Tropical Weather Discussion
Issued by NWS
Issued by NWS
595 AXPQ20 PGUM 010037 TWDPQ Tropical Weather Discussion National Weather Service Tiyan GU 1037 AM ChST Tue Oct 1 2024 Tropical Weather Discussion for the Western North Pacific between the Equator and 25N from 130E to 180. The following information is based on recent satellite imagery/data, weather observations, radar, and meteorological analysis. ...SPECIAL FEATURES... None. ...OTHER WEATHER SYSTEMS... SURFACE TROUGHS... A broad surface trough sits over far western Micronesia. The trough roughly begins over eastern Yap State near 10N144E and extends to the west-southwest, passing just south of Yap Proper and the Republic of Palau before exiting Guam`s Area of Responsibility (AOR) near 4N130E. Recent Himawari satellite imagery shows numerous showers and isolated thunderstorms along and just north of the trough`s axis, focused southwest of Yap and building directly over Palau. Model guidance indicates a gradual westward shift of the trough over the course of the week along with a a slight increase in steepness, bringing south- to southeast flow over Palau and Yap around mid- week. For the second half of the week, the trough looks to shift northwest over the Philippine Sea and gradually induce a light monsoon flow over far western Micronesia. Models disagree on the strength and eastward extent of this budding monsoon trough late in the week, but generally place Palau and Yap within a dry ridging regime by the weekend. In the meantime, Palau and Yap can expect on-and-off scattered showers into at least Thursday as the surface trough lingers nearby. TRADE-WIND TROUGHS... A few trade-wind troughs are seen across the AOR. The first is located north of the Marianas, extending south from near 19N144E to around 16N144E. Scattered showers and thunderstorms are seen just east of the trough axis, over the far northern Marianas, enhanced by a Tropical Upper Tropospheric Trough (TUTT) cell located northeast of the Marianas. Further east, the second trade- wind trough is seen south of Minamitorishima, extending southeast from around 22N155E to 18N157E. Scattered showers and thunderstorms are also seen just east of the trough axis, mainly along the northern extent where there is stronger influence from the aforementioned TUTT cell. These shallow troughs will continue shifting westward, dissipating over the next day or so. Further south, shallow trade-wind troughs are seen just east of Chuuk from around 12N156E extending southwest to 8N153E, between Pohnpei and Kosrae from around 6N160E to near 4N160E, and across the western Marshall Islands from around 12N165E stretching southeast to near 9N168E before curving southwest to around 4N164E. Scattered to numerous showers and isolated thunderstorms are seen to the northeast of Chuuk and south of Pohnpei roughly along trough axes. Scattered showers are roughly focused along the trough axis over the Marshall Islands. The trough over the Marshall Islands is weakening and should dissipate over the next day or so, while the other troughs will continue to meander westward through eastern and central Micronesia for the next few days, increasing showers from time to time near Kosrae, Pohnpei, and Chuuk. TUTT... A TUTT cell is seen northeast of the Marianas near 22N155E where it is interacting with two weak trade-wind troughs, discussed above, to produce scattered showers and thunderstorms over the far northern Marianas and to the south of Minamitorishima. A TUTT extends southwest from this cell to southeast of the Marianas near 12N147E, and to the northeast, where it exits the AOR near 25N166E. Scattered showers and isolated thunderstorms are seen to the south and southeast of the TUTT axis, just north of Chuuk State and west of Wake Island. The TUTT will continue to slide westward over the coming days, and looks to enhance shower and thunderstorm development west of and over the Marianas for the second half of the week before lifting northwest away from the area this weekend. A TUTT fragment is also present along the far eastern AOR near 16N180, extending just westward to around 16N178E. Upper-level divergence associated with this TUTT is helping to enhance showers well northeast of Majuro. Models show this TUTT fragment lingering at the far edge of the AOR for the next day or so before shifting west, moving over the northern Marshall Islands by the coming weekend where it may contribute to wet conditions across far eastern Micronesia. $$ DeCou