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 xtremeweathertracker:
Pull up Katia, PULL UP!!! AHHHHH!!!





lol
Member Since: May 21, 2006 Posts: 5091 Comments: 114711
Yes! Here we go...Hurricane 5 of the 2nd most active 1933 Atlantic Hurricane Season

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Quoting midgulfmom:
Could someone post it? Thanks!


post 753
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Quoting Dennis8:
NOTHING put blue skies and puffy Cu in Houston 97 degrees 38% RH. The west side of Lee would only moisten up and throw a dog a bone!


That ULL over texas is both killing yalls chances for rain..but also keeping louisiana from being hit by a nicer hurricane. lol
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Quoting GTcooliebai:
Unfortunatley, I'm looking back in the archives and not finding one single storm that hit FL. and then went on to hit Texas, crazy aye? I'll post one if I find one.


Yeah, please do... I could not find one either. It is amazing. But yet, understandable with the semi-permanent A-B High anchored off the Atlantic and High pressure along the western CONUS during the summer months.
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Quoting midgulfmom:
Could someone post it? Thanks!
Nevermind, FLdewey did...Thanks!
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Quoting Drakoen:
UKMET 12z is really far south with Katia...almost into Cuba.


UKMET is channeling Ike.
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Quoting Hurlo:


Please don't quote Pat I have him on ignore to avoid those annoying radar loops of New Orleans.



That what Pat does! Pat has been on this board for a longtime.... his a link master...
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Quoting Levi32:


My track remains between Cape Hatteras and Bermuda. That doesn't mean that the east coast shouldn't watch the system, as again, this pattern is dangerous and fragile, and thus these recurving storms are fuzzy things. As long as we have at least some models hinting at the possibility of Katia affecting the east coast under this pattern, then she is worth keeping an eye on.


Is it almost as dangerous and fragile as the forecast track for Lee in regards to tracking it further west (please) or east?
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Quoting angiest:


When your rainfall deficits look like the following:


GALVESTON When your rainfall deficits look like the following:


GALVESTON 43.84 37.16 33.14 9.88
-6.68 -10.70 -20.02 -37.40

You can kinda start to go crazy. It looks like our WFO is leaning towards our drought starting in 2009 (they actually state shortly after Ike). So what you are looking at above is Galveston's average annual rainfall, followed by the actual total and deficit for 2009, 2010, and 2011 YTD, and finally the cumulative deficit.
He doesn't care. He just wants to out-complain the complainers he's complaining about.

Meta complaining, it's all the rage these days.
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775. 996tt
Quoting wolftribe2009:
WHY am I the only one concerned that the remnant low of "Lee" could turn Katia into the Northeast?

I am not hearing anyone talking about this. I just keep hearing about the "through" but Lee will be a lot closer than the trough IMO

Is anyone else concern that Lee could alter the path of Hurricane Katia


I thought Lee was going to Texas. I dunno. Talk of that a few days ago, but not last 24 hours so perhaps not or perhaps no-one really knows since a very unusual set-up. I can see Katia staying low and missing "trough" or "weaknesses" though similar to Gustav. That could sling shot it straight through the Pennisula and into the GOM. Maybe Texas get their dreams or fantasies then as I don't think Lee is going to grant their deepest wishes.
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NOTHING put blue skies and puffy Cu in Houston 97 degrees 38% RH. The west side of Lee would only moisten up and throw a dog a bone!
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Quoting Drakoen:
UKMET 12z is really far south with Katia...almost into Cuba.
Could someone post it? Thanks!
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a hard right and then a hard left..not believing that scenario one bit
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Future Lee, Flowrida... Really? Guess you havent checked the blog or the NHC website. IT IS LEE, not future Lee. :-))
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UKMET 12z is really far south with Katia...almost into Cuba.
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Pull up Katia, PULL UP!!! AHHHHH!!!

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Quoting FLdewey:
Adios Katia...



At least for that model run...
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Two good websites that show a lot of maps, charts, and models.

Link

Link

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Quoting ecflweatherfan:


Texas never gets Florida's sloppy seconds. If anyone does, it is LA or MS.
Unfortunatley, I'm looking back in the archives and not finding one single storm that hit FL. and then went on to hit Texas, crazy aye? I'll post one if I find one.
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Quoting tiggeriffic:


so was Hugo...


so was Katrina and Allen and Carla and...and...and...
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On the hi-res visible imagery from University of Washington I think I see a low level partialy exposed swirl near 27.5N 92W. Link
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Quoting 996tt:


Are you serious? Rhetorical so don't answer, but seriously. You guys say this over and over like some wierd OCD superstitous thing. We get it. You guys need rain and you guys WANT a hurricane or tropical storm.


When your rainfall deficits look like the following:


GALVESTON   43.84      37.16       33.14     9.88
                                            -6.68        -10.70    -20.02    -37.40

You can kinda start to go crazy.  It looks like our WFO is leaning towards our drought starting in 2009 (they actually state shortly after Ike).  So what you are looking at above is Galveston's average annual rainfall, followed by the actual total and deficit for 2009, 2010, and 2011 YTD, and finally the cumulative deficit.
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Katia seems to have shrunk,that dry air is really impacting her
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WHY am I the only one concerned that the remnant low of "Lee" could turn Katia into the Northeast?

I am not hearing anyone talking about this. I just keep hearing about the "through" but Lee will be a lot closer than the trough IMO

Is anyone else concern that Lee could alter the path of Hurricane Katia
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Hurricanejunky: LOL...a floating open bar would be nice...head my way of you've got any frozen libations. That shower curtain would be a nice backdrop :)
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754. 996tt

Quoting tiggeriffic:


it isnt OCD...it is CDO, they are similar mind you, but with CDO the letters are in alphabetical order just as they should be...now lighten up...tx needs rain, the east coast needs to cool down, the polar ice caps need to refreeze...yada yada yada...nothing wrong with someone saying something


Your right. Oh mother nature I have been a real good boy and this summer sucked for surfing except my trip to SA, PR and CR, mind you, nevertheless, I have been good and it has been since, well last week Irene, since I got to surf any really really good waves, and my step up board may dry rot and blow over in my closet if it does not get some action real soon so I have this fantasy that a real big triple over head A frame peelers come my way. I wouldn't ask cept really been long dry summer and I just down right deserve it. Thank you mother nature for listening.
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Convective burst on NW side of Katias' eyewall...
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Quoting sarahjola:
is lee weakening? thanks



no
Member Since: May 21, 2006 Posts: 5091 Comments: 114711
Quoting CaicosRetiredSailor:


Thanks, I just got my Internet back last evening after no access for eight days.


Welcome back
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749. yoboi
Levi have you visited the HAARP facility in alaska???
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The Florida residents need to take their eyes off of future Lee, and direct their attention to Katia! Really don't have a good feeling about this biatch.
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Quoting hurricanejunky:


I said on the model runs, not in reality. Floyd was huge, so was Irene, so was Ike, so was Super Typhoon Tip.


so was Hugo...
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Quoting wunderweatherman123:

still a cat 1 that could bring 24 inches of rain IS NOT GOOD for lousiana. also, is it possible that when katia gets her shove back to the west for quite sometime and once she gets passed 70 or 75w starts to turn north, there a chance she could take an irene into north carolina and then out to sea or does the trough support the recurve more to the east of north carolina rather than over


My track remains between Cape Hatteras and Bermuda. That doesn't mean that the east coast shouldn't watch the system, because again, this pattern is dangerous and fragile, and thus these recurving storms are fuzzy things. As long as we have at least some models hinting at the possibility of Katia affecting the east coast under this pattern, then she is worth keeping an eye on.
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Quoting TampaFLUSA:

Francis in 2004 was huge.


I said on the model runs, not in reality. Floyd was huge, so was Irene, so was Ike, so was Super Typhoon Tip.
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Quoting stormwatcherCI:
He has been on sporadically. I think he was on for a few minutes yesterday or the day before.


Thanks, I just got my Internet back last evening after no access for eight days.
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is lee weakening? thanks
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Quoting curiousjen1:
I am definately a newbie here...so I have been lurking for a while...I am trying to ask you smart weather people...what the odds of North west louisiana getting rain from this TS Lee...


The frontal system moving in seems to be decreasing the chances of widespread rainfall in NE Texas and NW Louisiana from Lee. At the same time, it may be increasing the chances for widespread rainfall in NE Louisiana and central Mississippi... possibly from a predecessor-type event. Still lots of uncertainty, so keep watching the forecast in case the front slows down or Lee's track trends westward/faster.
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An I see thing southern vortex of Lee strengthening more than the northern? If they both head north, that would provide the potential for a stronger Lee to hit shore, and on top of another 24 hours or more additional rain.

NO is going to be seriously WET by the end of this!
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Quoting Levi32:


Well the high this year isn't fully breaking down, but rather shifting westward at times and letting troughs eat away at its eastern flank. This is why we even have the possibility of Lee moving into western Louisiana on the table, because the high isn't as fully over Texas as it was. It likely will never go away entirely, but there are still chances before the season is over, especially as troughs start becoming stronger this fall, that the eastern side of the high will give way enough to allow a storm into Texas, but again, that will be hard to do. We're hoping though.

and praying and all that.After about September 20th we are going to be out of luck as those same troughs will send the storms NE.
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Quoting flowrida:
Lots of the latest model runs have katia right at Florida's doorstep!!!
gfs, nogaps
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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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