Complicated Gulf of Mexico disturbance 93L primarily a rain threat

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

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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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1562. homegirl
11:40 PM GMT on September 20, 2007
I think the Doc did a blog not to far back about La Nina causing less shear over the Atlantic so if La Nina develops then we would have an extended season, too!

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1561. TerraNova
7:39 PM EDT on September 20, 2007
I tanked up today at a pretty 2.59/ gallon. Everyone get your gas now because it's about to sky rocket.

Apparently some oil rigs are already closing down in advance of this system.
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1560. taco2me61
11:39 PM GMT on September 20, 2007
Okay Baybuddy I will build me a raft and meet you on water street...LOL
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1559. LightningCharmer
11:39 PM GMT on September 20, 2007
Posted By: truecajun at 11:38 PM GMT on September 20, 2007.

I tanked up today at a pretty 2.59/ gallon. Everyone get your gas now because it's about to sky rocket.


Maybe not skyrocket but I filled 'r up too just in case. Good recommendation.
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1556. truecajun
11:36 PM GMT on September 20, 2007
I tanked up today at a pretty 2.59/ gallon. Everyone get your gas now because it's about to sky rocket.
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1555. hurricanehanna
7:35 PM CDT on September 20, 2007
Good job lightning charmer.....a picture is worth a thousand words!
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1554. LightningCharmer
11:36 PM GMT on September 20, 2007
That does not mean this year will have more storms after September 10. That graph is just the historical accumulation.
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1553. Patrap
6:32 PM CDT on September 20, 2007
sandcrab,..our Blogger Who is Emg Mgr for Jackson County ,Miss will be on the BrometerBob Show tonight. 7 CST
He has info on the Emergency Actions in Miss and other too.

Link
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1552. taco2me61
11:32 PM GMT on September 20, 2007
Posted By: Weather456 at 11:31 PM GMT on September 20, 2007.

ok..i didnt wanted to stir up anything. Just was looking at some data and it looked like the 2007 season could spawn some more storms in oct and nov.

Yes this is true this year... I do see that we could even have a 2nd one in mid November aswell....

We will have are 2nd peek in October and I think that everyone should not discount anything that might form over the next 2 months.... We do have a long way to go....

:0) :0) :0)
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1551. TerraNova
7:35 PM EDT on September 20, 2007
To determine number of storms over a certain time period, using this chart, one has to calculate the area between two points.

Without getting out the slide rule and integration tables, obviously there is more area after Sept 10 than prior hence more storms after.


Exactly.
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1548. seafarer459
11:31 PM GMT on September 20, 2007
Seasons over????

Dang I missed Thanksgiving!!
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1547. LightningCharmer
11:33 PM GMT on September 20, 2007
Seasonal Activity Chart
To determine number of storms over a certain time period, using this chart, one has to calculate the area between two points.

Without getting out the slide rule and integration tables, obviously there is more area after Sept 10 than prior hence more storms after.

I submit this for peer review.
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1544. TerraNova
7:30 PM EDT on September 20, 2007
I dont think that is the COC that is moving.... If you check the wind map it shows the COC staying almost stationary moving a little to the S or SW... imo

The steering layer is very confusing in the Gulf right now. 93L is very near or right under the ULL and there is only 5-10 knots of steering...not very fast. but if the ULL moves away or dissipates this would move faster, with 20 knots of steering.
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1543. Weather456
7:29 PM AST on September 20, 2007
ok..i didnt wanted to stir up anything. Just was looking at some data and it looked like the 2007 season could spawn some more storms in oct and nov.
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1541. opbandman
6:31 PM CDT on September 20, 2007
truecajun

good post
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1540. mobal
6:28 PM CDT on September 20, 2007
25% of rigs shut down in Gulf now (TWC Reports)....There goes gas prices..
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1538. opbandman
6:29 PM CDT on September 20, 2007
If anything, this season has proved that the unexpected should be expected.
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1537. TerraNova
7:28 PM EDT on September 20, 2007
thats why I stay with 16 storms

I think we will see 3 systems before the end of this month

this one here will be Jerry, SW Caribbean I think will be Karen and then another system will be in its formative stage at the end of the month. the we get 3 more storms in October and 1 in November


I agree JP; I do beleive that this year will end up with a total of 14-16 named storms...
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1536. pottery2
7:20 PM AST on September 20, 2007
Yeah, I hear you guys.
But I'm not buying that. This is 2007. This is a completely different year. We have never been here before. It is not like any other. The climate is changing. For whatever reason. Its not playing by the same rules anymore.
And we are all trying to figure it out. So keep an open mind, and look for the things that have influenced the last couple of years.
The Sahara. The reduction in Arctic ice. Just 2 to start with.
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1535. truecajun
11:25 PM GMT on September 20, 2007
Please, let's not start an argument about the season and times/peaks of seasons--we are NOT truly capable of knowing what the season will bring--No one REALLY knows. This is not something to fuss about. Everyone has been getting along so well today. Let's not start now.
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1534. fldude99
11:24 PM GMT on September 20, 2007
Posted By: extreme236 at 11:22 PM GMT on September 20, 2007.
Posted By: fldude99 at 11:21 PM GMT on September 20, 2007.

Thats not true...after the 9th/10th the activity does not drop off dramatically, if that was the case then why do most named storms in a season form after the peak?

Wrong..the peak is Sept 10..look it up. After that it falls off big time
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1533. taco2me61
11:25 PM GMT on September 20, 2007
BayBuddy....
With all due respect I think you might want to build an ark.....
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1531. Baybuddy
11:20 PM GMT on September 20, 2007
How can people call the season already?
Besides, wasn't there a storm a week or so ago that became a cat one without any support from the experts? Had that storm stalled for a short while, it could have made landfall in the early morning hours as a cat 3 ! The season is not nearly over. A few pleasant days does not mean the tropical season is over.
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1530. mississippiwx23
11:21 PM GMT on September 20, 2007
Reason being IMO is that after 9/10 or so the amt of storm activity drops off dramatically..and whats more is the threat to US mainland is much less about this time going forward..and really most folks don't care much for anything other than their own area..but most don't admit that



Actually, it goes down, but a secondary peak is in october. The rise to the peak is actually more 'spiked' than the fall in the later half of the season. Storms are MORE likely to occur near land than out to sea later into the year.
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1527. SomeRandomTexan
6:18 PM CDT on September 20, 2007
TerraNova---

I dont think that is the COC that is moving.... If you check the wind map it shows the COC staying almost stationary moving a little to the S or SW... imo
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1524. truecajun
11:20 PM GMT on September 20, 2007
I like that Baybuddy, ark or boards. As of now, I'd say neither, but eventually, an Ark should suit you just fine!
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1523. extreme236
11:22 PM GMT on September 20, 2007
Posted By: fldude99 at 11:21 PM GMT on September 20, 2007.

Posted By: mississippiwx23 at 11:17 PM GMT on September 20, 2007.
Why are people killing the season on the 20th of September?!?

A long, long way to go. Another 5-6 storms, I think (including Jerry).

Reason being IMO is that after 9/10 or so the amt of storm activity drops off dramatically..and whats more is the threat to US mainland is much less about this time going forward..and really most folks don't care much for anything other than their own area..but most don't admit that


Thats not true...after the 9th/10th the activity does not drop off dramatically, if that was the case then why do most named storms in a season form after the peak?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1522. NormalGuy
11:08 PM GMT on September 20, 2007
Wow, So many factors affecting this thing, it is hard to tell if it is going to survive or not. I am hoping not, living here is MS has gotten expensive in the last 2 years.
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1521. Weather456
7:20 PM AST on September 20, 2007
Maybe some ppl misuderstood me

The 2007 atlantic season seems more favorable than 2006 so there is potential for more storms to develop this year than last year when the season last year was winding down at this time.
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1520. wundergroundfan
11:19 PM GMT on September 20, 2007
i think the 2007 tropics could squeeze out at least one more name storm (Jerry)..conditions seem more favorable over the basin this time than last year the tropics were winding down.

I don't think so. Jerry will be bring some cousins.
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1519. extreme236
11:21 PM GMT on September 20, 2007
shear forecast calls for shear to be favorable extending from africa to the antilles in 48hrs time...any african wave has good potential, and that non tropical low in the NE atlantic could become karen soon enough
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1518. fldude99
11:19 PM GMT on September 20, 2007
Posted By: mississippiwx23 at 11:17 PM GMT on September 20, 2007.
Why are people killing the season on the 20th of September?!?

A long, long way to go. Another 5-6 storms, I think (including Jerry).


Reason being IMO is that after 9/10 or so the amt of storm activity drops off dramatically..and whats more is the threat to US mainland is much less about this time going forward..and really most folks don't care much for anything other than their own area..but most don't admit that
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1517. TerraNova
7:18 PM EDT on September 20, 2007
Too many people are using 2006 as a basis for their thoughts of this season...just because we had one quiet season does not by any means decide that the next one will also be quiet. Shear in the GOM, SW Caribbean and CATL have been decreasing over the past few days and I think we could still see 3 or 4 more storms this year.

Also; a "quiet season" does not necessarily mean a lack of named storms...we broke several records this year. The US was hit by a hurricane for the first time since Wilma.
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1516. extreme236
11:20 PM GMT on September 20, 2007
93L should flare up overnight...conditions are ripe for it to do so
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1515. truecajun
11:18 PM GMT on September 20, 2007
I definitely think the season has some more steam, but as for 93L, he looks pififul on the Visible AVN. The rainbow pumps him up---some
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1514. Baybuddy
11:16 PM GMT on September 20, 2007
Okay party people, whats the skinny, should I board up or save the wood to build an ark?
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1513. floridafisherman
11:16 PM GMT on September 20, 2007
i dont see how ppl are dismissing or calling the season "dying down".

the season goes until nov. wilma, the most powerful hurricane in atlantic history, reached max strength in late oct.

SST are still warm and there is plenty of time for storms to form. this isnt 2006, when shear ruled the atlantic
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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