TD 13 intensifying; Katia may pass uncomfortably close to U.S.

By: Dr. Jeff Masters , 3:28 PM GMT on September 02, 2011

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Tropical Depression Thirteen formed last night over the Northern Gulf of Mexico and is slowly intensifying, but isn't in a hurry to go anywhere. What TD 13 will do is dump torrential rains along the northern Gulf Coast over the next three or more days. So far, rain amounts along the coast have mostly been below one inch. At New Orleans Lakefront Airport, just 0.32" inches of rain had fallen from TD 13 as of 10 am CDT. Some coastal regions have received up to two inches, according to radar rainfall estimates. TD 13 is generating a large area of 30 - 35 mph winds over the Gulf of Mexico. At 7:20 am CDT, winds at the Mississippi Canyon 711 oil rig were southeast at 47 mph. This is above tropical storm force, but the wind instrument was 348 feet (106 m) above the ocean surface, and winds near the surface were probably considerably lower, near 35 mph. Latest surface wind observations from an Air Force hurricane hunter aircraft support leaving TD 13 as a tropical depression. Long range radar out of Mobile, Alabama shows heavy rain showers building along the northern Gulf Coast, but these rain showers are not well-organized into spiral bands. Strong upper-level winds out of the west-northwest are creating a moderate 10 - 20 knots of wind shear over TD 13, keeping the storm's heavy thunderstorms disorganized and pushed to the east side of the storm. However, latest satelllite loops show TD 13 is becoming increasingly organized, with a respectable spiral band forming on the southeast side, and an increase and areal coverage of heavy thunderstorm activity. This is very likely to be a tropical storm later today.


Figure 1. Radar-estimated rainfall from TD 13 from the New Orleans radar.


Figure 2. U.S. drought conditions on August 30. The rains from TD 13 have the potential to bring major drought relief to drought-stricken portions of the coast. Note how Eastern North Carolina is no longer in drought, thanks to the rains from Hurricane Irene. These rains also came close to putting out a persistent fire that had been burning in the Great Dismal Swamp near the Virginia/North Carolina border. Image Credit: U.S. Drought Monitor.

Forecast for TD 13
TD 13's large size, ill-formed circulation center, and the presence of dry air on its west side due to an upper-level trough of low pressure argue against rapid intensification of the storm for the next three days. Also tending to slow intensification will be the slow movement of the storm, which will allow cold water from the depths to rise to the surface, thanks to wind and wave action. Tropical cyclones strongly cool the water's surface when they pass over it, as seen in the time vs. depth chart of sea surface temperatures during Hurricane Irene's passage along the New Jersey coast (Figure 3.) However, the Gulf of Mexico has some very warm waters near TD 13 that extend to great depth (Figure 4), so the surface cooling imparted by TD 13 will be less than that seen for Hurricane Irene. As TD 13 moves closer to the coast, more and more of its circulation will be over land, which will also slow intensification. NHC's 11 am EDT wind probability forecast for TD 13 gave the storm a 23% chance of intensifying into a hurricane by Sunday. Assuming TD 13 does not attain hurricane strength, wind damage and storm surge damage will likely not be the main concern--fresh water flooding from heavy rains will be the most dangerous impact. Also of concern is the possibility of tornadoes. NOAA's Storm Prediction Center is currently not highlighting the Gulf Coast in their "slight risk" area for severe weather, due to the lack of enough solar heating to create instability. However, there will be plenty of wind shear in the lower part of the atmosphere that can potentially create spin in the coastal thunderstorms, and it is possible that as TD 13 intensifies, it may be able to generate several dozen tornadoes.

Coastal Louisiana, Mississippi, Alabama, and the extreme western Panhandle of Florida will likely receive very heavy flooding rains that will intensify Saturday and peak on Sunday. These rains should be able to put out the stubborn marsh fire east of New Orleans that has brought several days of air quality alerts to the city, but may cause moderate to severe flooding problems in other areas. The latest rainfall forecast from NOAA Hydrological Prediction Center shows that a large area of 15+ inches of rain is expected over Southeast Louisiana and coastal Mississippi. The region is under moderate drought, so flooding problems will be delayed compared to what we'd normally expect from heavy rains of over a foot. Flash flood watches are posted for New Orleans and surrounding areas, and rainfall amounts of 1 - 3 inches per hour are possible in some of the heavier rain squalls. Ocean temperatures are near record warmth, 88°F (31°C), which will provide plenty of moisture for heavy rains, and plenty of energy to help TD 13 strengthen into a strong tropical storm. Steering currents will be weak in the Gulf this weekend and early next week, which will likely make the motion of TD 13 erratic at times.


Figure 3. EPA, in conjunction with Rutgers University and the NJ Department of Environmental Protection, has an Autonomous Underwater Vehicle (AUV, aka the Glider) deployed off the coast of NJ (since early August) continuously monitoring ocean temperature, density, salinity, sound velocity and dissolved oxygen at different depths. The AUV's path and data are displayed at the following website: http://marine.rutgers.edu/cool/auvs/index.php?did =221&view=imagery. The plot of temperature versus time above shows that in the weeks prior to the arrival of Irene, the ocean was heavily stratified, with warm waters of 24 - 26°C (75 - 79°F, red colors) extending from the surface to a depth of 10 - 15 meters. A sharp thermocline existed at a depth of about 15 meters, and ocean temperatures were colder than 14°C (57°F, dark blue colors) below the thermocline. The strong winds and high wave action of Hurricane Irene on August 28 - 29 stirred up cold water from the depths to the surface, cooling the surface waters to 17 - 19°C (63 - 67°F). In the days since the hurricane, surface waters have begun to warm again. Thanks go to Kevin Kubik, Deputy Director of the Division of Environmental Science and Assessment for EPA Region 2, for making me aware of this data.


Figure 4. The total amount of heat energy in the ocean available to fuel a tropical cyclone, in kilojoules per square centimeter of surface area. Tropical cyclones that move over ocean areas with TCHP values in excess of 70 - 90 kJ/cm^2 commonly undergo rapid intensification. Waters that are warm to a great depth have the highest TCHP, and the Loop Current that brings warm water northwards from the Caribbean to the Gulf of Mexico usually has the highest TCHP values in the Atlantic. Currently, we have an eddy that broke off from the Loop Current earlier this summer, now located a few hundred miles south of the Louisiana coast, that also has high TCHP values. Image Credit: NOAA/AOML.

Hurricane Katia
Hurricane Katia is continuing its long trek across the Atlantic Ocean today, and will not pose a danger to any land areas over the next five days. Katia is still struggling with dry air and moderate wind shear of 10 - 20 knots. Latest satellite loops show surface-based arc-shaped clouds racing to the southwest away from Katia's core, a sign that dry air is penetrating into Katia's thunderstorms and creating strong downdrafts that are robbing the storm of heat and moisture. Katia is over warm ocean waters of 28.5°C, and these waters will increase in temperature to 29°C over the next five days. Katia will pass well north of the region of cooler waters stirred up by the passage of Hurricane Irene last week.

The models are split on when the upper-level trough of low pressure bringing the wind shear to Katia will move away, and the storm may spend two more days battling wind shear and dry air before the upper-level trough pulls away to the north and allows Katia to intensify more readily. It is still unclear how much of a threat Katia may pose to the U.S., but it is becoming increasingly clear that Katia will pass uncomfortably close to the U.S. East Coast. The trough of low pressure currently steering Katia to the northwest will lift out early next week, and a ridge of high pressure is expected to build in, forcing Katia more to the west. This decreases the danger to Bermuda, but increases the danger to the U.S. A second trough of low pressure is expected to begin affecting Katia by the middle of next week, and will potentially recurve the storm out to sea before it hits the U.S. However, the models differ widely on the strength and timing of this trough. Meteorologist Grant Elliot of Australia's Bureau of Meteorology in Perth pointed out to me yesterday that the long-range forecast for Katia has more than the usual amount of uncertainty, due to the inability of the computer models to agree on what will happen to Tropical Storm Talas in the Western Pacific. Talas is expected to hit Japan early on Saturday as a strong tropical storm, then race northwestwards into the Bering Sea off the coast of Alaska. Talas is then expected to transition into a powerful extratropical storm in the waters south of Alaska. This storm will create a ripple effect downstream in the jet stream, all the way to North America, by early next week. The timing and amplitude of the trough of low pressure off the U.S. East Coast expected to potentially recurve Katia out to sea next week is highly dependent upon the strength of Tropical Storm Talas during its transition to an extratropical storm. The computer models are not very good at handling these sorts of transitions, leading to more than the usual amount of uncertainty in the long-range outlook for Katia. It will probably be another 2 - 3 days before the models will begin to converge on a solution for the long-term fate of Katia. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have a 17% chance of hitting North Carolina, a 21% chance of hitting Canada, a 13% chance of hitting New England, and a 55% chance of never hitting land. One almost certain impact of Katia on the U.S. will be large waves. Long period swells from Katia will begin affecting the Bahamas on Sunday night, then reach the Southeast U.S. by Monday morning. By Tuesday morning, the entire U.S. East Coast will see high surf from Katia, and these waves will increase in size and power as the storm grows closer. Given the slow movement of Katia as it approaches the coast, plus its expected Category 1 to 3 strength as it approaches, the storm will probably cause extensive beach erosion and dangerous rip tides for many days.

94L
A well-organized low pressure system with a surface circulation but limited heavy thunderstorm activity due to high wind shear is 450 miles south of Halifax, Canada. This disturbance, (94L), is headed northeast out to sea, and is being given a 60% chance of developing into a tropical depression by NHC. 94L is under a high 25 - 30 knots of wind shear, but this shear is expected to fall to the moderate range, 10 - 20 knots, by Saturday morning. However, sea surface temperature will fall from 27°C today to 25°C Saturday morning underneath 94L, and the storm will have a very short window of time to get organized enough to get a name. At this point, it's really a subjective judgement call on whether or not 94L is already a tropical storm.


Figure 5. A Portlight volunteer works to clear storm debris from Hurricane Irene in Hollywood, Maryland.

Portlight disaster relief effort in Maryland
Hurricane Irene heavily damaged the town of Hollywood, Maryland, when a tornado cut off electric power, water, and phone service. Portlight and Team Rubicon volunteers arrived before emergency personnel, after following up on a local tip. What they found was an isolated area whose plight was unknown to the larger community. Most residents were trapped at their homes by heavy debris. Portlight and Team Rubicon worked for two days to clear paths to each address, extract vehicles from debris, and cut down trees that constituted safety hazards. Portlight also instructed local residents how to operate and maintain chainsaws and safely clear debris. No other volunteer organizations or emergency personnel arrived at any time, and Portlight succeeded in meeting the specific needs of the underserved, unserved, and forgotten. Visit the Portlight blog to learn more; donations are always welcome.

I'll have a new post each morning over the coming holiday weekend; wunderground meteorologists Angela Fritz, Rob Carver, and Shaun Tanner will be handling the afternoon and evening posts. Have a great holiday weekend, everyone!

Jeff Masters

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AL, 12, 2011090300, , BEST, 0, 183N, 539W, 65, 988, HU,
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
AL, 12, 2011090300, , BEST, 0, 183N, 539W, 65, 988, HU, 64, NEQ, 30, 0, 0, 0, 1013, 275, 25, 0, 0, L, 0, , 0, 0, KATIA, D
Member Since: July 6, 2010 Posts: 113 Comments: 31858
Quoting Tazmanian:




it means where all DOOM


??...you messin with me taz...
Member Since: July 17, 2008 Posts: 0 Comments: 1242
2033. CCkid00
Quoting KoritheMan:


Where do you live? I'm near Baton Rouge.

Korithe......I'm in Denham Springs.
Member Since: Posts: Comments:
Quoting Tazmanian:




she has been looking a lot better in the pass few hrs


Yep. No denying that.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
2030. HCW
Member Since: August 10, 2002 Posts: 0 Comments: 1408
2029. scott39
Lee will look the worst hes going to for the next 24 hours and then after that, not until hes inland for awhile.
Member Since: Posts: Comments:
Quoting tennisgirl08:


What does that mean?


2011090300?

2011: Year
09: Month
03: Day
00: UTC time update (00:00 UTC)
Member Since: July 6, 2010 Posts: 113 Comments: 31858
Quoting tennisgirl08:


What does that mean?




it means where all DOOM
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
Lee isn't weakening.... The pressure is falling and thunderstorms are firing up near the center nicely. Still to much shear on the west side
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2025. Zeec94
Quoting KoritheMan:


Where do you live? I'm near Baton Rouge.


I'm in Palm Beach. I always take my video equipment out and get footage. I give it to the local news stations and sometimes national. When the teams are dispatched, they always get stretched short so I go out and grab shots for them in places they can't get reporters too.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:


grrr....

AL, 13, 2011090300, , BEST, 0, 280N, 915W, 40, 1001, TS, 34, NEQ, 175, 175, 0, 90, 1007, 175, 75, 0, 0, L, 0, , 0, 0, LEE, M,


What does that mean?
Member Since: July 17, 2008 Posts: 0 Comments: 1242
Quoting TropicalAnalystwx13:


grrr....

AL, 13, 2011090300, , BEST, 0, 280N, 915W, 40, 1001, TS, 34, NEQ, 175, 175, 0, 90, 1007, 175, 75, 0, 0, L, 0, , 0, 0, LEE, M,



heh heh
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
2021. 996tt
Quoting scott39:
I feel like convection will build back once it pulls away from Texas to the NE. Not to mention its not rushing into land anytime soon, so potential is there for strengthening.


Yep, exactly what I said two pages ago. If it drifts more eastward and remains slow, it can potentially wrap and intensify. if it drifts westward any more, it will continue to get shredded. I can see some feeder bands off shore right now. We shall see. Be interesting.
Member Since: September 5, 2008 Posts: 0 Comments: 308
Quoting KoritheMan:


There really isn't a way for her to. That flow is being caused by an upper trough to the west, the same one that's been shearing her.




she has been looking a lot better in the pass few hrs
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
Quoting Neapolitan:
AL, 13, 2011090300, , BEST, 0, 280N, 915W, 40, 1001, TS, 34, NEQ, 175, 175, 0, 90, 1007, 175, 75, 0, 0, L, 0, , 0, 0, LEE, M,


TS Lee's 00Z ATCF update:

AL, 13, 2011090300, , BEST, 0, 280N, 915W, 40, 1001, TS, 34, NEQ, 175, 175, 0, 90, 1007, 175, 75, 0, 0, L, 0, , 0, 0, LEE, M,

Quoting Neapolitan:
AL, 13, 2011090300, , BEST, 0, 280N, 915W, 40, 1001, TS, 34, NEQ, 175, 175, 0, 90, 1007, 175, 75, 0, 0, L, 0, , 0, 0, LEE, M,


grrr...lol.
Member Since: July 6, 2010 Posts: 113 Comments: 31858
What ATCF says:

AL, 13, 2011090300, , BEST, 0, 280N, 915W, 40, 1001, TS, 34, NEQ, 175, 175, 0, 90, 1007, 175, 75, 0, 0, L, 0, , 0, 0, LEE, M,
Member Since: Posts: Comments:
Quoting hurricanehanna:

wow ... look how similar!


Lee is TS Allison's twin. They are identical....wow!
Member Since: July 17, 2008 Posts: 0 Comments: 1242
Quoting hurricanehanna:

My personal opinion is that Florida's beaches are more beautiful. I'm not saying they are nicer, as I grew up going to Galveston often, but the sand is white and the water is emerald green to blue. Just my take.


Up until 2000 (when I moved to Minnesota - now back down here in Kemah) the whitest Christmas was the one I spent at my grandparents in Destin. But Hurricane eloise hit and for years the beach was different. The sand was a little darker, more tar, more jelly fish. They lived right on the bluff so their house was virtually destroyed by wind damage.
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Quoting Zeec94:


I'm with you there bro. haha


Where do you live? I'm near Baton Rouge.
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Quoting TropicalAnalystwx13:
Taz, don't forgot to tell people to wear a lifejacket if they get in the water.




LOL
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
Quoting Tazmanian:



ok but what if she is miss that


There really isn't a way for her to. That flow is being caused by an upper trough to the west, the same one that's been shearing her.
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2012. Zeec94
Quoting KoritheMan:


My new video camera beckons otherwise. ;)


I'm with you there bro. haha
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Taz, don't forgot to tell people to wear a lifejacket if they get in the water.
Member Since: July 6, 2010 Posts: 113 Comments: 31858
Quoting luigi18:


We are waiting for Her! Her in PR lets keep an eye on Her she looks like Stevie Nicks! look her Hair



yup
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
2009. 996tt
As a side note, the wedge was pumping yesterday. Wow.
Member Since: September 5, 2008 Posts: 0 Comments: 308
2007. luigi18
Quoting Tazmanian:
too me Katia is moveing right a long 18N 54W or 19N 54W wish do you guys think all so Katia is starting too come vary cloes too the Leeward Islands even no it may still be a few 100 ms off too there W but when you look at it it looks like it is a lot closer then you think it is all so if this keeps moveing W i think a TS watch or hurricane watch could go up for the Leeward Islands if this dos not start turning a little WNW soon


so if you live any where on the Leeward Islands i would keep a vary close eye on this has this may be comeing closer then mode runs are saying



but hey what do i no lol



any commets?

"Gold Dust woman"
Member Since: Posts: Comments:
Quoting hurricanehanna:
Best bet is to stay in and stay safe :)


My new video camera beckons otherwise. ;)
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2005. CCkid00
Quoting stormpetrol:
Looks like Katia might be temporarily caught between a rock and a hard place


True....Katia AND the people who may (or may not) end up in her path.
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Quoting notanothergoof:
STOP BLOWING SMOKE LOL


lol
Member Since: September 18, 2007 Posts: 0 Comments: 1074
2003. beell
Quoting Drakoen:
500mb set up like this would probably lead to some action for the Mid-Atlantic states.



Something to look at for sure. Maybe, a saving grace on that particular scenario would be the positive tilt (in the model, lol) to Lee's capturing trough. A negative tilt and Katia could get tugged back towards the coast.
Member Since: September 11, 2007 Posts: 142 Comments: 16478
has any one noted how march better Katia is looking all so it seen like wind shear is now vary low all so it looks like it has slow way down
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
Quoting Drakoen:


Adrian (hurricane23) has a B.S. in Meteorology and Applied Math

Atmoaggie has a B.S. in Atmospheric Science

Thank you Drak.
I was never sure about that.
Both great posters.
Wish they would post more.
Member Since: August 3, 2005 Posts: 10 Comments: 5557
2000. scott39
Quoting 996tt:


I hear you, but no surge and no winds to speak off also. Won't get those either unless convection can build in and wrap around the center of circulation.
I feel like convection will build back once it pulls away from Texas to the NE. Not to mention its not rushing into land anytime soon, so potential is there for strengthening.
Member Since: Posts: Comments:
1998. yoboi
is something trying to form south of cuba>??????
Member Since: Posts: Comments:
1997. luigi18
Quoting Tazmanian:
too me Katia is moveing right a long 18N 54W or 19N 54W wish do you guys think all so Katia is starting too come vary cloes too the Leeward Islands even no it may still be a few 100 ms off too there W but when you look at it it looks like it is a lot closer then you think it is all so if this keeps moveing W i think a TS watch or hurricane watch could go up for the Leeward Islands if this dos not start turning a little WNW soon


so if you live any where on the Leeward Islands i would keep a vary close eye on this has this may be comeing closer then mode runs are saying



but hey what do i no lol



any commets?


We are waiting for Her! Her in PR lets keep an eye on Her she looks like Stevie Nicks! look her Hair
Member Since: Posts: Comments:
Quoting KoritheMan:


Water vapor imagery shows that a weakness within the ridge still exists, as the flow is southeasterly or even east-southeast. She should turn again soon.



ok but what if she is miss that
Member Since: May 21, 2006 Posts: 5091 Comments: 114914
Quoting 5Rockets:


Well, here's worse news. It's gonna become even drier in Texas because of Lee,
because Texas has been very hot and dry, wind is gonna make that fire.


I know, they have been posting FIRE DANGER warnings all day. We have had some wind, but that is a bad thing here with all the fires around. Poor firefighters are working around the clock as it is.
Member Since: September 18, 2007 Posts: 0 Comments: 1074
1992. Caner
Looks like all that moisture blasted into the atmosphere by the collapsed convection from this morning is slowly pushing the dry air from Texas back across the LA/TX border...

If the coc remains over the gulf for long enough for that moisture to push the dry air back far enough for that moisture to get wrapped back around the coc, that will be interesting.

Member Since: Posts: Comments:
1990. Drakoen
Quoting CosmicEvents:
Thank you for your opinion WX03, it carries a lot of weight with me...for those who don't know WX03 is the ONLY formally trained met that posts on this blog, besides the Dr., Angela, and Rob of course. We do have some other promising posters currently studying and close to getting their degree who do great as well.


Adrian (hurricane23) has a B.S. in Meteorology and Applied Math

Atmoaggie has a B.S. in Atmospheric Science

Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting Tazmanian:
too me Katia is moveing right a long 18N 54W or 19N 54W wish do you guys think all so Katia is starting too come vary cloes too the Leeward Islands even no it may still be a few 100 ms off too there W but when toy look at it it looks like it is a lot closer then you think it is all so if this keeps moveing W i think a TS watch or hurricane watch could go up for the Leeward Islands if this dos not start turning a little WNW soon


so if you live any where on the Leeward Islands i would keep a vary close eye on this has this may be comeing closer then mode runs are saying



but hey what do i no lol



any commets?


Water vapor imagery shows that a weakness within the ridge still exists, as the flow is southeasterly or even east-southeast. She should turn again soon.
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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.

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