SYNOPTIC DISCUSSION

WEDNESDAY 21st JANUARY 2026 PM SHIFT

TONIGHT INTO TOMORROW:

In the past 12 hours, the trough of low pressure remains over Samoa, while convective activities concentrated to the northwest slowly dissipated within short-lived single cells over the central areas of both island. The sounding profile, depicted low-level moisture content and instability. In addition, the system’s extends through (850-700) mb an implication vertical cloud formation, yet the lack of the upper level system and strong wind shear.  Thus, it led to the easing weather conditions across the area of concern.

However, based from the latest model consensus which suggest increased precipitation amount through tomorrow, as the trough of low pressure continues to linger over the area of responsibility, coupled with a convergence zone may stationed to the north. The coupled systems, gradually shifted to the north of Samoa later tomorrow.

FRIDAY THROUGH TUESDAY:

Weather model, predicted that the SPCZ relocated near the area on Friday, as an area of high pressure centered east of Australia while propagating eastward. At the same time, a low level circulation focus to the south of the Southern Cooks descend southward whereas an established ridge of high pressure to  the north of Samoa. This forecasted synoptic setting, the SPCZ may relocate over our country on Saturday and likely to remain stationary within the vicinity throughout the outlook period. At this period, an upper diffluence steadily developed and could enhanced surface system. So, expect increase in significant weather activities. Induced large waves, strong winds and heavy rain activity. Henceforth, there’s a low chance for an upgrade is likely to issued products for all land areas of Samoa.

MARINE OUTLOOK:

As of now, the marine observational data from Aunu’u and King Poloa wave buoys, as well as altimeter data, continues to showcase that wave and swell heights across Samoa’s coastal and marine areas remain well below 2 metres. Global wave models suggest that this wave trend is likely to persist through at least Friday. From Saturday, increased wave activities may enter the forecast area and are likely to exceed the advisory threshold of 2.5 metres.

ADVISORIES/WARNINGS:

VALID: HEAVY RAIN ADVISORY

VALID: FLOOD ADVISORY

Weather Duty Team:

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