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Hurricane Dorian (05L)


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Ok, probably my last post for the night. The 11 pm update will probably show a CAT5 hurricane, we shall see. And if you've followed Cranky, then you know we'll have a much better idea in the morning a

My disclaimer... As always, please refer to the latest official forecast from the National Hurricane Center as well as your local NWS forecast offices. 🙂 I'm here to pass along information from a

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This is an exceptionally hard forecast. For the time being it's hard to have much faith in modeling of very small discrepancies. It's clear forward speed, and the ridge/trough alignment and amplitude are the keys. The models have really started to deepen that trough a lot more which causes a strong pull north. But given that it's still late summer, it's possible that the models are overdoing the trough which would mean a slower turn to the north. And then depth of the trough aside if the storm is just to far south to be influenced by it, it can start tracking SW like the euro briefly showed. Just immensely complicated with multiple moving pieces whose strength matters. 

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Thursday, August 29, 5 PM Update

BULLETIN
Hurricane Dorian Advisory Number  22
NWS National Hurricane Center Miami FL       AL052019
500 PM AST Thu Aug 29 2019

...DORIAN FORECAST TO INTENSIFY DURING THE NEXT COUPLE OF DAYS...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...22.5N 67.7W
ABOUT 330 MI...535 KM E OF THE SOUTHEASTERN BAHAMAS
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

Interests in the northwestern and central Bahamas should monitor the
progress of Dorian.  Watches may be required for portions of this
area on Friday.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Hurricane Dorian was located
near latitude 22.5 North, longitude 67.7 West. Dorian is moving
toward the northwest near 13 mph (20 km/h), and this general
motion is expected to continue through Friday.  A west-northwestward
to westward motion is forecast to begin by Friday night and continue
into the weekend.  On this track, Dorian should move over the
Atlantic well east of the southeastern and central Bahamas tonight
and on Friday, approach the northwestern Bahamas Saturday, and move
near or over portions of the northwest Bahamas on Sunday.

Maximum sustained winds are near 85 mph (140 km/h) with higher
gusts.  Strengthening is forecast during the next few days, and
Dorian is expected to become a major hurricane on Friday, and
remain an extremely dangerous hurricane through the weekend.

Hurricane-force winds extend outward up to 15 miles (30 km) from the
center and tropical-storm-force winds extend outward up to 90 miles
(150 km).

The estimated minimum central pressure is 986 mb (29.12 inches).


HAZARDS AFFECTING LAND
----------------------
RAINFALL:  Dorian is expected to produce the following rainfall
accumulations this weekend into early next week:

The central Bahamas...1 to 2 inches, isolated 4 inches.
The northwestern Bahamas...3 to 5 inches, isolated 7 inches.
Coastal sections of the Southeast United States...5 to 10 inches,
isolated 15 inches.

This rainfall may cause life-threatening flash floods.

SURF:  Swells around the U.S. and British Virgin Islands and
Puerto Rico should gradually diminish today.  Swells are likely to
begin affecting the east-facing shores of the Bahamas and the
southeastern United States coast during the next few days.  These
swells are likely to cause life-threatening surf and rip current
conditions.  Please consult products from your local weather office.

204603_5day_cone_with_line_and_wind.png.2a8ac5f640144567017db549681a8ecc.png

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Wednesday, August 29 - 5 PM Discussion

Hurricane Dorian Discussion Number  22
NWS National Hurricane Center Miami FL       AL052019
500 PM AST Thu Aug 29 2019

There has been little overall change in the structure of Dorian
today
.  The hurricane has several well-defined bands of convection
wrapping into the center and a small central dense overcast.  The
small eye has not been as apparent in geostationary satellite
imagery this afternoon, but the NOAA Hurricane Hunter aircraft
reported concentric eyewall diameters of 4 and 22 n mi several
hours ago
.  The latest satellite intensity estimates still support
an initial intensity of 75 kt, which is also in line with the
earlier SFMR data from the aircraft.  The next reconnaissance
aircraft is scheduled to investigate the hurricane this evening.

Dorian is moving northwestward or 325 at 11 kt.  The hurricane
should continue moving northwestward tonight between an upper-level
low just to the west of Dorian and a mid-level ridge near Bermuda.
On Friday, the ridge is forecast to begin building westward to the
north of the cyclone, and this pattern is expected to cause the
hurricane to turn west-northwestward
.  A west-northwestward to
westward motion should then continue into the weekend with Dorian
moving near or over the northwestern Bahamas and toward the Florida
peninsula.  The guidance envelope has nudged southward this cycle,
with the ECMWF and HMON along the southern side, and the GFS
bracketing the northern side
.  There has also been an increase in
along-track spread or speed differences with day 5 positions among
the dynamical models ranging from near the northwestern Bahamas to
the northeastern Gulf of Mexico.  This appears to be the result of
differences in the models' depiction of the strength or lack thereof
of the western portion of the ridge by day 5.
 The new NHC track
forecast is essentially unchanged through the first 2 to 3 days, but
has been adjusted southward and somewhat slower than the previous
advisory at 96 and 120 hours
.  Users are reminded to not focus on
the exact forecast track, as typical forecast errors at days 4 and 5
are around 155 and 205 miles, respectively.

The new intensity forecast is unchanged from the previous one.
Dorian will be moving through a favorable environment of low
vertical wind shear and warm sea surface temperatures.  This should
allow for at least steady intensification, and Dorian is forecast to
become major hurricane on Friday
.  Dorian is predicted to remain a
dangerous hurricane throughout the remainder of the forecast period.
The NHC intensity forecast is again near the upper end of the
guidance in best agreement with the HWRF and FSSE models
.

The National Weather Service has begun 6-hourly upper-air soundings
across portions of the mid-Atlantic and southeastern United States.
Six-hourly balloons are also being launched in Bermuda and Nassau in
the Bahamas.  A NOAA G-IV synoptic surveillance mission is ongoing,
and the data from this flight will be assimilated into the 0000 UTC
model cycle.

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  29/2100Z 22.5N  67.7W   75 KT  85 MPH
 12H  30/0600Z 23.8N  68.7W   90 KT 105 MPH
 24H  30/1800Z 25.2N  70.4W  100 KT 115 MPH
 36H  31/0600Z 26.0N  72.3W  105 KT 120 MPH
 48H  31/1800Z 26.5N  74.2W  110 KT 125 MPH
 72H  01/1800Z 27.0N  77.7W  115 KT 130 MPH
 96H  02/1800Z 27.5N  80.0W  115 KT 130 MPH
120H  03/1800Z 28.1N  81.4W   65 KT  75 MPH...INLAND

204603_earliest_reasonable_toa_34.png.342220d81585811373e94d5824e7456f.png

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Here's the path so far of the NOAA Gulfstream IV "Gonzo". You can see the drop locations for the radiosondes that they've dropped so far. Right now they are flying at around 45,000 feet and doing upper air samples. This flight is to analyze the upper air steering currents to help determine where Dorian will go. All of this data is sent back for the next model run, and this data will be available for the 00z model initialization. In case you were wondering, the air temp at that altitude is -83 F. 🙂

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