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 WeatherNerdPR:
This is what I'm seeing.


On the latest vapor and ir loop it looked like Lee was fighting the injection of NW dry air and trying to close the loop. Thoughts?
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Link


Check this link. Looks like Katia is back down to a TS again.
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Quoting P451:
24 Hours, AL13



24 Hours, Katia (Steadily moving NW over the long haul)



NW is not where Katia's been headed for some hours. Looks more like 280 to me.

I saw Irene make lots of 'wobbles' and people on here made far too much out of them, as the overall direction was pretty much what the NHC had predicted.

Not sure about Katia, though. Predictions are less reliable this far south.
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Link

Switching gears to our landfalling storm it actually looks like the COC gets towards the coast then turns back west...if that happens and it stays over water that could be bad
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So Lee......you're going to be stingy with your rain and not help us here on the TX Gulf Coast, but you're going to come ashore where the rest of my family is in Houma & Point-aux-Chenes where they don't need the rain or storm surge...Thanks!   

Tropical Storm Lee - Intermediate Advisory 6a
Issued: Saturday, September 3rd 2011 7:38am CDT

Current Location: 29.0N/91.9W
Geographic Reference: 40 miles south-southeast of Intracoastal City, LA
Movement: North-northwest at 5-7 mph
Max Winds: 60 mph gusting to 75 mph
Organizational Trend: Slowly getting better organized

A reconnaissance aircraft found the center of Tropical Storm Lee at 29.0N/91.9W at 7am. The maximum sustained winds have increased to 60 mph this morning. Some additional strengthening is possible before the center moves inland in a few hours. The chances of Lee becoming a hurricane remain small.

The greatest threat from Lee will be the heavy rainfall. Doppler radar indicates that very heavy rainfall is falling over much of southern Louisiana. This rain will last through the weekend.

Our next full advisory will be issued by 10AM CDT

Meteorologist: Jim Palmer/Steven Abreu-Hill

Tropical Storm Lee Advisory 6
Issued: Saturday, September 3rd 2011 3:07am CDT

Current Location: 28.9N/92.1W
Geographic Reference: 60 miles south of Intracoastal City, LA and 70 miles west-southwest of Morgan City, LA
Movement: North-northwest at 5 mph
Max Winds: 50 mph gusting to 65 mph
Organizational Trend: Increasing
Current Hurricane Severity Index: 4 out of a possible 50 points (2 size / 2 intensity)
Peak Hurricane Severity Index:
6 out of a possible 50 points (3 size / 3 intensity)
Forecast Track Confidence: Average due to the slow movement of this system. This slow movement is expected to continue over the next few days.

Changes From Our Previous Forecast
No significant changes.

Our Forecast
The center of Lee reformed a little to the northwest overnight, and is now about 60 miles south of the western portions of Vermillion Bay. While additional reformations of the center are possible today, a very slow northward track is expected, bringing the system toward the central Louisiana coast late this afternoon or tonight. Thereafter, a turn to the northeast is expected. The motion is expected to be very slow initially. The center is not expected to pass to the north of New Orleans until Monday. Thereafter, an acceleration to the northeast is expected as a cold front captures Lee.

Lee is becoming better organized. The winds are being held at 50 mph pending additional aircraft data later this morning. However, satellite and radar indicate that Lee is becoming better organized. Continued intensification is expected and Lee is forecast to make landfall with 65 mph winds. If the center remains over the water longer than forecast, Lee could become a hurricane. Slow weakening is forecast after the system moves inland. The system will likely merge with the cold front by Tuesday morning. The confidence in the intensity forecast remains average.

Expected Impacts on Land

Louisiana/Mississippi Coasts: Squalls with tropical storm conditions will continue to affect southern and southeastern Louisiana and southern Mississippi through Monday morning. Conditions will begin to improve from the west on Sunday night as Lee begins accelerating off to the northeast.
Upper Texas Coast: Most of the squalls should remain east of Sabine Pass over the next few days. No significant impact.

Expected Impacts Offshore
Northwest Gulf Lease Areas: Squalls have spread westward to between 92W-93W and extend from the Louisiana coast south to 25N. This area of squalls will move a little more to the west over the next day or two, probably to between 93-94W. Conditions offshore will remain rough with heavy squalls through early Monday. Conditions will begin improving from the west Sunday night as Lee begins accelerating off to the east and northeast.

An intermediate advisory will be issued at 7AM CDT. The next full advisory will be issued by 10AM CDT.
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Interestingly, Katia means "pure". Not sure how it correlates with the storm.
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Lee still offshore @ ~91.7W, 29N.
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Quoting flwthrfan:
. Don't forget to add Home Depot...we know you love them too


don't forget publix, target and winn dixie
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Quoting WeatherNerdPR:
ACE so far: 40.3. Below average, but rising.
Definitely with Katia.
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Link Anyone from texas want the next couple of weeks i will gladly trade the creeks are still raging and i need some hot sun to get my tan/sunburn on.
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3675. MZT
Still not liking that movement of Katia toward the US, but it does seem like the models that wanted to bend her west recently are not playing out, and she's going more NNW and NW. Even on a straight line (an unlikely scenario historically, in the mid latitudes) she'd be a coastal NC event, so I'm safely away in Charlotte.

But the room for curvature is diminishing and we're probably going to be reading speculation soon about a re-flood event in the northeast.
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ACE so far: 40.3. Below average, but rising.
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Will Katia turn out to sea later next week?
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Quoting P451:



That must feel fantastic for you guys down there.

Been enjoying lows consistent in the 50s each morning up in SE NY with highs in the 70s.

If only I could send some from Texas to Florida.


Im in the poconos and these cool lows bring the fear that WINTER is just around the corner...*cowers in a corner*
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3670. franck
Quoting mojofearless:


And I'm going to Brown Derby for eggs and hot sausage. That's it - I've come to the conclusion that I can no longer stomach the NC DOOM scenario without eggs and sausage.


Patties or links!? I like Cracker Barrel red ham sausage patties. They should advertise those on the Weather Channel. Abrams could point out how patties are round and flat like huurricanes. She would need someone else to hold the patty though, I'm sure.

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Quoting WeatherNerdPR:
Katia looks pretty.
Yep, she's definitely a looker. She would be hotter if she has an eye.
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Good morning, everyone! We are getting RAIN!! And it's starting to rain over towards Jasper, TX which has had a lot of problems with fires.
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Quoting FLdewey:


:-|

<---- closes curtains




I'm sticking on the UKMET solution to up the hysteria factor.
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Quoting FLdewey:


:-|

<---- closes curtains




Im putting my money in xtrap that model is never wrond ;)... also the the folks talking about eggs and sausage i rock ramen noodles every single meal :D
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Just went out this morning and checked my rain gauge
last checked 7:00 pm last night 7:30 this morning read 5.80 inchs accurate
24 hr reading yeasterday 1.60 inchs accurate giving me a toatal rain fall of 7.4 inchs so far 36 hr in

Link
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Quoting mojofearless:


And I'm going to Brown Derby for eggs and hot sausage. That's it - I've come to the conclusion that I can no longer stomach the NC DOOM scenario without eggs and sausage.
mmmmm eggs and sausage. I think you've just answered the burning question for me this morning...
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I think Dewey has his chain out and is getting his morning exercise with Rocket!
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Katia looks pretty.
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Quoting notanothergoof:
i live close to a walmart so we get the scare every year here at least 4 times a year
. Don't forget to add Home Depot...we know you love them too
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Quoting clwstmchasr:


Sticking my head in the toilet and repeatedly flushing it.t


And I'm going to Brown Derby for eggs and hot sausage. That's it - I've come to the conclusion that I can no longer stomach the NC DOOM scenario without eggs and sausage.
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Quoting FLdewey:


Yep... I usually can spot them - my mistake for playing along.

<--- pours a lil booster into his coffee


Hey, I'm doing the same thing.

Trolls and bomb throwers.

And for 5Rockets, the cone shows you the general model movement up to a time period.

The WX channel is not showing an NC landfall.

It's saying Thurs morning that storm could be anywhere due east of Daytona to due east of nearly the NC VA line.

As Dewey points out, the WX channel is for entertainment purposes only.
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Quoting FLdewey:
One beautiful day for Florida today... before the rain returns tomorrow.

Sunshine and a nice breeze on the beach.




Good news because we are headed for the beach sometime today...
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Quoting 5Rockets:


Well, actually, yeah, Like once before.

Why don't you use that other handle or has it been banned permanently?
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Quoting FLdewey:


It's actually a cone, not a point.

Think of it this way:

NHC: Does not need to sell advertising

TWC: Desperately needs to sell advertising

The Weather channel is going to do anything they can to convince you if you don't watch, you'll die. They're in the business of selling ads.

The Weather Channel is good for entertainment only.
You could also make the argument that if TWC produces unreliable forecasts, then people will stop watching, vs if the NHC produces unreliable forecasts, the govt will keep on paying anyway. Not sure economics is the best argument for a reliability arguments. Lot's of govt funded projects aren't necessarily reliable or effective.
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This is what I'm seeing.
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It almost looks like the COC is now moving WNW or W along the coast lol
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Quoting AussieStorm:


There is nothing there. Not Found.
Your quiet active for someone that's been here for only a few days. Did you have another handle?


Well, actually, yeah, Like once before.
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Quoting notanothergoof:
how come the weather is having like 20 walmart commercials every hour


That's a great place for you to go get your supplies for the "supercane" headed your way....
Member Since: September 1, 2008 Posts: 0 Comments: 672
NHC says Katia's going EXACTLY where I say it will.
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Quoting 5Rockets:
http://image.weather.com/images/maps/tropical/map _t ropprjpath12_ltst_5nhato_enus_600x405.jpg

There's my point.


There is nothing there. Not Found.
Your quiet active for someone that's been here for only a few days. Did you have another handle?
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Yup. NHC says what I said.
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Quoting notanothergoof:
hey weve had 3 storms predicted to hit us in florida already and all the models said so so we are getting prepared not a laughing matter this could be serious again


It sure never hurts to be prepared in the state of Florida. Just comes with the territory. We all have have been through the "drill" before. Got my food backed up for family and pets and house is set as well. So far so good but the season is still young imho...

Hudson, FL weather
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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.