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 mojofearless:


Which model shows that? I don't see any that show a NC landfall yet.


Oh, Wunderground has a chart.
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Quoting Patrap:
Bumpy Uptown still..NOAA radio yakking Like a Super Bowl

how you faring over there Pat? Pumps doin' their job?
Member Since: September 5, 2007 Posts: 0 Comments: 3488
Basically, Lee knows its target, but is wobbling all over the place to get there.
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Quoting mojofearless:

Yes. We're swamp people. We're used to lots of water.


yes but we DON'T have alligators in our back yard haha

winds are up around thirty the lake front was almost flooding yestterday cant imagine wwhat its doin now
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Quoting 5Rockets:
Well, good news. Katia will reach cat 3 before the N. Carolina coast(Yes, that's it's landfall point), then weaken to cat 2.

Bad news, warm water is on the very coast of North Carolina, thus it will weaken pointlessly and strengthen before landfall. Hope you N. Carolina people are ready.


Which model shows that? I don't see any that show a NC landfall yet.
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3529. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129844
welcome
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got 4 more tornado warnings. Orleans, Jefferson, St. bernard, and Plaquemines Parish. SMH!!!
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3526. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129844
3524. Patrap
TORNADO WARNING NEW ORLEANS LA - KLIX 637 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 629 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 626 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 617 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 546 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 541 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 518 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 511 AM CDT SAT SEP 3 2011
SVR T-STORM WARNING MILWAUKEE/SULLIVAN WI - KMKX 500 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 458 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 456 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 445 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 441 AM CDT SAT SEP 3 2011
SVR T-STORM WARNING MILWAUKEE/SULLIVAN WI - KMKX 441 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 436 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 433 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 418 AM CDT SAT SEP 3 2011
SVR T-STORM WARNING MILWAUKEE/SULLIVAN WI - KMKX 417 AM CDT SAT SEP 3 2011
TORNADO WARNING NEW ORLEANS LA - KLIX 340 AM CDT SAT SEP 3 2011
SVR T-STORM WARNING MILWAUKEE/SULLIVAN WI - KMKX 339 AM CDT SAT SEP 3 2011
SVR T-STORM WARNING RAPID CITY SD - KUNR 338 AM CDT SAT SEP 3 2011
Member Since: July 3, 2005 Posts: 428 Comments: 129844
Quoting blsealevel:


Link


thank you
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Quoting 5Rockets:
Are you Louisiana residents ready for Lee? It's almost made landfall.

Yes. We're swamp people. We're used to lots of water.
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3521. Patrap
Bumpy Uptown still..NOAA radio yakking Like a Super Bowl
Member Since: July 3, 2005 Posts: 428 Comments: 129844
In other words, Katia will hit where Irene did, but it'll be much stronger than Irene.
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Local Storm Report New Orleans
Click "Previous Version" to read through.
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Quoting FLdewey:


It's not my place to say you're wrong, but I don't think she's going to have a problem making the turn.


the question is where, the more west she goes the better chance of CONUS glance. let's hope not!
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Link
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Quoting notanothergoof:
2 of the models show a big wave comming off africa then end of next week hope not


youve posted that already
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Quoting breald:


?? I don't follow.


tornado warnings
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Yet another tornado warning for nola
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Well, good news. Katia will reach cat 3 before the N. Carolina coast(Yes, that's it's landfall point), then weaken to cat 2.

Bad news, warm water is on the very coast of North Carolina, thus it will weaken pointlessly and strengthen before landfall. Hope you N. Carolina people are ready.
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Quoting blsealevel:


Where you at? what parish


ST TAMMANY
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3507. WxLogic
Quoting Tropicsweatherpr:


Good morning.

Maybe, this is why the models dont have developments for the next seven days. But the wet MJO will be back by mid-month.



- Indeed... given the forecasts for MJO it should be arriving late next week and lingering into Oct. for the Carib.



- This is also depicted in the eagerness of GFS attempting to develop a system in the C/W Carib in the long range (consistency has been increasing).
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3506. breald
Quoting bigwes6844:
3 more warnings ascension, east b.r., and livingston


?? I don't follow.
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Quoting weatherh98:
can someone post a radar of the area im under a tornado warn. uh oh


Where you at? what parish
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Quoting wxobsvps:


THERE IS A LOW CHANCE, NEAR 0 PERCENT, OF THE BLOG AVOIDING ANDREW REFERENCES OVER THE NEXT 24 HOURS.


THE NATIONAL HURRICANE CENTER

IS NOW ISUING ADVISORIES ON AL THERE WILL BE A REFERENCEE ON ANDREW TODAY, MAX SUSTAINED WINDS 285KNOTS AND WILL CONTINUE TO DO SO UNTIL WARRANTED
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They must really be working those pumps. Street hasn't filled up yet. Usually when the water does the geyser thing we have about 5-10 minutes before it's calf-deep.
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3 more warnings ascension, east b.r., and livingston
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3497. breald
Morning All, Katia seems to be getting closer and closer. NOLA folks stay safe from TD13.
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Quoting notanothergoof:
94 had some good circulation on all 4 sides last night

Looks to me that it has been deactivated
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Are you Louisiana residents ready for Lee? It's almost made landfall.
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check out link, it shows katia last 4 hours going more west, you also can see the high (in blue) behind her building back in, and also 94lL blocking her from feeling the weakness above. please correct me if i'm wrong?


Link
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3490. WxLogic
Due to dry air and close proximity to land... I wouldn't expect any more intensification from what already is:



One thing is for sure and is that the dry air will provide assistance in production stronger wind gusts on deeper the deeper convection (specially closer to the dry/wet air boundary).
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Quoting mojofearless:
TWC just said a 26 ft sailboat broke morings and is coming over the harbor wall in Pass Christian.


oh goodness
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Quoting aquak9:

(images of pigs floating in geysers)


Image of me wading in to grab it and throw it on our giant grill.
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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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