SYNOPTIC DISCUSSION
SUNDAY 08th MARCH 2026 AM SHIFT

TODAY:

Unstable atmospheric conditions persist over Samoa as a trough of low-pressure remains just south of the group, coupling with a prevailing moist northerly wind flow. Satellite data indicate developing major convection to the south of Samoa, with upper clouds being steered over the group by the strong southwesterly aloft. The morning ascent from Pago (12z) reveals a moist and unstable atmosphere with deepening northerlies refining that warm and moist airmass advection over the region. MIMIC Total Precipitable Water (TPW) imagery well reflects significant moisture advection over the forecast area. In addition, upper data indicate significant low-level vorticity and a weak wind shear environment just south of the group, which corresponds to the position of active convective storms to the south. Patches of congestus clouds streaming toward the group along the wind flow may contribute in periods of rainfall activity today. For today, expect isolated showers with heavy falls in some areas and a few thunderstorms. Gusty winds are also expected during heavy showers.

MONDAY THROUGH FRIDAY:

Global weather models suggest that the aforementioned low-pressure trough will continue to move southward, as a weak high-pressure ridge builds over the group. Model consensus hints that the SPCZ may fluctuate over the forecast area in a disorganized formation throughout this outlook period. In addition, a weak short-wave trough is forecast to move across the group on Monday, bringing showery conditions with the potential for periods of moderate to heavy falls. From Tuesday, speed convergences along the Easterly trade winds are expected to induce showery conditions in the upcoming week, with surface winds potentially exceeding 25 knots occasionally. 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 at 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, S. Maualaivao & F. Namulau’ulu.