SYNOPTIC DISCUSSION

MONDAY 06thAPRIL 2026 AM SHIFT

TODAY:

A moist easterly wind flow continues to prevail across Samoa, while a convergence zone lies just south, bringing clouds and some showers in parts of the group. Satellite data this morning indicates active convection to the further west of Samoa, with the convergence zone linked to Tropical Cyclone Vaianu (CAT 1) centred northwest of Fiji. The morning ascent from Pago (05/12z) shows strong atmospheric instability with a fairly moist vertical profile where precipitable water reaches 58.79mm. Relative vorticity fields at 850mb and 700mb reveal a weak vorticity environment over the forecast area with a strong deep-layer wind shear. In addition, the upper data indicate the lack of a significant upper-level forcing over the region. Therefore, expect cloudy periods with some isolated showers and a few thunderstorms possible.

Tropical Depression 11F (TD11F) has intensified and named Tropical Cyclone VAIANU (Category 1) this morning at 1:00 am. TC Vaianu lies to the northwest of Fiji, moving south to southeastward. The cyclone is expected to continue tracking southeastward while intensifying over the next 24 hours. TC Vaianu poses no direct threat to Samoa

TUESDAY THROUGH SUNDAY:

Global weather models suggest Tropical Cyclone VAIANU will continue its southeastward movement as a strengthening high-pressure ridge builds from the north. This cyclone is not expected to directly impact Samoa throughout this outlook period. Ensemble and deterministic models continue to indicate minimal precipitation activity across Samoa as the aforementioned ridge becomes the dominant weather feature in the new week. The lack of a significant mid to upper level lifting over the forecast area during this period suggests that cloud development will be largely diurnally driven.

MARINE OUTLOOK:

The latest marine observations from King Poloa, Aunu’u wave buoys, and altimeter data indicate that wave and swell heights fluctuate around 2 metres. Global wave models suggest that wave activity may occasionally exceed 2.5 metres over Samoa’s marine waters during this outlook period.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

F. Kalapani, L. Tuatipi, P. Huch & C. Baker.