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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Taking all bets on how long it will be before someone asks whether Katia is going annular...
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1736. USCGLT
Geroge W. Bush of course!!1

2 inches of rain so far in Vancleave, MS. More to come!

Quoting HoustonTxGal:
If New Orleans were to flood, who would get blamed this time??
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1735. JLPR2
Quoting MiamiHurricanes09:
Nah, but it's definitely having its troubles. Dry air is penetrating into the inner-core, giving the appearance of a warm spot on infrared satellite imagery. The cyclone is also under about 20 knots of northerly wind shear.


Reminds me of Irene east of PR.
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1734. Patrap
Yeah,,no one from NOLA helped Texas after IKE at all.

LoL
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Well, by looking at AllStar17's pics from his blog, I can say a few things about the storms:

1. If it weren't for wind shear, Katia would have been on this long adventure across the Atlantic just to gain enough power to smash the SE region of the US (Yes, people. Katia will hit. Guarantee. Maybe not in the place I expect it to, but it will.

2. At this rate, Lee is gonna do some serious reversing on New Orleans' repair after Hurricane Katrina.

Feel free to tell me I'm wrong, but these are only very strong predictions.
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1732. franck
Quoting HoustonTxGal:


And Houston is still paying the price for it's kindness. Crime was bad before as with any large city, but it went through the roof after Katrina.


Yes, knew that as well, but wanted to keep comment on the lighter side.
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1730. breald
Quoting HoustonTxGal:


Guess that would be the "smug, self-righteous Houstonians" who took in all the NOLA evacuees after Katrina, most of which they are still stuck with.


Many places took them in, however, they are not bragging about it.
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1729. pcola57
Quoting CC45:


It's all good. We've been on here so long, plays tricks on ya lol.


Thanks CC45..Been on today too much I guess..Probab. because I've got so much to keep an eye on here at home and Blog too...think I'll just read and leave the posting alone for awhile LOL..LOL!!
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Quoting MiamiHurricanes09:
Nah, but it's definitely having its troubles. Dry air is penetrating into the inner-core, giving the appearance of a warm spot on infrared satellite imagery. The cyclone is also under about 20 knots of northerly wind shear.
Katia wants the envieriment to do this on purpose so that she can get closer to the U.S.Please no Bonnie and Fran or Jeanne and Frances tracks.
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Quoting PensacolaDoug:



Yeah...But that's enough.
Ahum...enough for what?
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Quoting cat5hurricane:

Oh that was sweet.

+1


Thanks, I'm here all week :o) LOL
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did any notice the small blow up of convection next to lee's center? and right now is lee weakining or strengthining?
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Quoting TropicalAnalystwx13:


Or it is actually an eye...
Look at post 1674. It's dry air intrusion.
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Quoting connie1976:
is katia falling apart?



no
Member Since: May 21, 2006 Posts: 5091 Comments: 115074
Quoting HoustonTxGal:


Guess that would be the "smug, self-righteous Houstonians" who took in all the NOLA evacuees.

Nola person myself and that was a callous comment - If I
Quoting CC45:


Wow. I hope you're joking.

ditto - sick humor at best
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Report from mandeville la, RAIN RAIN RAIN AND MORE RAIN it doesn't stop bout 20 mph sustained 30 at gusts round here
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Quoting CC45:


It's all good. We've been on here so long, plays tricks on ya lol.



Sometimes even the slightest update, like a typo, gives the blog a new time stamp even though the comment threads don't change. Confuses me too.
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Quoting MiamiHurricanes09:
Nah, but it's definitely having its troubles. Dry air is penetrating into the inner-core, giving the appearance of a warm spot on infrared satellite imagery. The cyclone is also under about 20 knots of northerly wind shear.


Or it is actually an eye...
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Quoting franck:


Yes, Houston did take in many homeless people from the flood.


And Houston is still paying the price for it's kindness. Crime was bad before as with any large city, but it went through the roof after Katrina.
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Quoting TropicalAnalystwx13:


Banned from Dr. Masters' blog.
Owwwww yeah wouldn've explained the long absence.
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1713. CC45
Quoting Tazmanian:
now this is going too be some in too watch with Katia with the next few hrs or so it seem like too me that Katia is geting ready too come a part with one part of here going N and the other part of here going W


If that happens, both parts would have a good shot at further development as they move away from each other wouldn't they?
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Quoting connie1976:
is katia falling apart?
Nah, but it's definitely having its troubles. Dry air is penetrating into the inner-core, giving the appearance of a warm spot on infrared satellite imagery. The cyclone is also under about 20 knots of northerly wind shear.
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Quoting mojofearless:


We'd blame smug, self-righteous Houstonians of course. How's that drought working out for you guys, anyway?
Great! Thanks for asking.

I've only had to mow the pasture once all year. I got the pond dredged and expanded and I didn't even have to wait for it to drain and dry out. I had to use the well to refill it, but that's OK - the critters appreciate it. The irrigated garden is doing great 'cause there are hardly any insects at all this year. I got a lot of dirt work done and I'm thinking about topping the driveway if it stays like this much longer.

The best part is, when you sweat, the breeze actually cools you off.

How's the weather working out for you? Good, I hope.
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1710. franck
Quoting HoustonTxGal:


Guess that would be the "smug, self-righteous Houstonians" who took in all the NOLA evacuees.


Yes, Houston did take in many homeless people from the flood.
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Quoting washingtonian115:
Whatv happened to Destin Jeff?


Banned from Dr. Masters' blog.
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Quoting notanothergoof:
probably again but they didnt forcast it to fall apart at all not alone 2 times now


Nearly 300 comments in less than a week...tells you something.
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Quoting mojofearless:


We'd blame smug, self-righteous Houstonians of course. How's that drought working out for you guys, anyway?


Guess that would be the "smug, self-righteous Houstonians" who took in all the NOLA evacuees after Katrina, most of which they are still stuck with.
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Quoting canehater1:


don't you ever get banned..I miss Jeffs humor too
Whatv happened to Destin Jeff?
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Quoting PensacolaDoug:



Yeah...But that's enough.


Lol. Yeah you right.
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TWC says Lee is sucking in lots of dry air from the west. Lee should stay weak if that continues.
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1701. CC45
Quoting pcola57:


Sorry All...Thought it was new...my fault..


It's all good. We've been on here so long, plays tricks on ya lol.
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Quoting FLdewey:
Oh God don't get him started on NOLA history.

We'll be watching random Gustav videos by 7.


don't you ever get banned..I miss Jeffs humor too
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is katia falling apart?
Member Since: September 1, 2008 Posts: 0 Comments: 672
Quoting TropicalAnalystwx13:
Katia wants to come to the U.S so badly.Can't she see the "HURRICANES STAY AWAY" sign posted?.
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Quoting brazocane:
Probably has been posted already but if we don't get any rain at least I have this to HOPEFULLY look forward too:

Houston Area Forecast Discussion

TEMPERATURES IN HOUSTON ONCE AGAIN REACHED 100 DEGREES TODAY...
THAT`S 32 OUT OF THE LAST 33 DAYS NOW. LEANED TOWARD THE WARMEST
NAM 2M GUIDANCE SINCE THE AREA WILL REMAIN IN THE SUBSIDENT ZONE.
READINGS WILL STILL APPROACH OR EXCEED 100 MANY INLAND AREAS
SATURDAY/SUNDAY ADDING TO THE TALLIES. TEMPS WILL BE TRICKIEST
OVER THE EASTERN ZONES WHERE CLOUD COVER COULD AFFECT THEM
ESPECIALLY SUNDAY. 12Z MODEL RUNS SHOW A SIGNIFICANT AMOUNT OF
COOLING IN THE LOW LEVELS BEHIND THE FRONT...WITH 850 MB TEMPS
DROPPING TO 13-16C BY TUESDAY/WEDNESDAY AND SFC DEWPOINTS DROPPING
INTO THE 40S (POSSIBLY 30S). MIN TEMPS SHOULD EASILY FALL INTO THE
60S NEXT WEEK...WITH 50S...YES 50S...POSSIBLE IN SOME RURAL INLAND
AREAS.



Those forecasters sure are desperate for good news :P

Then again...

...

...So are we...
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1694. pcola57
Quoting pcola57:
NEW Blog


Sorry All...Thought it was new...my fault..
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1693. JLPR2
Quoting TropicalAnalystwx13:


It sure looks like convection building around an eye.
But eh... we need to see if it becomes better defined tonight or disappears.
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now this is going too be some in too watch with Katia with the next few hrs or so it seem like too me that Katia is geting ready too come a part with one part of here going N and the other part of here going W
Member Since: May 21, 2006 Posts: 5091 Comments: 115074
1691. CC45
Quoting pcola57:
NEW Blog


Nuh uh. But you made me look.
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1690. Bijou
I am very proud to live in the same city as this man:)

Quoting Patrap:
We enjoy the NOLA hate,,it shows how true some are as Humans.




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1689. hamla
we all need a good bowl of PULDU GUMBO
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Quoting HoustonTxGal:If New Orleans were to flood, who would get blamed this time??



AGW
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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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