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Post-Tropical Cyclone Sebastien Forecast Discussion (Text)


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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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Page last modified: Monday, 25-Nov-2019 02:32:12 UTC