SYNOPTIC DISCUSSION

FRIDAY 09th JANUARY 2026 AM SHIFT

REST OF TODAY:

The forecast for partly cloudy skies with isolated afternoon showers and a low chance of brief thunderstorms under north easterly winds is supported by a complex atmospheric profile featuring strong convective potential countered by significant suppression. Moist north easterly flow at low levels provides adequate moisture while satellite indicated convergence to the north offers a weak focus for ascent. Although mid-level analysis reveals a weak trough supporting weak synoptic lift and the sounding indicates very high CAPE exceeding 2000 J/kg favourable for severe storms, this instability is effectively capped by strong upper level convergence which promotes large scale subsidence and inhibits deep, organised convection. Therefore, thunderstorm development will be isolated and contingent upon strong localised forcing, primarily orographic lift over interior highlands, where any convections that form will be high based, pulse type, and capable of producing brief moderate falls, gusty outflows, and possible lightning, but are expected to be short lived due to the overarching suppressive environment aloft.

SATURDAY THROUGH THURSDAY:

While a deep surface trough and developing tropical low south of the Solomons will dominate the region, Samoa will remain on its northern, more stable flank, experiencing only few isolated showers and moderate easterly winds. At the mid-levels [500 hPa], weak troughing provides just enough lift to support afternoon convection, particularly over northern and eastern windward areas. Upper-level analysis [200 hPa] shows neutral to slightly divergent flow, inhibiting widespread organized ascent but allowing for diurnally driven showers. The main heavy rain and strong winds are confined well to the south near Fiji and Vanuatu, with the primary local impacts being passing showers, whereas an increase in showery activities from Tuesday onward as the low deepens southwest of the islands, tightening the pressure gradient with possibly enhanced showery activities.

MARINE OUTLOOK:

Recent conditions anticipated to be calm to moderate. Significant wave heights of 1 to 2 metres from a mix of local wind waves and easterly swells are expected. No hazardous swell from distant weather systems is predicted. Marine conditions are expected to remain stable throughout the outlook period. All model guidance and observational data agree that a significant swell event developing to the southwest will propagate on a northerly track, passing well north of the Samoan islands. Significant wave heights for Samoa are consistently forecast to remain in the 1 to 2.5 metre range, with no indication of swell heights reaching or exceeding the 2.5m advisory threshold from this system. Dominant swell directions are expected to vary between east and southeast, associated with local weather patterns.

ADVISORIES/WARNINGS:

NONE

Weather Duty Team:

MJS, Albert Niko, Aquinas Uili & Fuimaono Uili Namulau’ulu