SYNOPTIC DISCUSSION
FRIDAY 16th JANUARY 2026 AMSHIFT
TODAY:
Unsettled weather conditions persisted inside Samoa’s vicinity last night through the early hours of today as the trough of low pressure slowly enters our forecast area. Observations of satellite animation and latest sounding profile indicate moisture and instability remaining over our islands. Favorable wind sheared environment with a weak outflow in the uppers are additional mechanisms that may contribute to the onset of afternoon convections expected to develop as the synoptic feature increase cloudy and moist conditions across the island chain. Snapshots of TPW MIMIC indicate large values of precipitable water situated north where the trough is located. As observations of 10m winds remain light and from a northeasterly direction, advection of moisture for windward locations within the now-cast period will allow surface heating to occur before late afternoon. The SPCZ remains active over the western part of the SWP region with the developing low circulation maintaining its position south of Solomon islands within the past day. Models are hinting an increase in showery activities during the afternoon through tonight due to the aforementioned weather situation. Therefore, advisories for Heavy Rain and Flood are now in force for Samoa.
SATURDAY THROUGH WEDNESDAY:
The SPCZ will fluctuate over the western part of the SWP for the next 4 days and global model consensus agree with the potential of development of the low circulation centered to the south of Solomon Islands. The extended ridge to the north of the group will reside slightly near our area keeping the moist northerly wind flow over the area through the weekend until the start of the new week. Interesting weather is expected for the latter part of this outlook period, the aforementioned surface to mid level ridge will swerve over Fiji Group as the wind gradient near the invest area increase whilst moving across the Coral Sea by mid-week. The northwest wind flow will take over the last few days of next week increasing moisture and instability over our area as the upper diffluence hovers aloft, enhancing the outflow. MOGREPS 25mm/12h probability marks our area around this period as highly likely based on the latest update.
MARINE OUTLOOK:
The latest marine observations from Aunu’u and King Poloa wave buoys, as well as altimeter data, indicate that wave and swell heights remain well below 2 metres. Global wave models suggest that this wave trend is likely to persist throughout this outlook period. However, episodes of a northerly swell are recorded from the latest observations, which may bring periods of rough seas and strong currents through Friday, but are unlikely to exceed the advisory threshold of 2.5 metres.
ADVISORIES/WARNINGS:
VALID: HEAVY RAIN ADVISORY
VALID: FLOOD ADVISORY
Weather Duty Team:
Gafa, Sofeni, Baker & Tavana.