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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
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