Hurricane Dorian Discussion Number 31
NWS National Hurricane Center Miami FL AL052019
1100 PM EDT Sat Aug 31 2019
Data from both Air Force and NOAA Hurricane Hunter aircraft indicate
that Dorian remains a very powerful hurricane, and the satellite
presentation is still quite impressive with a very stable,
well-defined eye. There has been no evidence of concentric eyewalls
in aircraft or microwave data, which is somewhat surprising given
that the intensity has been at category 4 strength for 24 hours.
Both aircraft measured peak flight-level winds that support an
initial intensity of 130 kt. There have been some higher surface
wind estimates from the SFMR, but these data are questionable based
on our experience of very high SFMR-measured wind speeds in recent
strong hurricanes that didn’t match standard flight-level wind
reductions.
Dorian is forecast to continue moving over very warm waters and
into a low-shear environment during the next 12-24 hours, so some
additional strengthening is possible. Difficult-to-predict
eyewall cycles, however, are likely to begin at some point within
the next day or so and could cause fluctuations in intensity. After
72 hours, increasing southerly shear is likely to produce gradual
weakening, but Dorian is foreast to remain a dangerous hurricane
through the forecast period.
The hurricane is moving westward or 280/7 kt. A high pressure ridge
to the north of Dorian is predicted to remain intact into early
Sunday, and the hurricane should continue westward. By late Sunday,
the dynamical models erode the western portion of the ridge, which
should cause the hurricane to slow down and become nearly stationary
over the northwestern Bahamas in 36 to 48 hours. After that time,
the weakness in the ridge becomes more pronounced, and Dorian is
expected to turn northwestward, and eventually northeastward near
the southeastern United States coast. Although there is general
agreement on this overall scenario, there is still considerable
spread on how close the storm will track to the east coast of
Florida and the southeastern coast of the United States. The latest
HWRF run has shifted westward and takes Dorian across the coast of
central Florida. The 18Z GFS also shifted a little left closer to
the Florida coast. The latest multi-model consensus aids shifted
west closer to the previous NHC track, so very little change to
that forecast was made. Although the exact NHC track forecast lies
east of the Florida peninsula, a track closer to the coast or even
a landfall remain a possibility. Since the updated track was
slightly slower than the previous advisory, no additional watches
are needed for Florida at this time.
Key Messages:
1. A prolonged period of life-threatening storm surge, devastating
hurricane-force winds, and heavy rains capable of life-threatening
flash floods are expected on the Abaco Islands and Grand Bahama
Sunday through Monday, and a hurricane warning is in effect for
these areas.
2. A tropical storm watch is in effect for a portion of the Florida
east coast. Since Dorian is forecast to slow down and turn northward
as it approaches the coast, life-threatening storm surge and
dangerous hurricane-force winds are still possible along portions of
the Florida east coast by the early to middle part of next week.
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. There is an increasing risk of strong winds and dangerous storm
surge along the coasts of Georgia, South Carolina, and North
Carolina during the middle of next week. Residents in these areas
should continue to monitor the progress of Dorian.
4. Heavy rains, capable of life-threatening flash floods, are
possible over coastal sections of the southeastern United States
from Monday through Thursday.
