SYNOPTIC DISCUSSION

WEDNESDAY 08th APRIL 2026 PM SHIFT

TONIGHT AND TOMORROW:

A trough associated with Tropical Cyclone Vaianu is expected to result in an increase in shower activity from tonight through Wednesday morning. The upper-air sounding from this afternoon indicates an unstable atmospheric profile, which corresponds with convection observed in satellite data. Isolated showers are anticipated for tonight, with a slight chance of thunderstorms. Showers are expected to become scattered by morning as the trough weakens. Light winds and scattered showers are likely to persist through Friday. By Saturday, another trough is forecast to move into the area. Model data indicates that numerous showers will return during the weekend. However, as the trough weakens on Tuesday, rainfall is expected to decrease. Limited precipitation, with isolated to scattered showers, will persist through the end of the week.

FRIDAY THROUGH TUESDAY:

Numerical weather prediction models indicate a moderate to high probability of minimal rainfall throughout the outlook period. A ridge of high pressure extends over Samoa from the south, resulting in generally fine weather with showers primarily over the highlands. This ridge is expected to shift southward on Friday as a Category 3 tropical cyclone continues to move southeastward, with no anticipated impact on the Samoa Islands. The trade wind regime, or easterlies, is forecast to return, bringing showers along the prevailing wind flow from Saturday through Monday. Additionally, model guidance indicates an upper-level trough over the island chain this weekend, likely triggering rainfall.

MARINE OUTLOOK:

Recent marine observations from King Poloa, Aunu’u wave buoys, and altimeter data indicate that wave and swell heights are fluctuating around 2 metres. Global wave models project that wave activity will remain below 2.5 metres over Samoa’s marine waters until Saturday into Sunday. During this period, there is a low probability of significant wave heights entering Samoa’s southern marine waters.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

MJS, Fa’auiga Kalapani, Christopher Baker & Ne’emiaTutasi