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Chill falls over the Atlantic as the official season heads towards close
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| #990432 (Received by flhurricane at: 9:53 AM 24.Nov.2019) TCDAT5 Tropical Storm Sebastien Discussion Number 21 NWS National Hurricane Center Miami FL AL202019 1100 AM AST Sun Nov 24 2019 It is not clear if Sebastien is a closed cyclone at the surface. The fast forward motion of the cyclone (28 kt) may have caused it to open into a trough of low pressure. The ship MSC Beijing (DFDE2) recently reported northwest winds about 70 n mi north-northeast of the cyclone`s estimated center, and it has been difficult to identify easterly winds in visible imagery this morning. That said, ASCAT data was inconclusive regarding the state of Sebastien`s circulation and the system is still producing some deep convection near its center. AMSU data at 1135 UTC also indicated that Sebastien still has a weak warm core. For those reasons, it appears prudent to maintain advisories at this time. As mentioned above, Sebastien is moving very quickly northeastward and it should accelerate in that direction during the next 24 h. This is shown by all of the dynamical models which are finally in decent agreement. Based on simulated satellite imagery, it appears that the cyclone will continue to produce central deep convection for the next 12 h or so, and extratropical transition is forecast to finish within 24 h. Although an extratropical point is shown at 36 h for continuity purposes, in reality Sebastien will more likely open into a trough of low pressure, given the forecast forward motion of nearly 40 kt relative to its 50 kt forecast intensity at this time tomorrow. This could happen at any time. Regardless of whether it is a tropical cyclone, extratropical cyclone, or a remnant trough, Sebastien or its remnants will likely bring gusty winds and heavy rains to portions of the Azores later today and tonight. Please see products issued by the Portuguese Institute for the Sea and the Atmosphere (IPMA) for more information. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 37.4N 37.0W 55 KT 65 MPH 12H 25/0000Z 39.8N 31.0W 55 KT 65 MPH 24H 25/1200Z 43.8N 22.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 26/0000Z 47.7N 14.8W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 26/1200Z...DISSIPATED $$ Forecaster Zelinsky |
