SYNOPTIC DISCUSSION

FRIDAY 01st AUGUST 2025 PM SHIFT

TONIGHT INTO TOMORROW:

Samoa’s experienced partly cloudy conditions at sea, apart from afternoon brief showers that were captured mainly over highland. Locally, generated by the decreased in cloud coverage, light and variable wind winds, and weak steering low-to-mid level winds which lead to intense daytime heating causing upslope winds. Concurrently, in the upper atmosphere, the wind shear is observed to be weaken, yet the persistence of upper-level dry airmass lingered over the country. For those reasons, the satellite loop captured lumpiness of towering cumulus in both islands at late afternoon. Later tonight, a weak trough moving northward is currently over Samoa, bringing cloudiness with brief showers in parts of the country. With this, the radiosonde profile and blended total precipitable water channel collaboratively revealed a decent amount of available moisture content in the lower atmosphere. 

Tomorrow, a weak is expected to remain within the vicinity, with certainty it could support afternoon showers and a few thunderstorms mainly elevated windward locations. There is a likelihood, the predicted mean wind flow could be weak, similarly to the low-to-mid level winds, with absence of upper-level support system. 

SUNDAYTHROUGHTHURSDAY:

Global weather model, generally stated a minimal showers and thunderstorms formation with a very low chance of severity. Where, the previously stated weak trough proceeds northward, due to a broad area of high-pressure over New Zealand steadily propagate eastward. So, on Sunday into Wednesday, there is a good chance the dry and cool southeasterly winds to dominate across Samoa. Then, on Thursday where a probable speed convergence moving along the forecasted mean wind flow, bringing an increase of showery activities. Therefore, expect mostly fine weather apart from afternoon showers for the early days of August.

MARINE OUTLOOK:

Recently, a collection of available marine observational readings clearly recorded wave activities to fluctuated below 2 metres. Thus, it justify that there’re no imminent threat for Samoa’s coastal and marine waters. This wave trend, it may be prolonged through at least early Sunday. Simultaneously, elevated southerly swell with increased wave period of (15-17s) perhaps reach our marine areas on Monday through the mid-week. The ensembles’ probability are forecasting a very low likelihood of occurrence. So, we’ll proceed to monitor the observations and current model performance. From there, we’ll provide usual updates if a SWI is possible ahead of its estimated time of arrival.

ADVISORIES/WARNINGS:

NONE

Weather On-Duty Team:

M.J.S, A. Liu, A. Niko, & N. Tutasi.