FORECAST DISCUSSION
SUNDAY 19th APRIL 2026 – A.M SHIFT
TODAY:
Mostly clear skies have been observed across Samoa over the past 12 hours as easterly trade winds predominate. As high-pressure systems generally dominate all the atmospheric levels, convection remains suppressed over the region. The morning ascent from Pago (18/12z) indicates sufficient convective potential energy with a fairly dry vertical profile, and precipitable water reaching 52.63mm. Upper data also reveal a weak vorticity environment over the region, with a strong deep-layer wind shear. These atmospheric conditions suggest the development of afternoon convection, particularly over highlands, although subsidence aloft may limit further intensification of clouds. Otherwise, mostly fine weather is expected across most areas today.
MONDAY THROUGH SATURDAY:
A high-pressure system currently centred east of Australia is expected to move eastward, forcing the South Pacific Convergence Zone (SPCZ) eastward and away from the group. This synoptic weather pattern may allow the easterly trade wind regime to predominate throughout the week. At mid-levels, a high-pressure ridge may linger over the region during this outlook period, providing light steering flow, which suggests a lack of vertical disruption to convective development. In addition, westerly to southwesterly winds aloft are forecast to dominate the uppers through at least Monday, before an upper high develops over the region. Models also hinted a weak short-wave trough embedded along the easterly flow on Tuesday and Wednesday, which may bring some showery conditions across 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 24 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. Kalolo, P. Huch & S. Maualaivao.