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Tropical Storm Dorian Discussion Number   2
NWS National Hurricane Center Miami FL       AL052019
500 PM AST Sat Aug 24 2019

Visible and passive microwave satellite imagery indicate that the
inner-core of the small cyclone has noticeably improved since the
previous advisory.  A 1705Z AMSR-2 overpass showed the development
of tightly curved bands and a 10 mile wide eye-like feature.  In
addition, a 1935Z SSMI/S microwave pass revealed a tightly curved
band in 91 GHz data that wrapped almost 75 percent around the
center. Based on the much improved inner-core structure and 33-kt
wind vectors in an earlier ASCAT-B pass, the depression has been
upgraded to Tropical Storm Dorian on this advisory. Upper-level
outflow has been improving to the northwest, but remains slightly
restricted to the southeast due to some modest southeasterly
vertical wind shear.

The initial motion is 280/11 kt.  The latest NHC model guidance
remains in excellent agreement that Dorian will generally move
west-northwestward for the next 5 days around the southern periphery
of the sprawling Bermuda-Azores high pressure ridge that is located
to the north of the Lesser and Greater Antilles.  This motion is
expected to bring Dorian through the central or northern Lesser
Antilles on Tuesday, possibly as a hurricane, and then into the
northeastern Caribbean Sea on Wednesday and Thursday. The official
forecast track was shifted slightly north of the previous advisory
track, and is close to the consensus model TVCN, which remains north
of the NOAA HCCA corrected-consensus model.

The moderate to strong vertical wind shear that has been hindering
development of this system for the past several days is forecast to
diminish significantly during the next 12 h, and remain near 5 kt
through Tuesday. The low shear conditions, along with warm SSTs and
the significantly improved small, inner-core structure, should allow
for at least slow but steady strengthening despite the abundance of
dry mid-level air nearby. However, the low vertical wind shear and
tight inner-core wind field are also harbingers of possible rapid
intensification. For now, the new intensity forecast remains
conservative and similar to the previous advisory, and is above all
of the available intensity guidance, including the HWRF model.

Key Messages:
1. Dorian is forecast to strengthen and could be near hurricane
strength when it approaches the Lesser Antilles on Tuesday.

2. It is too soon to determine the specific timing or magnitude of
impacts in the Lesser Antilles, but tropical storm or hurricane
watches may be needed for a portion of the area on Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 10.7N  49.1W   35 KT  40 MPH
 12H  25/0600Z 11.0N  50.7W   40 KT  45 MPH
 24H  25/1800Z 11.4N  52.8W   45 KT  50 MPH
 36H  26/0600Z 11.9N  54.9W   50 KT  60 MPH
 48H  26/1800Z 12.7N  57.0W   55 KT  65 MPH
 72H  27/1800Z 14.6N  61.1W   65 KT  75 MPH
 96H  28/1800Z 16.5N  65.3W   75 KT  85 MPH
120H  29/1800Z 18.4N  69.0W   70 KT  80 MPH...INLAND

$$
Forecaster Stewart

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