Complicated Gulf of Mexico disturbance 93L primarily a rain threat

By: Dr. Jeff Masters , 1:42 PM GMT on September 20, 2007

A very complicated weather situation over the Gulf of Mexico and Atlantic waters off the Southeast U.S. coast associated with a non-tropical low pressure system (93L), has brought heavy rains to Florida, Georgia, and South Carolina over the past 12 hours. A cold-cored upper level low pressure system a few hundred miles southwest of Tampa, Florida is primarily responsible for the the action. Late yesterday afternoon, a separate area of surface low pressure formed near Daytona Beach, bringing high surf and heavy rains of up to five inches along the Florida coast from Daytona to Jacksonville. This low moved inland over Florida, but the associated surge of moisture rotated northwards all the way to South Carolina. High surf warnings and coastal flood watches have been posted for Charleston, South Carolina today. This morning's QuikSCAT pass showed winds up to 50 mph well offshore of South Carolina. These winds have created a storm surge of up to two feet along the South Carolina coast. This second low pressure system was identified as "93L" by NHC beginning at 2 pm EDT yesterday. However, now that the low has weakened crossing the Florida Peninsula, the "93L" designation has been taken away from it, and attached to the upper level low pressure system in the Gulf of Mexico.

Recent Satellite loops and the Tampa Bay long range radar show that this non-tropical low pressure system is beginning to get more organized and is acquiring tropical characteristics. Substantial pressure falls are occurring at the surface underneath the upper level low, and this system is on its way to becoming a subtropical depression. A surface low pressure system vertically aligned with a cold-cored upper level low will usually take two or more days to make the transition to a warm-cored tropical storm. Rapid intensification cannot occur until the system is fully warm-core. Since landfall is expected Saturday between the Florida Panhandle and Southeast Louisiana, 93L probably does not have time to become fully tropical. If 93L makes landfall Saturday, it should not have winds stronger than about 55 mph. The GFDL, HWRF, and SHIPS intensity models all keep 93L's winds below 55 mph. If the storm spends an extra day over water and makes it to Texas, as the ECMWF model predicts, 93L could become fully tropical and make landfall as a strong tropical storm with 60-70 mph winds. However, there is plenty of dry air in the environment, and I don't think the storm will be able to intensify to a strong tropical storm. The primary threat from 93L will be heavy rain, and the northern Gulf Coast from the Florida Panhandle to Texas border can expect a soaking from this system.

The Air Force Hurricane Hunters are scheduled to investigate 93L this afternoon at 2pm EDT.


Figure 1. Current long range radar out of Tampa Bay, Florida.


Remains of Ingrid
The remains of Tropical Storm Ingrid are still active, triggering some heavy thunderstorm activity a few hundred miles north of the northernmost Lesser Antilles Islands. Puerto Rico long range radar and satellite loops show that this activity remains disorganized. Wind shear has dropped to about 10 knots today, and we will need to watch this area for development. However, the upper level winds are not in a particularly favorable configuration, and Ingrid's remains are so disorganized, that any development will be slow to occur. The remains of Ingrid are in a region of weak steering currents, and little movement is expected over the next 3-5 days.

I'll have an update Friday morning.

Jeff Masters

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1713. Michfan
12:50 AM GMT on September 21, 2007
Ill find a way to get them up! Just gimme a few.
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1712. SETXHchaser
12:49 AM GMT on September 21, 2007
Been out for a while. Are we are are we not going to get a hurricane out of 93l???
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1711. CanePredictor
12:49 AM GMT on September 21, 2007
Hello all i know this is sort of off topic but i have a question....i know it has to do with RSS feeds but how do people post radars on their site that automatically updates itself??
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1710. tpawxguy
12:45 AM GMT on September 21, 2007
Looks like it might stay just to the North of the eddy. If it redevelops to the West...could easily tap that energy. Eddy nothing more than area of warm water which would energize the developing system.
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1709. Progster
12:42 AM GMT on September 21, 2007
My pleasure, truecajun. I'm just an old met sometime bored by the extratropics so i look down S every now and then. It is a very interesting situation with 93L but, as tpawxguy's prof said, its often a guessing game, perhaps fueled by the subconcious recognition of similar past patterns. This one just looks pretty juicy to me.
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1707. houstex
12:45 AM GMT on September 21, 2007
Evening everyone,
This is my first post in a long time and I felt I had to get my one cent into the discussion. Two things I noticed from the most recent WV loop:

1. The ULL that's been a real learning experience now seems to be centered just south of Panama City and moving W.
2. There is a second ULL of interest, this one is just north of Hispanola and moving W.

To the uneducated mind like my own, it seems that the movement of both ULLs would increasingly aid the LLC SW of Tampa - the movement of the GOM ULL would lessen the shear over the LLC and the approach of the eastern ULL would in time provide venting to the SE.

Any thoughts on this?

(I know y'all having a tough time figuring out where I'm from.)
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1706. truecajun
12:45 AM GMT on September 21, 2007
extreme236, I watched something about Eddies today--but it didn't say anything about how they affect storms. What does 93L being close to an eddie mean?
Member Since: August 24, 2006 Posts: 0 Comments: 1874
1705. pottery2
8:41 PM AST on September 20, 2007
Nice pic. of the head of a lizzard hanging down. But what does it mean ???????
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1704. TerraNova
8:42 PM EDT on September 20, 2007
MichFan the WAVCIS images can't be put onto the blog.
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1702. Patrap
7:42 PM CDT on September 20, 2007

744
WUUS52 KTAE 210030
SVRTAE
FLC029-210115-
/O.NEW.KTAE.SV.W.0166.070921T0027Z-070921T0115Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE TALLAHASSEE FL
827 PM EDT THU SEP 20 2007

THE NATIONAL WEATHER SERVICE IN TALLAHASSEE HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
DIXIE COUNTY IN FLORIDA...
THIS INCLUDES THE CITY OF CROSS CITY...

* UNTIL 915 PM EDT

* AT 825 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING
9 MILES NORTHWEST OF CEDAR KEY TO CHIEFLAND...AND MOVING NORTHWEST
AT 35 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
CROSS CITY BY 900 PM EDT...

THESE ARE DANGEROUS STORMS. IF YOU ARE IN THEIR PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS AND FREQUENT CLOUD TO GROUND LIGHTNING.
PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...PREFERABLY INSIDE A STRONG
BUILDING BUT AWAY FROM WINDOWS.

THESE STORMS HAVE A HISTORY OF PRODUCING WIND GUSTS OVER 60 MPH.
SEEK SHELTER NOW INSIDE A STURDY STRUCTURE AND STAY AWAY FROM WINDOWS!

RELAY REPORTS OF SEVERE WEATHER TO THE NATIONAL WEATHER SERVICE IN
TALLAHASSEE AT (8 5 0) 9 4 2 8 8 3 3. OR...YOU MAY CONTACT THE
NEAREST LAW ENFORCEMENT AGENCY OR YOUR COUNTY EMERGENCY MANAGEMENT.
THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE.

LAT...LON 2929 8318 2933 8318 2941 8323 2941 8328
2954 8342 2962 8342 2975 8323 2959 8293
2948 8296 2935 8305 2928 8316
TIME...MOT...LOC 0027Z 121DEG 32KT 2929 8314 2943 8287
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1701. Michfan
12:41 AM GMT on September 21, 2007
Currents in the GOM:

The pictures are layered dammit.

Go here:

http://wavcis.csi.lsu.edu/forecasts/forecasts.asp?modelspec=temperature
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1700. cattlebaroness
12:25 AM GMT on September 21, 2007
Evening all, I have been out all day, can someone give me an update. Please. Do we have a TS or TD out there? Anything. I appreciate the info. Thanks.
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1699. tpawxguy
12:31 AM GMT on September 21, 2007
Interesting reading...bad taco, burrito. Funny stuff. That being said, my met prof at Penn State told me forecasting was 50% science, 50% gut feeling, instinct, art. Call it what you like. There are MANY times something tells you a forecast will go a certain way...and it's NOT the weather channel. Instinct ABSOLUTELY comes into play. FYI, my prof knew about as much as one could know about the science, yet he told me he "couldn't forecast his way out of a paper bag" Call it what you like, HE didn't have it. And was the first to admit it.
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1698. stormlovr
12:40 AM GMT on September 21, 2007
Posted By: StormJunkie at 12:39 AM GMT on September 21, 2007.

sl, I don't think it will be a huge deal, likely not more then a 50mph TS at best, but I am not a professional and that is jmvho.

Be back in a bit, got to eat ☺


Thanks, puts my mind @ ease a little bit. It's hard taking care of things and worry about your loved one in the "sand box"
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1697. nrtiwlnvragn
12:40 AM GMT on September 21, 2007
Latest update

...INITIAL CONDITIONS...
LATCUR = 27.4N LONCUR = 83.9W DIRCUR = 270DEG SPDCUR = 1KT
LATM12 = 27.4N LONM12 = 83.8W DIRM12 = 241DEG SPDM12 = 1KT
LATM24 = 28.4N LONM24 = 80.9W
WNDCUR = 25KT RMAXWD = 90NM WNDM12 = 25KT
CENPRS = 1005MB OUTPRS = 1010MB OUTRAD = 120NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

Link
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1696. taco2me61
12:39 AM GMT on September 21, 2007
Posted By: sceerdycat at 12:38 AM GMT on September 21, 2007.

A few observations:
spelling doesn't matter
Taz is not banned-he is king
You don't have to live on the coast to experience a hurricane
most of us are not mets
there-I think I am caught up


you forgot the Bad Taco and gut feeling...

Taco :0) (the bad taco here)
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1695. Patrap
7:38 PM CDT on September 20, 2007
Warnings out for this Feeder in Fla...Link
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1694. pottery2
8:37 PM AST on September 20, 2007
Presslord.
heheheheh
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1693. Michfan
12:37 AM GMT on September 21, 2007
sadf

Its over some pretty warm water atm.
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1692. Tropicnerd13
12:39 AM GMT on September 21, 2007
does anyone else care about the two lows that have recently came off africa???
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1691. extreme236
12:39 AM GMT on September 21, 2007
Ok all, I will be back in the morning briefly to see what happened overnight....should be interesting
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1690. StormJunkie
12:38 AM GMT on September 21, 2007
sl, I don't think it will be a huge deal, likely not more then a 50mph TS at best, but I am not a professional and that is jmvho.

Be back in a bit, got to eat ☺
Member Since: August 17, 2005 Posts: 26 Comments: 17383
1689. sceerdycat
8:35 PM EDT on September 20, 2007
A few observations:
spelling doesn't matter
Taz is not banned-he is king
You don't have to live on the coast to experience a hurricane
most of us are not mets
there-I think I am caught up
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1688. truecajun
12:35 AM GMT on September 21, 2007
StormW was on earlier today as well.
Progster, thank you for your insight.
Member Since: August 24, 2006 Posts: 0 Comments: 1874
1687. extreme236
12:37 AM GMT on September 21, 2007
yes, recon I think stopped reporting about 15-20min ago...noaa should be in soon to take upper air samples
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1686. stormlovr
12:36 AM GMT on September 21, 2007
Stormjunkie .... sitting in Panama City solo. Better 1/2 deployed; what is your take on this "storm". Should I be concerned?
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1685. Michfan
12:35 AM GMT on September 21, 2007
That was the last one from the Air Force. I don't NOAA is close yet.
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1684. extreme236
12:36 AM GMT on September 21, 2007
93L is also very close to a eddy in the gulf
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1683. presslord
8:35 PM EDT on September 20, 2007
my ex-wife lives in Corpus...I'm gonna recuse myself from commenting on what I'd like to see happen...
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1682. pottery2
8:33 PM AST on September 20, 2007
Sorry for the large wasted space. Not intentional.
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1681. StormJunkie
12:32 AM GMT on September 21, 2007
gm, now see that is a good learning tool. Firefox just makes me dumber because all you have to do is right click to get the suggested corrections. Personally, I usually backspace and try to correct it myself prior to resorting to that though.

And again, I am no English major or bee champ and I am not really harping on anyones spelling. Most folks are hear to learn and that is a good thing even if the spelling isn't great.
Member Since: August 17, 2005 Posts: 26 Comments: 17383
1680. Baybuddy
12:32 AM GMT on September 21, 2007
I went to the landfill today, and the Lady operating the scales mentioned the weather. I suggested she use WU, and she showed me that she already had it in her favorites!
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1679. truecajun
12:32 AM GMT on September 21, 2007
Taz was on earlier today.
Member Since: August 24, 2006 Posts: 0 Comments: 1874
1678. destruction4u
12:33 AM GMT on September 21, 2007
Taz, what are your thoughts regarding 93L?
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1677. Progster
12:21 AM GMT on September 21, 2007
I've seen ULL's transition very rapidly. Overnight convection will tend to intensify due to the destabilzation caused by cloud top cooling...now normally this isnt a big deal, but in an unstable atmosphere and given the forcing of high SST's, there is probably a low level vorticity threshold that, if 93L crosses, will promote the positve feedback between convergence and convection a TD or STD needs to rapidly intensify. So my guess is that by tomorrow morning we'll see a developing TS in the NE gulf. The intensificiation of cyclones by an increase in local low level vorticity forced by strong convection is what often casues the CMC global model to go wild...(convective feedback) but in this case it looks like it could happen for real.
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1676. stormyjm
12:32 AM GMT on September 21, 2007
Question: What is everyone's thoughts regarding Corpus Christi and the threat to that area??
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1675. SomeRandomTexan
7:34 PM CDT on September 20, 2007
STORMW

is actually a met I'm not sure if any of the other are.....
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1674. stormlovr
12:32 AM GMT on September 21, 2007
Stormjunkie, you on?
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1673. pottery2
8:32 PM AST on September 20, 2007
Great timing Taz........
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1672. Michfan
12:31 AM GMT on September 21, 2007
00:10:00Z
29.73N 90.97W
548.4 mb(~ 16.19 inHg)
5,159 meters(~ 16,926 feet) -
274 meters(~ 899 feet)
From 15░ at 27 knots (From the NNE at ~ 31.0 mph) 0.2░C
(~ 32.4░F) -40.9░C
(~ -41.6░F) 28 knots
(~ 32.2 mph)
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1671. beell
12:22 AM GMT on September 21, 2007
Maybe a useful interactive link for wind and pressure fields.
A better overview. Zoom out to include more stations

Link
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1670. surfmom
12:31 AM GMT on September 21, 2007
There are a few others Stormyjm, but those dudes are on my fav list....I've been wondering all night...where's stormw???
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1669. extreme236
12:33 AM GMT on September 21, 2007
i dont think noaa is in there yet though
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1668. extreme236
12:32 AM GMT on September 21, 2007
well anyone who was monitoring the air force obs on the tropical atlantic site make sure you go back to the recon page and click on the NOAA plane stuff, as the NOAA plane is taking over
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1667. edhanna
12:32 AM GMT on September 21, 2007
Taz!, lol.
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1666. edhanna
12:30 AM GMT on September 21, 2007
Posted By: sullivanweather at 12:24 AM GMT on September 21, 2007.

Hey Ed,

What's your thoughts on this, thus far, non-tropical low(93L)?

Sull, if you're still lurking, I completely agree with you. This is not tropical as of right now.
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1665. truecajun
12:29 AM GMT on September 21, 2007
yes stormyjm, they are all informative, as well as Drak and terranova--I'm sure i've left some out
Member Since: August 24, 2006 Posts: 0 Comments: 1874
1664. Baybuddy
12:30 AM GMT on September 21, 2007
I think it will be a cat 1 by sheer will.... landfall however....
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1663. StormJunkie
12:31 AM GMT on September 21, 2007
lol press, but see I did not misspell all :~)
Member Since: August 17, 2005 Posts: 26 Comments: 17383

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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