FORECAST DISCUSSION
SATURDAY 11th APRIL 2026 – A.M SHIFT
TODAY, INTO TONIGHT:
A moist easterly wind flow prevails across Samoa, directing patches of congestus clouds that bring cloudy periods with showery conditions that are moderate to heavy in some areas. The latest satellite data shows these clouds developing into thundery activities while approaching the group. The morning ascent from Pago (10/12z) indicates an unstable atmosphere with precipitable water reaching 59.97mm, favourable for convective storm development and growth. MIMIC Total Precipitable Water (TPW) imagery reveals this abundant moisture advection over the region. A weak easterly steering flow suggest slow-moving storms and a lack of vertical disruption in convective development. Relative vorticity field at 850mb also indicates a moderate vorticity environment over the forecast area, suggesting cyclonic curvature and convective initiation over the area. For today through tonight, expect cloudy periods with isolated showers, brief moderate to heavy falls in some areas and a few thunderstorms.
SUNDAY THROUGH FRIDAY:
Global weather models suggest that the easterly trade winds will predominate 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:
The latest marine observations from Aunu’u and King Poloa wave buoys indicate that wave heights occasionally exceeded 2.5 metres over the past 12 hours. These wave activities may continue to slightly increase above 2.5 metres mainly 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:
F. Kalapani, A. Sofeni P. Huch F.U. Namulau’ulu.