textproduct: WSO Pago Pago

DISCUSSION

Heavy thunderstorm activity developed earlier this morning on the far west side of Tutuila Island produced strong and gusty winds with heavy downpours for a short time. These gusty winds prompted a wind advisory for the west side of the island, only, as trees were uprooted and tree branches breaking, loose items being blown around with a hut roof blown off. The thunderstorms remained active offshore to the north of the area throughout the day. These conditions are also shown on the upper air observations (RAOB) from this afternoon (21/00Z). The atmosphere remains unstable for the rest of the day. On the latest satellite imageries, these are embedded at the tail end of the trough linge that brought torrential rainfall at the beginning of the week.

However, model data shows this trough migrating further east- southeast by Thursday morning as a ridge builds from the northeast. Once the trough passes the area, another broad high pressure system to the southwest moves south of the area. This high pressure system will bring fair weather conditions from Thursday through at least Sunday. By Sunday night, model solutions show a low pressure system move just south of the islands, turning winds northeast and pulling in moisture from the north. This will increase the potential for showers for the rest of the forecast period.

Thus, expect scattered to numerous showers with possible thunderstorms and variable winds for tonight. Scattered showers with variable winds is expected for Thursday through the rest of the week, with winds increasing to southeast at a gentle to moderate breeze. Showers will likely increase to numerous with light and variable winds thereafter.

Marine

Seas have been gradually subsiding to lower heights within the last 12 to 16 hours. Seas of 6 to 8 feet recorded at the PacIOOS Aunu'u buoy is expected to continue on a downward trend tonight through at least Thursday morning. However, model data show seas slightly building to around 6 to 8 feet again by Thursday afternoon and likely remaining through the end of the forecast period. Thunderstorm activity within the area of responsibility (AOR) can also elevate seas and surfs nearby. The elevated seas may pose a threat to small crafts for this time frame. In the meantime, no other significant swell is expected for this forecast period, and ocean conditions will be monitored for any changes.

PPG WATCHES/WARNINGS/ADVISORIES

NONE