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Hurricane Dorian (05L)


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Friday, August 30 - 5 AM Discussion Update

WTNT45 KNHC 300854
TCDAT5

Hurricane Dorian Discussion Number  24
NWS National Hurricane Center Miami FL       AL052019
500 AM AST Fri Aug 30 2019

There hasn't been a lot of new data since the Hurricane Hunter
planes departed Dorian several hours ago.  The convective pattern
on infrared satellite imagery has been nearly steady state,
although the latest Dvorak estimates from TAFB and SAB rose to
T5.0/90 kt.  These estimates, combined with the earlier aircraft
data, support maintaining an initial intensity of 90 kt.

Dorian's heading is very gradually turning toward the left, with
the latest estimate northwestward, or 320 degrees at 10 kt.  Dorian
is now being steered between a mid-tropospheric high centered near
Bermuda and a mid-/upper-level low located over the Bahamas
.  The
high is expected to expand westward, with a blocking ridge becoming
established over the western Atlantic during the next several days.
With the exception of COAMPS-TC and HMON, the other reliable models
are in excellent agreement through day 3, with Dorian turning
westward south of the ridge and moving near or over the
northernmost islands in the Bahamas Sunday and Monday.  After day
3, steering currents collapse as a break develops in the ridge, and
Dorian will likely slow down considerably as it approaches the
Florida peninsula
.  There is more spread among the deterministic
models and their ensemble members during that time, with
disagreement on exactly when and where Dorian will turn
northwestward and northward on days 4 and 5.
 That being said, the
tracks of the simple and corrected consensus models on this cycle
did not warrant much change to the official NHC forecast, with
perhaps just a slight southward adjustment on days 3 and 4.  The
biggest concern will be Dorian's slow motion when it is near
Florida, placing some areas of the state at an increasing risk of a
prolonged, drawn-out event of strong winds, dangerous storm surge,
and heavy rainfall.

The upper-level low to the west of Dorian continues to impart some
southwesterly shear over the hurricane, which has prevented it from
strengthening rapidly.  However, Dorian is expected to enter a more
favorable upper-level environment during the next 24 hours, which
should allow its structure to become more well developed.  Although
overall the environment ahead of the storm appears conducive for
strengthening, some models (in particular the ECMWF) suggest that
some northerly shear could come into play while Dorian moves
through the northwestern Bahamas, and for that reason the NHC
official intensity forecast is not quite as bullish as the HCCA,
Florida State Superensemble, and HWRF models
.  Still, Dorian is
forecast to become a dangerous major hurricane later and maintain
that status as it heads for the northwestern Bahamas and the
Florida peninsula.


Key Messages:

1. A Hurricane Watch is now in effect for the northwestern Bahamas,
where the risk of life-threatening storm surge and hurricane-force
winds this weekend has continued to increase.  Residents should
begin to execute their hurricane plans and listen to advice given
by local emergency officials.

2. There is an increasing likelihood of a prolonged period of
hazardous weather conditions that could last for a couple of days
in parts of Florida early next week.

3.  The risk of life-threatening storm surge along portions of the
Florida east coast has increased, although it is too soon to
determine where the highest storm surge will occur.  The risk of
devastating hurricane-force winds along the Florida east coast and
peninsula early next week has also increased, although it is too
soon to determine where the strongest winds 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.

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  30/0900Z 23.8N  69.1W   90 KT 105 MPH
 12H  30/1800Z 24.8N  70.3W  100 KT 115 MPH
 24H  31/0600Z 25.6N  72.0W  105 KT 120 MPH
 36H  31/1800Z 26.1N  73.8W  110 KT 125 MPH
 48H  01/0600Z 26.4N  75.5W  115 KT 130 MPH
 72H  02/0600Z 26.7N  78.3W  120 KT 140 MPH
 96H  03/0600Z 26.9N  80.1W  115 KT 130 MPH...INLAND

120H  04/0600Z 28.1N  81.4W   65 KT  75 MPH...INLAND

085550_5day_cone_no_line_and_wind.png.093a379bce0dd4e00584439ae757a0b5.png

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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

Posted Images

Notice how the wind field expands are Dorian approaches the coast. The red lines are hurricane force winds. I think Dorian will make landfall along Palm Beach County, but the counties to the north will take the worst of the battering from waves. The Bahama's will take a direct and devastating hit and there may not be much of Freeport left.

Snap346062449.thumb.jpg.566a37b7b3508987aaeeeea9201316c0.jpg

 

Snap346062448.thumb.jpg.8053e461790c29994016b0583807a5d0.jpg

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The slow forward speed is going to be the really big issue. Best I can figure right now, Dorian may be moving at 6 mph on the approach to the coast, and once inland, slows down even further to about 4-5 mph. I tried to get close to the NHC track markers for illustration purposes.

Snap346062450.thumb.jpg.00da7612a5bbf94744c60ea5e1c38b59.jpg

 

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This image depicts the steering currents in the atmosphere. You can see Dorian shooting the gap and the red arrow shows the path of least resistance for now. The big question is how much the Bermuda high builds back to the west. The stronger it becomes, the further west Dorian goes. After landfall the question is when does it allow Dorian to move NE. You can find this image here: http://www.daculaweather.com/4_sea_conditions.php

Snap346062457.jpg.b72cadeb1bbda79c45d965338cc45638.jpg

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We are borderline CAT3 right now, and I would bet that the next advisory brings it up to that speed. 

Conditions are getting more favorable for strengthening with each passing mile that she moves, and you can see the striated outflow in the southwest quadrant of the water vapor image, and now in the new visible images that are just coming in.

Snap346062464.thumb.jpg.289f09a8384e550a4fb36447cc19fe7f.jpg

Snap346062465.thumb.jpg.7ba72b7541dbf8366f64f1dca7d6b14f.jpg

 

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The red square box in the image is the latest center coordinate from the hurricane hunters. The NHC had Dorian as a CAT3 at 2:00 pm this afternoon, but she is just a few miles per hour off right now at 8:35 am. Dorian is certainly an over performer and keeps outpacing the models and the forecast. 

Snap346062471.thumb.jpg.fefaad035231d725a0d96be032e62cb9.jpg

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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 myriad of sources, not to make a hurricane forecast. It's not my job and I don't get paid to do it. 🙂 If you catch me saying "I think" (which is dangerous in itself), just know those are my personal opinions that carry little to no weight. So if "I think" don't go telling people that "I said". 😜 LOL!

In closing,  always heed the warnings from the experts. I'll do my part to make sure you have the VERY latest information regarding Dorian, from all of the official and unofficial sources. 

hurricanewarningflag_1070279.jpg.51b491d03b60efb945b637233f1e3af6.jpg

Thanks for following!

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SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS COLLEGE PARK MD
1325Z FRI AUG 30 2019

The 12Z NCEP model production suite is currently running on time.

CRITICAL WEATHER DAY STATUS...
CWD is currently not in effect. However, CWD is expected to be
declared within the next 24 hours due to Hurricane Dorian and
associated impacts to Florida.

 

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