Bobgram 13 Oct

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 Sunday 13 October 2024

Southwest Pacific Tropical Cyclone Outlook – October 2024

The NIWA and MetService assessment of tropical cyclone activity
indicates six to 10 named TCs could occur in the Southwest Pacific
from November 2024-April 2025.

The NIWA and MetService assessment of tropical cyclone (TC) activity
for the coming season indicates normal to below normal activity.
(Tropical cyclones are categorised in strength from 1 to 5, with 5
being most intense. Tropical cyclones that reach category 3 or higher
are classified as severe, with mean (10 minute) wind speeds of at
least 119 km/h.)
Six to 10 named TCs could occur in the Southwest Pacific from November
2024-April 2025. The long-term average number of named TCs per season
is around nine.
TCs have a significant impact across the Southwest Pacific, with the
season starting in November and lasting through April. For the coming
season, significant differences are expected between the western and
eastern halves of the basin.
The risk of impact from a TC is expected to be higher near the Coral
Sea, Solomon Islands, and Papua New Guinea, as illustrated in the
following map. Normal to reduced risk is anticipated in the central
and eastern part of the basin.


Watch the NIWA video at youtu.be/Jdy9lJ2tOv4

Tropical cyclone outlook summary for New Zealand

On average, at least one ex-TC passes within 550 km of New Zealand
each year. This season, the risk is considered normal-elevated.
If an ex-TC tracks close to the country, there is a near-equal
probability of it tracking to the east or west of the North Island
based on historical climate data.
Two out of five analogue years considered in this outlook had at least
one ex-TC passing within 550 km of the country.
Analogue years suggest that a decaying ex-TC entering the New Zealand
region could affect maritime and coastal areas around the North
Island, but an interaction with the South Island cannot be ruled out.
El Niño-Southern Oscillation outlook

As of early October 2024, sea surface temperatures across the eastern
and central equatorial Pacific Ocean are below average and close to La
Niña thresholds.
Atmospheric circulation patterns related to ENSO over French Polynesia
and northern Australia indicate neutral ENSO conditions as of early
October 2024.
Oceanic and atmospheric forecasts for ENSO suggest La Niña, of
weak-to-moderate intensity, has a 60-70% chance of emerging by
December 2024. La Niña conditions, should they develop, are likely to
persist through the back half of the TC season in February-April.

TROPICS
Hurricane Milton pummelled Florida's central Gulf Coast as a
Category-3 storm and the fifth hurricane to make landfall in the U.S.
this year. The storm brought storm surges, wind damage and record
rainfall.

• Hurricanes Kirk and Leslie churned the open Atlantic Ocean.

• Typhoon Krathon left two people dead after striking southern Taiwan.

• Tropical Storm Ancha formed in the Indian Ocean out of season (South
Indian Ocean cyclone season nominally open mid-November).

WATHER ZONES

The wind accumulation shows several zones of strong wind this week,
which cruising yachts should avoid this week

The South Pacific Convergence zone is building and shifting southward
across Vanuatu next few days. It is expected to form a Low L3 near
Tanna late on Wednesday and this Low should then travel quickly
southeast to be around 1004 over Minerva on Thursday and then quickly
away. AVOID. Associated trough should cross Tonga on local Thursday
with gusty northly winds.

Travelling to Australia: There is a small squash zone of 25kt SE winds
in the Coral Sea around Tuesday maybe Wednesday, and a south to
southeast wind change from a passing trough at Brisbane around
Thursday, otherwise it looks OK.

HIGHS and LOWS

HIGH H1 has been blocking movement and remains near 35S to south of
Tahiti.

Low L1 is crossing central NZ on Monday then expected to travel east
along about 40S.

A High currently in the central Tasman Sea is expected to travel NE
and fade near Norfolk Island

Low L2 is expected to form well offshore of Sydney on Monday then
travel NE following a High, and then fade away on Friday., leaving a
lull of light winds over New Caledonia for the weekend.

HIGH H2 is expected to travel into the South Tasman Sea 1032 by late
Tuesday then travel onto central NZ, maintaining an easterly flow
between Northland and the tropics this weekend and early next week.

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