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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

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

2502. OUSHAWN
First time poster here...

I just noticed that NRL had taken 93L off as well...I have no idea what that is all about unless they figure time has run out on it...

Shawn
2503. Bonedog
ah gotcha Taz. Thanks for the heads up
The low-level cloud level circulation over Bonifay (north of Panama City) is basically moving South-South-West...
thats my concern with that carib moisture
2506. Bonedog
thanks weather seemed wierd to me
Good morning all from under the SW Carib Blob. Having a real bad lightning storm here for the past few hours. Winds calm though and lots of rain. Will continue to update IF conditions deteriorate further.
21/0645 UTC 28.2N 85.5W T1.5/1.5 93L -- Atlantic Ocean


note that 93L is no longer a ST note that you dont see the S in front of the T this time a round T # are now 1.5
2509. Patrap
NEXRAD Radar
Red_Bay Base Reflectivity 0.50 Degree Elevation Range 248 NMI

Link
2511. IKE
It's back up on the Navy site as 93L.
93L is back up
Something interesting: the last image of 93L was 1045 UTC (0645 EDT)

Morning All...

Ike - gonna be a wet drive home today?
2516. OUSHAWN
JP,

I'm seeing 93L moving almost due west at this time...do you see the same? As of yet I haven't been able to spot the weakness between the two ridges that would push it more NW. Need help here...

Shawn
So Taz.... does that mean that 93L is already tropical in nature and that it could skip the subtropical classifications?

just curious...
2519. IKE
Posted By: F1or1d1an at 7:22 AM CDT on September 21, 2007.
Morning All...

Ike - gonna be a wet drive home today?


Yes...rain is moving in here now. Just starting.

And good morning.
No spin evident as of now with the Caribbean disturbance.
http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8dlm1.GIF

Flow West??
2526. Patrap
GOES Water Vapor Loop of Gulf and Caribbean


Link
JP, just was strange that they prolong the images. anyways they updated them

2528. Patrap
GOES IR Loop of Gulf of Mexico

Link
2530. OUSHAWN
The front door of the Tropical on here now has 93L moving NNW...I just don't see that...what am I missing?
As 93L gets better organized this AM, my main concern is whether it can generate some T-Storms and the possibility of tornadoes from the Panhandle West in the NE Quadrant....That question will probably be answered over the next 12-24 hours.....However, I agree that it appears to be moving more West than North and the extra time over the Gulf will give it a chance to develop some more......
2533. IKE
Looking at the satellite presentation on 93L...appears to be more tropical looking...I think the NHC will upgrade this based on the current recon.

If I'm wrong...more crow.
93L is back up on the Navy NRL site... that was weird how they took it down for a little while
2535. Bonedog
looking better now

better
2536. Drakoen
I see 93L is slightly better organized. Still i don't think it deserves to be called
2537. Patrap
Why is everything Weird that the Navy does?.
They replaced the pic,thats all.Jeez,,,ya think the whole invest rest on the NRL image..LOL!
2539. IKE
From the Navy site...

93LINVEST.30kts-1005mb-287N-853W

Pressure up a MB. On the floater of 93L..the pressure is down to 1004 mb's.
IKE 93L is now tropica note that you dont see the S in front of the T this time

21/0645 UTC 28.2N 85.5W T1.5/1.5 93L -- Atlantic Ocean
ok.. everyone please look at the Tallahasee NEXRAD and see if ya'll can see the COC to the SSW of Appalac. area... I'm talking less than 40 miles off the coast of Florida...


I believe this is the first time that I've noticed a closed-in circulation on Radar...

Is anybody else seeing this?
2542. Patrap
Its tropical is right Taz.The radar presentation shows it nicely
2543. IKE
Posted By: Tazmanian at 7:32 AM CDT on September 21, 2007.
IKE 93L is now tropica note that you dont see the S in front of the T this time

21/0645 UTC 28.2N 85.5W T1.5/1.5 93L -- Atlantic Ocean


Yeah...I noticed that.

30 knot winds from the Navy site...that's close to 35 mph.
patrap, seems to be going a little more west than before, what do you think?
2545. Drakoen
It looks like it doesn;t have much time to organized
In anticipation of the storm system's arrival, Louisiana Gov. Kathleen Blanco declared a state of emergency late Thursday and oil companies evacuated workers from oil rigs in the Gulf, according to AP.
Recon didn't find much on the first pass.

1006.8mb and 11kts
2550. Patrap
93L seems to moving around 270/275 at 7-9mph by radar

Link
2552. Bonedog
nice overshooting cloud tops now on the visables

tops
The key to look for today... IF 93L begins to get some anti-cyclonic action on top of this thing, it could explode into a moderate-strong TS in a matter of 6 hours or so...

Hurricane WOULD NOT be out of the question at that point...
2555. amd
i see the center of 93L is JUST off Applachicola, Florida. Considering that WU has the storm moving NNW at 8 mph, it's going to have to make a hard left turn to stay offshore.

Also, I have to give 93L some credit here. It is trying to become a tropical storm, but will it have enough time?
2557. Patrap
000
ABNT20 KNHC 211137
TWOAT
TROPICAL WEATHER OUTLOOK...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 AM EDT FRI SEP 21 2007

...CORRECTED DATE...

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

THE LOW PRESSURE AREA OVER THE NORTHEASTERN GULF OF MEXICO HAS BEEN
MOVING NORTHWESTWARD DURING THE NIGHT AND IS NOW CENTERED ABOUT 100
MILES SOUTH OF APALACHICOLA FLORIDA. SATELLITE IMAGERY...RADAR
DATA...AND SURFACE OBSERVATIONS INDICATE THAT SYSTEM IS GRADUALLY
BECOMING BETTER ORGANIZED...BUT DOES NOT YET HAVE THE
CHARACTERISTICS OF A SUBTROPICAL OR TROPICAL CYCLONE. SQUALLS WITH
GUSTY WINDS UP TO 30 TO 35 MPH HAVE BEEN REPORTED AT OFFSHORE NOAA
AUTOMATED STATIONS. ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR
THIS SYSTEM TO BECOME A SUBTROPICAL OR TROPICAL CYCLONE AT ANY TIME
DURING THE NEXT 24 HOURS AS IT MOVES GENERALLY TOWARD THE
WEST-NORTHWEST. ALL INTERESTS ALONG THE NORTHERN GULF COAST SHOULD
CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM...AND TROPICAL STORM
WATCHES AND WARNINGS COULD BE REQUIRED FOR PORTIONS OF THIS AREA
LATER TODAY. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL
BE INVESTIGATING THE SYSTEM IN A FEW HOURS.
21/1215 UTC 28.7N 85.5W ST1.5/1.5 93L -- Atlantic Ocean


its back to ST 93L now
2559. Bonedog
acording to the NHC the center is 85miles off the coast so at 8mph its 10hrs away
It will stay offshore - don't worry - movement is just north of west (275). The presentation on the radar is not the location of the L itself...
Look what the European has in 240 hrs:

Link
With most of the activity North and East of the COC??? NOLA should just get rain, and not that much, from this system right??
morning everybody.....

93L looks like it deserves to be a TD now..... I expect recon will confirm this..... and we may have Jerry by days end! :)

Saintsfan -

Probably - but this is a good opportunity to test your "preparedness plan".
2565. IKE
Posted By: thelmores at 7:49 AM CDT on September 21, 2007.
morning everybody.....

93L looks like it deserves to be a TD now..... I expect recon will confirm this..... and we may have Jerry by days end! :)


I agree. We may both have crow!
Observation Time: Friday, 12:43Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 28.7N 84.6W (View map)
Location: 120 miles (194 km) to the SSE (148) from Panama City, FL, USA.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 460 meters
Flight Level Wind: From 190 at 26 knots (From the S at ~ 29.9 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 23C
Flight Level Dew Point: 22C
Weather (within 30 nautical miles): Thunderstorm(s)
Mean Sea Level Pressure (MSLP): 1008 mb (extrapolated)

Optional Data...

Estimated Surface Wind: From 190 at 20 knots (From the S at ~ 23.0 mph)
2568. Patrap
A new center is forming..Sw of the Old one ..on the sw side of this convection,,south of Panama City..the last frame shows it nicely.
NEXRAD Radar
Red_Bay Base Reflectivity 0.50 Degree Elevation Range 248 NMI
Link

2569. IKE
Posted By: thelmores at 7:51 AM CDT on September 21, 2007.
Ike, you got any hot sauce....I like my crow extra hot! LOL


Yup....plus A1 sauce.

Take mine medium-rare.
Morning all :~)

I see 93 is getting very close to land now. Still looks pretty sloppy imho.

NRL imagery
LAweatherguy:
What does 93L need to get anticyclonic action?
Boy, that Bastardi sure pegged this one!
dangit SJ..... Ike and I are trying to build 93L up, and you come along and tear it down! LOL
I c what u c Pat - but I can't figure it out.

Is it another L forming, or is it de-coupling of the surface L and the ULL? The fact that it went from T back to ST makes this more believable - guess the basement and the penthouse are duking it out on this one...
Wait Patrap, what you seeing? about where is this new center you are seeing? That can't be good!
It is a shame 93 deserved a name. Time is running out. We have had about 5 systems this yr that have been borderline.
2582. Bonedog
looking at the long range from Tally does have some nice banding features I will give it that
Posted By: Thunderground at 8:54 AM AST on September 21, 2007.

LAweatherguy:
What does 93L need to get anticyclonic action?


deep thunderstorms
SJ, the way I see it, a little moisture from 93L may help us out.... since we can't pass block or have any receivers that can get open, we can just run the ball! Maybe a little rain will even thing out more??

I got it..... crow today.... no crow tomorrow!

You don't think the game is at risk of being postponed do you? If so, i will jump the fence and play down 93L! lol
Thx LA
2591. beell
Posted By: GulfScotsman at 12:24 PM GMT on September 21, 2007.

we are certainly glad that only 50 homes have been damaged and one injury in this non system


Hope 1 injury is the worst we hear about.
Tornadoes probably a threat still in parts of GA and FL panhandle.
Observation Time: Friday, 12:56Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 29.2N 84.7W (View map)
Location: 89 miles (143 km) to the SE (139) from Panama City, FL, USA.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 460 meters
Flight Level Wind: From 160 at 23 knots (From the SSE at ~ 26.4 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 23C
Flight Level Dew Point: 21C
Weather (within 30 nautical miles): Thunderstorm(s)
Mean Sea Level Pressure (MSLP): 1007 mb (extrapolated)

Optional Data...

Estimated Surface Wind: From 150 at 20 knots (From the SSE at ~ 23.0 mph)
I doubt it thel, not sure Baton Rogue will get on the NW side of this thing where the worst of the weather will be. I am thinking risk of nados will be the biggest threat with 93, but again, jmho.
Morning bl, good to see you.

Sorry Dixie, not sure why. Strange they would not let you know why.
CURRENT RECON GREEN.....

posted this before, but it never showed up??



37mph SFMR

12:58:30Z 29.28N 84.83W 959.5 mb
(~ 28.33 inHg) 421 meters
(~ 1,381 feet) Missing - From 154 at 25 knots
(From the SSE at ~ 28.7 mph) 21.0C*
(~ 69.8F*) -* 25 knots
(~ 28.7 mph) 32 knots
(~ 36.8 mph)
Well,

It appears to be tracking the HWRF path pretty well.

Guess we can be thankful for the rain!
Anyone know what is up with QS, seems to be having some issues this morning...
Good morning all. 93L, unlike the majority, does not look better organized to me as this remains a rather lop-sided system tilted in a SW to NE orientation. The only thing I would agree happened last night was that convection did increase and it may have started to gain tropical characteristics for a time, but as I said yesterday, I expect this system to remain subtropical throughout its lifetime.

The Western Caribbean continues to look more interesting with each passing image as convection has continued to flare and in fact somewhat maintain itself in the past 24 hours despite strong wind shear. All the Gulf Coast (even Florida) should watch this in the case it does develop into a tropical cyclone as some models predict. It just seems to me with the current pattern in the Gulf of Mexico, this system would move NNE towards Florida and not towards the Yucatan and the BOC like the models show happening.

I will update my website later this morning with information regarding 93L and the Western Caribbean disturbance.
2606. Bonedog
great the blog is eating posts again


repost....

Taz...

During active periods of hurricane season, these rules will be strictly enforced. Violations will be met with a minimum 24 hour ban....

just follow the rules and your fine. Its not that hard to do.
thx patrap. good info for greenhorns
Tropical Update

2611. Bonedog
wow SJ I just took a look at the QS site. Looks like it missed everything!! Unless they are in the process of updateing the new pass information.

If not then I would definatley say something is up with QS
13:07:30Z 29.35N 85.38W 959.9 mb
(~ 28.35 inHg) 400 meters
(~ 1,312 feet) 1004.7 mb
(~ 29.67 inHg) - From 227 at 14 knots
(From the SW at ~ 16.1 mph) 24.1C
(~ 75.4F) 20.8C
(~ 69.4F) 16 knots
(~ 18.4 mph) 0 knots
(~ 0 mph)
Thunder:

I was saying if upperlevel outflow begins to develop over this thing (aka Anticyclonic turing in the upper levels) we could see a rapidly intensifying system - - - that's IF we see one develop...

I believe it's not out of the question... I'm already seeing signs of outflow already happening, but at the same time - DRY AIR is preventing this thing from completely wrapping into itself
Quikscat is processing those areas...look at quikscat about 1, 2 ,3 hours from now and u will see new passes added hour by hour.
deleted
....
i walked outside this morning and can hardly believe there is a storm of anytype coming this way... its cool, a little breezy, no clouds, and smells like fall!!! i LOVE this time of year
man, the blog is hosed this morning!


.....
A lot further north this morning than has been progged.
dixiegal: Last night he e-mailed asking me to try to find out and PascagoulaGal said it was some word he said. And PascagoulaGal said she e-mailed him and told him.
Sheri
So where do you all think 93 is going?
what is with the Modify Comment evere time you try to Modify Comment your commet it takes you too the Complete Archive or one of dr m old blogs Archive
2623. Bonedog
I think once the blog surpasses 50 pages it goes into post eating mode :)
Is there any interest in the "blob" south of Cuba in NW Carib? I think the UKMT had this developing earlier in the week, but now none of the models show anything for it.
SUBJ/TROPICAL CYCLONE FORMATION ALERT 211200Z SEP 07//
WTNT 01 KNGU 211200Z
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 28.8N 85.5W TO 30.0N 88.5W
WITHIN THE NEXT 00 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 25 TO 30 KNOTS. METSAT IM-
AGERY AT 211200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 28.8N 85.5W. THE SYSTEM IS MOVING WEST-NORTHWEST AT 05 KNOTS.2. REMARKS:
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 221200Z
Good Morning All.

Can someone tell me what the currect thinking is on the blob/disturbance in the caribean. What is this forecast to do @ what intensity?

Thanks
Observation Time: Friday, 13:07Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 29.3N 85.3W (View map)
Location: 64 miles (104 km) to the SSE (160) from Panama City, FL, USA.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 450 meters
Flight Level Wind: From 240 at 15 knots (From the WSW at ~ 17.2 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 24C
Flight Level Dew Point: 21C
Weather (within 30 nautical miles): Shower(s) (continuous or intermittent precipitation - from cumuliform clouds)
Mean Sea Level Pressure (MSLP): 1005 mb (extrapolated)

Optional Data...

Estimated Surface Wind: From 360 at 30 knots (From the N at ~ 34.5 mph)
Posted By: Weather456 at 1:19 PM GMT on September 21, 2007.
Quikscat is processing those areas...look at quikscat about 1, 2 ,3 hours from now and u will see new passes added hour by hour.


Not sure about this 456, The Ascending pass is the morning pass and it seems that all of those are from yesterday. The descending is the evening pass and it seems to have not hit any of it's passes either as much of the descending are still blank.

QuickSCAT


Find that page as well as forecast models, imagery, marine data, preparedness info, and much more from the
Quick Links page.
2633. Bonedog
I know this doesnt have to do with 93L but look at how far the extratropical Low in the central north atlatic is pulling convection! Almost has convection to the LA's

w
SJ, ohh well

Thats how i normally see it...lets see if anything changes.
That convection in the carribian looks like something to watch.
If this developes we could have another hurricane landfall.
2638. Bonedog
yea I read that JP. I have been watching that since it brough rains to my area earlier last week. Its got the potential, the time, the water and the environment to make the transition.

Don't forget that a system thats extratropical can use cooler waters (as low as 21*c) to make itself tropical. I found that information out the other day reading the psu met:241 online course material
2639. NEwxguy
bonedog,I've been watching that low the past couple of days,it's really been wrapping up.
The non tropical low is a shallow warm-core system. These are either warm seclusions or subtropical cyclones and the non tropical low is definately not a warm seclusion.
Dixiegal: You welcome. Anytime.
Sheri
456, click on the ascending pass right off the African coast. Shows the pass on the QS front page, but there is no data when you select it. Something is fishy with the QS, maybe it will get back on track with the descending pass.
2644. Bonedog
huh 456? I lost yea there
Mandatory Data...

Observation Time: Friday, 13:27Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 29.5N 85.3W (View map)
Location: 52 miles (83 km) to the SSE (155) from Panama City, FL, USA.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 460 meters
Flight Level Wind: From 120 at 23 knots (From the ESE at ~ 26.4 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 22C
Flight Level Dew Point: 21C
Weather (within 30 nautical miles): Thunderstorm(s)
Mean Sea Level Pressure (MSLP): 1007 mb (extrapolated)

Optional Data...

Estimated Surface Wind: From 90 at 20 knots (From the E at ~ 23.0 mph)
Thanks, Dr. M
new blog up.


looks like recon is trying to get a vortex fix....
well LA, I'm very new at this, but IMO the WV seems to support what you're saying
2656. v7fan16
the steering is now running from south to north over florida, I can see why 93L is drifting NNE, plus its feeling a little tug from the front off the east coast, but I think it will stall before getting to the coast, the high to the north and east is expected to shift a bit further south, therefore we may see 93L drift southward this afternoon
Its not drifting NNE... its moving wnw at about 5mph.
2657. msphar
Dust and shear. Dust and shear. Time ticking by. CV not producing much this month, 10 day til Oct starts. Its been eight days since the last storm was named. Maybe the downward adjusted Dr. Gray number will be reached or maybe not.
Posted By: Bonedog at 9:41 AM AST on September 21, 2007.

huh 456? I lost yea there


When i say shallow warm-core, I mean a system that is warm-cored in the low levels but becomes cold-core in the upper levels. TCs are warm-core thoughout the atmopshere and thus are termed deep warm-core systems.

There are two systems that present themselves as shallow warm-core systems - subtropical cyclones and warm-seclusions systems.

A warm seclusion is the mature phase of the extratropical cyclone lifecycle. This was conceptualized after the ERICA field experiment of the late 1980s, which produced observations of intense marine cyclones that indicated an anomalously warm low-level thermal structure, secluded (or surrounded) by a bent-back warm front.
Our Houston area weather folk seem more interested in the Pacific NW storm-how will this affect the GOM activity. Some one please give me an idea?
NEW BLOG IS UP
looks to me 93L is trying to close off its center, and build convection.....

West end