FORECAST DISCUSSION

SATURDAY 16thMAY 2026 PMSHIFT

TONIGHT INTO TOMORROW:

The southeasterlies continued to prevail over the area of responsibility, with isolated cumulus congestus from the south, as the weak SPCZ slowly moving near Samoa, bringing moist and cloudy conditions. In the upper atmosphere, observed strong westerlies which induce strong wind shear environment, hindering vertical cloud growth to the surface that leads to overshooting cloud tops. As a result, this aligned with the water vapor image capturing present upper-mid moisture across the country. So, such upper weather patterns does not promote surface enhancement, yet the sounding profile and total precipitable both depicted abundant low-level moisture, weak dry slot and a moderate instability. With this, coupled with localized and topographic effects in the afternoon, it triggered short-lived convective clouds mainly highlands and elevated windward areas as shown by various satellite images, that generate a peak rainfall value of 9.2 mm from Afiamalu, then gradually eases in the evening. For tomorrow, expect the weak SPCZ to closely locate near Samoa, bringing periods of showery activities and a few thunderstorms in some areas. Furthermore, there’s a chance of moderate to fresh southeasterlies mainly to the southern district with a some gustiness.   

MONDAY THROUGH FRIDAY:

Numerical weather predictions, forecasted showery activities to continued on Monday until Tuesday afternoon, as the previously stated high pressure continues to move eastward, shifting the weak SPCZ slightly to the south of Samoa. In this time frame, the persisted wind flow will swerve from the northeast-to-north then northwesterly on Wednesday into Thursday as a broad area of low pressure formed over Fiji’s area, while tracking southeastward. As the system’s course continues to the predicted pathway, expect the mean wind flow to become slightly weak, with showery and thundery activities are mainly driven diurnal variation atmospheric condition.

MARINE OUTLOOK:

The current marine observations still signified wave heights from the southern marine areas of Samoa, fluctuating between 2-2.5 metres. Meanwhile, a high-pressure system is now located over New Zealand and is slowly moving eastward. It is expected to bring elevated waves and high southerly swells of more than 2.5 metres from the south later tonight through Tuesday in the new week. Furthermore, these wave conditions are expected to coincide with the highest tide of May at 06:10 a.m. tomorrow, which could impact the country’s southern marine seas. Therefore, the above-mentioned advisory, remains in effect for the southern waters.

ADVISORIES/WARNINGS:

VALID: MARINE ADVISORY – SOUTHERN MARINE WATERS

Weather Duty Team:

A. Liu, A. Sofeni, S, Tavanā, & C. Baker.