SYNOPTIC DISCUSSION

SATURDAY 28th  MARCH 2026 AM SHIFT

TODAY INTO TONIGHT:

A collection of satellite channels, variously defined that the major rainfall and thunderstorms  focus slight to the north which resulted to sunny breaks, even though the active trough of low pressure embedded within the SPCZ which remains over the vicinity of Samoa. In detail, it is a broad area consist of several formed low pressure systems across the area of responsibility based on the current pressure charts from the Fiji met office. Atmospherically, the sound profile signify abundant moisture below the 500 hPa, a present mid tropospheric dry slot, and moderate instability. In addition, the 850 vorticity relative field indicate a good cyclonic signature an implication of vertical cloud growth, weak steering wind flow coupled with the diurnal weather pattern during the afternoon. Further, persisted upper level moisture, that correlated to a upper divergence aloft, and weak wind shear environment supporting the system at the surface. Expect this weather condition to persist through tonight, so the heavy rain warning and flood advisory remains in effect for all land areas of the country.

SUNDAY THROUGH FRIDAY:

The global model consensus, suggested that the severe weather system may continue to linger across the forecast area through Tuesday, which sustaining accumulated showers and thunderstorms, potentially affecting rivers and low-lying areas. Furthermore, deterministic models hint a possible low-level circulation may gradually formed to the west of Samoa, with a low chances of wind strength reaching moderate-to-fresh. On that note, in this period a upper trough approaching from the southwest, directing northwesterlies that would maintain support for the surface system. Then on Wednesday through Friday, an elongated ridge of high pressure stretches from the southeast, shifting the significant the system through the west as the prevailing wind flow becomes easterly with moisture content.

MARINE OUTLOOK:

Generally, the observed marine data show that wave and swell heights (waves: surface water movement; swells: longer-period waves from farther away) across Samoa’s waters are still below the 2.5 metre threshold, so there is no threat. Wave models suggest this will continue for the forecast period.

ADVISORIES/WARNINGS:

VALID: HEAVY RAIN WARNING

VALID: FLOOD ADVISORY

Weather Duty Team:

A. Liu, A. Sofeni, C. Baker, & S. Tavanā.