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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Member Since: Posts: Comments:
Quoting atmoaggie:
I think a good model name would be PATRAP. But then I envisioned Patrap as a model and (ouch)

(Just joshing ya, Pat.)
I could imagine.

WUNDERGROUND HURRICANE CENTRE

TROPICAL STORM LEE IS HEADING WEST BASED ON MODEL CONSENSUS.

HURRICANE KATIA IS HEADING WEST BASED ON MODEL CONSENSUS AND WILL CONTINUE A GENERAL WESTWARD MOTION THROUGHOUT ITS LIFETIME.
Member Since: Posts: Comments:
2734. JGreco
Quoting HoustonTxGal:



ahhhhhahahahahaha....best this week...lololol...you just made my day:)
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2733. scott39
Quoting Patrap:
July5/6 2005

I do believe im starting to see a very slow bend to the right?
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Quoting rushisaband:



hey ts, you a bolts fan? they come awful close last year.
untill the 40 year old Rolo ran out of gas...he will be even older this season and expected to carry the load in Tampa the entire year. Sorry, StevieY put all his eggs in one basket, enjoy Stammer and fighting against Bryzgalov in Ilyadelphia and Vokoun in Washington.

Now, what do you think the little Miss Ruskie in the Atlantic will do in the long run...
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2731. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129902
Quoting atmoaggie:
Most of the higher ones to ENE of center are from a 8-minute average.


That is probably the most important statement in this debate.

While I agree that the wind field may not be as large as indicated yet, it certainly could be later tonight assuming convection begins blowing up again. Lee still has a very large circulation. There are more than likely tropical storm force winds to the east and northeast of the center.

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2727. beell
Lee has lost his tail. More than likely due to 30 knots of westerly dry air intrusion along 26/27N

click either/or for loop.



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2726. ncstorm
Quoting HoustonTxGal:


LOL!!! the official manual of WU..
Member Since: August 19, 2006 Posts: 13 Comments: 16225
I don't post much, but for those complaining about the NHC wind swath map, the following is taken from the NHC web-site, pertaining to this map.

"This graphic shows how the size of the storm has changed, and the areas potentially affected so far by sustained winds of tropical storm force (in orange) and hurricane force (in red). The display is based on the wind radii contained in the set of Forecast/Advisories indicated at the top of the figure. Users are reminded that the Forecast/Advisory wind radii represent the maximum possible extent of a given wind speed within particular quadrants around the tropical cyclone. As a result, not all locations falling within the orange or red swaths will have experienced sustained tropical storm or hurricane force winds, respectively."
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2724. Patrap
July5/6 2005

Member Since: July 3, 2005 Posts: 428 Comments: 129902
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Why is it that questioning a heading that is obviously due West and not NW when you look at the change in the coordinates over the past 6 hours is such a cardinal sin. If the NHC said tomorrow morning that the sky was green would that be taken at face value too ?

I am no basher of the NHC, far from it I have a very high regard for them as they do an excellent job on the whole but if I lived my life accepting everything told to me by an expert and never questioning anything I dare say I might live to regret some of that.
Member Since: Posts: Comments:
Kman's explanation makes the most sense. Avila's not a novice. The center is still pretty close to the trop point. In all likelyhood it will work out to be NW over the next few hours as the wobbles work themselves out - maybe a little south of what the forecast was but not much. It's going to go the path of least resistence and they have a good handle on where that path is in the short term, so even if it veers off for a few hours, it will end up getting back on.
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Quoting P451:
LOL...








Yeah....no.




Ive noticed the NHC always overdoes the wind fields, the New Jersey coast was not getting 75 mph sustained winds from Irene. And, there aren't tropical storm force winds anywhere in Louisiana right now, lol.


New Orleans getting tropical storm force winds? That wind field map is just a wee bit off, shall I say?
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Until the NHC can get the wind shear maps right they will never be able to get the INTENSITY right!
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2718. Patrap
Quoting atmoaggie:
I think a good model name would be PATRAP. But then I envisioned Patrap as a model and (ouch)

(Just joshing ya, Pat.)


Tis Ok,,

Im "Joshable" last I checked atmo..

BONUS Radar of Swirly Swirling

Member Since: July 3, 2005 Posts: 428 Comments: 129902
Quoting floodzonenc:


And Patrap will make our dropsondes out of empty Fresca cans...
He would make a good equivalent to Max Mayfield.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
2715. scott39
Looks like lees convection is trying to make another attempt to expand the NE convection over the COC.
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2714. ncstorm
Quoting Walshy:


Fox.


LOL!!!!!!!!!!!!..can you imagine bill o'reilly interviewing one of the bloggers..probably will quote "The Carolinas" as a possible hit..it would be a wrap then..
Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting MississippiWx:


LOL. WU would invent its own model called WEST.


+1 SWEET!!
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Quoting MississippiWx:


LOL. WU would invent its own model called WEST.
I think a good model name would be PATRAP. But then I envisioned Patrap as a model and (ouch)

(Just joshing ya, Pat.)
Member Since: Posts: Comments:
2711. JGreco
Quoting washingaway:
Lee will be inland in less than 36 hours I think.


Especially if it is North at 5mph being so close to the coast due to the relocation.
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2710. JGreco
Quoting MississippiWx:


LOL. WU would invent its own model called WEST.



hahahahaha +1000:)
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Lee will be inland in less than 36 hours I think.
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Quoting floodzonenc:


And Patrap will make our dropsondes out of empty Fresca cans...


LOL. Deal.
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Quoting emcf30:


Could you imagine evacuation of the entire coastal regions of the US when each model run comes out or for every wobble... Heck, just the evacuations cost would run in the Billions.


LOL. WU would invent its own model called WEST.
Member Since: Posts: Comments:
2705. JGreco
Quoting ncstorm:


but then who will complain about the blog forecasting?


Seriously the behavior of some people on this blog is down right nasty tonight. Who spiked the Kool-Aid? If you guys don't like what the NHC is doing then I suggest you acquire Met degrees yourselves. Wow...i mean it's like I'm hearing a bunch of JB's on this forum right now...:0
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2704. Walshy
Quoting ncstorm:


but then who will complain about the blog forecasting?


Fox.
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Quoting P451:
LOL...








Yeah....no.


Most of the higher ones to ENE of center are from a 8-minute average.
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Quoting ncstorm:


but then who will complain about the blog forecasting?
That's easy the public media, then we will see the pressure they go through.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting TampaSpin:strong>


hey buddy



hey ts, you a bolts fan? they come awful close last year. dry air doing a number on lee's west side
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Member Since: Posts: Comments:
2698. emcf30
Quoting MississippiWx:
I say burn down the NHC and let's take over control of tropical forecasting on WU.


Could you imagine evacuation of the entire coastal regions of the US when each model run comes out or for every wobble... Heck, just the evacuations cost would run in the Billions.
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Quoting P451:


Bashers? No.

The NHC has been doing some questionable things with both systems.

Calling Katia NW movement when it's had maybe 275 movement for six hours now.

Calling Lee a tropical storm with a large area of TS force winds - when no observations, surface or otherwise, even remotely corroborate such a statement.

Users have been posting images in regards to both systems to back up assertions that the NHC seems to be out of touch this evening.



As for katia that would give others a false sense of security. For Lee well they are overestimating. Poor calls by the NHC today, what is with them?
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Quoting MoltenIce:
I find it funny that Lee avoids Texas like the plague.


Avoids is not the word for it.. more like runs with it's tail between it's legs...LOL!!
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Quoting HurricaneHunterJoe:


what did NHC do wrong now?
Some are saying the NHC got the heading wrong on Katia, at 5PM she was located at 18.4N 53.5W, as of the 11PM advisory she is located at 18.5N 54.3W, moving NW at 12mph
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting MississippiWx:


You guys take these buoy readings way too seriously. The buoys are not gospel truth and are often inaccurate. In fact, I have seen several of them that don't have any change in wind direction ever. It's always constant. The most accurate readings from the buoys are normally the pressure readings. I'll take recon data over buoy data any day.
A retired NDBC guys told me that the barometers are the absolute last instrument to fail.
Anemometers end up with the bearings no longer being sealed and giving erroneously low readings.

That said, I do think the TS force wind field to be a bit much.

H*Wind, entirely based on observations and persistence from previous observations:
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Quoting P451:


Rip TS Lee. We hardly knew ye. Even though a number of us are fairly certain you were there at one point in time.




lol again
Member Since: June 22, 2010 Posts: 0 Comments: 140
2690. xcool
TampaSpin heyyy
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Quoting HoustonTxGal:
May wonder just how dry it is in Texas.. Well....

It’s so dry, the the dogs are marking their territory with chalk lines

It’s so dry the government has announced a water pistol buy back program

It’s so dry that the cows are giving powdered milk

Its so dry here that the fire hydrants are chasing the dogs around.


Now, that is dry!!
I find it funny that Lee avoids Texas like the plague.
Member Since: Posts: Comments:
Wouldn't be shocked to see the models continue to shift west tomorrow with Katia - but I still think they will adjust eastward in the next few days and she will stay offshore with a near miss.

We will see though.
Member Since: Posts: Comments:
2687. jrblx
My first post. I am not in any way connected to meteorology other than I love this blog. Lurker since 2004. In 2005, because of this blog, I knew about Katrina coming before local authorities started putting out the word, so I had a plan. Lost house and office but things are great now! I'm in Biloxi, MS on the back bay almost within sight of Keesler's runway. HH fly over my house daily! At this time, intermittent rain, minimal wind it seems to me. Just walked down to our pier. High tide is at 2:45 am at +2.5 feet. We are already a good bit above what we see at a 2.5 foot tide. Pier will be under water soon, but the bay is very calm. I plan to go out about 2 am to see just how high it gets.
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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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