SYNOPTIC DISCUSSION
SUNDAY 15th MARCH 2026 PM SHIFT

TONIGHT AND TOMORROW:

Easterly winds continue to dominate the island group and influence the region. The dominance of easterlies generally brings warm weather, high temperatures, and high heat indices. Isolated cumulus congestus clouds are present along the main wind flow, while most areas remain mostly sunny. Radiosonde data show low-level moisture restricted near the surface, with CAPE of 1617 kJ/kg, moderate instability, stronger wind alignment from the surface to mid-levels, and some atmospheric instability. Diurnal pressure drops toward this evening, and solar heating reaches its maximum, inducing instability and leading to the typical afternoon peak in precipitation and thunderstorm development. However, although this scenario may have been the case, only limited showery activity was experienced. Although conditions are generally stable, afternoon showers and brief thunderstorms may occur over the highlands due to upper-level convergence or subsidence. These patterns are expected to persist through tonight into tomorrow as the prevailing winds continue. 

TUESDAY THROUGH SUNDAY:

Forecast models indicate minimal precipitation for the outlook period, with trade winds expected to prevail. Diurnal weather patterns may still develop across the region. The SPCZ will remain mainly west of the area, while moist easterly winds dominate. An upper trough is expected to move in from the north by late Wednesday, but the lack of a significant surface rain-maker will limit rainfall intensity. Moist easterly winds in the lower atmosphere may still produce occasional showers. Overall, expect mostly fine weather with some afternoon showers through the weekend and into early next week as the easterly wind flow continues.

MARINE OUTLOOK:

The latest marine observations from the Aunu’u and King Poloa wave buoys, as well as altimeter data, indicate wave and swell heights fluctuating around 2 meters, suggesting no imminent threat across Samoa’s marine waters. Global wave models suggest that wave activities will persist below the advisory threshold of 2.5 metres throughout this outlook period.

ADVISORIES/WARNINGS:
NONE

Weather Duty Team:
MJS, Albert Niko, Samuelu Tavana & Fuimaono Uili Namulau’ulu