FORECAST DISCUSSION

WEDNESDAY 13thMAY 2026 AMSHIFT

TODAY INTO TONIGHT:

As of now, the moderate easterlies still prevails across the vicinity, with a few fair weather cumulus streaming along the wind flow. Cooperatively, the sounding profile and total precipitable water animation both revealed persisted low-level moisture content over the area. Furthermore, it also depicted mid-to-upper level dry slot, weak instability and inversion layer at the lower-levels. What’s more, the west-to-southwesterly winds dominate in the upper atmosphere, which maintained the strong wind shear environment. With the decreased in cloud coverage, surface heating is certain and topographic effects, this may support afternoon showers or orographic precipitation only at highlands and windward locations and slowly eased through tonight.

THURSDAY THROUGH TUESDAY:

The numerical weather prediction, basically suggested that the easterlies is expected to predominate, as an area of high pressure located to the Tasman sea propagated to the east. On top of that, a weak low-level circulation formed at the southeast of the area of responsibility, it is projected to drift southeastward, causing the mean wind flow to be weakening on Friday through Saturday. But of the movement of the high, the weak SPCZ to the south may slowly near over Samoa on Sunday through Tuesday, with a low probability of accumulated rainfall. Yet during this period, no upper level system that could support the surface system. It is advisable to investigate further any upcoming changes.

MARINE OUTLOOK:

Generally, the current marine observational data continues to showcase that the wave and swell heights across Samoa’s marine waters are fluctuated 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:

A. Liu, L. I. Tuatipi, F. U. Namulau’ulu & N. Tutasi.