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Hurricane Dorian Discussion Number  21
NWS National Hurricane Center Miami FL       AL052019
1100 AM AST Thu Aug 29 2019

The small eye of Dorian has appeared intermittently in infrared
satellite imagery this morning.  Recent reports from a NOAA P-3
aircraft indicate that there is now a double eyewall structure,
with a small inner eye only 5 n mi in diameter and a larger 25-n mi
diameter outer eyewall. The minimum pressure has fallen to
around 986 mb.  The concentric eyewall structure is likely why the
aircraft has not found any stronger winds yet in the storm, despite
the decrease in central pressure. The initial intensity remains 75
kt for this advisory.

Aircraft and satellite fixes show that Dorian is moving
northwestward, or 325 degrees at 11 kt.  Dorian is forecast to
continue moving northwestward during the next 24-36 hours between an
upper-level low that will be dropping southwestward across the
Florida Straits and a mid-level ridge to the northeast of the
hurricane.  After that time, a ridge is forecast to build to the
north of Dorian, which should cause the track to bend back toward
the west-northwest. The track guidance becomes more divergent beyond
72 hours, primarily due to model differences in the strength of the
ridge and whether a weakness develops in the ridge late in the
period. The new NHC track forecast is virtually unchanged from the
previous advisory, and lies very close to the multi-model consensus.
It should be noted that the ECMWF, UKMET, and HFIP corrected
consensus models remain south of the official forecast. The spread
of the deterministic models and the various ensemble guidance is
still considerable at days 4 and 5, and it is too soon to specify
where along the Florida east coast the greatest impacts could
occur.

Environmental conditions consisting of warm waters and low vertical
wind shear along the path of the hurricane should allow for at least
steady intensification during the next 2 to 3 days.  With the small
inner core and favorable conditions, rapid strengthening also
remains a possibility, although not likely in the very short term
given the concentric eyewall structure.  The updated NHC intensity
forecast calls for Dorian to become a major hurricane on Friday, and
shows a slightly higher peak intensity than the previous forecast.
The official forecast is at the upper end of the guidance, in best
agreement with the HCCA and HWRF models.

Key Messages:

1. The risk of life-threatening storm surge and hurricane-force
winds this weekend continues to increase in the northwestern
Bahamas, and hurricane watches could be issued there tonight or
Friday.  Residents should have their hurricane plan in place and
listen to advice given by local emergency officials.

2. There is an increasing likelihood of life-threatening storm surge
along portions of the Florida east coast late this weekend or early
next week, although it is too soon to determine where the highest
storm surge will occur. Residents should have their hurricane plan
in place, know if they are in a hurricane evacuation zone, and
listen to advice given by local emergency officials.

3. The risk of devastating hurricane-force winds along the Florida
east coast and peninsula late this weekend and early next week
continues to increase, although it is too soon to determine where
the strongest winds will occur.

4. Regardless of the exact track of Dorian, heavy rains are expected
to occur over portions of the Bahamas, Florida, and elsewhere in the
southeastern United States this weekend and into the middle of next
week.


FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 21.4N  67.2W   75 KT  85 MPH
 12H  30/0000Z 22.9N  68.1W   85 KT 100 MPH
 24H  30/1200Z 24.5N  69.6W  100 KT 115 MPH
 36H  31/0000Z 25.6N  71.4W  105 KT 120 MPH
 48H  31/1200Z 26.3N  73.4W  110 KT 125 MPH
 60H  01/0000Z 26.7N  75.2W  110 KT 125 MPH
 72H  01/1200Z 27.0N  76.9W  115 KT 130 MPH
 96H  02/1200Z 27.5N  79.8W  115 KT 130 MPH
120H  03/1200Z 28.1N  81.5W   65 KT  75 MPH...INLAND

$$
Forecaster Brown

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