SYNOPTIC DISCUSSION

SUNDAY 29thMARCH 2026 PM SHIFT

TONIGHT INTO TOMORROW:

The broad area of low pressures still existed across the vicinity, that characteristically display the active elongated trough of low pressure embedded within the South Pacific Convergence Zone (SPCZ). The sounding profile, depicted abundant moisture content, mid tropospheric dry slot, weak steering flow and instability. As for the upper atmosphere, mid-to-upper level water vapor channel captured a mid-to-upper level of sinking air just southwest of Samoa. Further, it compose of a weak wind shear with a good upper divergence aloft as the upper trough of low pressure located near the southwest. Thus, major system, continuously ushered unstable weather patterns, that triggered isolated convective rain, thunderstorms and gusty periods during rain this afternoon into the nighttime. The model consensus, suggested that the severe weather system to remain over the area of responsibility with possible periods of brief heavy falls and isolated thunderstorms.

TUESDAY THROUGH SATURDAY:

According to the model guidance, that the major system slowly shift to the south on Tuesday through Wednesday, allowing the moist north-to-northeast wind flow dominate the forecast area. Then on Thursday, the prevailing wind flow steadily increased in wind strength, that would hint moderate mean wind flow with moisture content and periods of gustiness in windward locations. Later on Friday through Saturday, the mean wind flow veered northeast-to-east as the severe weather system move southwestward, and such introducing the trade wind regime with brief showers.  In the upper level, the upper trough of low pressure may linger over the forecast area on Tuesday that would provide support at the surface system until Thursday where it will relocated to the southeast, with predicted weak wind shear and southwest-to-west winds.

MARINE OUTLOOK:

The current marine observational data continues to indicate that the wave and swell heights across Samoa’s waters are fluctuated below the 2.5 meter threshold, which poses no imminent threat. So, based on the global wave models on this wave trend, there’s a low-to-moderate chance it may prolong through the forecast period.

ADVISORIES/WARNINGS:

VALID: HEAVY RAIN WARNING

VALID: FLOOD WARNING

Weather Duty Team:

A. Liu, A. Niko, C. Baker, & N. Tutasi.