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578
WTNT45 KNHC 250232
TCDAT5

Post-Tropical Cyclone Sebastien Discussion Number 23
NWS National Hurricane Center Miami FL AL202019
1100 PM AST Sun Nov 24 2019

Sebastien has lost its tropical characteristics this evening. The deep convection has decoupled from the low-level circulation, and these features are now separated by a distance of 100 n mi and increasing. Two partial ASCAT passes revealed that the surface low is becoming stretched out, and there is some evidence of a boundary, possibly a front, extending northeast from the center. Furthermore, recent observations from Corbo and Flores islands in the Azores indicated a slight temperature decrease as the center passed by to the north of those islands, suggesting that a weak cold front is associated with the the cyclone. Based on all of these data, there is high confidence that Sebastien has transitioned to an extratropical cyclone. The initial advisory intensity is 50 kt which is based on 47 kt winds sampled by the scatterometer and a subjective intensity estimate from TAFB.

Post-tropical cyclone Sebastien is moving northeastward at 35 kt, embedded in the strong flow to the southeast of a mid- to upper- level trough. This motion, and the cyclone's current intensity, is expected to persist for the next day or so, before the cyclone merges with a higher-latitude low.

The cyclone will likely bring gusty winds and heavy rains to portions of the Azores through Monday morning. Please see products issued by the Portuguese Institute for the Sea and the Atmosphere (IPMA) for more details.

Additional information on this system can be found in:

High Seas Forecasts issued by Meteo France under WMO header FQNT50 LFPW and on the web at www.meteofrance.com/previsions-meteo-marine/bulletin/grandlarge/ metarea2.

FORECAST POSITIONS AND MAX WINDS

INIT 25/0300Z 41.0N 28.9W 50 KT 60 MPH...POST-TROP/EXTRATROP 12H 25/1200Z 43.6N 22.7W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 26/0000Z 48.1N 14.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 26/1200Z...MERGED WITH ANOTHER LOW

$$ Forecaster Latto



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