Area Forecast Discussion
Issued by NWS Pago Pago
Issued by NWS Pago Pago
950 FXZS60 NSTU 210112 AFDPPG Area Forecast Discussion National Weather Service Pago Pago AS 212 PM SST Thu Feb 20 2025 .DISCUSSION... Observations throughout the day have been slightly lower than yesterday`s wind and rain observations. However, ASCAT swaths from earlier this morning and observations from local residents shows high winds peaking at 35 to 40 knots with higher gusts and heavy downpours over the Manu`a Islands. On the latest satellite imageries and upper air observations (RAOB) from this afternoon (21/00Z), the South Pacific Convergence Zone (SPCZ) still remains over the area. Wind data from the ROAB show winds around 35 knots at the 960 mb level. Also on satellite, deep convections observed to the north-northwest of the Samoa Islands continues to move east-southeast, and is expected to bring more rain and winds over Tutuila and Manu`a Islands. TD08F (92P) to the south-southeast of the islands and attached to the SPCZ, is expected to pull the aforementioned deep convections over the area in the next couple of hours. These convections align with model data showing an increasing trend in winds and rainshowers within the next 16 to 24 hours over American Samoa. Thus, the warnings for high winds remains in effect for all of American Samoa through at least early Friday. Additionally, model data shows a ridge of high pressure to the north building and pushing the SPCZ further south by Saturday evening. Once this scenario comes into play, weather conditions will improve with decreasing winds and showers over the territory. Therefore, expect widespread showers, heavy at times with embedded thunderstorms and gale force winds with higher gusts to remain across the territory for tonight through early Friday morning hours, trending down afterwards. Expect winds to decrease to a strong breeze with scattered to numerous showers by Friday through the weekend, and further decreasing into the new week. Winds will turn north on Friday night becoming northeast by Saturday night, and east on Monday through the rest of the forecast period. && .Marine... Ocean conditions have been observed throughout the day with the latest observations from the PacIOOS buoys to the west and east of Tutuila Island. Seas reported from these buoys have been relatively around the same heights (11 to 13 feet). However, periods to the northwest to north shorelines are around 15 to 17 seconds long, compared to the data of short periods (<10 seconds) at the Aunu`u buoy to the east. These long periods indicate the enhancement of surfs at these shorelines. Additionally, data from the latest altimeter swaths over the Manu`a Islands are showing heights around 13 to 15 feet high. Also, with the gale force winds with higher gusts from the northwest will continue through at least early Friday morning, keeping the likelihood for hazardous ocean conditions to remain across the coastal waters of American Samoa. These strong northwest winds will also continue to have a funneling effect into the harbor/Fagaloa area, with much higher wind speeds and gusts experienced elsewhere in the area. Hence, the warnings for high surfs and gale force winds remains in effect through at least Friday morning. && .PPG WATCHES/WARNINGS/ADVISORIES... High Wind Warning High Surf Warning Gale Warning Flash Flood Watch && $$ JTAllen