SYNOPTIC DISCUSSION

SATURDAY 31ST JANUARY 2026AM SHIFT

REST OF TODAY:

A low-level circulation that was formed within the South Pacific Convergence Zone (SPCZ) to the southeast of the island yesterday has been named Tropical Disturbance 08F (TD08F). As of 11:00 AM, this circulation was located approximately 390 km southeast of Apia and is expected to drift southwestward near Tongan island group with little intensification. An active convergence zone associated with TD08F is slowly entering the island, bringing developing northwesterly wind flow and heavy rainfall. Total precipitable water indicates a significant amount of moisture descending from the northwest. An upper-level low to the south contributes to strong upper-level divergence overhead, enhancing convective activity in the vicinity of Samoa. The unstable vertical profile of the atmosphere is likely to sustain unsettled weather conditions. Model consensus suggests that TD08F will maintain its southwestward movement away from Samoa; however, the active convergence will continue to bring wet and windy conditions. Strengthening northwesterly winds and heavy rain are anticipated for the rest of the afternoon.

SUNDAY THROUGH FRIDAY:

Global weather models suggest that the South Pacific Convergence Zone (SPCZ) will continue to influence Samoa’s weather through at least Monday of the upcoming week. A low-pressure system currently located east of Samoa may track across the south of the group by Saturday, drawing significant convections with strong northwesterly winds over the forecast area. This low-pressure system extends through the mid-levels, increasing instability loading and moisture advection over the region accompanied by deepening warm and moist northerly winds. Area of good upper diffluence is forecast to persist over the group during this period, further enhancing convective storm growth and development. This synoptic setting is likely to intensify deteriorating weather conditions across Samoa through early Sunday, maintaining the risk of flooding in rivers and low-lying vulnerable areas. In addition, a high-pressure ridge is forecast to establish north of Samoa by the new week, becoming the dominant synoptic feature.  This ridge is expected to suppress convective activities over the forecast area while keeping the SPCZ and associated convections further south through the remainder of the outlook period.

MARINE OUTLOOK:

The latest wave observations from Aunu’u and King-Poloa wave buoys, as well as altimeter data, signify wave heights exceeding 3 metres. This is mainly due to the convergence zone directing strongand gusty Northwesterly winds, maintaining elevated wave activity over our marine waters. The global wave models suggest that this weather system will keep these high wave activities over the forecast area through at least Monday of the upcoming week.

ADVISORIES/WARNINGS:

VALID: HEAVY RAIN WARNING

VALID: FLOOD WARNING

VALID: WIND WARNING

VALID: MARINE WARNING

Weather Duty Team:

LMSA, S. KALOLO & A. UILI