Tropical Weather Discussion
Issued by NWS
Issued by NWS
315 AXPQ20 PGUM 091028 AAA TWDPQ Tropical Weather Discussion...UPDATED National Weather Service Tiyan GU 828 PM ChST Sat Nov 9 2024 Updated to add information on the development of Tropical Depression Toraji and upgrade Man-yi (25W) from tropical depression to tropical storm. 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 CYCLONES... The Joint Typhoon Warning Center`s (JTWC) has upgrade Tropical Depression 25W to Tropical Storm Man-yi. Man-yi is northwest of the Marshall Islands near 14.78N 158.3E, roughly halfway between Pohnpei and Wake Island. Himawari infrared satellite imagery shows a broad region of moderate to deep convection consolidating about the circulation center. Bands of numerous showers and isolated thunderstorms extend far north and northeast to the south of Wake Island. Man-yi continues to move northwest over the next day or so as it consolidates and strengthens, possibly reaching strong tropical storm strength (maximum sustained winds > 49 kts) by Monday as it passes Pohnpei far to the north. However, recent model trends point to a weakening and loss of structure as Man-yi continues on westward toward the northern Marianas. Man-yi will potentially pass near Saipan Tuesday night into Wednesday as a tropical depression, bringing locally heavy showers and gusty winds. The Joint Typhoon Warning Center has upgraded 92W to Tropical Depression Toraji (26W) this evening with winds around 30 kt (35 mph). Toraji is located well within the Philippine Sea, well northwest of Yap and Palau, centered near 14.6N 130.9E, and is expected to move northwest towards the northern Philippines and exit our region. For more information, please refer to bulletins from the Joint Typhoon Warning Center under WMO headers WTPN32 PGTW and WTPN33 PGTW and from the National Weather Service under WMO headers WTPQ32 PGUM and WTPQ33 PGUM. TROPICAL AND MONSOON DISTURBANCES... Tropical disturbance, JTWC`s Invest 94W, is located west-south west of Chuuk near 6.5N 149.5E, having moved slowly northwest since yesterday. Heavy showers and thunderstorms are disorganized about the elongated center of circulation, extending in bands north, east, and south of the center, with the heaviest showers mainly focused along the eastern flank over the Nomoi Islands extending northwest over Chuuk Proper. Surface observations at Chuuk have reported wind gusts to around 22 knots associated with showers. 94W looks to remain disorganized as it moves northwest through Chuuk State tonight, continuing to move northwest. Model trends keep 94W on a northwest trajectory moving roughly "in sync" with TS Man-yi (25W), passing between Yap and Guam on Monday potentially as a tropical depression, with model disagreement regarding wind strength and overall organization. For more information on Invest 94W, see bulletins issued by the JTWC under WMO header ABPW10 ...OTHER WEATHER SYSTEMS... TRADE-WIND AND SURFACE TROUGHS... A broad surface trough extends northwest over Pohnpei State from Invest 94W, passing over Pohnpei Proper before extending north through TD 25W, continuing onward to the west of Wake Island near 20N163E. Scattered showers near Pohnpei extend northward into an area of numerous showers focused about 25W, spreading northward to around 19N and eastward across the southern periphery of Wake Island`s coastal waters. This trough will shift west to northwest with the movement of TD 25W and 94W, breaking apart during the latter half of the week as these systems move west into the Philippine Sea. A shallow trade-wind trough extends southeast from the south of Wake Island near 17N166E, along the leading edge of a trade-wind surge, mentioned in the section below. This trough passes east of the RMI`s Ratak (sunrise) Chain and extends southeast into an Intertropical Convergence Zone (ITCZ) to the east of Majuro, mentioned in the relevant section below. Scattered showers and a few thunderstorms are seen along this trough axis, focused mainly east of Majuro within a portion of the ITCZ close to the Date Line. Slightly further west, a weak trade-wind trough extends southeast along the RMI`s Ralik (sunset) Chain, from near Ailinglaplap Atoll to around EQ175E. Scattered showers are seen along this trough axis to the west and south of Majuro. These features will shift west over the next few day or so, diminishing by Monday as TD 25W moves northwest away from the area. TRADE-WIND SURGE... Scatterometry shows an area of moderate to strong trades north and northeast of the Marshall Islands across a broad area between 10N and 24N, from roughly 170E to beyond 180. This moderate trade wind surge has shrunk closer to the Date Line since yesterday. Scattered showers and a few thunderstorms are seen within this broad region associated with a tightened pressure gradient between TD 25W and the subtropical ridge to the north. This continues over the next few days before weakening by early next week as the pressure gradient relaxes over the area. ITCZ... An ITCZ fragment extends westward into the AOR near 6N180 and continues to around 6N176E to the east of Majuro Atoll. Scattered showers and isolated thunderstorms extend west along this ITCZ fragment and northwest along a trade-wind trough east of the Marshall Islands, mentioned above. The ITCZ will extend west across the RMI over the next day or so, becoming ill-defined as a fragment shifts west across eastern Micronesia as a surface trough through the midweek. $$ DeCou/Schank