FORECAST DISCUSSION

WEDNESDAY 15th APRIL 2026 – P.M SHIFT

TONIGHT:

A moist easterly wind flow continues to prevail across Samoa, aiding the development of single cells over the interior highlands during the afternoon. Clidesk portal indicates rainfall observations exceeding 5mm within 5 minutes from these convective development, otherwise fine weather has been observed across most areas. The afternoon ascent from Pago (15/00z) shows strong atmospheric instability with a fairly dry vertical profile and precipitable water reaching 54.62mm. MIMIC Total Precipitable Water (TPW) imagery reveals this sufficient moisture advection over the region. In addition, high-pressure systems dominate the mid- and upper-levels of the atmosphere, inducing some subsidence aloft over the forecast area. For tonight, expect partly cloudy skies with some brief showers possible.

THUSRDAY THROUGH TUESDAY:

Global weather models suggest that gentle to moderate easterly trade winds will dominate the surface through at least Thursday. A high-pressure system currently centred east of Australia is expected to move eastward, pushing the South Pacific Convergence Zone (SPCZ) near south of Samoa during the weekend, and is likely to bring showery conditions over the group. A high-pressure ridge may linger over the region during this period, providing light, variable steering flow, suggesting a lack of vertical disruption to convective development. In addition, southwesterly to westerly winds aloft are forecast to dominate the uppers through at least Sunday, before an upper high moves over the region. These synoptic weather patterns may inhibit significant widespread convection over Samoa, although moderate to heavy falls are still likely in parts of the group.

MARINE OUTLOOK:

The latest marine observations from Aunu’u and King Poloa wave buoys as well as altimeter data indicate that wave heights have fluctuated below 2 metres over the past 12 hours. These wave activities are forecast to persist throughout this outlook period, posing no significant wave-related hazards to the islands’ marine waters.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

F. Kalapani, S. P. Kalolo, A. Sofeni & N. Tutasi.