FORECAST DISCUSSION

TUESDAY 12th MAY 2026 PMSHIFT

TONIGHT INTO TOMORROW:

Easterly trades remain prevalent across the islands in the afternoon with only a few short-lived single-cell cumulonimbus clouds observed to the west of the major airport. None of the AWSs captured significant rainfall amounts during daytime as verified by the CLiDEsc portal. Mostly fine weather were experienced across more than 80% of the country and the vertical profile of the atmosphere with reference to the sounding trace clearly presents drier mid-atmospheric conditions with moisture concentrated near the surface. Apia AWS recorded more than 20 knots gust around 3.30pm as episodes of moderate Easterlies entered the area before sunset. Based on the current model updates, the ACCESS model are over forecasting precipitation amounts as well cloud coverage as expected as we are still within the transition period. However, the trade wind pattern is expected to dominate through tomorrow with minimal showers and breezy weather conditions.

THURSDAY THROUGH TUESDAY:

Global weather models continue to indicate an easterly wind flow across the islands during the outlook period with localized afternoon convection mainly over inland areas. However, a weak surface low – level circulation is predicted to develop southeast of the group on Friday. This synoptic setup is expected to weaken the surface easterly winds through Saturday. A high pressure system located over the Tasman Sea is forecasted to generate southeasterly winds of 15 – 20 knots just south of Samoa over the weekend. A convergence of southeast and easterly winds will likely increase instability and moisture over the forecast area for the start of the new week. The eastward movement of the above mentioned high pressure will likely strengthen the pressure gradient leaving room for the development of a low – level circulation over the Fiji group.

MARINE OUTLOOK:

The latest marine observations from Aunu’u and King Poloa wave buoys, as well as altimeter data, indicate that wave heights continue to fluctuate well below 2 metres. However, a southwesterly swell event is anticipated to enter our southern seas by the end of the week as an intense high-pressure system stationed over the Tasman Sea advances eastward. JMA predictions are hinting at a 30% chance of elevated swells and waves of more than 3 metres during this period and may prompt the issuance of a marine advisory if wave models persist in the next day. Furthermore, tide table predictions are hinting the peak tide of May on Sunday at 06:10am which will likely elevate swells for mostly our Southern Seas.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

S. Gafa, S. Kalolo, P. Huch & C. Baker