService Streamline even had a Low directly on the equator in a recent
streamline analysis:
TROPICS
. Hurricane Lowell caused extensive damage and power failures across the
western Hawaiian Islands.
. Hurricanes Marie and Karina passed well to the west of Baja California.
. Japan was drenched by Tropical Storm Krovanh.
WEATHER ZONES
SPCZ is active from Solomons to northern Fiji/Tonga.
High H1 in Tasman Sea is moving to the NE and decaying.
The isobars over Coral Sea and near Fiji have been squeezed between this
high and the low pressures over the equator to north of Fiji= a windy start
to Musket Cove regatta week. However, winds there are expected to weaken by
Friday.
L1 is the broad and deep trough east of NZ which left NZ last Friday. On its
northern side is an area of light winds making its way eastwards across the
tropics. There is a convergence zone in this area with a line of
showers/drizzle crossing the southern Cooks next few days.
Low L2 is a broad trough that is expected to cross southern NZ on
Wednesday, central NZ on Thursday and then deepen into a Low over northern
NZ on Friday.
An accompanying zone of strong SW wind and swell NZ is expected to travel
north as far as Fiji on Saturday. Uncomfortable
High H2 is expected to travel NE from Aussie Bight to Brisbane area by end
of the week and then might stall in the mid Tasman Sea after that.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
>>>>>>>>>>>>>>>>
Subject: Weathergram
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 13 September 2026
The PDO and how it mitigates a strong El Nino.
Ask the salmon. they know about climate cycles. Salmon are cold water fish.
When the sea is cold (<14C) they grow well, and when the sea is warm they
get underweight. Also, they are also anadromous, meaning they spawn in fresh
water
In NW America people depending on salmon have over the year observed
several patterns in the good years and the bad years. (Sadly, salmon
populations there have plummeted this century). The strong El Nino in
1957-58 triggered a symposium that linked a bad-salmon year to the weather
and sea-surface temperature. Then years later Bjerknes published the first
description on ENSO.
El Nino favours a warmer and drier winter in the Pacific NW along with
warmer ocean near the coast, so is bad news for their salmon with coastal SE
winds.
La Nina, with a NW coastal wind, is usually good news for their salmon.
Cooler and wetter spring/winters are best for Californian Salmon.
But there was NOT a good correlation between ENSO and Californian rainfall.
When Steven Hare was investigating the good-year/bad-year patterns in the
1990s he came across a paper plotting pink salmon catches in the Gulf of
Alaska with air and sea temperature measurements from 1925 to 1985. The
three timeseries rose and fell together - high until the mid-40s, then low
to mid 70s, then high again.
This hinted to another climate pattern sometimes mitigating and sometimes
reinforcing the ENSO. Some warm or cold phases of this pattern are lasting
20 to 30 years.
Steven joined forces with others (Mantua and Zhang)
and coined the term Pacific Decadal Oscillation or PDO in a paper that
appeared in 1997.
Now in September2026 the current El Nino is strong and getting stronger.
However, we are having a NEGATIVE PDO. This is mitigating the resulting
weather around California.
However, the Walker circulation is clearly located now over the central
Pacific, produced many low-pressure centres near the equator. The
MetService Streamline even had a Low directly on the equator in a recent
streamline analysis:
TROPICS
. Hurricane Lowell caused extensive damage and power failures across the
western Hawaiian Islands.
. Hurricanes Marie and Karina passed well to the west of Baja California.
. Japan was drenched by Tropical Storm Krovanh.
WEATHER ZONES
SPCZ is active from Solomons to northern Fiji/Tonga.
High H1 in Tasman Sea is moving to the NE and decaying.
The isobars over Coral Sea and near Fiji have been squeezed between this
high and the low pressures over the equator to north of Fiji= a windy start
to Musket Cove regatta week. However, winds there are expected to weaken by
Friday.
L1 is the broad and deep trough east of NZ which left NZ last Friday. On its
northern side is an area of light winds making its way eastwards across the
tropics. There is a convergence zone in this area with a line of
showers/drizzle crossing the southern Cooks next few days.
Low L2 is a broad trough that is expected to cross southern NZ on
Wednesday, central NZ on Thursday and then deepen into a Low over northern
NZ on Friday.
An accompanying zone of strong SW wind and swell NZ is expected to travel
north as far as Fiji on Saturday. Uncomfortable
High H2 is expected to travel NE from Aussie Bight to Brisbane area by end
of the week and then might stall in the mid Tasman Sea after that.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
>>>>>>>>>>>>>>>>