SYNOPTIC DISCUSSION

THURSDAY 09thAPRIL 2026 AM SHIFT

TODAY:

Calm winds continue to impact the islands as the surface to mid-level ridge lies just southwest of the island chain. Throughout the earlier hours of today, the upper levels were mainly broken due to the prevailing southerlies aloft with less cloud cover present at the lower levels. Localized weather conditions observed yesterday are anticipated for today as calm winds dominated the lower troposphere during daytime. Sounding profile indicated unstable and moist atmospheric state persisting through the certain layers increasing chance of afternoon convections over elevated areas of both main islands. However, these convective activities may be short-lived as there is an upper convergence persisting at the uppers. Therefore, expect partly cloudy with some showers and a few thunderstorms likely, mainly over highlands for today.

FRIDAY THROUGH WEDNESDAY:

The movement of TC Vaianu through the mid-latitudes allows the abovementioned ridge to direct the easterlies across the forecast area in the upcoming weekend. Thus, maintaining stable weather apart from passing showers for Saturday and Monday of the new week. However, there is an upper trough predicted to landfall for the start of next week which may increase uplifting of air parcels especially during the afternoon time. There is also higher levels of PWAT hinted by the ECMWF model which may linger over the trade wind regime for the first half of this outlook period. The currently active TC systems [TC Maila and TC Vaianu] are predicted to weaken through the weekend and will pose NO threat to Samoa’s area of responsibility.

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 to increase slightly more than 2.5 metres over Samoa’s southern marine waters for tomorrow into Monday. During this period, there is a low probability of significant wave heights entering Samoa’s northern marine waters for this outlook period.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

Gafa, Niko, Sofeni & Maualaivao.