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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1587. Patrap
Getting it done..
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#1380

Up to 26 and counting... :)
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Quoting Patrap:
New Frame






Looks like he's trying to wrap around....
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Quoting HoustonTxGal:
If New Orleans were to flood, who would get blamed this time??


How about the blaming a woman for once? Afterall it is mother nature.
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1581. luigi18
Quoting ackee:
look WSW to me wondering too


Good for Us here in Puerto Rico ouch!
Member Since: September 21, 2008 Posts: 0 Comments: 481
lol, wow...

New Orleans, LA

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Quoting PrivateIdaho:


+ 17 and counting.


That post required so much effort to execute it deserves +1000. Still giggling.
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1578. Patrap
New Frame



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does anyone know what the hh are finding if anything? they were supposed to beleaving foe 4p.m right? so they should have some info by now right? thanks!
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1575. HCW
Quoting WaterWitch11:
god pat, the tornado warnings could last for days.


LIX NWS is trigger happy compared to other offices issuing tornado warnings for waterspouts but I guess that we can debate that at another much slower time
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Quoting TropicalAnalystwx13:


You're misunderstanding me - I didn't say there wasn't a chance that 94L could become a tropical cyclone, I said the chances were lower than they were last night and this morning. In fact, they are significantly lower. It would not surprise me if it is dropped to code yellow at 8PM.






oh ok
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1572. franck
I like Yosemite Sam, and Rick Perry.
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TS Lee and Hurricane Katia Evening Update
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The Channel 12 local met in SE Texas states that we can expect 1-2" of rain between Sat night and Sun. And... there is a cool front coming Monday and the low Tuesday morning is 64 and 61 on Wednesday with highs in the 80's. If we don't get the rain over the weekend our fire dangers will skyrocket!
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1567. pcola57
Quoting Patrap:


Rick Perry,,





LOL>>>LOL!!!
I LIKE HIS Style though.
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Quoting Patrap:


Rick Perry,,or as I like,,Yosemite Sam





LMAO@ Yosimite Sam!!
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Quoting Tazmanian:



lol will ok if you say so but i still giveing it a ch at lest not giveing up on it


You're misunderstanding me - I didn't say there wasn't a chance that 94L could become a tropical cyclone, I said the chances were lower than they were last night and this morning. In fact, they are significantly lower. It would not surprise me if it is dropped to code yellow at 8PM.
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Quoting Patrap:


There is a Chance TS Lee could reach Cane Status before Landfall as the environment is getting better by the Hour.

But the Effects will be the same regardless if a Strong TS or Cat 1, Rain and Tornadoes are the threats as flooding is too.
thanks so much for being patient and offering your knowledge to me. it is really appreciated.
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Well....looks as though Morgan City is NOT cancelling the Shrimp and Petroleum Festival tonight...Gonna be playing music in a boat I guess.....
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I'd be wary of those tornadoes. The way this year has gone the tornadoes may be the legacy of this cyclone. They're the wild-card in any storm, and they're on you so quick it's easy to be in the way before you can react to weather radio warnings. If I was in the area I know I'd sleep better if I slept in the safest room I have in the house.
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THE NATIONAL WEATHER SERVICE IN NEW ORLEANS HAS ISSUED A * TORNADO WARNING FOR...
NORTHERN ST. BERNARD PARISH IN SOUTHEAST LOUISIANA...
* UNTIL 530 PM CDT *
AT 456 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO 9 MILES NORTHEAST OF YSCLOSKEY...OR 25 MILES EAST OF CHALMETTE...MOVING WEST AT 30 MPH.
* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO VIOLET
Member Since: August 10, 2009 Posts: 0 Comments: 64
1557. Patrap
Quoting HoustonTxGal:
If New Orleans were to flood, who would get blamed this time??


Rick Perry,,or as I like,,Yosemite Sam



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1556. pcola57
Quoting BahaHurican:
Afternoon everybody... it's pouring here at my house right now... what I think of as typical AUG-SEP transitional rain.

If you can find the little eye-shaped island in the centre of the map, u can tell where my house is... sort of.... lol



Hi Baha..I can't decipher any eye but I have bad eyesight anyway..LOL LOL...
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Quoting HoustonTxGal:


Most I have seen dead have been oaks, maples.. hardwoods. I have also seen many dead bradford pears, I have 2 dead in my yard alone. I also have a Palm tree in my yard that is about half dead and I thought they would live forever!


We just cut 17 dead trees down. Mostly pines and a couple of oaks.
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Quoting HoustonTxGal:
If New Orleans were to flood, who would get blamed this time??


Bush, just because they can...
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Quoting HoustonTxGal:


Yeah, they said the beginning of the week we would only see high's in the 80-90 the end of this week and here it is Friday and yet 105 at my house again..


Well, there wasn't a lot of confidence in the forecast earlier this week, with this trough/cold front, and whether the high pressure would move or not. HOWEVER, there is a lot more confidence in the current forecast, which shows that tomorrow may be the last 100F day, if it makes it there. After that, expect low to mid 90s all the way through the middle/end portion of next week, with lows in the 60s. Considering how hot it has been there lately, it will feel cold, lol.
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If New Orleans were to flood, who would get blamed this time??
Member Since: September 18, 2007 Posts: 0 Comments: 1074
1548. CC45
Quoting HoustonTxGal:


Most I have seen dead have been oaks, maples.. hardwoods. I have also seen many dead bradford pears, I have 2 dead in my yard alone. I also have a Palm tree in my yard that is about half dead and I thought they would live forever!


I know what you mean, I have several trees and can't believe that they are actually dying, but they are. I hope I don't lose them all.

I live near the Sabine River and our local news recently showed a video of a 5 year old child walking ACROSS it, barely got wet feet. The Sabine is barely flowing here, if at all. When you look out at what used to be the river, all you see are sand dunes, very little water at all.

When rain even gets close, it is quickly terminated as we have seen all summer. What has happened to Texas, did we forget to sign the Rainmaker's Membership Agreement or what?
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What doom and gloom are the models showing now?
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Quoting HoustonTxGal:


Yeah, they said the beginning of the week we would only see high's in the 80-90 the end of this week and here it is Friday and yet 105 at my house again..


Yep Hence the Hopefully
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Afternoon everybody... it's pouring here at my house right now... what I think of as typical AUG-SEP transitional rain.

If you can find the little eye-shaped island in the centre of the map, u can tell where my house is... sort of.... lol

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Quoting notanothergoof:
arizona topped out with an average temperature of 119 for the summer always the hottest spot in the country


But it's a dry heat...lol
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Quoting cat5hurricane:
Look at the size of that monster right off the coast of the Aleutian Islands. Wow. Kind of interesting being that the 7.1 magnitude earthquake earlier this morning was right near that vicinity.





grrr can you guys plzs stop posting that here your showing us nothing other then a black boxs you can see it we cant they made it too where you can no longer hot link from that site
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Quoting franck:


Are you tokkin' ta me?
Theres no doubt a real rain is gonna come...
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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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