FORECAST DISCUSSION
MONDAY 20^th MARCH 2023 – AM SHIFT

TODAY:
Unstable and moisture atmospheric conditions remain over the area of concern. Furthermore, the Himawari satellite loop clearly reveals a major group of convective clouds resides at west of Samoa. Thus, such weather patterns signify the trough of low-pressure system with developed single cells across the island chain which ushers an escalated amount of moistness and cloudiness. The radar profiler data depicted signals of abundant moisture and limited moisture throughout the layers of the atmosphere. The scatterometer and wind profiler observations consolidate for Northeast wind flow to be light-to-gentle in wind strength which contributes to the lifespan and longevity of convective clouds. The surface-to-mid-level charts are agreeably aligned, plus an area of a mid-level high-pressure system (blocking high) lies in the mid-region and is responsible for withholding the active trough of low-pressure system west of the group. The upper atmosphere composes of an active divergence zone that lies within the area of interest and supports the surface-to-mid level system in the nowcast period. Henceforth, the atmosphere is conditionally unstable, regardless of whether the wind shear tendency is neutral. Therefore, the forecast for today is anticipated cloudy with isolated showers. Moderate falls in some areas and a few thunderstorms.

TUESDAY THROUGH SATURDAY:
The Ensemble guidance forecasts a receding trend of rainfall activities through the mid-week. The trough of low-pressure system may further descend southward as the surface-to-mid-level ridge of high-pressure system is gradually established by Tuesday into Wednesday. Expect winds to become light and variable through Thursday awaiting the Easterly surge on Friday which also affiliates another episode of rainfall activities. Thence, such a predicted weather system driver is an expected trough of low-pressure system moving westward and likely to migrate over the forecast zone by Saturday. Interestingly enough, the approaching system is well extended and reflects in the mid-region alongside signals of light-to-gentle wind strength. The upper level is likely to be driven by an upper-level ridge of high pressure just southwest of the group, which directs southerly aloft with an upper cyclonic flow further North of Samoa. Hence, numerical predictions hint at a probable signature of convergence signifying dry airmass over the forecast region.

MARINE:
The latest wave observations show waves and swell heights fluctuating within the range of 1-2 metres for all marine waters. The wave models suggested that wave heights would remain below the advisory threshold of 2.5 metres for all coastal to marine waters of Samoa for the rest of the forecast outlook. 

WARNING/ADVISORY:
NONE

TEAM AM-SHIFT:
A. Niko, A. Liu & I. Tuatipi