SYNOPTIC DISCUSSION
MONDAY 01stDECEMBER 2025 PM SHIFT

TONIGHT:

Partly cloudy spells were observed across the area of interest as the surface trough remains within our vicinity over the past 12 hours. Sounding profile was able to depict a near-surface stable layer [CIN] which prevented air parcels from rising towards the Level of Free Convection throughout the daytime. Moisture and instability presence within the atmosphere are sufficient for deep convections, however, lifting is the only mechanism absent for the formation and development of deep convective cells. The dry airmass from the western side of the upper trough now persists aloft with a strong signature of vorticity favorable for circulating  surface to mid level air flow. The water vapor view clearly presents this along with the update of CIMMS atmospheric motion vectors at the upper level. Models are suggesting a reduction in precipitation later tonight as the trough slowly resides southward of our island chain.

TUESDAY THROUGHSATURDAY:

The weather model consensus, as the trough of low pressure system slowly moves to the south on Tuesday, there’s a chance it could evolve into a weak circulation with a low-to-moderate chance of precipitation amount. Concurrently, the axis of the upper trough may hover over the surface system, which this synoptic setting it would potentially aid vertical cloud formation from the surface. Meanwhile, easing conditions may persist on the mid-week with the reduction in rainfall accumulation and may likely towards the conclusion of the outlook period. Periods of passing showers may likely to landfall as the southeasterly trades on Friday towards the latter day of this outlook period. Southeasterly into southwesterly aloft will likely to dominate the upper atmosphere by Thursday into the conclusion of the forecast period which corresponds to the slight mostly fine anticipated conditions.

MARINE OUTLOOK:
The current marine observations this morning across Samoa's marine and coastal waters show that the wave and swell heights remain below 2.5 meters. However, the most recent wave models forecast a high northerly swell moving from the north, which may impact the country's marine areas tomorrow and continue through Wednesday expected a wave period of more than 18s.

ADVISORIES/WARNINGS:
VALID: HEAVY RAIN WARNING

VALID: FLOOD ADVISORY

VALID: MARINE ADVISORY -  ALL OF SAMOA

Weather Duty Team:
Gafa, Niko, Uili & Tavana.