SYNOPTIC DISCUSSION
TUESDAY 10thMARCH 2026 PM SHIFT
TODAY INTO TONIGHT:
A trough of low-pressure remains just west of Samoa, while a moist northeasterly wind flow continues to persist across the group. This weather setup jointly induces unstable conditions over Samoa, keeping the risk of heavy downpours with strong gusty winds across some areas of the group. Satellite data indicates developing convective storms to the north and west of Samoa, moving over the area and bringing cloudy conditions and periods of heavy falls with gusty winds in parts of the group over the past 12 hours. The afternoon sounding from Pago (10/00z) reveals an unstable atmosphere and moist vertical profile with precipitable water reaching 66.31mm. In addition, deepening northeasterlies refine that moisture advection over the region, which is reflected on MIMIC Total Precipitable Water (TPW) imagery. Vorticity fields at 850-700mb indicate vorticity signals over the forecast area, under a weak to moderate wind shear environment. Strong southwesterly winds aloft persists, steering upper clouds and moisture over the islands. The lack of a significant uplift over the forecast area may result in easing weather through tonight, although heavy falls and a few thunderstorms are likely in some areas.
WEDNESDAY THROUGH MONDAY:
Global weather models suggest that the easterly trade winds will dominate the forecast area through at least Saturday. Model consensus hints that the SPCZ may fluctuate further south of the group in a suppressed and disorganized formation throughout this outlook period. Speed convergences along the easterly trade winds are expected to induce showery conditions with gusty periods this week, although predominantly fine weather is expected across most areas. In addition, a weak short-wave trough is forecast to move across the group on Saturday, but unfavorable environmental conditions may suppress the system. The lack of a significant upper-level forcing throughout this outlook period suggests that cloud development will be largely diurnally driven over the forecast area.
MARINE OUTLOOK:
The latest marine observations from Aunu’u, King Poloa wave buoys and altimeter data indicate that the wave and swell heights fluctuate below 2 meters, suggesting no imminent threat across Samoa’s marine waters. Global wave models suggest that wave activities will persist below the advisory threshold of 2.5 metres throughout this outlook period.
ADVISORIES/WARNINGS:
VALID: HEAVY RAIN ADVISORY
Weather Duty Team:
F. Kalapani, S. Kalolo, A. Uili & S. Maualaivao.