FORECAST DISCUSSION

TUESDAY 21ST APRIL 2026 – A.M SHIFT

TODAY:

Isolated convections were observed leading up to sunrise with the southeast portion of the AOR being the most favorable. Such is driven by the dominant moist Easterly wind flow prevailing at the low to mid-levels. Moisture and instability are hinted over the sounding profile with mostly stratified rain impacting the forecast zone during the early hours of today. CIMMS observations indicate the absence of any upper divergence, low-level vorticity and convergence being marked over our Samoa for the past 9 to 12 hours. However, a weak vortex signature present aloft with favorable [weak] wind sheared environment available for parcel entrainment. Thus, anticipate cloudy periods with isolated showers, brief moderate falls and a few thunderstorms mainly over elevated areas for today.

WEDNESDAY THROUGH SUNDAY:

Global weather models suggest that the easterly trade winds will predominate the region throughout this outlook period. An embedded weak short-wave trough at the surface may move across the group on Tuesday, likely bringing some showery conditions. The trades may persist at gentle to moderate intensity throughout the week, with a fresh wind surge entering the forecast area by Saturday. In addition, high-pressure systems are forecast to dominate the mid and upper levels during this period, suggesting subsidence aloft, which may inhibit widespread significant convection over the region. Therefore, mostly fine weather is expected across the group, apart from possible localised afternoon thunderstorms over the interior highland areas.

MARINE OUTLOOK:

The wave watch model predicts wave activities ranging well below the advisory and warning thresholds for the rest of the outlook period. Recent observations across the group’s coastal and marine waters indicate non-significant wave activity and may remain so, as mentioned above.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

Gafa, Sofeni, Uili & Namulau’ulu.