A large area of disturbed weather extends across western Micronesia, associated with the Near-Equatorial Trough (NET) and embedded disturbances. The disturbance the Joint Typhoon Warning Center (JTWC) and the National Weather Service (NWS) has been watching the last few day is Invest 99W, a broad area of rotation just west-southwest of Koror, Palau, located near 6N133E this afternoon. Today's satellite scatterometer data does not show a well defined circulation with 99W but this disturbance is associated with locally heavy showers and thunderstorms, that are now more concentrated around Palau and extending up toward Yap Proper, that could produce gusty winds and choppy seas. The Joint Typhoon Warning center rates 99W as a "sub-low" for development, which means significant development into a tropical cyclone is unlikely over the next 24 hours. Farther east in Yap State, JTWC has opened Invest 90W on a weak circulation near 4N144E, close to where the broad area of mid-level vorticity was noted yesterday. Similar to 99W, this system is disorganized but currently showers and thunderstorms around 90W cover a much larger area compared to 99W, likely due to the support of the mid-level vorticity in the area. JTWC also rates 90W's potential over the next 24 hours as "sub-low". Model trends continue support one, possibly two, defined circulations developing within the NET and shifting northwest through the end of the week, with significant development not occurring until the feature is northwest of Palau and Yap. The likely locations are associated with Invest 99W and 90W. This slow and disorganized development will lead to widespread variability in conditions across Palau and Yap State, however the potential for locally heavy showers, gusty winds and choppy seas still exists across the region. As the feature shifts northwest of Palau and Yap, a monsoon-like pattern may develop across Palau and western Yap state, potentially leading to higher seas and surf along the westward sides of the islands and impacting areas sensitive to southwest to westerly winds. At this time, landslides are unlikely, due to the high variability in rainfall potential. However, if soils become saturated by heavy rain, this potential will increase with the onset of additional rainfall. Residents and mariners should monitor the latest forecasts for the region at weather.gov/gum/PublicForecasts and any information shared by WSO Palau and WSO Yap for their local regions.
