Ex-Dorian Attempting a Comeback off the Florida Coast

By: Dr. Jeff Masters , 1:44 PM GMT on August 02, 2013

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After a long trek over the Atlantic Ocean from the coast of Africa, the remains of Tropical Storm Dorian (now called Invest 91L) have finally arrived at the shores of North America. Ex-Dorian is nearly stationary, and is situated over the Northwestern Bahama Islands, just off the coast of Southeast Florida. Satellite loops and Melbourne, Florida radar images show that ex-Dorian has only a limited amount of heavy thunderstorms, which are not well-organized. There does appear to be a surface circulation center trying to form just north of the storm's heaviest thunderstorms, about 70 miles east of Vero Beach, Florida. However, dry air to the northwest, as seen on water vapor satellite loops, is inhibiting development. WInd shear is moderate, 10 - 20 knots, but is expected to rise to the high range, 20 - 30 knots, by Saturday morning. Ex-Dorian is expected to move slowly northwards and then north-northeastwards on Saturday. This motion will get ex-Dorian tangled up with a cold front that extends from Northern Florida northeastwards, just offshore from the Southeast U.S. coast. Before it merges with the front, ex-Dorian has some potential for regeneration into a tropical depression, and in their 8 am Friday Tropical Weather Outlook, NHC gave ex-Dorian a 30% chance of becoming a tropical cyclone by Sunday. Ex-Dorian will likely bring heavy rains to the Northwest Bahamas on Friday, and these heavy rains may also clip the coast of Southeast Florida. However, the bulk of ex-Dorian's rains should stay offshore.


Figure 1. Morning radar image of ex-Dorian from the Miami radar.

Jeff Masters

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1128. vis0
TS 2013DORIAN q1 (quasi1) MIAMI FL NWS RADAR time stamp magnified. Of course  vist Wxu or NWS (at the moment) miami radar pg. for the latest.
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Quoting 1121. FIUStormChaser:
91L has now stalled over the Gulf Stream, with the trough digging down from the north albeit slowly. It has maintained convection all day, although it has waned recently. The question now is, will the trough kick it out to sea, as the models say, or will it go west into Florida and then into the gulf, as some has mentioned?

Still amazing to see what happens to a weak system over those warm Gulf Stream waters, definitely wouldn't want a storm to traverse that area later this year when conditions become more conducive..:.
. Not according to the TWC! The tropical specialist on there said that front , will pick it up, and eject it out to sea , that what they said . Not what I believe will happen .
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1126. sar2401
Quoting RascalNag:
I think I'm going to head in for the night, I have an early flight out of PR tomorrow. I'll let myself be surprise by xDorian when I wake up.

Have a good flight. It will be a cat 5 by morning and mess up all the airline schedules, so bring a good book. :-)
Member Since: October 2, 2004 Posts: 0 Comments: 15997
Quoting 1107. beell:


Not really true , Cos. Many storms have some probability of developing in the first 48 and the probability may increase if the disturbance is forecast to move into a better genesis environment.
I was speaking to storms or potential storms that have lower probs as time went on, like 91L. It should be conveyed as 40/10, with the 120hr figure representing day 3-5, and to put it simply for the public, it's now or never.
.
For the storms with more probability out in time(day3-5), then that can be conveyed as 40/60(as an example).
.
I thought that they'd communicate a situation like we see right now with our first potential TD as 40/10, with 10 representing day3-5. If it's day1-5 it's not worth as much. In any case, it's just more confusing until they do explain the number plainly.
.
Is the 2nd number day 1-5 or day 3-5 would be a great place to start with a yes or no answer.
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1124. sar2401
Quoting RascalNag:


I don't think this would quite be fast fading, considering this is the best it's looked at DMIN in perhaps it's entire life. DMAX will be interesting, for sure...

It will, but for the blob that forming to the NNE of the Bahamas, not what's around Florida now.
Member Since: October 2, 2004 Posts: 0 Comments: 15997
1123. whitewabit (Mod)
Member Since: August 17, 2005 Posts: 364 Comments: 31536
I think I'm going to head in for the night, I have an early flight out of PR tomorrow. I'll let myself be surprise by xDorian when I wake up.
Member Since: October 24, 2012 Posts: 0 Comments: 209
91L has now stalled over the Gulf Stream, with the trough digging down from the north albeit slowly. It has maintained convection all day, although it has waned recently. The question now is, will the trough kick it out to sea, as the models say, or will it go west into Florida and then into the gulf, as some has mentioned?

Still amazing to see what happens to a weak system over those warm Gulf Stream waters, definitely wouldn't want a storm to traverse that area later this year when conditions become more conducive..:.
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1120. guygee
Main area of convection seems to be stationary for now.
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1119. sar2401
Quoting EyEtoEyE:
Hey guys , Did you see what the TWC! The strong front will move 91L out to sea , I see alot you saying that front is washing out , I agree with the bloggers , all I can see by the sat pics , is it will force it more southwards! With the high forcing things westbound ! It's going to get messy for Florida soon.

What? Seriously, that made absolutely no sense.
Member Since: October 2, 2004 Posts: 0 Comments: 15997
TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI AUG 02 2013

SPECIAL FEATURES...

AN AREA OF LOW PRESSURE CENTERED ABOUT 75 MILES EAST OF
MELBOURNE FLORIDA...ASSOCIATED WITH THE REMAINS OF DORIAN...IS
MOVING SLOWLY NORTHWARD. SATELLITE AND RADAR DATA INDICATE THAT
THE ASSOCIATED SHOWER ACTIVITY HAS BECOME BETTER ORGANIZED
DURING THE PAST SEVERAL HOURS...AND SOME ADDITIONAL DEVELOPMENT
IS POSSIBLE TONIGHT. HOWEVER...THE LOW IS EXPECTED TO ENCOUNTER
STRONG UPPER-LEVEL WINDS ON SATURDAY WHICH WILL NOT BE CONDUCIVE
FOR DEVELOPMENT...AND IT IS EXPECTED TO MERGE WITH A FRONTAL
TROUGH OFFSHORE OF THE EASTERN UNITED STATES ON SUNDAY. THIS
SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT... CLOUDINESS AND
SHOWERS WILL CONTINUE TO AFFECT PORTIONS OF THE NORTHWESTERN
BAHAMAS...THE FLORIDA PENINSULA...AND THE ADJACENT WATERS
TONIGHT AND SATURDAY.

...TROPICAL WAVES...

A TROPICAL WAVE JUST W OF THE CAPE VERDE ISLANDS EXTENDS FROM
22N25W TO AN EMBEDDED 1009 MB LOW NEAR 16N26W TO 11N26W. THE LOW
IS FORECAST TO BE MOVE W TO 17N30W IN 24 HOURS WITH THE WAVE.
THE SYSTEM IS MOVING AT 10 KT. THE WAVE IS SURROUNDED BY A LARGE
AREA OF VERY DRY AND DUSTY SAHARAN AIR SUPPRESSING CONVECTION.
SCATTERED SHOWERS ARE WITHIN 120 NM OF THE WAVE AXIS TO INCLUDE
THE CAPE VERDE ISLANDS.
Member Since: March 12, 2013 Posts: 26 Comments: 50836
1117. Pallis
Quoting 1074. EricSFL:
A stationary storm sitting on the Gulf Stream current (which moves at about 12mph at its strongest point) would receive a constant supply of warm water without much upwelling of cold water, correct?
Yes when weak, but no when the wind starts to blow the top water away from the center, depending on the direction of the current relative to the direction the storm is taking, and the speed in which it travels in that direction. Depending on what part of the gulf stream, wave height might be another small factor. In other words ... depends.
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1116. sar2401
Quoting nrtiwlnvragn:
Dvorak technique, all interpretation.
Two different analysts, one from SAB the other from TAFB. SAB says too weak to classify. TAFB says dvorak 2.0, 30 kts.


AL 91 201308022345 DVTS 2780N 7900W SAB DT=0.0 BO CBND MET=0.0 PT=0.0 FTBO DT


AL 91 201308022345 DVTS 2810N 7890W TAFB 2020 ///// 0.35 BANDING = DT=MET= FT= 2.0. CLOUDS POINT TO ELO

Not sure what ELO means in the TAFB comment.

Electric Light Orchestra? No, probably not. Seriously, though, why not do these in plain English. I know METARS are still done with this code too, and it started from the days when there wasn't enough computer RAM to handle whole words. Now it's almost like medicine, where you need to know the abbreviations to show you're part of the gang.
Member Since: October 2, 2004 Posts: 0 Comments: 15997
Just as I came home from watching the smurfs 2. I see 91L is up to 50% would probably become Dorian again,Gil is dying slowly and a possible cyclone developing in the NW caribbean later on.Nice!
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Hey guys , Did you see what the TWC! The strong front will move 91L out to sea , I see alot you saying that front is washing out , I agree with the bloggers , all I can see by the sat pics , is it will force it more southwards! With the high forcing things westbound ! It's going to get messy for Florida soon.
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Quoting 1109. whitewabit:


that would really bring in the stars .. what brand are you looking at ??

would love to have one but back ground light where I live doesn't allow that .. would have to drive a distance if I could find a spot to set up ..


Zhumell, with a proper light pollution filter you've don't got to go anywhere. Winter nights are the best for astronomy, keeps the primary mirror cool.
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Quoting 1107. beell:


Not really true , Cos. Many storms have some probability of developing in the first 48 and the probability may increase if the disturbance is forecast to move into a better genesis environment.


I think Cos was specifically referring to 91L about if it doesn't develop in 2 days it won't develop.
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Sar2104, yes you are right 1811/12, couldn't recollect exactly. A friend has redone the plantation and it's part of the tour. The frightened residents dropped religious medals into the cracks and prayed mightily. It is indeed a mind bending possibility given the increased population and development. :0!
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Quoting 1106. sar2401:

Looks like some convection inland is going offshore and keeping some of the convection in the fast fading 91L alive, assuming that's where 91L is, which I'm not sure about either. Either way, it doesn't look like it's moving much, if at all.


I don't think this would quite be fast fading, considering this is the best it's looked at DMIN in perhaps it's entire life. DMAX will be interesting, for sure...
Member Since: October 24, 2012 Posts: 0 Comments: 209
1109. whitewabit (Mod)
Quoting 1102. CybrTeddy:


Nice! I've got a nice 4" Meade, GoTo mount. Getting a 10" Zhummel with SkyGlow filter when I can scrape up the money.


that would really bring in the stars .. what brand are you looking at ??

would love to have one but back ground light where I live doesn't allow that .. would have to drive a distance if I could find a spot to set up ..
Member Since: August 17, 2005 Posts: 364 Comments: 31536
Quoting 1107. beell:


Not really true , Cos. Many storms have some probability of developing in the first 48 and the probability may increase if the disturbance is forecast to move into a better genesis environment.



Agree with both of you, and, hence, I rest my case. ;)
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1107. beell
Quoting 1097. CosmicEvents:
That's how I interpret it, but if that's true than we can never have a second 120hr prob that's lower than the first 48hr prob.
.
Seems like that's a bit of a problem, and we see it here in the very first test case. Common sense and the small met knowledge I have tells me that if it doesn't become a TD in 48 hours...it's probably not going to be something to watch in day3-5. If the purpose is to communicate plainly to the most people then they should convey that message in the numbers. 40/40 tells folks to watch it for 5 days. 40/10 tells folks it can happen but it's a more immediate threat than a long-range threat.
.
It's confusing...and I expect it to get worse when they go graphical.


Not really true , Cos. Many storms have some probability of developing in the first 48 and the probability may increase if the disturbance is forecast to move into a better genesis environment.
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1106. sar2401
Quoting RascalNag:


Link

Looks like it would be simply south to me though, if not still stationary.

Looks like some convection inland is going offshore and keeping some of the convection in the fast fading 91L alive, assuming that's where 91L is, which I'm not sure about either. Either way, it doesn't look like it's moving much, if at all.
Member Since: October 2, 2004 Posts: 0 Comments: 15997
1105. Patrap
A nice choice CT.

I'm not a dobs fan but that is a nice one.

Member Since: July 3, 2005 Posts: 426 Comments: 128630
Quoting 1097. CosmicEvents:
That's how I interpret it, but if that's true than we can never have a second 120hr prob that's lower than the first 48hr prob.
.
Seems like that's a bit of a problem, and we see it here in the very first test case. Common sense and the small met knowledge I have tells me that if it doesn't become a TD in 48 hours...it's probably not going to be something to watch in day3-5. If the purpose is to communicate plainly to the most people then they should convey that message in the numbers. 40/40 tells folks to watch it for 5 days. 40/10 tells folks it can happen but it's a more immediate threat than a long-range threat.
.
It's confusing...and I expect it to get worse when they go graphical.



Agreed. The general public reads and comprehends tantamount to a fifth grade level. Pictures are better, but only if they're not complex.
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1103. sar2401
Quoting nrtiwlnvragn:


I think we as weather nerds nit-pick too much. I think once they get the graphical forecast which shows the possible positions within the 5 day most will just be interested if it is heading their way. My 2 cents.

I tend to agree, but they are going to have to at least explain the formula to the media. Good luck!
Member Since: October 2, 2004 Posts: 0 Comments: 15997
Quoting 1088. Patrap:


I am too, but did I mention that?

NO.

I have a very old, but working 4.5" Newtonian.


Hard to colimate, but worth the Views,esp with the 9mm inch and a quarter Pfossel Eyepiece.

Easy eye relief.

Seems I'm out o Bandwitdh in my P-Bucket too.

: )



Nice! I've got a nice 4" Meade, GoTo mount. Getting a 10" Zhumell with SkyGlow filter when I can scrape up the money.
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Quoting 1092. sar2401:

Which radar? What storm? How much rain?


Link

Looks like it would be simply south to me though, if not still stationary.
Member Since: October 24, 2012 Posts: 0 Comments: 209
1100. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128630
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Gil down to 55 knots.

EP, 07, 2013080300, , BEST, 0, 147N, 1300W, 55, 995, TS
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Quoting 1070. nrtiwlnvragn:
The way I understand the new genesis forecast is from this diagram from the NHC presentation NHC Experimental 5-day Tropical Weather Outlook page 6.




There is 1-2 day genesis, 3-5 day genesis and 1-5 day genesis. 1-5 day is the addition of 1-2 plus 3-5.

So for the most recent TWO where the 48 hours is 50% and the 5 day is 50%, I interpret as 0% for days 3-5.
That's how I interpret it, but if that's true than we can never have a second 120hr prob that's lower than the first 48hr prob.
.
Seems like that's a bit of a problem, and we see it here in the very first test case. Common sense and the small met knowledge I have tells me that if it doesn't become a TD in 48 hours...it's probably not going to be something to watch in day3-5. If the purpose is to communicate plainly to the most people then they should convey that message in the numbers. 40/40 tells folks to watch it for 5 days. 40/10 tells folks it can happen but it's a more immediate threat than a long-range threat.
.
It's confusing...and I expect it to get worse when they go graphical.
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1096. sar2401
Quoting interstatelover7165:
Flying... :)

Forgot about flying. Have one of those too, but it's a heck of a lot more expensive than amateur radio...and I don't need a medical exam to keep my radio license. :-)
Member Since: October 2, 2004 Posts: 0 Comments: 15997
1095. sar2401
Quoting RascalNag:
To heck with it, I'm sure I can deal with some crow - I'm going to get behind the idea that XDorian misses the trough and drifts into FL. That front seems awfully weak and xDorian refuses to budge towards it, even a little. With such low steering winds in his vicinity, he seems content to just sit there and enjoy the bath water before becoming a huge mess for FL.

I understand from some of my hunting friends that we have crows in Alabama as big as turkeys. I'll have them rustle one up for you. :-)
Member Since: October 2, 2004 Posts: 0 Comments: 15997
Quoting 1091. sar2401:

And amateur radio operators...I even have an official FCC license, which makes me a licensed amateur. I can't think of any other amateur hobby that requires a license...well, except for driving, which really doesn't count as being a hobby. :-)
Flying... :)
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1093. whitewabit (Mod)
Member Since: August 17, 2005 Posts: 364 Comments: 31536
1092. sar2401
Quoting 7544:
rain over the radar seems to be moving sse ?

Which radar? What storm? How much rain?
Member Since: October 2, 2004 Posts: 0 Comments: 15997
1091. sar2401
Quoting CybrTeddy:


But there are amateur astronomers (which I consider myself proudly to be). :-)

And amateur radio operators...I even have an official FCC license, which makes me a licensed amateur. I can't think of any other amateur hobby that requires a license...well, except for driving, which really doesn't count as being a hobby. :-)
Member Since: October 2, 2004 Posts: 0 Comments: 15997
1089. 7544
rain over the radar seems to be moving sse ?
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1088. Patrap
Quoting 1086. CybrTeddy:


But there are amateur astronomers (which I consider myself proudly to be). :-)


I am too, but did I mention that?

NO.

I have a very old, but working 4.5" Newtonian.


Hard to colimate, but worth the Views,esp with the 9mm inch and a quarter Pfossel Eyepiece.

Easy eye relief.

Seems I'm out o Bandwitdh in my P-Bucket too.

: )

Member Since: July 3, 2005 Posts: 426 Comments: 128630
1087. sar2401
Quoting midgulfmom:
sar2401... at the risk of sounding COMPLETLY crazy! I said to "go with your gut" because a few things I've had a gut premonition about came true. I can't fortell the future or anything but more than once I've had a nagging knowing that proved true. And the atmosphere here in S LA has been pretty humid and heavy as well. My dad used to have a store on Irish Bayou in eastern N.O. and there is a fault line there as well and a few times there were quakes that knocked people there from their beds. It was even reported on the local news. Also in St. James Parish, LA at the Laura Plantation property, there is a fault line that opened up in around 1840 (thereabouts). The Mississippi river flowed upstream (backwards)for a while then.

Yeah, that was the New Madrid fault on the Mississippi, just north of the TN/MO border. Four earthquakes from December 16, 1811 to February 7, 1812. The last was probably the strongest to have occurred in North America that we know of, somewhere around an 8.6 to 8.9. Almost no one lived in the area at the time, but what was there was destroyed, and the quake caused church bells to ring in Boston. We know that fault is going to break again at some point in the future, we just don't know when.

The really scary part is the Mississippi Valley is buried in tens of thousands of feet of alluvium, material collected over millions of years of the river flowing. There are undoubtedly other faults buried in the Valley but we won't know where they are until they break. If it's a repeat of the 1811-1812 shocks, it will make five of the worst hurricanes we've ever had combined look like peanuts when it comes to death and destruction.
Member Since: October 2, 2004 Posts: 0 Comments: 15997
Quoting 1073. Patrap:


I'm not a met.

So go with the NHC.


There are no amateur Mets just as there are no amateur astronauts.


But there are amateur astronomers (which I consider myself proudly to be). :-)
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Quoting 1082. moonlightcowboy:



I may need some time to soak this in, but my initial reaction is that this will be more confusing to the general public than the freaking Saffir-Simpson Scale of rating.


I think we as weather nerds nit-pick too much. I think once they get the graphical forecast which shows the possible positions within the 5 day most will just be interested if it is heading their way. My 2 cents.
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To heck with it, I'm sure I can deal with some crow - I'm going to get behind the idea that XDorian misses the trough and drifts into FL. That front seems awfully weak and xDorian refuses to budge towards it, even a little. With such low steering winds in his vicinity, he seems content to just sit there and enjoy the bath water before becoming a huge mess for FL.
Member Since: October 24, 2012 Posts: 0 Comments: 209


Shows a weak low, but that was over 24 hours ago.
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Quoting 1070. nrtiwlnvragn:
The way I understand the new genesis forecast is from this diagram from the NHC presentation NHC Experimental 5-day Tropical Weather Outlook page 6.




There is 1-2 day genesis, 3-5 day genesis and 1-5 day genesis. 1-5 day is the addition of 1-2 plus 3-5.

So for the most recent TWO where the 48 hours is 50% and the 5 day is 50%, I interpret as 0% for days 3-5.



I may need some time to soak this in, but my initial reaction is that this will be more confusing to the general public than the freaking Saffir-Simpson Scale of rating.
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Blob off Nicaragua been holding its own most of the day, doubt it will amount to much though.

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00z Best Track for 91L.

AL, 91, 2013080300, , BEST, 0, 279N, 796W, 25, 1015, LO
Member Since: April 29, 2009 Posts: 75 Comments: 14308
Dvorak technique, all interpretation.
Two different analysts, one from SAB the other from TAFB. SAB says too weak to classify. TAFB says dvorak 2.0, 30 kts.


AL 91 201308022345 DVTS 2780N 7900W SAB DT=0.0 BO CBND MET=0.0 PT=0.0 FTBO DT


AL 91 201308022345 DVTS 2810N 7890W TAFB 2020 ///// 0.35 BANDING = DT=MET= FT= 2.0. CLOUDS POINT TO ELO

Not sure what ELO means in the TAFB comment.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.