FORECAST DISCUSSION

TUESDAY 14thAPRIL 2026 – P.M SHIFT

TONIGHT:

Fair weather conditions have persisted across Samoa over the past 12 hours, apart from some showers over interior highlands due to afternoon cloud development, although mostly suppressed and thus shallow. The moist easterly winds continue to prevail at the surface over the region with a light and variable steering flow, allowing for vertical growth. The sounding trace from Pago this afternoon (14/00z) indicates sufficient convective potential energy, alongside a fairly dry vertical profile indicating limited cloud presence at most levels of the atmosphere. However, precipitable water remains sufficient, reaching 55.69mm, which is consistent with MIMIC Total Precipitable Water (TPW) imagery, which reveals ongoing moisture advection over the region. The lack of a significant surface synoptic lifting is evident in the weak vorticity environment. Additionally, southerly winds aloft are advecting a relatively cooler and drier air mass into the forecast area. Therefore, expect partly cloudy skies with some showers tonight, brief moderate falls possible in some areas.

WEDNESDAY THROUGH MONDAY:

The gentle to moderate easterly trade winds are forecast to dominate the surface through at least Thursday, with an embedded weak trough of low-pressure that may linger over the group on Wednesday and Thursday. A high-pressure system currently centred over southern Australia is expected to move across the Maritime, pushing the South Pacific Convergence Zone (SPCZ) near south of Samoa during the weekend, likely increasing showery conditions. Therefore, a broad area of low pressure may reside just south of the group, prompting the development of embedded low-pressure systems. Light and variable steering flow is forecast over the forecast area through Wednesday, suggesting the lack of vertical disruption in convective development. Northwesterly to westerly steering flow may predominate from Thursday, possibly enhancing moisture advection over the region. The abovementioned weak upper trough is forecast to exit through the north of Samoa by Tuesday, allowing strong southerly winds aloft to dominate.

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 gradually fall well below 2.5 metres through this week and may not pose serious wave-related hazards to the islands’ marine waters.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

F. Kalapani, A. Sofeni, P. Huch & S. Maualaivao.