FORECAST DISCUSSION

SATURDAY 25th APRIL 2026 – A.M SHIFT  

TODAY:

Satelite imagery as of this morning indicates the active SPCZ located west of the region with major rainfall and thunderstorms activities. Meanwhile, experience clear skies periods as the persistence of the easterlies across the area of concern, with few patches of low-level cumulus congestus. The radiosonde profile depicted abundant low-level moisture content, deepening mean wind flowwith a weak-to-moderate instability. The upper level water vapor channels collectively indicated mid-to-upper level moisture. Coincidently, present weak wind shear environment this support vertical cloud formation. Henceforth, late morning through noon, the current satellite data showcase developed convective clouds with showers and possible thunderstorms, as the diurnal weather patterns slowly kicks in. Expect this weather condition may persist through the evening.

SUNDAY THROUGH FRIDAY:

Global weather models suggest that the trade-wind weather regime will persist across Samoa throughout this outlook period. By Saturday, a surge of 15-20 knots winds may move across the group; otherwise, surface trades are forecast to persist at 10-15 knots. A high-pressure system is expected to dominate the mid-levels, maintaining an easterly steering flow. The lack of a significant upper-level forcing mechanism suggests that cloud development will be largely diurnally driven during this outlook period. This synoptic pattern may induce a relatively dry airmass and subsidence aloft over the region, which may inhibit significant convective storm development and growth. Therefore, generally fair weather conditions are expected, with a chance of typical afternoon thunderstorms particularly over highlands and west of both large islands as sea breeze convergence kicks in.

MARINE OUTLOOK:

The latest marine observations from Aunu’u and King Poloa wave buoys indicate that wave heights continue to fluctuate below the advisory threshold of 2.5 metres. The wave watch models suggest that wave activities will persist well below the advisory threshold for the rest of this outlook period.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

AN, S. Kalolo & P. Hunch