ATL: DEBBY - Post-Tropical

[wxman57]

Debby's best days are way behind it. It's merged with the cold front and is ingesting plenty of dry air as it accelerates up the front into higher and higher shear. NHC will probably issue the final advisory this morning or they may wait until this afternoon. Bones says it's time to call this one. And he says he's looking forward to a nice [b]quiet[/b] 4th of July week.

Always nice to see Bones but he may be replaced by Lazarus soon. I agree its got a tough road ahead to re-strengthen, but for clarification, the latest HPC surface analysis and their forecast charts show Debby is not merged with the front (it's a stationary front now) and isn't forecast to merge with it either.
Here's the HPC?NCEP loop (for those who don't know, all TC positions are done in cooperation with the NHC):

http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html

Just because the met didn't indicate that they'd merged, doesn't mean it isn't so. They probably kept the front away from Debby because the NHC hadn't declared it frontal yet. But I can clearly see that it's part of the front now. The front was incorrectly analyzed as being in southern Georgia when it's actually south to near Tampa now. Dew points are in the mid 60s down to the north-central FL peninsula. That's not MT air, it's behind the front.

My current analysis (below) indicates that the cold front is not in Georgia, it's well south into central Florida. The wind shift has just about reached Tampa, but the mid 60s dew points lag a bit behind the front. The frontal boundary clearly connects into what's left of Debby - it's not way off to the north.

[ozonepete]

I see what you're saying. Thanks for the great, detailed analysis. I never thought the front was way off to the north. But I'm just saying that it's not merged yet either. For a complete merge the cold and warm sectors of the front would have to be feeding into the center of circulation, which they aren't. The front is still to the north and west of Debby's center if you look at the winds analysis from SPC at 1300. Also, the main circulation still contains very moist air. You can see the sharp line where dewpoints drop off rapidly to the northwest and over Florida but hasn't been entrained into Debby, YET.... Not sayin' it won't happen soon.

I'm just bringing this up because I enjoy getting down to the granular with you. Nobody knows the details more than you do. Thanks for the discussion.

And imho we should all have a pretty quiet fourth hopefully.

I'm adding the color key for dewpoints since it's too hard to read on the main chart.

[cycloneye]

WTNT34 KNHC 271436
TCPAT4

BULLETIN
TROPICAL DEPRESSION DEBBY ADVISORY NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012
1100 AM EDT WED JUN 27 2012

...DEBBY MOVING AWAY FROM FLORIDA...HEAVY RAIN THREAT DECREASING...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...29.7N 79.8W
ABOUT 90 MI...145 KM E OF ST. AUGUSTINE FLORIDA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...E OR 85 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...1001 MB...29.56 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 AM EDT...1500 UTC...THE CENTER OF TROPICAL DEPRESSION DEBBY
WAS LOCATED NEAR LATITUDE 29.7 NORTH...LONGITUDE 79.8 WEST. THE
DEPRESSION IS MOVING TOWARD THE EAST NEAR 10 MPH...17 KM/H. A TURN
TOWARD THE EAST-NORTHEAST IS EXPECTED DURING THE NEXT DAY OR TWO
WITH SOME INCREASE IN FORWARD SPEED. ON THE FORECAST TRACK...DEBBY
SHOULD CONTINUE TO MOVE AWAY FROM FLORIDA.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 48
HOURS.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB...29.56 INCHES.


HAZARDS AFFECTING LAND
----------------------
STORM SURGE...ELEVATED WATER LEVELS IN AREAS OF ONSHORE WINDS ALONG
THE SOUTHWESTERN AND NORTHEASTERN COASTS OF FLORIDA SHOULD SUBSIDE
LATER TODAY. FOR INFORMATION SPECIFIC TO YOUR AREA...PLEASE SEE
PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE OFFICE.

RAINFALL...RAINFALL ASSOCIATED WITH DEBBY WILL CONTINUE TO DIMINISH
ACROSS THE FLORIDA PENINSULA TODAY. ADDITIONAL ISOLATED RAINFALL
AMOUNTS OF UP TO ONE INCH WILL BE POSSIBLE IN SOME OF THE LINGERING
RAIN BANDS...MAINLY OVER SOUTHERN FLORIDA.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 PM EDT.

$$
FORECASTER KIMBERLAIN

WTNT44 KNHC 271438
TCDAT4

TROPICAL DEPRESSION DEBBY DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012
1100 AM EDT WED JUN 27 2012

DEBBY IS STRUGGLING TO SURVIVE AS A TROPICAL CYCLONE. OCCASIONAL
BURSTS OF CONVECTION CONTINUE TO FORM NEAR THE CENTER...BUT ARE
IMMEDIATELY BEING PUSHED TO THE EAST BY STRONG WESTERLY SHEAR. IN
FACT...AT 12Z...THE CONVECTION WAS TOO DISORGANIZED TO WARRANT A
DVORAK CLASSIFICATION. THE LOW-LEVEL CENTER HAS BECOME INCREASINGLY
DISTORTED...WITH AN ELONGATED NORTHEAST-TO-SOUTHWEST APPEARANCE. A
LOW-LEVEL BAROCLINIC ZONE IS ALSO IMPINGING ON THE CYCLONE BUT HAS
NOT YET BECOME INVOLVED WITH THE CIRCULATION CENTER. BUOY REPORTS
NEAR THE CENTER SHOW 1-MINUTE WINDS OF AROUND 25 KT. IT IS ASSUMED
THAT STRONGER WINDS ARE OCCURING IN THE CONVECTION TO THE EAST...SO
THE INITIAL INTENSITY IS KEPT AT 30 KT.

SATELLITE...RADAR...AND SYNOPTIC DATA INDICATE THAT THE CENTER OF
DEBBY MOVED INTO THE WESTERN ATLANTIC AROUND 8Z. USING THESE DATA
SOURCES...THE INITIAL MOTION ESTIMATE IS 085/09. ALTHOUGH A DEEP
TROUGH OVER THE WESTERN ATLANTIC WILL BE IN THE PROCESS OF LIFTING
OUT OVER THE NEXT COUPLE OF DAYS...GLOBAL MODELS SHOW IT HAVING
SUFFICIENT AMPLITUDE TO DRAW DEBBY EAST-NORTHEASTWARD. HAVING
GAINED ENOUGH LATITUDE...STRONGER MID-LATITUDE WESTERLY FLOW SHOULD
THEN CAUSE DEBBY TO ACCELERATE NORTHEASTWARD FOR THE REMAINDER OF
THE FORECAST PERIOD. THE ECMWF/GFS/UKMET ARE IN GOOD AGREEMENT ON
THIS SCENARIO...BUT THE REGIONAL DYNAMICAL MODELS SHOW DEBBY BEING
LEFT BEHIND BY THE WESTERN ATLANTIC TROUGH. ASSUMING THAT DEBBY
REMAINS A DISTINCT ENTITY...THE FORMER CAMP OF MODELS FAVORS THIS
SCENARIO AND SO DOES THIS OFFICIAL FORECAST.

ALTHOUGH THERE SHOULD BE A RELATIVE DECREASE IN THE SHEAR OVER THE
CYCLONE AFTER 24 HOURS...DEBBY WILL REMAIN SURROUNDED BY A LARGE
POOL OF VERY DRY AND STABLE AIR OVER THE WESTERN ATLANTIC EVEN
AFTER THE FRONTAL BOUNDARY RETREATS. THESE FACTORS SHOULD TEMPER
ANY SIGNIFICANT RE-INTENSIFICATION. THE SHIPS/LGEM GENERALLY AGREE
WITH THIS IDEA...NO LONGER SHOWING MUCH STRENGTHENING. IT SHOULD BE
NOTED THAT THE GFS SHOWS DEBBY LOSING ORGANIZATION DURING THE NEXT
48 HOURS AND BECOMING AN OPEN WAVE OVER THE CENTRAL ATLANTIC. IN
THE FACE OF THESE NEGATIVE ENVIRONMENTAL FACTORS...THERE IS A
POSSIBILITY THAT DEBBY WILL DISSIPATE SOON.


FORECAST POSITIONS AND MAX WINDS

INIT 27/1500Z 29.7N 79.8W 30 KT 35 MPH
12H 28/0000Z 30.1N 77.5W 30 KT 35 MPH
24H 28/1200Z 30.5N 74.8W 30 KT 35 MPH
36H 29/0000Z 31.3N 71.8W 30 KT 35 MPH
48H 29/1200Z 32.3N 69.5W 30 KT 35 MPH
72H 30/1200Z 35.5N 65.3W 30 KT 35 MPH
96H 01/1200Z 40.0N 60.0W 35 KT 40 MPH
120H 02/1200Z 46.0N 48.0W 35 KT 40 MPH

$$
FORECASTER KIMBERLAIN

[wxman57]

The low-level dry air behind the front isn't feeding into Debby's center because there isn't much inflow at all into Debby. I think the NHC will take a long look at it today and declare it dead on the afternoon advisory.

[ozonepete]

The low-level dry air behind the front isn't feeding into Debby's center because there isn't much inflow at all into Debby. I think the NHC will take a long look at it today and declare it dead on the afternoon advisory.

I agree with you they may stop advisories today, but I would think they will wait until the 12Z model runs are in and see what they say. I also wouldn't be surprised if they said it's merged or partially merged with the front either; I could see the latter especially. We will see shortly in the 11AM discussion.

[ozonepete]

11 AM says it's not merged yet. But they are listening closely to Bones.

[cycloneye]

A reminder to the members that we have a Debby advisories thread where the discussions are posted.

[ozonepete]

A reminder to the members that we have a Debby advisories thread where the discussions are posted.

Oops. sorry Luis.

[Sanibel]

Plenty of spin to re-establish over the Gulf Stream, in my opinion.

[ROCK]

Toast.....I agree with Bones.....time to move on....

[PTrackerLA]

Goodbye Debby. I'm so tired of seeing your name in caps and my mind initially reading it as "DERBY" lol.

[jdray]

CR218 in Clay County, big corridor for many Middleburg residents is closed due to washout.
Nolan Rd is also washed out, leaving some residents stranded, they have temp patched Nolan Rd, but CR218 will take weeks.


US 301 bridge near Otis Rd is closed due to washout.


Alerts from FDOT:
http://www.fl511.com/Alerts.aspx

[cycloneye]

18z Best Track upgrades once again to Tropical Storm.

AL, 04, 2012062718, , BEST, 0, 295N, 794W, 35, 1003, TS

http://ftp.nhc.noaa.gov/atcf/tcweb/inve ... 012.invest

[Chickenzilla]

18z Best Track upgrades once again to Tropical Storm.
AL, 04, 2012062718, , BEST, 0, 295N, 794W, 35, 1003, TS

Weird. I think this may be an error given Debby still has an elongated and exposed LLC.

[Dean_175]

I didnt realize you could have a cold front extending into a tropical system. http://weather.unisys.com/surface/sfc_map.gif
How is this thing not classified as post-tropical? Obviously I am not a pro-met.

This is the surface analysis at time 1745 UTC June 27.

[jaxfladude]

The sun is finally trying to break thru the clouds.... the flood waters on the neighborhood roads are still here but are slowing receding...got way too close to the house during the worst of Debby....

[ozonepete]

I didnt realize you could have a cold front extending into a tropical system. http://weather.unisys.com/surface/sfc_map.gif
How is this thing not classified as post-tropical? Obviously I am not a pro-met.

This is the surface analysis at time 1745 UTC June 27.

Don't think that chart is correct. We will have to wait for NHC at 5PM but it could be quite interesting. Looks to me like the center is reforming well to the NE close to where the convection is.

[wxman57]

The chart is correct...

POST-TROPICAL CYCLONE DEBBY ADVISORY NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012
500 PM EDT WED JUN 27 2012

...DEBBY LOSES TROPICAL CHARACTERISTICS...NOW A POST-TROPICAL
CYCLONE...

[cycloneye]

Final Advisory

WTNT34 KNHC 272036
TCPAT4

BULLETIN
POST-TROPICAL CYCLONE DEBBY ADVISORY NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012
500 PM EDT WED JUN 27 2012

...DEBBY LOSES TROPICAL CHARACTERISTICS...NOW A POST-TROPICAL
CYCLONE...


SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...29.5N 78.3W
ABOUT 180 MI...295 KM E OF ST. AUGUSTINE FLORIDA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...E OR 90 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
SATELLITE DATA AND IMAGERY INDICATE THAT DEBBY HAS LOST TROPICAL
CHARACTERISTICS AND IS NOW A POST-TROPICAL CYCLONE.

AT 500 PM EDT...2100 UTC...THE POORLY DEFINED CENTER OF
POST-TROPICAL CYCLONE DEBBY WAS ESTIMATED NEAR LATITUDE 29.5
NORTH...LONGITUDE 78.3 WEST. DEBBY IS MOVING TOWARD THE EAST NEAR
13 MPH...20 KM/H. A GENERAL EASTWARD MOTION WITH A TURN TOWARD THE
EAST-NORTHEAST AND AN INCREASE FORWARD SPEED EXPECTED DURING THE
NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/H...WITH HIGHER
GUSTS. THE POST-TROPICAL CYCLONE IS EXPECTED TO MAINTAIN THIS
INTENSITY OVER THE NEXT COUPLE OF DAYS.

GALE-FORCE WINDS EXTEND OUTWARD UP TO 105 MILES...165 KM
TO THE SOUTHEAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB...29.62 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...RAINFALL ASSOCIATED WITH DEBBY WILL CONTINUE TO DIMINISH
ACROSS THE FLORIDA PENINSULA TODAY. ADDITIONAL ISOLATED RAINFALL
AMOUNTS OF UP TO ONE INCH WILL BE POSSIBLE IN SOME OF THE LINGERING
RAIN BANDS...MAINLY OVER SOUTHERN FLORIDA.


NEXT ADVISORY
-------------
THIS IS THE LAST PUBLIC ADVISORY ISSUED BY THE NATIONAL HURRICANE
CENTER ON THIS SYSTEM. ADDITIONAL INFORMATION ON THE POST-TROPICAL
CYCLONE CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE NATIONAL
WEATHER SERVICE...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER
FZNT01 KWBC.

$$
FORECASTER KIMBERLAIN


WTNT44 KNHC 272037
TCDAT4

POST-TROPICAL CYCLONE DEBBY DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012
500 PM EDT WED JUN 27 2012

STRONG WESTERLY SHEAR AND DRY AIR CONTINUE TO TAKE A TOLL ON DEBBY.
ASCAT AMBIGUITY VECTORS FROM A 1527 UTC OVERPASS SUGGEST THAT THE
LOW-LEVEL CIRCULATION HAS BECOME ELONGATED TO THE POINT THAT IT IS
NOW A SHARP TROUGH AXIS WITHOUT A WELL DEFINED CENTER. IN
ADDITION...THE SYSTEM LACKS ENOUGH ORGANIZED DEEP CONVECTION TO BE
CLASSIFIABLE. ON THIS BASIS...DEBBY IS NOW DESIGNATED AS A POST-
TROPICAL CYCLONE. THE EARLIER ASCAT PASS HAD UNCONTAMINATED WINDS
TO 32 KT...AND NOAA BUOY 41010 HAD 1-MINUTE WINDS AS HIGH AS 31 KT.
IT IS ASSUMED THAT HIGHER WINDS COULD BE OCCURRING IN THE REMAINING
CONVECTION WELL REMOVED FROM THE CENTER...SO INTENSITY OF THE
SYSTEM IS ESTIMATED TO BE 35 KT.

BASED UPON RECENT SATELLITE FIXES...THE INITIAL MOTION ESTIMATE IS
095/11...ALTHOUGH THIS IS DIFFICULT TO DETERMINE PRECISELY DUE TO
THE POOR DEFINITION OF THE CENTER. DEBBY SHOULD BE STEERED BY THE
FLOW ON THE SOUTH SIDE OF A DEEP TROUGH COVERING THE WESTERN
ATLANTIC...EVEN AS THIS WEATHER SYSTEM BEGINS TO LIFT OUT. ONCE
REACHING A HIGHER LATITUDE...DEBBY IS EXPECTED TO FEEL THE
INFLUENCE OF THE MID-LATITUDE WESTERLY FLOW AND ACCELERATE
NORTHEASTWARD DURING THE REMAINDER OF THE FORECAST PERIOD. GLOBAL
MODELS ARE IN GOOD AGREEMENT ON THIS SCENARIO BUT STILL DIFFER ON
THE TIMING ASPECTS OF THE FORECAST. THE GFS IS SUBSTANTIALLY SLOWER
THAN THE ECMWF/UKMET SINCE ITS MORE SOUTHERN INITIAL HEADING KEEPS
IT EQUATORWARD OF THE STRONGER WESTERLY FLOW. THE NEW TRACK
FORECAST IS SLOWED A BIT TO ACCOUNT FOR THIS POSSIBILITY...BUT IS
ESSENTIALLY SIMILAR TO THE PREVIOUS ONE.

LARGE-SCALE MODELS CONTINUE TO SHOW A RELATIVE DECREASE IN THE SHEAR
OVER DEBBY AS IT TRAVERSES THE CENTRAL ATLANTIC OVER THE NEXT DAY
OR TWO. ALTHOUGH AN ABUNDANCE OF VERY DRY AND STABLE AIR OVER THIS
REGION AND DECREASING SEA SURFACE TEMPERATURES COULD BE FACTORS
THAT PREVENT DEBBY FROM REGENERATING AS A TROPICAL CYCLONE...GLOBAL
MODELS CONTINUE TO INDICATE THIS TO BE A POSSIBILITY. THE OFFICIAL
NHC FORECAST CARRIES DEBBY AS A POST- TROPICAL CYCLONE THROUGHOUT
THE FORECAST PERIOD...THOUGH DEBBY COULD REACQUIRE TROPICAL
CHARACTERISTICS AT SOME POINT.


FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 29.5N 78.3W 35 KT 40 MPH...POST-TROPICAL
12H 28/0600Z 29.4N 76.5W 35 KT 40 MPH...POST-TROPICAL
24H 28/1800Z 29.7N 73.8W 35 KT 40 MPH...POST-TROPICAL
36H 29/0600Z 30.7N 71.0W 35 KT 40 MPH...POST-TROPICAL
48H 29/1800Z 32.1N 68.5W 35 KT 40 MPH...POST-TROPICAL
72H 30/1800Z 35.7N 64.2W 35 KT 40 MPH...POST-TROPICAL
96H 01/1800Z 40.0N 59.0W 40 KT 45 MPH...POST-TROPICAL
120H 02/1800Z 46.0N 48.0W 40 KT 45 MPH...POST-TROPICAL

$$
FORECASTER KIMBERLAIN

[cycloneye]

The chart is correct...

POST-TROPICAL CYCLONE DEBBY ADVISORY NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012
500 PM EDT WED JUN 27 2012

...DEBBY LOSES TROPICAL CHARACTERISTICS...NOW A POST-TROPICAL
CYCLONE...

Although,they leave a slim door open.

THE OFFICIAL
NHC FORECAST CARRIES DEBBY AS A POST- TROPICAL CYCLONE THROUGHOUT
THE FORECAST PERIOD...THOUGH DEBBY COULD REACQUIRE TROPICAL
CHARACTERISTICS AT SOME POINT