


Tropical Weather Discussion
Issued by NWS
Issued by NWS
571 AXPQ20 PGUM 200038 TWDPQ Tropical Weather Discussion National Weather Service Tiyan GU 1038 AM ChST Wed Aug 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... TROPICAL AND MONSOON DISTURBANCES... Invest 90W remains disorganized and has been downgraded to "Low" by JTWC, as it`s now located north of Koror near 11N135E. The models show this feature remaining weak as it continues west, with no real organizing, exiting Guam`s AOR by the weekend. ...OTHER WEATHER SYSTEMS... TRADE-WIND TROUGHS... A trough in the trades extends north from near Kapingamarangi to just east of Chuuk, ending near 21N152E. Convection is widely scattered along and ahead of this feature, which looks to be the case as it continues west the next few days. Another surface trough in the trades has strengthened more than the models suggested it would, while also stretching both southwest and northeast, which wasn`t anticipated. It now stretches from southeast of Kosrae at 3N165E, to just east of Majuro, to 10N175E. Scattered showers and isolated thunderstorms are occurring along this feature, which looks to continue in the latest model forecasts as it heads west the next several days. Finally, a third trough is quickly following on the heels of the Kosrae/Majuro trough. It`s a sharp but compact trough approaching the Date Line. This feature will cross it tomorrow, bringing additional convection to the region the next several days as it continues west in the trade flow. TUTT... The TUTT has become more defined today and stretches from 25N180 westward to a cell northwest of Wake Island at 25N160E, then extends southwest to 20N155E where another cell is trying to form, continuing west to a cell west of the northern most part of the CNMI at 20N140E. Most of the convection is associated near the TUTT cells and to the south of the TUTT axis where better divergence is present. The models do show the cell near 20N155E developing, becoming a dominant feature by Friday, as it helps to expand the TUTT westward to near 130E by the weekend while maintaining a similar orientation. ...ITCZ... A weak ITCZ stretched from south of Pohnpei to east of the Date Line, centered between 4N and 10N. Widely scattered convection is occurring with this feature, locally enhanced by surface troughs in the trades. The ITCZ is forecast to expand westward and gradually intensifies through the weekend, perhaps lifting northward slightly as well. $$ Doll