####018005581#### AXPQ20 PGUM 290045 TWDPQ Tropical Weather Discussion National Weather Service Tiyan GU 1045 AM ChST Tue Apr 29 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... A tropical disturbance, known as JTWC's Invest 99W, is currently centered near 6N132E northwest of Sonsorol. Moderate to occasionally deep convection is associated with this feature, mainly in two different sectors. The first sector is within a compact area near the center, extending 150 to 175 miles outward to bring numerous showers and some thunderstorms to northwestern waters of Sonsorol. A second sector is an area where the disturbance and associated NET are interacting with the incoming trades, between Palau Proper, Ngulu, Yap Proper and Sorol; producing numerous showers and some thunderstorms in the area. As the system remains largely disorganized, the center axis of rotation is expected to continue to shift over the next day or so, followed by a potential consolidation phase as early as Thursday. However, recent trends have indicated a chance for further delays in any development, so various agencies will continue to monitor this area for any changes over at least the next several days. ...OTHER WEATHER SYSTEMS... NEAR EQUATORIAL TROUGH... A Near Equatorial Trough (NET) enters the region near 6N130E, extending east-southeast to an embedded disturbance Invest 99W mentioned above, to then extend farther across portions of the Republic of Palau and Yap State, to end near EQ146E in southeast Yap State. Moderate to occasionally deep convection is associated with this feature, bringing this convection to three separate sectors, two of which are mentioned in the special features section above. The third sector covers much of southwestern fringes of the region over the Indonesian islands of Fani and Bras, as well as Tobi and Helen's Reef; producing numerous to widespread showers and scattered thunderstorms across this area. Model guidance has continued to indicate a development of two separate circulations within the NET that would develop independently by the end of the week. 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 disturbance 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 zone extends across much of central and east Micronesia, spanning from 150E to the Date Line, between 9N and the Equator. Most of the convection is concentrated in two different sectors. Moderate convection is associated with the first sector, producing scattered to numerous showers along the western edges colliding with the aforementioned NET west and over Chuuk, and eastward to Pohnpei between 8N and 5N. Moderate to occasionally deep convection is associated with the second sector, producing numerous to widespread showers to much of Kosrae State and the Marshalls, especially near Majuro. This region is expected to enhance potential for cyclogenesis in eastern Yap State, providing the necessary moisture flux to the NET downstream and weakening in the second half of the week. TRADE-WIND TROUGHS... Multiple surface trade-wind troughs are embedded within the aforementioned trade-wind convergence, producing moderate to occasionally deep convection to bring unsettled weather across much of central and eastern Micronesia. These features are expected to remain transient of nature for the next several days, as they continue moving along with the trades. ...OTHER SYSTEMS... UPPER-LEVEL TROUGH... An upper-level trough extends laterally from 20N174E well east- northeast of Wake Island, eastward to cross the Date Line near 20N180. Little to no convection is associated with this system, producing some shearing with passing minor surface troughs below. This feature is expected to move east and re-developing 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 25N135E halfway between Naha, Okinawa and Iwo To. It extends southwest, to then exit the region near 22N130E. Moderate convection is associated with this feature, producing periods of rain, widespread cloudiness and strong shear within 200 miles north of the frontal axis. 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