####018006656#### AXPQ20 PGUM 300134 TWDPQ Tropical Weather Discussion National Weather Service Tiyan GU 1134 AM ChST Wed Apr 30 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... A tropical disturbance, known as JTWC's Invest 99W, is currently centered near 7N133E north of Sonsorol and west-southwest of Palau, based on the broad rotation seen in the most recent visible satellite imagery. 99W continues to look like a loosely organized system, so the potential for development into significant tropical cyclones in the next 24 hours is still very low. Moderate to occasionally deep convection is associated with this feature, producing scattered to occasionally numerous showers and isolated thunderstorms within 150 miles of the center, and within a compact zone over and east of Palau, passing just south of Yap Proper this morning. Another tropical disturbance, known as JTWC's Invest 90W, is centered near 4N146E well south of Satawal in eastern Yap State. Overnight scatterometer passes clipped the edge of 90W, but suggest a weak surface circulation may be present at the center, and this may become more clear with this afternoon's scatterometer data. Similarly to 99W, Invest 90W is still loosely organized, so the potential for development into a significant tropical cyclone over the next 24 hours is very low. Moderate to deep convection extends up to 350 miles from the center of 90W, producing scattered to numerous showers and isolated thunderstorms; extending from 2N and northward across the eastern Islands of Yap state, such as Eauripik, Woleai, and other nearby islands. Model guidance continues to vary in development, if one or two distinct circulations will develop from 99W and 90W; however, consensus is that the overall pattern will shift northwest towards Palau and Yap, with any significant development favored only once the feature is northwest of Palau and Yap. Even so, potential remains for locally heavy showers, gusty winds, and choppy seas across Palau and Yap State. Further discussion can be found in the Special Weather Statement issued for Palau and Yap by the National Weather Service under WMO header WWPQ82 PGUM. ...OTHER WEATHER SYSTEMS... NEAR EQUATORIAL TROUGH... A Near Equatorial Trough (NET) enters the region near 6N130E, extending east-southeast through the embedded disturbances Invest 99W and 90W mentioned above, and then extend farther to the very southern portions of Chuuk State, ending near EQ148E. Most of the convection across the NET is associated with the two tropical disturbances mentioned above, in addition to more convection found across the southwestern fringes of the region over the Indonesian islands of Fani and Bras, as well as Tobi and Helen's Reef and extending eastward along the Equator to 146E; producing scattered to occasionally numerous showers and isolated thunderstorms across these areas. Model guidance has continued to indicate a development of one or two separate circulations within the NET that would develop by the weekend. While the stages of potential development vary greatly between the models, delays in initial disturbance formation are expected to continue as the environment directly to the north of the NET remains unfavorable for the next few days. Confidence in any potential disturbances to form is mostly supported by other seasonal features in the region that are already present, such as the semi- permanent low forming along the northeastern coasts of Papua New Guinea in the Southern Hemisphere, and a general weakening in the trades upstream. As such, one or two disturbances are to be expected in the region within the next 3 to 5 days, but high uncertainty remains in potential for development of a significant tropical cyclone. TRADE-WIND CONVERGENCE... A trade-wind convergence is observed across much of central and east Micronesia. This feature spans from 150E to the Date Line, between 9N and the Equator, and has shown a weakening trend over the last 24 hours across the region. Most of the convection is now concentrated near Kosrae and extends east-northeast towards the Date Line, passing just south of Majuro. This convection looks to be moderate, with scattered to occasionally numerous showers extending along this area of convergence, with isolated thunderstorms seen mainly well southeast of Majuro, near 4N175E. There is another area of weak convergence extending from the trough near Pohnpei, and extending northeast to the Date Line near 13N, with showers remaining widely scattered in nature around said convergence zone. TRADE-WIND TROUGHS... One notable trade-wind trough is seen near Pohnpei, extending from 6N159E to 9N160E. This trough is producing scattered showers over and just east of Pohnpei, with widely scattered showers continuing northeast along the weak area of trade convergence mentioned above. ...OTHER SYSTEMS... UPPER-LEVEL TROUGH... An upper-level trough, slowly being cut off from the mid-latitudes, extends from 21N180 southwest across Wake Island to end north of Pohnpei near 11N157E. The upper-level divergence south of the trough axis is aiding the convection along the area of weak trade convergence that extends from the trade-wind trough near Pohnpei and northeast to the Date Line. This feature is expected to move east and re-develop through multiple cycles over the next several days, with a TUTT potentially developing in its place by the middle of next week. COLD FRONT... A cold front enters the region near 25N148E halfway between Minami Torishima, and Iwo To. It extends southwest, to then exit the region near 20N130E. Moderate convection is associated with this feature, producing periods of rain, widespread cloudiness and strong shear within 200 miles north of the frontal axis, east of 140E, and then decreasing along the feature west of 140E. This feature is expected to weaken and dissipate over the next few days, as the associated low continues its exit from Japan's eastern shores, and the edges of the cold front encounter the subtropical ridge immediately to the southeast of the frontal axis. $$ Montvila/Schank