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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1137. Oct8
Quoting Neapolitan:

NOAA's Hurricane Research Division says:

"At present there are no plans to retire letters of the Greek alphabet from the list, but if a very bad hurricane occurs with a Greek letter name, this may have to be revised."


Oh the could rename alpha Aphrodite I imagine. You'd hate to waste perfectly good Greek letters ;-)

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1136. franck
If the shear were to relax Lee would probably spin up pretty strong, drag half the Gulf on shore.
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Quoting Matt1989:
The dry air will keep this thing in check.. 45 mph storm max imo.
That's what I hear too. Bout the only thing good about this storm.
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1134. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127803
Quoting thesituation:


I dont understand all the foot jokes on this page.


Granma?
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1132. Patrap
Lawdy,,..jeez,
Member Since: July 3, 2005 Posts: 423 Comments: 127803

Quoting TexasHurricane:


hi AtHome. I posted a link that I guess I wasn't suppose to. (a link to someone who used to be on the blog - not saying names)

Didn't realize I wasn't suppose to, but now I do. :)

how are you?
Oh I'm ok. Let down like everyone around here. But what can you do. I gave up frustration a couple hours earlier so I'm good.  :) How you doing today?
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Quoting GTcooliebai:
I know I was just teasing P451, since he believes this is not a tropical storm.
Indeed, carry on!
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The dry air will keep this thing in check.. 45 mph storm max imo.
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Quoting washingaway:


The ULL and the surface low are mating. That gives birth to a mutated tropical storm.


newbee Here, Question what is a : . hybrid/sub tropical system,,
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Quoting AegirsGal:
LOL!! Attempting to do that would earn you a Darwin Award, or maybe just an Honorable Mention.
I know I was just teasing P451, since he believes this is not a tropical storm.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1123. pcola57
Quoting DontAnnoyMe:


His site is directly relevant.


And your not Don't Annoy Me
2.12" so far today in Myrtle Grove,P'cola
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Good luck Patrap, hope that moves in before it gets to strong. Have a feeling it's starting to wrap up. And I'm beginning to get a little nervous about Katie with the high moving westward with the storm, hopefully the high doesn't get to big.
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Quoting clwstmchasr:


Especially to that guys site. Whenever he is mentioned people get a bit testy on this blog. And that idiot keeps posting pics of feet.


I don't understand why, but anyways. Enough of that. Moving on...
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Quoting Neapolitan:

NOAA's Hurricane Research Division says:

"At present there are no plans to retire letters of the Greek alphabet from the list, but if a very bad hurricane occurs with a Greek letter name, this may have to be revised."


That almost did happen in 2005, if that unnamed system would have been named 'Vince', Wilma would have been Category 5 Hurricane Alpha.
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Well now this stinks for Georgia...WTH!



Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting AtHomeInTX:

Afternoon Tex. Are you getting in trouble? Lol. Afternoon All. From sunny bleeping dry and breezy!  :)


hi AtHome. I posted a link that I guess I wasn't suppose to. (a link to someone who used to be on the blog - not saying names)

Didn't realize I wasn't suppose to, but now I do. :)

how are you?
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Quoting CosmicEvents:
All of you who posted links to another site, if you care about staying on the blog, should consider removing them. WUBA Admin takes a dim view of spamming. It violates 3 out of the 10 RULES OF THE ROAD.


His site is directly relevant.
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1113. JNCali
Looks like Lee is getting ready to swallow  the Texas Coast link
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Quoting Neapolitan:

NOAA's Hurricane Research Division says:

"At present there are no plans to retire letters of the Greek alphabet from the list, but if a very bad hurricane occurs with a Greek letter name, this may have to be revised."


After all we would go a very long time without running out of Greek letters.
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Quoting GTcooliebai:
Hey do you want to come with me and paddle out into the GOM to see if we find tropical storm forced winds?
LOL!! Attempting to do that would earn you a Darwin Award, or maybe just an Honorable Mention.
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1109. HCW
Quoting Patrap:


How much rain have you received Pat ?

We are up to 2.75 inches of rain on the day
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1108. ncstorm
Quoting GTcooliebai:
Sure Link make sure you reduce the Domain to CONUS :)


Thanks!
Member Since: August 19, 2006 Posts: 13 Comments: 15045
I am thinking that the NHC will have to come further west and northwest with their track...all the models are basically lining up for the Vermillion Bay area with the Euro a hair west of that...they are on the Eastern side of the guidance
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1106. pcola57
Quoting 996tt:


Is he in Beach Club??? If so, I think I know who you are talking about. I lived in beach Club for about a year. Great little break right off my balcony.


Yes He is,His name is David...He did'nt say which unit
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1105. IKE
Big flooding event on the 18Z NAM @ hour 51.....


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Quoting loophole29902:
What happens if a greek alphabet named storm is retired? what do they do the next year?

NOAA's Hurricane Research Division says:

"At present there are no plans to retire letters of the Greek alphabet from the list, but if a very bad hurricane occurs with a Greek letter name, this may have to be revised."
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1103. HCW
Quoting 996tt:


You gotta say that model runs have been amazingly accurate short term. I wouldn't bet against the models on Lee.


Hopefully this doesn't turn into another Danny 1997 for the Gulf Coast but I have a feeling that it will be worse . We will be out streaming live video tomorrow till when ever the storm passes
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1102. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127803
Quoting CosmicEvents:
All of you who posted links to another site, if you care about staying on the blog, should consider removing them. WUBA Admin takes a dim view of spamming. It violates 3 out of the 10 RULES OF THE ROAD.


hmmm, ok. I won't post it anymore. Didn't realize I wasn't suppose to.
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Quoting P451:
Maybe it's just me but this does not have the appearance of a purely tropical system on satellite imagery. Seems hybrid/sub tropical in nature given it's satellite signature. Note I said seems...given it's satellite imagery signature.





The ULL and the surface low are mating. That gives birth to a mutated tropical storm.
Member Since: July 14, 2006 Posts: 0 Comments: 1144
Quoting Patrap:


It's got a beautiful east side. If the west side looked like that, we'd be in real trouble.
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Quoting robj144:


Is Lee going to eventually be another rain maker for the Northeast?


Well, it sure as heck is not going to be a rain maker for us here in Texas.
Member Since: September 18, 2007 Posts: 0 Comments: 1074

Quoting TexasHurricane:


referring to me? ban for what?
Afternoon Tex. Are you getting in trouble? Lol. Afternoon All. From sunny bleeping dry and breezy!  :)
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Quoting P451:
Maybe it's just me but this does not have the appearance of a purely tropical system on satellite imagery. Seems hybrid/sub tropical in nature given it's satellite signature. Note I said seems...given it's satellite imagery signature.



Hey do you want to come with me and paddle out into the GOM to see if we find tropical storm forced winds?
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1095. robj144
...........
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1094. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127803
1093. robj144
Quoting HoustonTxGal:


Is the remnants of Lee going to eventually be another rain maker for the Northeast?
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1091. 996tt
Quoting pcola57:
David is a young surfer on P'beach.His parents are in Bermuda and he's staying in their condo.Kinda frightened really.He came in here for help and a Local contact so I stepped in.


Is he in Beach Club??? If so, I think I know who you are talking about. I lived in beach Club for about a year. Great little break right off my balcony.
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Quoting pcola57:
I'm not the blog police Texas but you can get a ban for tha,just saying.


referring to me? ban for what?
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Quoting pcola57:
I'm not the blog police Texas but you can get a ban for tha,just saying.
All of you who posted links to another site, if you care about staying on the blog, should consider removing them. WUBA Admin takes a dim view of spamming. It violates 3 out of the 10 RULES OF THE ROAD.
Member Since: August 3, 2005 Posts: 10 Comments: 5557
Quoting P451:
Maybe it's just me but this does not have the appearance of a purely tropical system on satellite imagery. Seems hybrid/sub tropical in nature given it's satellite signature. Note I said seems...given it's satellite imagery signature.




you keep saying this over and over again but the pros or the guys and girls at the NHC say otherwise so who do you think im going to listen to its gonna bring a lot of rain it makes no differnce if it is upgraded a llittle bit stronger or weaker its gonna bring a lot of rain like it already is right now....................
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1087. HCW
Quoting 996tt:


Cool. StormW. Can you give link to his blog.


you can find the link on my site :) Now back to LEE
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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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