FORECAST DISCUSSION

FRIDAY 10th APRIL 2026 – P.M SHIFT

TONIGHT AND TOMORROW:

The ridge of high pressure has remained ever persistent over the group – recent wind observations show a veering wind change towards the easterly. Sounding observations of the atmosphere have shown persistent instability and increased moisture abundance, which have aided the onset of thundery and showery activity observed in the afternoon. Relative vorticity at 850 mb indicates a shallow vortex near the lower atmosphere, concentrated to the southeast, extending eastward to the Manu’a group and the whole of Upolu, suggesting lingering instability within the forecast area. Observations of each layer of the atmosphere from CIMSS indicate a dominant high pressure over the group; however, the latest observations now indicate the migration of a warm equatorial northerly air mass, pushing the high pressure eastward, which may enable the availability of possible showery activities for tonight and tomorrow, likely to couple with localised effects from late tomorrow afternoon into the evening.

SUNDAY THROUGH FRIDAY:

Global weather models suggest that the easterly trade winds will predominate over Samoa throughout this outlook period, with a series of short-wave troughs passing across the group. This synoptic pattern may induce showery conditions over the forecast area, with the potential for moderate to heavy falls in some areas starting from Saturday. The easterly steering flow is forecast to be gentle to moderate during this period, implying minimal vertical disruption to convective storm development and growth. In addition, an upper trough approaching from the west is expected to lie near Fiji by Sunday, bringing upper diffluence that may enhance cloud development through at least Wednesday of the new week. This upper-level system is forecast to exit through the north by late Wednesday while dissipating.

MARINE OUTLOOK:

Recent observational wave data show wave heights ranging from 2 metres at most, mainly across Samoa’s marine waters. However, wave watch models indicate that wave activity may slightly exceed 2.5 metres over the southern marine waters from Saturday through at least Monday of the new week. During this outlook period, there is a low probability of significant wave heights entering the northern marine waters. Although this may be the case, activities may not pose serious wave-related hazards to the group’s marine waters.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

MJS, Sasamamao Kalolo, Siala Maualaivao & Christopher Baker.