SYNOPTIC DISCUSSION

THURSDAY 22nd JANUARY 2026 AM SHIFT

REST OF TODAY:

Cloudy periods with isolated showers, brief heavy falls and thunderstorms. Gusty winds can be expected during showers. Unsettled conditions will persist across the islands, with warm and moist equatorial north-westerly winds prevailing. An area of low pressure is extending a trough over the islands, sustaining the potential for a sudden deterioration in conditions along our coasts. The total precipitable water in the atmosphere has gradually accumulated and become more concentrated over the region, while also feeding into the low pressure system located further south, near the Southern Cook Islands. For today, the Heavy Rain Advisory and Flood Advisory remain in effect for all land areas.

FRIDAY THROUGH TUESDAY:

Recent analysis indicates that the South Pacific Convergence Zone (SPCZ) will be the primary weather driver for Samoa for the remainder of the forecast period. A surface high-pressure system, expected to centre east of Australia, will steer the ascent of the SPCZ and cause it to shift slightly north of Samoa from later tomorrow. Model consensus has consistently shown deteriorating weather conditions associated with this system, which is likely to prompt an upgrade to activated advisories, probably in the next issued forecast. The SPCZ is expected to remain nearly stationary just offshore to the north, extending its associated rain bands over the islands for the next several days. Coupling with an anticipated upper-level divergence aloft, this setup will enable and sustain unsettled conditions across the islands. Therefore, weather conditions are expected to deteriorate further in the coming days, and existing advisories may likely be upgraded to warning levels before the system's arrival.

MARINE OUTLOOK:

As of now, marine observational data from the Aunu’u and King Poloa wave buoys, along with satellite altimeter data, continue to indicate that wave and swell heights across Samoa’s coastal and marine areas remain well below 2 metres. Global wave models suggest this trend is likely to persist through at least Friday. From Saturday, increased wave activity may enter the forecast area and is likely to exceed 2.5 metres, reaching around 3 metres, due to wind-driven waves associated with the presence of the SPCZ.

ADVISORIES/WARNINGS:

VALID: HEAVY RAIN ADVISORY

VALID: FLOOD ADVISORY

Weather Duty Team:

MJS, Andrew Sofeni, Punipuao Huch & Ne'emia Tutasi.