000
WTNT44 KNHC 181634
TCDAT4
 
Subtropical Storm Alpha Special Discussion Number   1
NWS National Hurricane Center Miami FL       AL242020
430 PM GMT Fri Sep 18 2020
 
The small low pressure area that has been rotating around a larger 
extratropical low in the far northeastern Atlantic has become better 
organized this morning.  Moderate-to-deep convection has persisted 
near the center since last night, scatterometer data shows a closed 
40-kt low, and radar images from Portugal show a definite organized 
convective pattern.  While the system is still in the cyclonic 
envelope of the large extratropical low and likely neutral- or 
cold-core, it has developed enough tropical characteristics to be 
considered a subtropical storm.  The initial intensity is set to 45 
kt in accordance with the scatterometer data, assuming some 
undersampling for this small system.
 
Little change in strength is forecast until landfall in Portugal 
during the next couple of hours.  Global models show the small low 
moving northeastward at about 15 kt for the next 24 hours before 
dissipating over northern Spain or the Bay of Biscay. The track and 
intensity forecasts are consistent with the consensus guidance.

Additional information on the hazards from this system can be found 
in products from the Portuguese Institute for Sea and Atmosphere at
www.ipma.pt.

FORECAST POSITIONS AND MAX WINDS
 
INIT  18/1630Z 39.9N   9.3W   45 KT  50 MPH
 12H  19/0000Z 41.5N   7.5W   30 KT  35 MPH...POST-TROP/INLAND
 24H  19/1200Z 44.2N   4.2W   30 KT  35 MPH...POST-TROP/EXTRATROP
 36H  20/0000Z...DISSIPATED
 
$$
Forecaster Blake