SYNOPTIC DISCUSSION
WEDNESDAY 19TH NOVEMBER 2025 AM SHIFT

REST OF TODAY:

A trough of low pressure lies to west from Samoa – the system lies slow moving over the islands, maintaining cloudy and moist conditions. Although a break in deteriorating activities was experienced, Samoa remains vulnerable to sudden onset of showery activities. Therefore, the abovementioned warnings and advisories remains activated for all land areas. Recently, isolated convections now linger to the north of Upolu, and with the dominant aloft northerlies, shearing cold tops over both islands – now triggering showery activities. Conditions remains for the remainder of today.

THURSDAY THROUGH MONDAY:

Global weather models suggest that another trough of low pressure system is expected to be likely develop from the east of the forecast region on Thursday and is forecast synoptic system is anticipated to be transitioning into a low circulation by early Friday. This variability in the weather system is expected to maintain atmospheric instability and more abundant moisture over the region, potentially triggering severe heavy downpours, strong gusty winds and thunderstorms across the group. These anticipated intensifying convections may likely to be prolong over the group by the weekend as the converging of northwest and north-easterly winds likely over the area of concern likely by Sunday. The upper-level low from the upper trough likely to dominate the area of responsibility by Thursday into Friday which may be associated with the upper-level diffluence likely to continue providing significant dynamical forcing, enhancing convective storm development across the region.

MARINE OUTLOOK:
Elevated large waves and swells reaching more than 2.5 metres continue advance from the south of the group – due to a strengthening high pressure. These wave conditions are expected to prolong throughout the week. Therefore, the Marine Advisory continues to be in force for all marine waters of Samoa.

ADVISORIES/WARNINGS:
VALID: HEAVY RAIN WARNING

VALID: FLOOD WARNING

VALID: WIND ADVISORY

VALID: MARINE ADVISORY

Weather Duty Team:
MJS, Sasamamao Kalolo, Siala Maualaivao & Fuimaono Uili Namulau'ulu.