####018005105#### AXPQ20 PGUM 200116 TWDPQ Tropical Weather Discussion National Weather Service Tiyan GU 1116 AM ChST Sun Jul 20 2025 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... MONSOON TROUGH... The monsoon trough enters the area near 15N130E, extending east- southeast to north of Yap Proper near 11N139E. It then branches out, with one portion of the trough turning east-northeast, passing just south of Guam, ending east of Rota near 14N148E. A broad area of convergence is also seen north of the trough over the Philippine Sea. The trough and band of convergence are interacting with the strong divergence associated with the TUTT to produce scattered to numerous showers across the Philippine Sea. For the eastern end of the trough, interaction between the monsoon trough, TUTT and a trade-wind trough is generating rain, numerous showers and isolated thunderstorms across the Marianas. This portion of the monsoon trough is expected to slowly drift north over the coming days. The second branch turns south-southeast north of Yap Proper near 11N139E to end near the equator at 142E. Scattered showers and isolated thunderstorms are associated with this portion of the monsoon trough. This branch of the monsoon trough looks to rotate northeast over the coming days, eventually merging with the northern branch. TRADE-WIND TROUGHS... Several trade-wind troughs are evident across the region. The first one is found just east of the Marianas, extending north-northeast from near 13N147E to end near 24N151E. Only spotty clouds and showers are found with the trough north of Saipan. Over the Marianas, the trough is interacting with the monsoon trough and TUTT to generate rain, numerous showers and isolated thunderstorms across the region. The trough looks to continue moving west-northwest, passing through north of the monsoon trough. The second trough is found between Pohnpei and Kosrae, extending north-northwest from near 8N157E to 11N156E. Scattered showers and isolated thunderstorms are found with this trough. The trough and associated convection look to drift slowly northwest over the next few days. The next trade-wind trough is the leading trough in a series of weak troughs traversing the ITCZ across eastern Micronesia. It is located between Kosrae and Pohnpei, extending northeast from near 4N159E to 7N162E. This is along the far western end of the ITCZ. The interaction is producing scattered showers just east of Pohnpei. The next in the series is found just east of Kosrae, extending north- northeast from near 1N161E to end near 6N165E. The interaction here is generating numerous showers and isolated thunderstorms across Kosrae. The last in this series of troughs is found east of Majuro, extending north-northeast from near 2N171E to near 8N175E. Numerous showers and isolated thunderstorms are found along this interaction across the Marshall Islands, including Majuro. The series of troughs will continue to move west over the coming days, maintaining enhanced convection across the region. TUTT... A decaying TUTT enters the area near 5N152E, extending southeast to a weak TUTT cell centered near 20N161E. Scattered showers and isolated thunderstorms are found west of Wake Island. This TUTT and associated cell will remain quasi-stationary as it continues to weaken. Another weakening TUTT cell is centered near 25N135E with the TUTT extending southeast to end west of Saipan near 15N143E. Patchy showers and isolated thunderstorms are found with the cell. the divergence associated with the TUTT is interacting with the monsoon trough and convergence north of the trough to enhance convection across the Philippine Sea. Over the Marianas, the divergence is interacting with the monsoon trough and a trade-wind trough to produce rain, numerous showers and isolated thunderstorms across the area. The TUTT is expected to drift slowly west and continue to weaken over the next few days. OTHER SYSTEMS... A weakening high pressure ridge remains south of Palau, resulting in dry conditions over Yap and Palau. This ridge will continue to slowly weaken, allowing convection to build back into Palau and Yap. ...ITCZ... The ITCZ extends east-northeast from south of Pohnpei near 5N159E to beyond the Date Line near 9N. Scattered showers and isolated thunderstorms are found east of the Marshall Islands. Elsewhere along the ITCZ, patches of numerous showers and isolated thunderstorms are found where the ITCZ is interacting with weak trade-wind troughs. The ITCZ looks to remain active over the next couple of days, maintaining an overall unsettled pattern across eastern Micronesia. $$ Kleeschulte