TD 13 intensifying; Katia may pass uncomfortably close to U.S.

By: Dr. Jeff Masters , 3:28 PM GMT on September 02, 2011

Share this Blog
30
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 2237 - 2187

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77Blog Index

Quoting WeatherNerdPR:



So, that is what RAIN looks like! I had forgotten :o(
Member Since: Posts: Comments:
Awww---our shrimp boots have brown bottoms!
Member Since: August 10, 2009 Posts: 0 Comments: 64
Quoting stormpetrol:
It could change on a dime, but Katia is getting a little too close for comfort for the N Leewards IMO.


Hi there

I just ran the long shortwave loop and it looked to me that Katia had either slowed significantly or stalled. Maybe it's just night time imagery but even on the max speed the center did not seem to be going anywhere. Anyone else comment on this ?
Member Since: Posts: Comments:
Quoting Thunderpig75:
Here's an interesting note. The Taino society who gave us the term Juracan (they got it from the Mayan god Huracan) which we now know as Hurricane also gave us Barbacoa which we now know as Barbecue.


Close...barbacoa is still a widely consumed treat usually on Sundays...the roasted head of a cow, and the cheek and jowls are similar to roast beef.
Member Since: Posts: Comments:
2233. Bielle
Quoting Asta:


White wellies, then, or does the colour matter?
Member Since: Posts: Comments:
2232. yoboi
Quoting Bielle:
What's a "shrimp boot"?


white reebok boots....it's an la coast thing
Member Since: Posts: Comments:
Member Since: Posts: Comments:
2230. Asta
Quoting Bielle:
What's a "shrimp boot"?

perfect gear for flood waters, since you can see what is in the water net to them when they are white...
Member Since: Posts: Comments:
KATIA appears to be moving West the last 6 hours
Member Since: Posts: Comments:


7:00 PM CDT Fri Sep 2
Location: 27.8°N 91.6°W
Max sustained: 45 mph
Moving: N at 3 mph
Min pressure: 1001 mb

Member Since: Posts: Comments:
2227. Asta
Quoting yoboi:


yeah we have the white cameron reebks here also lol gotta love louisiana coast to get the reebok joke

I call mine 'Dulac Suedes" ...LOL. Perfect for walking in floodwaters... Seriously I hope that you all are spared the heavy rains that they are predicting....
Member Since: Posts: Comments:
2226. Bielle
What's a "shrimp boot"?
Member Since: Posts: Comments:
weather is still getting worse hear imo pressure down rain all day winds picking up
Member Since: Posts: Comments:
2224. yoboi
Quoting LouisianaWoman:
I live a mile from the Delcambre Canal, you know, where shrimp boots are called Delcambre reeboks.


yeah we have the white cameron reebks here also lol gotta love louisiana coast to get the reebok joke
Member Since: Posts: Comments:
2223. Dennis8
Quoting BiloxiGirl:
Does Lee even have a center. I really have no idea what I am even looking at. Just looks like a giant thunderstorm.


Tru Dat
Member Since: Posts: Comments:
http://argo.colorado.edu/~realtime/gifs_tmp/gom_ssh /gmt.4028.gif


Once Lee can inch northward off that eddy he can be his own storm? I wonder how much weight the models give eddies at initialization.
Member Since: Posts: Comments:
2221. Dennis8
Galveston 21mph gusting to 28mph at 8pm 29.75"

New Orleans 17-28mph
Member Since: Posts: Comments:
2219. yoboi
Quoting LouisianaWoman:
I live a mile from the Delcambre Canal, you know, where shrimp boots are called Delcambre reeboks.


wow how close to the bayou are you? is it training rain there yet? i am in cameron la gulf waves are brewing here not much rain but tides up 1-2 feet above normal
Member Since: Posts: Comments:
2218. luigi18
Quoting stormpetrol:
It could change on a dime, but Katia is getting a little too close for comfort for the N Leewards IMO.


She is definitively dancing a Tango!
Member Since: Posts: Comments:
Does Lee even have a center. I really have no idea what I am even looking at. Just looks like a giant thunderstorm.
Member Since: Posts: Comments:
2216. scott39
Quoting washingaway:


I'm begining to think the ULL worked it's way to the surface, cut the original system in two, and took over.

which could mean what?
Member Since: Posts: Comments:
It could change on a dime, but Katia is getting a little too close for comfort for the N Leewards IMO.
Member Since: Posts: Comments:
2214. ncstorm
Quoting StormJunkie:


They are in there now.


00z BAM Models for Katia have shifted W yet again...


Great..
Member Since: August 19, 2006 Posts: 13 Comments: 13457
2213. Dennis8
Quoting washingaway:


I'm begining to think the ULL worked it's way to the surface, cut the original system in two, and took over.



yeppers
Member Since: Posts: Comments:
Quoting Grothar:


You just gave away your age.
Proud of my YOUTH
Member Since: Posts: Comments:
2211. scott39
Quoting P451:


Well, sometimes that gut feeling is just gas. So, well, ya know. Keep a watch on the system. Never know what the upper level environment could be in 24 hours.



For sure, I know things can change quickly.....Im just glad hes being tamed as he gets closer to land.
Member Since: Posts: Comments:
Here's an interesting note. The Taino society who gave us the term Juracan (they got it from the Mayan god Huracan) which we now know as Hurricane also gave us Barbacoa which we now know as Barbecue.
Member Since: Posts: Comments:
Quoting Nolehead:
this is just 1 weird system..sucked the ULL right on up...could this be a new type of storm system we could be seeing more of in the near future???? HYDROCANE...lol!!!


I'm begining to think the ULL worked it's way to the surface, cut the original system in two, and took over.

Member Since: Posts: Comments:
Quoting 996tt:


Probably not. Not much wind though, so be nice if it would kick up a swell overnight. Waist high, choppy mess right now. Better than nothing. A spot over in Pensacola area may be okay if winds pick up tomorrow, but it will be super crowded.
Thanks guess ill stay put.
Member Since: August 2, 2011 Posts: 0 Comments: 22
Quoting LouisianaWoman:
When is the next flight into Lee?


They are in there now.


00z BAM Models for Katia have shifted W yet again...
Member Since: Posts: Comments:
2202. Grothar
Quoting lottotexas:
"My Little Margie"


You just gave away your age.
Member Since: Posts: Comments:
2201. Dennis8
Quoting downdabayou:
Hello everyone. I'm in Terrbonne Parish. I wanted to thank everyone for all the info. on Lee.


stay safe and you are welcome
Member Since: Posts: Comments:
I live a mile from the Delcambre Canal, you know, where shrimp boots are called Delcambre reeboks.
Member Since: August 10, 2009 Posts: 0 Comments: 64
Member Since: Posts: Comments:
Quoting vince1:

Take a Valium.


Speaking of feeding the trolls....
Member Since: Posts: Comments:
2197. Dennis8
Quoting HoustonTxGal:


In Spring TX also. The breeze is nice but it is bad for the fire danger.


see your mail baby
Member Since: Posts: Comments:
Hello everyone. I'm in Terrbonne Parish. I wanted to thank everyone for all the info. on Lee.
Member Since: Posts: Comments:
2195. luigi18
Quoting HoustonTxGal:


He has his own blog site now.

The Best
Member Since: Posts: Comments:
2194. yoboi
Quoting LouisianaWoman:
When is the next flight into Lee?


how close to vermillion bay are you?
Member Since: Posts: Comments:
Quoting Termite3344:


ok,, what is a Gale Storm
"My Little Margie"
Member Since: Posts: Comments:
Quoting doorman79:


There is no tropical weather in March! Furthermore, there was no gale in the gulf in 92. Maybe a stalled front, but no gale. Ask someone from Alaska or the northeast about that!


Not tropical. This is what is being referred to.
http://en.wikipedia.org/wiki/1993_Storm_of_the_Ce ntury
Member Since: Posts: Comments:
Member Since: Posts: Comments:
2190. yoboi
Quoting LouisianaWoman:
When is the next flight into Lee?


8 hrs
Member Since: Posts: Comments:
2189. Grothar
Member Since: Posts: Comments:
2188. KEEPEROFTHEGATE (Mod)
T.C.F.W.
012/H/K/C1
MARK
18.65N/54.25W


Member Since: Posts: Comments:
2187. scott39
Quoting P451:


Maybe I shouldn't assume it would be understood that surface winds under the barbs were being discussed.

Read the surface extrapolation. The one barb is flagged. The one right next to it is not but is at 59mph - clearly rain contaminated.

Surface observations of which we have access to are below TS strength throughout the Gulf and the only obs close - are anemometers as much as 100 meters above sea level on rigs.

It's a very sloppy system.

Right now, it looks like its getting punched in the gut by dry air. The convection is drying up and its moving closer to land. Lee is on the ropes for now. Hes going to have to shine in 24 hours or those rainfall totals may go way down. Im feeling better about the way he looks. Thank God for Texas and dry air. Its good for something.
Member Since: Posts: Comments:

Viewing: 2237 - 2187

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77Blog Index

Top of Page

About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.