[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 310833
TCDAT4

Subtropical Storm Rebekah Discussion Number   3
NWS National Hurricane Center Miami FL       AL192019
500 AM AST Thu Oct 31 2019

Rebekah's cloud pattern has eroded significantly since the previous
advisory and only a narrow band of fragmented convection remains in
the northeastern quadrant. There are no signs of any upper-level
anticyclonic outflow, so the cyclone will retain subtropical status.
Earlier ASCAT-A/B/C overpasses indicated several 38-39 kt surface
wind vectors in the southern semicircle and given that Rebekah is
now moving at a faster forward speed, the intensity remains at 40 kt
despite the degraded convective pattern.

The initial motion estimate is 065/18 kt. Rebekah is forecast to
move east-northeastward to eastward around the southeastern
periphery of a larger non-tropical low pressure system for the next
day or two before dissipating by 48 hours. The model guidance has
shifted northward significantly and the official forecast has been
moved in that direction as well, but not as far north nor as fast as
the model consensus, lying closer to a blend of the GFS and ECMWF
model solutions.

Rebekah will be moving over cooler waters that are less than 20 deg
C and into a stronger vertical wind shear regime by 12 h and beyond.
This combination of unfavorable dynamic and thermodynamic conditions
should cause the cyclone to steady weaken and become a post-tropical
cyclone in 24 h or less, with dissipation expected by 48 h. Although
the center of Rebekah is expected to pass north of the Azores, those
islands could still receive gusty winds and locally heavy rainfall,
especially on the southward-facing slopes of elevated terrain.

Since Rebekah is not expected to be a tropical or subtropical
cyclone when it nears the Azores, hazard information can be found
in regular products issued by the Portuguese Institute for the Sea
and Atmosphere (IPMA) for those islands at
https://www.ipma.pt/pt/index.html.


FORECAST POSITIONS AND MAX WINDS

INIT  31/0900Z 39.7N  36.7W   40 KT  45 MPH...SUBTROPICAL STORM
 12H  31/1800Z 40.6N  33.7W   40 KT  45 MPH...SUBTROPICAL STORM
 24H  01/0600Z 40.6N  29.4W   35 KT  40 MPH...POST-TROP/EXTRATROP
 36H  01/1800Z 40.3N  25.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
 48H  02/0600Z...DISSIPATED

$$
Forecaster Stewart
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