Tropical Weather Discussion
Issued by NWS
Issued by NWS
011 AXPQ20 PGUM 190042 TWDPQ Tropical Weather Discussion National Weather Service Tiyan GU 1042 AM ChST Tue Aug 19 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 is located near 10.8N 144.6E, south-southwest of Guam. It`s currently rated medium from JTWC. The disturbance looks much less organized than yesterday and the day before. The models continue to show an eventual strengthening of the system as it continues to head west- northwest over the next few days. ...OTHER WEATHER SYSTEMS... TRADE-WIND TROUGHS... A fairly sharp trough in the trades extends northeast from Koror, to just north of Yap, to Pagan in the CNMI. Widespread clouds, scattered showers, and isolated thunderstorms are continuing to develop. In general, this looks to remain the case the next few days as the trough heads west, with locally higher coverage probable as Invest 90W eventually gets more organized along it. A pair of troughs are seen in the trades further south and east. One stretches from northwest of Kapingamarangi northward through Chuuk, ending just north of there. A second trough, stretches from south of Pohnpei, through Pohnpei, ending north of there. Widespread clouds, scattered showers, and isolated thunderstorms are occurring here as well. This will continue to be the case the next several days as they trek west across the area. Finally, a trough is crossing the Date Line. This trough has less clouds and convection, both of which are present in a widely scattered form. The models show this trough strengthening with a gradual increase in moisture and convergence over the next few days, allowing for convection to increase in coverage as it heads west. TUTT... A TUTT fragment extends from north of Wake Island to northwest of the Marianas, with 4 high pressure cells aloft centered northwest, north, northeast, and southeast of this axis. This looks to be temporary though, as the pattern looks to reorganize, allowing the TUTT to reorganize in the next 24 to 48 hours along a similar axis. ...ITCZ... A weak ITCZ, anchored by the troughs mentioned above, is attempting to form. In general, the models show a modest ITCZ continuing to form over the next 24 to 48 hours, gradually expanding west towards weeks end, and possibly strengthening over the weekend. The greatest convective coverage and vigor will be tied to any embedded troughs, as additional ripples in the flow develops. $$ Doll