FORECAST DISCUSSION

FRIDAY 01stMAY 2026 PM SHIFT  

TONIGHT INTO TOMORROW:

A weak trough of low pressure system, initially located closely to the northeast of Samoa in the afternoon, now lingers within the vicinity, bringing isolated low-level cumulus congestus along the wind flow resulted to showery activities early evening and through tonight. In the afternoon, surface heating steadily took place over the landscape, coupled with topographic effects of both islands. In addition, both the sounding profile and precipitable water channel agreeably revealed sufficient moisture content, deepening weak wind structure, weak steering flow, and moderate instability. Thus, these atmospheric conditions were aligned, which led to the formation of convective clouds within the area of responsibility, inducing showers and thunderstorms, yet short-lived. On that note, since the present mid-to-upper dry slot that correlate with the positive vorticity, which hinders vertical cloud growth which subsided in the evening. Later on, the wind flow gradually veered northeast, followed with a line of low-level congestus clouds until later tonight, depositing periods of showers. For tomorrow, model guidance predicted showery activities with a potential of moderate falls, as the trough of low pressure slowly drifted to the west. So, anticipate cloudy periods with scattered showers. Expect moderate falls and a few thunderstorms.

SUNDAY THROUGH THURSDAY:

Numerical weather models, evinced that the trough of low pressure shifted further to the west, and wind flow become easterlies on Sunday. But slowly veered from the southeast, as a developed SPCZ gradually established to the south of Samoa on Monday through Tuesday, and is likely to extend rainfall activities over the group during the new week. The steering flow during this period is expected to remain light to gentle, suggesting the lack of vertical disruption in cloud development. Additionally, strong southwest to westerly winds aloft may persist over the region, and the lack of a significant upper-level forcing suggests that convective storms will be largely diurnally driven during this period.

MARINE OUTLOOK:

The latest marine observations from Aunu’u and King Poloa wave buoys indicate that wave heights continue to fluctuate below the advisory threshold of 2.5 metres until Wednesday in the new week. Where wave watch models suggest that there’s a low probability of a combined wind waves activities may impact the Samoa’s marine waters. So, it is advisable to monitor carefully and investigate further changes.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

A. Liu, A. Sofeni & A. Uili.