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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Quoting washingaway:
That Texas air is like a gaint ShamWow.



I never really equated Houston with dry air.... Strange year.
Member Since: Posts: Comments:
Quoting hurricanerunaway:


No doubt...
+100

Others post links to maps and other weather websites...there is no difference, someone started bumpin their cloth when Storm was mentioned...

PS...It is RAINING in Orange, Texas!! Woo Hoo :)


I have family in Orange, glad ya'll are getting some rain.. why not spread the wealth and send some up to us in Houston :o)
Member Since: September 18, 2007 Posts: 0 Comments: 1073
Quoting IKE:

It continues @ 992 through hour 69. Almost winter like system. Hard to believe.


lol, yeah, definitely not happening, unless it decides to pull a Fay.
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Bob Breck needs to look at the latest rainfall predictions.. 20+ inches of rain.. 'only a few showers' my rear end.
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1181. Patrap
Quoting cloudburst2011:
according to BOB BRECK IN NEW ORELANS we should not cancel any plans for the labor day weekend...he said we may get a few showers on sat and sunday as LEE MOVES NE towards miss and alabama...he has taken us out the cone completely...this makes me feel great wont have to cancel my fishing trip...


Phunny thing is,, Bob dont come on till 5pm.

So this is total BS and flagged and reported.
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Quoting washingaway:
That Texas air is like a gaint ShamWow.


sham how?
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1179. JNCali

Quoting Patrap:
Me want COOKIE!
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Quoting HoustonTxGal:


I followed StormW and a few others during Ike and they were spot on.. Not sure who, how or why feathers got ruffled by some but he knew his stuff and being it is weather related, I do not see how posting his link is more OFFENSIVE to the "rules of the road" than some of the other garbage people post in here.


No doubt...
+100

Others post links to maps and other weather websites...there is no difference, someone started bumpin their cloth when Storm was mentioned...

PS...It is RAINING in Orange, Texas!! Woo Hoo :)
Member Since: Posts: Comments:
Quoting washingaway:
That Texas air is like a gaint ShamWow.



LOL@ ShamWow!!
Member Since: September 18, 2007 Posts: 0 Comments: 1073
Quoting cloudburst2011:
according to BOB BRECK IN NEW ORELANS we should not cancel any plans for the labor day weekend...he said we may get a few showers on sat and sunday as LEE MOVES NE towards miss and alabama...he has taken us out the cone completely...this makes me feel great wont have to cancel my fishing trip...


typical of the New Orleans folks. The last thing i heard on my radio before having to scramble out of my house due to the storm surge was WWL reporters laughing and saying: "thank God for Mississippi! Katrina spared us!"
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1175. Patrap
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Lee will become a hurricane imo.
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That Texas air is like a gaint ShamWow.

Member Since: July 14, 2006 Posts: 0 Comments: 1144
Quoting Patrap:

I’m talking - pedicure on our toes, GOES-13?
Trying on all our clothes, clothes
RGB blowing up our phones, phones
Drak-toping, playing our favorite cds
Pulling up to the TD's
Trying to get a little bit tipsy

[CHORUS]
Don’t stop, make it pop


Lee turnin our speekers up tonight he'll fight till he sees the sunlight
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Tropical Update with Video
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1170. pcola57
Quoting HCW:


you forgot rolling in my 5.0 ragtop down so my hair can blow


Booooo Yaaaa!
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1169. IKE

Quoting TropicalAnalystwx13:


Not About to Materialize
It continues @ 992 through hour 69. Almost winter like system. Hard to believe.
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In spite of dry air inhibition, pressure continues to fall: Link

oh, yah, evacuate NOLA TD Godzilla
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1166. divdog
Quoting gulfbreeze:
What is going on on the west side of Lee is that an ULL or is the center trying to get wrapped?
exposed center of lee probably
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1165. HCW
Quoting Patrap:

I’m talking - pedicure on our toes, GOES-13?
Trying on all our clothes, clothes
RGB blowing up our phones, phones
Drak-toping, playing our favorite cds
Pulling up to the TD's
Trying to get a little bit tipsy

[CHORUS]
Don’t stop, make it pop


you forgot rolling in my 5.0 ragtop down so my hair can blow
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Quoting IKE:
NAM strengthens it over land....




Not About to Materialize
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1163. ncstorm
Quoting P451:
Those curious about the FIM here's an MSLP run on the systems.




Take note that this solution kind of mirrors what the GFS and ECMWF were doing with Lee/Katia a couple of days ago.



Yes, I've been seeing the model runs posted here but couldnt find it on the web..
Member Since: August 19, 2006 Posts: 13 Comments: 14451
Well later all I'm just saying don't like where that hot water eddy is in reference to Lee and no movement spells potentially trouble, good luck to all Gulf residents and hopefully have a soggy but save Labor Day weekend.
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Quoting TexasHurricane:


Yeah, it is depressing, but like you said. What can we do?

We just got to hope we will have another chance before the season is over....

Mother Nature.....Texas is calling... :)


Yeah. Only thing I'm worried about is if these so called cold fronts they're now hyping as the best thing ever, is going to end our chances for any tropical rain. But who knows? They probably changed their minds about that already too. :)

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1160. pcola57
Quoting Patrap:

I’m talking - pedicure on our toes, GOES-13?
Trying on all our clothes, clothes
RGB blowing up our phones, phones
Drak-toping, playing our favorite cds
Pulling up to the TD's
Trying to get a little bit tipsy

[CHORUS]
Don’t stop, make it pop


LOL LOL!!!
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Quoting P451:


I wasn't trying to say it wasn't a tropical storm, I was trying to make sense of the line in their discussion which reads:





I also have brought up the possibility it may be a hybrid system and not purely tropical.


I think the satellite imagery and the wind observations (that we have) make them valid questions about the system.

Well I do remember the NHC in one of there discussions mentioning the possibility of a sub-tropical depression. And I think what they mean when the tropical storm force winds extend out to 200 miles, they mean in individual thunderstorms on the outer rain bands, most likely on the east side of the system.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
What is going on on the west side of Lee is that an ULL or is the center trying to get wrapped?
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It's only spamming if you post StormW's link. Anything else tropic-related, it's pretty much ok.
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Quoting AtHomeInTX:

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?


Same boat here.. Decided to fry some shrimp and frog legs for supper.. Hope to ease the pain. So close... So far away...
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1154. pcola57
Were gettin' off and ons.prob tomor be worse
Got Grand Mariner close at hand !!
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1153. IKE
NAM strengthens it over land....


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Now, back to the Lee and Katia show.....:o)
Member Since: September 18, 2007 Posts: 0 Comments: 1073
1151. HCW
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1150. Patrap
ESL by LSU GOES-13 TS Lee Low Cloud Loop
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Quoting P451:


LOL!

Sure.

Gusts don't count though so we might be out there a while.
Well then we're gonna need a bigger boat, right?

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


At least the link is weather related even if it is connected to someone you may not like...not everyone feels that way though. It's a shame that when the trolls show up that the same claws aren't shown for them here...


I followed StormW and a few others during Ike and they were spot on.. Not sure who, how or why feathers got ruffled by some but he knew his stuff and being it is weather related, I do not see how posting his link is more OFFENSIVE to the "rules of the road" than some of the other garbage people post in here.
Member Since: September 18, 2007 Posts: 0 Comments: 1073
Wind really picked up at 9 and have been around 20 mph all day with constant rain looks to be gettingits act together a lot and with pressures at 1003 I wouldn't be surprisedif the nhc increased the winds I havent been home to check the pressure
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1146. Patrap
Quoting pcola57:
Keep on "postin" Pat.
Great to see ya this pm.'ya"ll gettin bouqu rain?


Steady,but light mostly this aft here Uptown
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Now its looking like minimal to none for the Texas or Georgia drought relief. Sad.
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Quoting AtHomeInTX:

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?


Yeah, it is depressing, but like you said. What can we do?

We just got to hope we will have another chance before the season is over....

Mother Nature.....Texas is calling... :)
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1143. Patrap
I say if we run outta Names we should use Bad Japanese Monster Movie Names.

TS Rodan continues to Improve this afternoon on Sat presentation
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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.


What 3 rules are violated broken?

Is posting a link to another site that provides weather information/analysis a no-no??

If yes, then how about NWS, university sites, imagery sites, references to weather channel, local TV mets...

I just want to understand what we are allowed and not allowed to do.
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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.


At least the link is weather related even if it is connected to someone you may not like...not everyone feels that way though. It's a shame that when the trolls show up that the same claws aren't shown for them here...
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1139. pcola57
Keep on "postin" Pat.
Great to see ya this pm.'ya"ll gettin bouqu rain?
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Quoting P451:


Either add to the discussion or quit whining. This goes for you and a few others who are taking offense to those asking questions and putting out their differing opinions.

This blog isn't about sucking up to the NHC it's about discussing tropical systems and I have a valid observation to add about the system.

If you don't like it go start a blog and feel free to ban anyone who questions you.


Well stop saying the storm is nothing it may not have strong winds but its gonna have a lot of rain with it.
Member Since: June 22, 2010 Posts: 0 Comments: 140
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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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.