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Hurricane Dorian (05L)


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August 26, 7:58 pm

"Interaction with Hispaniola and
possibly Puerto Rico should result in some weakening in 72-96
hours, followed by restrengthening on days 4 and 5 when Dorian will
be moving over the very warm waters in the Bahamas in low shear
conditions. Most of the global models along with the statistical-
dynamical SHIPS and LGEM intensity models are now showing pronounced
strengthening while Dorian is moving near or through the Bahamas, so
the official forecast shows a significant change to the previous
one at 96 and 120 hours
. However, confidence in the intensity
forecast at days 4 and 5 is very low given the uncertainty about how
much of Dorian's core will interact with Hispaniola."

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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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August 27, 5 am

 

Tropical Storm Dorian Discussion Number  12
NWS National Hurricane Center Miami FL       AL052019
500 AM AST Tue Aug 27 2019

Dorian passed over Barbados a few hours ago and it is now very near
the Windward Islands.  Data from the Air Force Hurricane Hunters
earlier this morning suggest that the storm has held steady in
intensity with a blend of the flight level and SFMR winds
supporting a wind speed of 45 kt
.  The Caribbean composite
radar data show that Dorian remains a very compact system and that
it still lacks a well-defined inner core.

Dry air in the mid-levels of the atmosphere around Dorian has been
causing the storm to remain in a fairly steady state during the
past day or so despite relatively low wind shear conditions and warm
SSTs.  The models show this dry air persisting in the vicinity of
the system while it tracks across the Caribbean during the next day
or two, so it seems likely that Dorian will continue to only
gradually intensify during that time.  When Dorian nears Hispaniola
in 36 to 48 hours, there will likely be some increase in wind shear
and those less favorable winds aloft and the interaction with the
landmasses of Puerto Rico and Hispaniola should cause considerable
weakening
.  Once the system moves north of the Greater Antilles, the
environmental conditions become more favorable for intensification,
and most of the intensity guidance responds by showing an increase
in winds
.  However, there remains considerable uncertainty for this
part of the forecast because the future intensity of Dorian will be
quite dependent on how much land interaction there is with the
mountainous island of Hispaniola
.  The NHC intensity forecast lies
near the upper end of the guidance in the short term, while the
system is over the Caribbean Sea, but near the middle of the
guidance envelope after that.

The storm is moving west-northwestward at 11 kt steered by a
subtropical ridge to the north.  This general motion should
continue for another 12 to 24 hours taking Dorian across the eastern
Caribbean Sea.  After that time, a slight turn to the northwest is
likely when the cyclone nears the eastern portion of a cut off mid-
to upper-level low and moves toward a weakness in the ridge.  This
should take Dorian across the Dominican Republic and the Mona
Passage and over the Bahamas in the 3 to 4 day time period
.  A ridge
is likely to rebuild to the north of Dorian when it is forecast to
be over the Bahamas and that could cause it to turn slightly to the
left by the end of the forecast period
.  The new NHC track forecast
is largely unchanged while Dorian is in the Caribbean, but it has
been shifted slightly to the north thereafter. Users are reminded
not to focus on the details of the extended track forecast as the
average 5-day track error is around 200 miles.


Key Messages:

1. Dorian is expected to bring tropical storm conditions to portions
of the Lesser Antilles during the next several hours, where
tropical storm watches and warnings are in effect.  Rainfall of 3 to
6 inches is expected from Martinique to St. Vincent with isolated
totals as high as 10 inches possible.

2. Tropical storm conditions are expected and hurricane conditions
are possible in Puerto Rico on Wednesday, where a tropical storm
warning and hurricane watch have been issued. Rainfall of 2 to 4
inches with maximum totals of 6 inches are possible across Puerto
Rico and St. Croix.

3. Hurricane and Tropical Storm Watches have been issued for
portions of the Dominican Republic.

4. While uncertainty remains high, wind and rain impacts are
possible in the Bahamas and Florida later this week and this
weekend. Residents in these areas should monitor the progress of
Dorian and ensure that they have their hurricane plan in place.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0900Z 13.5N  60.7W   45 KT  50 MPH
 12H  27/1800Z 14.4N  62.3W   50 KT  60 MPH
 24H  28/0600Z 15.7N  64.5W   55 KT  65 MPH
 36H  28/1800Z 17.0N  66.5W   60 KT  70 MPH
 48H  29/0600Z 18.5N  68.2W   60 KT  70 MPH
 72H  30/0600Z 21.7N  71.4W   50 KT  60 MPH
 96H  31/0600Z 24.7N  75.1W   60 KT  70 MPH
120H  01/0600Z 27.1N  79.6W   60 KT  70 MPH

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Tuesday, August 27, 6:30 am

Right now we're playing a waiting game with Dorian. Until it gets past the big island, we're not going to know a whole lot more than we do now. It will be important to note any slight changes in the track as that can have bigger implications down the road.  You can read the 5am update in the previous comment.

The hurricane hunters are up early this morning, flying out of Curacao and headed toward Dorian right now.

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The "Weather Recon Plan of the Day" is below, and you can see that they are now making flights every 6 hours. NOAA 49 is the Gulfstream jet and you can see that it is used to sample the upper air steering patterns around Dorian. That information is used to help determine the path of least resistance for Dorian and therefore the potential track. NOAA 42 is "Kermit", NOAA's P3, and the "Teal" call signs are from the Air Force Reserve 53rd Weather Reconnaissance Squadron flying WC-130J aircraft. Notice the different altitudes that the different aircraft fly at, sampling from the surface to 45,000 feet. 

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There is an area of dry air that Dorian has to pass through before things start to get better. Reminds me of the Wizard of Oz when they get to the dark forest. 🙂 Notice the darker area in front of Dorian. This is a low level water vapor image. 

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There is also an area of wind shear that will help to prevent any major strengthening between now and the big island. The area in the white circle is what Dorian will have to pass through

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As far as track

GFS Ensemble
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Early Cycle Track Guidance
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EPS Track Guidance
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Intensity Guidance
aal05_2019082706_intensity_early.thumb.png.7cb31b7d36af4fe28de8f852cb2b2aa1.png

 

So you can see why I'm starting to have a concern for Florida. We have no idea how much Dorian will fall apart as it passes Hispaniola, but its small size and defiant determination, it certainly has a fighting chance. Let's hope that once it does make it to more favorable conditions, that they aren't too favorable. Intensity forecast are difficult to predict.

Make a note of how the models view the eventual track of Dorian, and notice where it goes. That's another reason for us to keep a close eye on this little system right now.

 

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  • NorthGeorgiaWX changed the title to Tropical Storm Dorian (05L)

Tuesday, August 27, 11 am Update

Tropical Storm Dorian Discussion Number  13
NWS National Hurricane Center Miami FL       AL052019
1100 AM AST Tue Aug 27 2019

Dorian moved directly across the center of St. Lucia around 1000
UTC, which resulted in a significant disruption of the small
inner-core wind field
. An Air Force Reserve reconnaissance aircraft
had difficulty identifying a clear-cut center and radar data from
Martinique indicates that the mid-level circulation has also been
disrupted somewhat. Having said that, the overall appearance
of the cyclone in both satellite and radar imagery has improved
since this time yesterday, although a pronounced dry slot is now
evident in the southeastern quadrant of the circulation. The
initial intensity of 45 kt is being maintained based on aircraft
flight-level and SFMR surface wind data.

The initial motion remains west-northwestward or 295/11 kt. There
is still no significant change to the previous forecast track or
reasoning.
Although the inner-core wind field and low-level center
have been disrupted, the overall circulation envelope has remained
intact and is expected to move west-northwestward to northwestward
for the next 36-48 hours toward a break in the subtropical ridge
located well north of Dorian. The mid- to upper-level low currently
located east of the Bahamas that has weakened the ridge is forecast
to gradually weaken while digging southeastward across the central
Bahamas and toward central Cuba over the next 3-4 days, resulting in
Dorian turning northwestward on day 3 before turning back toward the
west-northwest on days 4 and 5. How quickly the west-northwestward
turn occurs will depend heavily on the evolution of the upper-low.

For now, the previous forecast track remains unchanged other than to
push out the track a little northeastward at 48 and 72 hours. The
NHC model guidance remains tightly packed and in good agreement on
this scenario, and the new forecast track lies very close to an
average of the various consensus track models. Users are reminded
not to focus on the details of the extended track forecast as the
average 5-day track error is around 200 miles.

Dry air continues to plague Dorian, and interaction with the
mountainous terrain of St. Lucia will likely hinder significant
development in the short term. However, the models continue to
indicate that the upper-level flow pattern and shear conditions are
expected to remain favorable for strengthening throughout the
forecast period, so it is uncertain why the dynamical models are not
showing more development and strengthening when compared to the more
robust statistical SHIPS intensity models, especially at days 4 and
5 when Dorian will be moving over SSTs greater than 29 deg C and
into a fairly moist environment.
For now, the official intensity
forecast remains basically midway between the stronger SHIPS model
and the much weaker global and regional models. Given the large
spread in the guidance, there is lower than normal confidence in the
intensity forecast, especially on days 4 an 5.

Key Messages:

1. Tropical storm conditions will continue in portions of the Lesser
Antilles during the next several hours. Tropical storm conditions
are expected and hurricane conditions are possible in Puerto Rico on
Wednesday and in portions of the Dominican Republic Wednesday night
and Thursday.

2. Heavy rainfall over portions of the Lesser Antilles, Puerto Rico,
and the Dominican Republic could produce flash flooding during the
next few days.

3. The threat of winds and heavy rains later this week into this
weekend in the Turks and Caicos, the Bahamas, and Florida is
increasing. Residents in these areas should monitor the progress of
Dorian and ensure that they have their hurricane plan in place.

4. Uncertainty in the intensity forecast later this week remains
higher than usual due Dorian's potential interaction with Hispaniola
and Puerto Rico.

FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 14.2N  61.8W   45 KT  50 MPH
 12H  28/0000Z 15.2N  63.4W   50 KT  60 MPH
 24H  28/1200Z 16.5N  65.5W   55 KT  65 MPH
 36H  29/0000Z 17.9N  67.4W   60 KT  70 MPH
 48H  29/1200Z 19.5N  69.0W   60 KT  70 MPH
 72H  30/1200Z 22.8N  72.0W   55 KT  65 MPH
 96H  31/1200Z 25.6N  76.0W   60 KT  70 MPH
120H  01/1200Z 27.8N  80.4W   60 KT  70 MPH

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You can see in this image exactly how that needle needs to be threaded.
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Here are two of the hurricane models based off the new GFS model. According to Tom Downs with Weatherbell, one of the side benefits to any improvements to the GFS would be improved forecasts from the HMON and HWRF, which use the GFS for initial conditions and/or to force the boundaries of the grids they are using.

HMON
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HWRF
hwrf-dorian05l-uv925_mslp-7339200.thumb.png.ca381226bcd8f790a199bd799ea4637c.png
 

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Seas near Dorian

--------------------------
TROPICAL STORM DORIAN NEAR 14.2N 61.8W 1005 MB AT 1500 UTC AUG
27

  • MOVING WNW OR 295 DEG AT 11 KT.
  • MAXIMUM SUSTAINED WINDS 45 KT
  • GUSTS 55 KT.
  • TROPICAL STORM FORCE WINDS WITHIN 40 NM N SEMICIRCLE...30 NM SE QUADRANT AND 0 NM SW QUADRANT.  
  • SEAS 12 FT OR GREATER WITHIN 30 NM NW AND SE QUADRANTS...45 NM NE QUADRANT AND 15 NM SW QUADRANT WITH SEAS TO 8 FT.


.24 HOUR FORECAST
TROPICAL STORM DORIAN NEAR 16.5N 65.5W.

  • MAXIMUM SUSTAINED WINDS 55 KT GUSTS 65 KT.
  • TROPICAL STORM FORCE WINDS WITHIN 50 NM N SEMICIRCLE...40 NM SE QUADRANT AND 30 NM SW
    QUADRANT.
  • SEAS 12 FT OR GREATER WITHIN 45 NM OF CENTER.
  • ELSEWHERE WITHIN 90 NM OF CENTER WINDS 20 TO 33 KT. SEAS 8 TO 12 FT.


.48 HOUR FORECAST

TROPICAL STORM DORIAN NEAR 19.5N 69.0W.

  • MAXIMUM SUSTAINED WINDS 60 KT GUSTS 75 KT.
  • TROPICAL STORM FORCE WINDS WITHIN 60 NM N SEMICIRCLE...50 NM SE QUADRANT AND 40 NM SW QUADRANT.
  • SEAS 12 FT OVER ATLC WATERS S OF 20N BETWEEN 68W AND 70W.
  • ELSEWHERE OVER ATLC WATERS S OF 21N BETWEEN 67W AND 71W WINDS 20 TO 33 KT. SEAS 8 TO 12 FT.


.72 HOUR FORECAST

TROPICAL STORM DORIAN NEAR 22.8N 72.0W.

  • MAXIMUM SUSTAINED WINDS 55 KT GUSTS 65 KT.
  • EXTENDED OUTLOOK...USE FOR GUIDANCE ONLY...ERRORS MAY BE LARGE.


.96 HOUR FORECAST

TROPICAL STORM DORIAN NEAR 25.6N 76.0W.

  • MAXIMUM SUSTAINED WINDS 60 KT GUSTS 75 KT.


.120 HOUR FORECAST

TROPICAL STORM DORIAN NEAR 27.8N 80.4W.

  • MAXIMUM SUSTAINED WINDS 60 KT GUSTS 75 KT.
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I'm assuming the center forming north almost the entire ensemble suite makes a Puerto Rico landfall a possibility. And at this point it seems certain that it's not going to get anywhere near the storm shredding mountains of Hispaniola as they are all from the central part of the island westward. The eastern side merely has a few 4-600 ft hills which will help but definitely won't stop a storm in its tracks. download.png.f5059c51d4a1548c076c6ac841df794b.png

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1 hour ago, KingOfTheMountains said:

I'm assuming the center forming north almost the entire ensemble suite makes a Puerto Rico landfall a possibility. And at this point it seems certain that it's not going to get anywhere near the storm shredding mountains of Hispaniola as they are all from the central part of the island westward. The eastern side merely has a few 4-600 ft hills which will help but definitely won't stop a storm in its tracks. download.png.f5059c51d4a1548c076c6ac841df794b.png

If you are rooting for Dorian, the more northern track is great.

 

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Ocean temps will not be a factor once Dorian gets past the islands. Nothing but clear sailing and warm water. Just what every sailor dreams of. 😉 Except in this case. 

Notice the colder water just off the central FL coast. That could help to contain the intensity assuming Dorian makes it that far. 

http://www.daculaweather.com/4_sea_temp.php
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satlanti_fc.thumb.gif.153eabecee29c3264f156b5c726c2785.gif

 

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It's really frustrating that out to sea doesn't appear to even be an option with this one. No matter what it does human impacts are certain. Obviously it going over the mountains of Hispaniola would be best case scenario for the US but that kind of terrain and a tropical system are a deadly combination for the people that live there and the western side of the island is very densely populated. And we all know what Puerto Rico has been through in the last year, so any storm hitting there would be traumatizing for many. Through the gap and out to sea would be the best option for all but unfortunately doesn't appear to be on the table. 

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1 minute ago, KingOfTheMountains said:

It's really frustrating that out to sea doesn't appear to even be an option with this one. No matter what it does human impacts are certain. Obviously it going over the mountains of Hispaniola would be best case scenario for the US but that kind of terrain and a tropical system are a deadly combination for the people that live there and the western side of the island is very densely populated. And we all know what Puerto Rico has been through in the last year, so any storm hitting there would be traumatizing for many. Through the gap and out to sea would be the best option for all but unfortunately doesn't appear to be on the table. 

The best option for all of those people is the thread the needle option. The interesting part is how the more northern track changes things in terms of intensity. "If" it makes it through relatively unscathed, I would not be surprised to see a stronger storm than what is currently advertised. 

12Z GFS ensemble

gfs-five05l-1566907200-6907200.thumb.png.1e22d330e046e0fc38508eb85209ee95.png

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