Tropical Depression Dorian

[wxtrackercody]

Well thats a bit of a windshift. A bit further west than I expected. We probably have a LLC and MLC discontinuity.

Might have several centers or several vorticies rotating around a common center as well.

[Superstorm93]

 

Vmax: 35 knots

Pmin: 1013mbs 

 

[Ground Scouring]

Convective organization is still highly spasmodic and seems to be influenced by outflow boundaries / propagation. Actual organization near the MLC seems nil.

[Weathergun]

SPECIAL TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

350 PM EDT SUN JUL 28 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

DATA FROM AN AIR FORCE RECONNAISSANCE MISSION IN THE REMNANTS OF

DORIAN...LOCATED A COUPLE HUNDRED MILES NORTH OF THE LEEWARD

ISLANDS...INDICATE THAT THE DISTURBANCE DOES NOT HAVE A WELL-

DEFINED CENTER OF CIRCULATION AND CONSISTS OF A SHARP SURFACE

TROUGH. THE SYSTEM IS PRODUCING WINDS TO GALE FORCE WELL NORTH OF

THE LEEWARD ISLANDS...HOWEVER THE ASSOCIATED SHOWER AND

THUNDERSTORM ACTIVITY HAS WEAKENED DURING THE PAST FEW HOURS.

ENVIRONMENTAL WINDS ARE EXPECTED TO BE ONLY MARGINALLY CONDUCIVE FOR

REGENERATION DURING THE NEXT COUPLE OF DAYS. THIS SYSTEM HAS A

MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING

THE NEXT 48 HOURS AS IT MOVES WESTWARD TO WEST-NORTHWESTWARD AT

AROUND 20 MPH...PASSING NORTH OF THE LEEWARD ISLANDS AND PUERTO

RICO THROUGH MONDAY...AND MOVING OVER THE TURKS AND CAICOS ISLANDS

AND SOUTHERN BAHAMAS ON TUESDAY.

ADDITIONAL INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS

FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS

HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER BERG

[dan88]

Some light West winds and a possible center

200000 2004N 06241W 9769 00328 0141 +235 +229 118012 013 020 000 03
200030 2004N 06243W 9772 00325 0140 +235 +232 119010 011 020 001 03
200100 2004N 06245W 9770 00325 0137 +247 +233 099007 008 019 000 03
200130 2004N 06247W 9783 00313 0136 +242 +234 116006 008 /// /// 03
200200 2002N 06247W 9745 00350 0140 +235 +234 169002 004 019 000 00
200230 2000N 06247W 9749 00346 //// +231 //// 210001 002 017 000 01
200300 1958N 06247W 9774 00324 0143 +230 +230 296003 003 016 000 00
200330 1956N 06247W 9769 00329 0143 +230 +230 301004 005 015 001 03
200400 1955N 06247W 9772 00328 0144 +235 +228 282005 006 015 001 00
200430 1953N 06247W 9770 00331 0144 +235 +225 282005 006 013 002 00
200500 1951N 06247W 9769 00332 0145 +232 +229 295005 005 016 001 03
200530 1949N 06247W 9769 00333 0145 +233 +231 308006 006 016 000 05
200600 1947N 06247W 9772 00330 0146 +235 +230 298006 007 015 000 03
200630 1945N 06247W 9768 00333 0146 +235 +230 297007 007 016 001 00
200700 1944N 06247W 9772 00330 0147 +235 +228 298005 007 014 002 00
200730 1942N 06247W 9770 00332 0146 +235 +226 301005 005 015 000 00
200800 1940N 06247W 9771 00331 0146 +235 +225 311004 005 011 002 03
200830 1938N 06247W 9769 00334 0147 +238 +219 315003 005 013 000 03
200900 1936N 06247W 9772 00332 0147 +240 +220 306003 003 015 000 03
200930 1934N 06247W 9768 00336 0148 +238 +222 321003 004 015 000 03
201000 1933N 06247W 9772 00333 0148 +236 +225 321003 004 015 000 03
201030 1931N 06247W 9766 00338 0149 +235 +231 354003 004 016 000 00
201100 1929N 06247W 9769 00335 0149 +236 +227 350005 005 016 000 00
201130 1927N 06247W 9772 00333 0148 +235 +222 354004 005 017 000 03
201200 1925N 06247W 9771 00333 0148 +235 +217 351005 005 017 001 03
201230 1924N 06246W 9766 00336 0148 +235 +218 320003 004 /// /// 03

[Srain]

The 12Z HWRF suggests the remnants of Dorian may slowly strengthen as it nears Andros Island and pass through the Florida Straights just N of Cuba. The 12Z GFS Ensemble tracks suggest a somewhat similar solution that may bring a weak TD or TS Dorian into the SE Gulf of Mexico.

[Superstorm93]

Hypothetically, I could see how the circulation that the NHC is using for 91L/Dorian completely dissipates and a new low level circulation forms farther east towards the robust mid level circulation. Looks rather decent at the moment and it could be interesting if it blows up again tonight. 

 

Otherwise, it's TUTT time for this one. 

 

[shaggy]

It went from 91L back to Dorian on the NHC floater page.

[phil882]

Convection completely collapsed. There are a couple of convective buds near the mid-level vortex, but you are going to need more than that to bring back to low-level circulation. The good news is that the low-level circulation is so poorly defined, its not unreasonable to thing it could redevelop given another decent convective burst near the mid-level vortex. 

 

[wxtrackercody]

Some news... NHC is relocating the center of Dorian ENE of where the current fix is. As of the last fix from NHC the plane flew on only the west side of the system and thus the surface center was placed there. But there is the realization that another center is likely ENE of there. It will need to be investigated by microwave data this evening and the next hurricane hunter flight. - Jeff Berardelli

 

91L is much better off than a lot of people otherwise think if this feature is indeed a low-level center like it seems to be.

[phil882]

Some news... NHC is relocating the center of Dorian ENE of where the current fix is. As of the last fix from NHC the plane flew on only the west side of the system and thus the surface center was placed there. But there is the realization that another center is likely ENE of there. It will need to be investigated by microwave data this evening and the next hurricane hunter flight. - Jeff Berardelli

 

91L is much better off than a lot of people otherwise think if this feature is indeed a low-level center like it seems to be.

 

The thing that bugs me is that both the GFS and ECMWF have this mid-level vortex pretty well identified in their respective model runs. However, the best low-level vorticity continues to remain about a degree west of the mid-level vortex, and without the proper coupling the entire system doesn't develop. 

 

Its worth noting (however) that both the GFS and ECMWF dropped the ball with Andrea this year which was a classic sheared relocation TC that all of a sudden thrived in its relocated environment under a mid-level vortex. Its rare, but these top down reformations do happen from time to time and can be game changers. 

 

Some recent examples:

 

Andrea (2013)

Ernesto (2012)

Ophelia (2011)

Jose (2011)

[Derecho!]

Some news... NHC is relocating the center of Dorian ENE of where the current fix is. As of the last fix from NHC the plane flew on only the west side of the system and thus the surface center was placed there. But there is the realization that another center is likely ENE of there. It will need to be investigated by microwave data this evening and the next hurricane hunter flight. - Jeff Berardelli

 

91L is much better off than a lot of people otherwise think if this feature is indeed a low-level center like it seems to be.

 

 

Berardelli is a Miami TV Met, correct?

 

Sort of by definition a system can't be well off in any respect if recon can miss its center.   

 

 This smacks a bit of the old Bastardian "They aren't flying in the right part of the storm" stuff.

[wxtrackercody]

A TROUGH OF LOW PRESSURE...ASSOCIATED WITH THE REMNANTS OF DORIAN...
IS PRODUCING A SMALL BUT CONCENTRATED AREA OF SHOWERS AND
THUNDERSTORMS...AS WELL AS GALE-FORCE WINDS...A FEW HUNDRED MILES
NORTH-NORTHEAST OF THE LEEWARD ISLANDS. ALTHOUGH THERE ARE
CURRENTLY NO INDICATIONS OF A CLOSED LOW-LEVEL CIRCULATION AND A
WELL-DEFINED CENTER...ONLY A SMALL INCREASE IN ORGANIZED
THUNDERSTORM ACTIVITY COULD LEAD TO THE REFORMATION OF A TROPICAL
CYCLONE. ENVIRONMENTAL CONDITIONS ARE MARGINALLY CONDUCIVE FOR
REGENERATION...AND THIS SYSTEM HAS A MEDIUM CHANCE...50 PERCENT...
OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WESTWARD TO WEST-NORTHWESTWARD AT 15 TO 20 MPH. THIS DISTURBANCE IS
EXPECTED TO PASS WELL TO THE NORTH OF THE LEEWARD ISLANDS AND
PUERTO RICO TONIGHT AND MONDAY...AND MOVE OVER THE TURKS AND CAICOS
ISLANDS AND THE SOUTHEASTERN BAHAMAS ON TUESDAY.

 

Berardelli is a Miami TV Met, correct?

 

Sort of by definition a system can't be well off in any respect if recon can miss its center.   

 

 This smacks a bit of the old Bastardian "They aren't flying in the right part of the storm" stuff.

Yes.

[Derecho!]

Well, the 18Z init center was 20N and 62.5W. We'll see where they move it.

 

Edit: Wow, I didn't realize how much further W that is than where the apparent MLC is even now at 0Z.

[Derecho!]

New Init:

 

At 0000 UTC, 29 July 2013, TROPICAL WAVE DORIAN (AL91) was located in the North Atlantic basin at 20.4°N and 62°W. The current intensity was 35 kt and the center was moving at 16 kt at a bearing of 280 degrees. The minimum central pressure was 1011 mb.

 

So they indeed moved the center east, and a little N. Forward speed dropped from 22 to 16 knots.

[Srain]

00Z Tracks & Intensity:

 

 

 

 

[phil882]

This doesn't really suggest the low-level vortex has relocated under the mid-level vortex. IR can play tricks sometimes.

 

[Superstorm93]

From Stacy Stewart

 

Recon will be wheelps up at 10:30pm 

 MLCC/MULT ORBITING LLCCS NR 20.1N60.5W & 21.3N62

[phil882]

MLCC/MULT ORBITING LLCCS NR 20.1N60.5W & 21.3N62

 

Where does this come from? From my viewpoint looking at IR, you can see the distinct llv and mlv disjointed from one another, just as both the GFS and ECMWF currently depicted for 00z. 

 

[Superstorm93]

Where does this come from? From my viewpoint looking at IR, you can see the distinct llv and mlv disjointed from one another, just as both the GFS and ECMWF currently depicted for 00z. 

 

 

 

 

ATCF Fix:

 

ftp://ftp.nhc.noaa.gov/atcf/fix/fal912013.dat

[wxtrackercody]

Looking a bit better here. Mid-level center may be giving way to a new low-level center. And just in time for recon.

 

Don't know for sure.

 

[Superstorm93]

GFDL ensembles have been fairly decent with the track of Dorian since it left Africa, but I wouldn't focus on intensity we get an actual center (if ever) 

 

Pretty cut and dry though. If it moves over Cuba, no intensification. If it stays over open waters, gradual strengthening. 

 

We'll have to see what this looks like tomorrow morning, but overall I think that it has a somewhat decent shot at development or redevelopment. The wave axis ahead needs to die and the vigorous mid level circulation has to take over soon. Also, convection must redevelop tonight and become deep in order to get the top down process going once again. Without that, this is just going to be an annoying wave. All in all, I'd give it a 30% chance within 48 hours. IF (and that's a huge if) 91L has deep convection and a respectable low level presence by the time it reaches 72 west, I think you could double those chances. I do like the 00z coordinates though...

 

[phil882]

Looks like an open wave... with best wave axis near where I mentioned the LLV before near 20N/64W

 

 

[HurricaneJosh]

Not ready to get excited about a regeneration just yet.  Stepping back and looking at it with a fresh perspective, it just doesn't look that hawt.  I dunno.

 

But I notice social-media channels are a-buzz about it-- including fans of the iCyclone Facebook page, many of whom are sounding bullish in their comments:  https://www.facebook.com/iCyclone

[Derecho!]

If anything the convection is returning to the old LLC now than the MLC to the NE.

[Amped]

Ugh this thing won't die. My uneducated guess is  it will hold off until the coast of Cuba and then drop from about 1010mb to 996mb in the 12 hrs prior to landfall.  

 

There's a nice cloud pattern with it now but that can be deceiving.

[wxmx]

If anything the convection is returning to the old LLC now than the MLC to the NE.

I think you are confusing where the old LLC is, extrapolating a bit it would be somewhere between 64 and 65W, just above 20N...there's some convection there but it's getting sheared to hell from the  anticyclone that is closer to the MLC just south of 21N and around 63W. Convection is still disorganized, and ASCAT shows that this has a long way to work it's way down from the mid levels. There's still some potential, but the wave formerly known as Dorian needs to fire continuous deep convection soon.

[HurricaneJosh]

No change with the 2 am EDT TWO.  And, not to be a buzzkill, but it mentions that conditions become less favorable on Tuesday.  Blah.

 

Tracking this thing is like trying to get excited by an old, third-rate porn mag found in a box in the back of the garage.

[phil882]

Radar shows some sort of circulation (mid-low level perhaps) near 20.5N/65W. This is near where the old llv was heading earlier.

 

[Sunny and Warm]