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 Levi32:
Good morning.

Blog update:

Tropical Tidbit for Friday, September 2nd, with Video


Mornin Levi! Nice update.
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386. 996tt
Quoting JupiterFL:


Two Yutes. Two what?


Haha, I used to practice before an old Judge who was practicaly deaf. He made you feel like cousin Vinny as he would butcher what you were saying and you would be practically yelling at him or you would get back he rendition of what he though you said.
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omg....be back when the moronic trolls are banned again....can't they ban by ip address????

don't drive through flooded streets!
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Looks like TD13 is wrapping its convection around the ULL to the west. WEIRD!!
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Quoting hunkerdown:
I don't have an "ignor" button...I thought your keyboard was missing the "E" but there it is in "meanie weanie". At least I'm not a meanie weenie :)


I'm a horrible speller! I should use spell check all of the time!
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CIMSS convergence/divergence couplet looking very impressive for 13, and shear below 20 and dropping.

http://tropic.ssec.wisc.edu/real-time/windmain.ph p?&basin=atlantic&sat=wg8&prod=dvg&zoom=&time=
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Quoting SWLACajun:


Hi to the REAL Taz. How's the weather? :)



doing good
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Quoting LakeWorthFinn:

Hi D., we know this is you :)


"Ditto" Taz from me.

Hi Finn!!!

lurking here mostly these days...

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Quoting Grothar:


Well, you finally got it! How long does it take you to cook your grits? :)
This lurker, at least, got it right away... ;)
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TD-13 GOES-13 Low Cloud Loop
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Quoting hunkerdown:
maybe you should heed your own advice...


you know....u r right!
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Quoting 996tt:


Economic tragedy. Where? I was just with a friend last night who owns a slew of beach front property and he did not express one single concern about the storm which we discussed. He is booked to capacity and most have either already paid or have large deposits down. Not sure how many people vacation in Lousianna where this is happening, especially since it seems like everyone from Lousianna comes here to vacation. I imagine people will still venture down since their last hoora weekend of the summer.


You have raised good points and I am headed to Destin tomorrow with the Family regardless. .... But keep the little ones out of the rough surf. Have a good weekend......... :)
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Good morning.

Blog update:

Tropical Tidbit for Friday, September 2nd, with Video
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Quoting flowrida:
Is plywood tape just as good?


Oh yes, plywood tape is the way to go... Run out to Home Depot or Lowes and be sure to ask for the Hurricane Proof Plywood Tape.  

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Quoting connie1976:



sigh....people need to learn to not be so serious...sigh ....life is just too short!
maybe you should heed your own advice...
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Quoting overwash12:
That dry air over Texas is a beast!

This drought-causing dry-air just won't die!
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The upper level low looks like its degenerating into an upper level trough. The GFS keeps localized upper level vorticity in the area so while the low may be weakening it may stick around for a bit.
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hunkerdown,

please put me on ignor and stop being such a meanie weanie!
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Quoting Tazmanian:
hello guys


Hi to the REAL Taz. How's the weather? :)
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Jim Cantore was saying last night around midnight new model data was suggesting a westward turn with Katia in 5 days. It sounds like he is grasping for a US hit.
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Gonna take a break for a bit....It's a shame to see the crazies come out in force at the most critical times with a pending storm threatening land and regular folks coming on here for weather info. Please ignore the trolls folks and don't "re-quote" their posts and clog up the good info.

Back Later.
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340. Patrap 4:48 PM GMT on September 02, 2011 0
Quoting flowrida:
What is the best kind of tape to use to keep your windows from busting in?

Plywood tape


ha ha ha! i was thinking the same thing:)
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353. jpsb
Quoting Patrap:
Are my eyes deceiving me or is td 13 starting to move south around the Texas high?
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Quoting yoboi:

try salt works well
so does fire...wait, better not, will be accused of telling someone on to burn their house down.
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Quoting flowrida:
Where can I buy that?


OMG!!   Try the plywood tape section in WalMart

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Quoting flowrida:
What is the best kind of tape to use to keep your windows from busting in?



Tape will not do you any good on your windows.
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348. 996tt
Quoting weathermanwannabe:
TD 13 is already an economic tragedy for many hotels and vendors along the Northern Gulf Coast hoping for much needed traffic and business this weekend cause many folks might be cancelling their weekend beach plans in the region.


Economic tragedy. Where? I was just with a friend last night who owns a slew of beach front property and he did not express one single concern about the storm which we discussed. He is booked to capacity and most have either already paid or have large deposits down. Not sure how many people vacation in Lousianna where this is happening, especially since it seems like everyone from Lousianna comes here to vacation. I imagine people will still venture down since their last hoora weekend of the summer.
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Quoting flowrida:
What is the best kind of tape to use to keep your windows from busting in?


Tape is useless... Plywood and masonary screws are the way tog o.. Did that on the MS gulf coast in Katrina, did not lose one single window.
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Quoting hunkerdown:
and now yo want advice for pest control, again, from a majority of people not old enough to drive that have no clue what it is like to own property and be responsible for the care thereof. I suppose this question was just for fun also?

Since I am already in the group of "cranky jerks" that PMS, I really don't care that you will classify me as such again.



sigh....people need to learn to not be so serious...sigh ....life is just too short!
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Quoting Patrap:
Price gouging law in effect, Caldwell says
Published: Friday, September 02, 2011, 10:38 AM


BATON ROUGE -- Gov. Bobby Jindal's emergency declaration as the tropical depression nears the Louisiana coast has triggered the state's price gouging law, Attorney General Buddy Caldwell said on Friday.


Caldwell said merchants cannot sharply raise the price of retail products, gasoline, hotel rooms and other goods and services unless the prices they have to pay are suddenly raised.

Civil and criminal penalties apply, he said.
Caldwell said suspected instances of price gouging can be reported to the attorney general's office at 800-351-4889.
This seems kind of wrong to me. Price is based on supply and demand right? If a bunch of people come into the store to buy everything, then this reduces supply, so shouldn't the price go up? Why be so particular about it? The storm might not even happen. Businesses exist to make money.

Seems a bit ham-fisted to me. I realize some companies might overcharge because the customers really need it (for storm supplies), but I think that forbidding a price increase that's reasonably within supply/demand expectations should be allowed. Unfortunately, it appears the governments don't want to be bothered with having to do it on a case by case basis, so they just make a sweeping change.

EDIT: ok i re-read more closley. It forbids a SHARP increase. Basically, what businesses will do is add a kind of hidden tax to their prices in order to pay for these instances when people buy out the entire place because of a storm that threatens. This rewards businesses that plan head - not a bad thing.
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Ahh...Joe Pesci. Now he's a fish.blockquote class='blogquote'>Quoting Patrap:
..I bet its a Yute,
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Quoting FtMyersgal:

My Cousin Vinny!


Well, you finally got it! How long does it take you to cook your grits? :)
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Quoting flowrida:
What is the best kind of tape to use to keep your windows from busting in?


Plywood tape
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Quoting Tazmanian:
HELLO GUYS ANY ONE READ THIS POST HELLO HELLO



PLZS SAY SOME IN ALL SO IF YOU LOOK AT MY JOIN DATE IFS IS THE REAL ME

Hi D., we know this is you :)
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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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