Dr. Jeff Masters' WunderBlog

Lee drenching the Gulf Coast; Katia a Cat 2
Posted by: Dr. Jeff Masters, 3:31 PM GMT on September 04, 2011 +24
Tropical Storm Lee made landfall on the southern coast of Louisiana near 4 am CDT this morning, and continues to inch slowly northward and dump very heavy rains. The storm is not a threat to intensify, since its center lies over land, but enough of the storm's circulation is over water that Lee will be slow to weaken. At New Orleans Lakefront Airport, 8.85" inches of rain had fallen from Lee as of 9 am CDT this morning. Top winds this morning hit 46 mph, gusting to 57 mph, at 6:28 am CDT, when a heavy squall blew in. Latest satellite loops show Lee has lost quite a bit of its heavy thunderstorms since yesterday, but the storm remains a formidable rain-maker. Lee brought a storm surge of 4 feet to New Canal Station in Lake Pontchartrain and at Shell Beach east of New Orleans yesterday afternoon. NOAA's Storm Prediction Center reported eight probable tornadoes from Lee yesterday. These tornadoes damaged approximately ten buildings, but caused no deaths or injuries.


Figure 1. Observed rainfall for the seven-day period ending at 8 am EDT Sunday Sep 4, 2011. Tropical Storm Lee had dumped 5 -10 inches of rain over a large swath of the coast, with a few areas in excess of ten inches (pink colors). Image credit: NOAA/AHPS.


Figure 2. Predicted rainfall for the 5-day period 8am EDT Sunday - 8 am EDT Friday, Sep 9, 2011. Lee is expected to bring a large swath of 4+ inches of rain all the way to the mid-Atlantic. Image credit: NOAA/HPC.

Forecast for Lee
Lee's large size and slow movement will make heavy rains the main concern today. Later in the week, the remnants of Lee's may be a problem for the mid-Atlantic and Northeast, where recovery efforts from the devastating flooding due to Hurricane Irene may be hampered by an additional 2 - 3 inches of rain. Tornadoes from Lee are a potential hazard today, as NOAA's Storm Prediction Center is highlighting the Northern Gulf Coast in their "slight risk" area for severe weather. A tornado watch is posted for the region, but no tornadoes have been reported as of 9 am CDT.

Hurricane Katia
Hurricane Katia finally overcame the wind shear and dry air interfering with it, and intensified into a Category 2 hurricane with 100 mph winds this morning. Latest satellite loops show a well-defined eye for the first time, but the hurricane still has a lopsided appearance, due to he impacts of dry air and moderate wind shear of 10 - 20 knots on its southwest side.

Katia will not pose a danger to any land areas over the next five days, but may be a threat to the U.S. late this week. The computer models disagree considerably on the position and strength of a trough of low pressure that will develop over the Eastern U.S. late this week, and thus how Katia will be steered. The evolution of this trough will be strongly affected by Tropical Storm Lee, and the models are not very skillful at predicting transitions from tropical storm to extratropical storm, which will happen to Lee by Wednesday this week. We have two of our reliable models--the ECMWF and UKMET--predicting that the trough will form farther west, steering Katia very close to North Carolina late this week. The rest of the models predict a more easterly position of the trough, which would force Katia to turn northwards towards Canada well before reaching North Carolina. Either scenario is possible, and it will probably be at least another day before the models converge on a solution for the long-term fate of Katia. It's likely that locations on the U.S. coast south of North Carolina will not receive a direct hit from Katia, but the entire coast from North Carolina northwards to New England and Canada's Maritime Provinces is definitely at risk. Long period swells from Katia will begin affecting the Bahamas tonight, 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.


Figure 3. Morning satellite image of Hurricane Katia.

Elsewhere in the tropics
This week and next week typically mark the two most active weeks of the Atlantic hurricane season, and there are two potential threat areas we need to watch. The GFS model predicts that a tropical depression could form in the southern Gulf of Mexico's Bay of Campeche by Friday or Saturday this week. Several other models give support to this idea, and predict such a storm would track northwards or north-northeastwards towards the northern Gulf Coast between Louisiana and the Florida Panhandle. The other region to watch is between the Lesser Antilles and the coast of Africa. The NOGAPS model is predicting that a tropical wave currently near the coast of Africa could develop into a tropical depression late this week, and arrive in the northern Lesser Antilles by Saturday or Sunday.

Jeff Masters
Tropical Strom Lee (taco2me61)
This is what happens when you do not tie up your boat.... This was taken in Pass Christian MS
Tropical Strom Lee
Categories: Hurricane
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101. ackee 4:14 PM GMT on September 04, 2011    
Quoting Skyepony:


I wanna say 6hrs.
katia seem to be going west if u look at the eye to me guess we see
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103. TropicalAnalystwx13 4:14 PM GMT on September 04, 2011    
Watch how many times Katia changes her center location:

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104. Orcasystems 4:14 PM GMT on September 04, 2011    
Complete Update

Beautiful day here... has Golfing wrote all over it :)

TS BUSTED FORECAST ALIBI





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105. stoormfury 4:15 PM GMT on September 04, 2011    
two areas of disturbed weathe, and the other south of the cape verdes, the gfs and the nogaps have a strog disturbance or depresiion east of the lesser antilles in 8 days
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106. Seastep 4:15 PM GMT on September 04, 2011    
Nice thing about having an eye is that there can be no question about movement.
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107. PcolaDan 4:15 PM GMT on September 04, 2011    
LOL

@JimCantore
Jim Cantore
Looks like our chase today has us in Biloxi, MS for #Lee. If you get a chance come down with coffee to keep me awake. #Lee is boring me!
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108. scott39 4:18 PM GMT on September 04, 2011    
Quoting P451:


Worse is the ones that come out of tropical rain bands quickly drop and just as quickly lift away or dissipate. They also have a rapid forward motion.

They are not the type that are spotted early and can be warned to give a lot of folks time to assess the threat and move to safety if needed.

By the time you're trying to alert the next person along it's path it's already come and gone.

It wouldnt have been so tense last night, if there wasnt one after another coming off the GOM last night. They did say they are mostly small and not long tracking, which is better than an F5 wedge on the ground for miles. My concern is with only having only a blanket "slight" risk posted for servere weather, is misleading for pockets of land areas. Most people werent awake late last night when we had are threat for tornados. I think a moderate risk is warranted, when you have possible tornados forming at any time.
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109. TropicalAnalystwx13 4:18 PM GMT on September 04, 2011    
Northern eyewall is tightening up...deep convection continues to burst there.

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110. GTcooliebai 4:18 PM GMT on September 04, 2011    
Quoting aislinnpaps:


Does this mean the Texas ridge will be leaving, or is it more eastern Louisiana?
Unfortunatley it is still showing the Ridge in place, I'm trying to get a good chart to illustrate this...

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112. Vero1 4:19 PM GMT on September 04, 2011    
Quoting stoormfury:
two areas of disturbed weathe, and the other south of the cape verdes, the gfs and the nogaps have a strog disturbance or depresiion east of the lesser antilles in 8 days

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 04 2011

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 09N22W TO 17N23W MOVING W AT
10-15 KT. EXAMINING RECENT UPPER AIR TIME SECTION ANALYSES FROM
DAKAR SENEGAL AND HOVMOLLER DIAGRAMS OF SATELLITE IMAGERY OVER
WESTERN AFRICA AND THE EASTERN TROPICAL ATLC FROM THE PAST FEW
DAYS...IT APPEARS THIS WAVE PASSED DAKAR BETWEEN 03/0600 UTC AND
03/1200 UTC ALOFT IN THE 800-900 MB RANGE. GLOBAL MODEL GUIDANCE
ALSO INDICATES THE CYCLONIC ATTRIBUTES ASSOCIATED WITH THE WAVE
ARE EXPECTED TO CONTINUE A WESTWARD MOTION AT LOW LATITUDE THE
NEXT FEW DAYS.
SCATTERED MODERATE CONVECTION IS FROM 05N-10N
BETWEEN 22W-29W.

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114. Melagoo 4:20 PM GMT on September 04, 2011    


I wonder how much stronger Katia will get looking better and better
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116. hurricanehunter27 4:22 PM GMT on September 04, 2011    
Quoting TropicalAnalystwx13:
Northern eyewall is tightening up...deep convection continues to burst there.

If it can keep the convection going up on the eye wall it wont collapse like Irenes eye.
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117. TropicalAnalystwx13 4:22 PM GMT on September 04, 2011    
Texas' temperature relief is currently in the western portion of the state...

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118. taco2me61 4:22 PM GMT on September 04, 2011    
Quoting scott39:
It wouldnt have been so tense last night, if there wasnt one after another coming off the GOM last night. They did say they are mostly small and not long tracking, which is better than an F5 wedge on the ground for miles. My concern is with only having only a blanket "slight" risk posted for servere weather, is misleading for pockets of land areas. Most people werent awake late last night when we had are threat for tornados. I think a moderate risk is warranted, when you have possible tornados forming at any time.


Tornado Warning in Green Co MS moving north at 20MPH... By the time this was put out a few seconds ago it will be gone....

Taco :o)
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120. scott39 4:22 PM GMT on September 04, 2011    
Quoting P451:
*While the tropical position is only updated every 6 hours on this map, the wind observations are up to date and frequently updated.

"Lee" continues to hold onto a single 40kt sustained reading out in the Gulf. Land observations are far below TS strength as has been the case through the majority of the event.



If Lee is tracking ENE do you look for more potiential developement.
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122. EYEStoSEA 4:23 PM GMT on September 04, 2011    
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123. ncstorm 4:23 PM GMT on September 04, 2011    
the 12Z GFS keeps Lee near tennessee..never having it in the NE..
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124. scott39 4:24 PM GMT on September 04, 2011    
Quoting taco2me61:


Tornado Warning in Green Co MS moving north at 20MPH... By the time this was put out a few seconds ago it will be gone....

Taco :o)
There lies the problem. Lets hope that none reach the ground!
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125. scott39 4:25 PM GMT on September 04, 2011    
Quoting scott39:
There lies the problem. Lets hope that none reach the ground!
problem for forecasters.
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128. washingtonian115 4:26 PM GMT on September 04, 2011    
Quoting wxobsvps:


Got to love this time of year.
Where does it send it.Texas could sue use it.
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130. Melagoo 4:27 PM GMT on September 04, 2011    


Dvorak showing icy tops sticking around Katia will be a 3 soon I think
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131. Ameister12 4:28 PM GMT on September 04, 2011    
Looks to me like Katia is nearing major hurricane status.
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132. GTcooliebai 4:28 PM GMT on September 04, 2011    
Quoting aislinnpaps:


Does this mean the Texas ridge will be leaving, or is it more eastern Louisiana?


Total Accumulated Precip:

18 GFS yesterday Link

00 GFS last night Link

06 GFS this morning Link
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136. Vlad959810 4:29 PM GMT on September 04, 2011    
Quoting stoormfury:
two areas of disturbed weathe, and the other south of the cape verdes, the gfs and the nogaps have a strog disturbance or depresiion east of the lesser antilles in 8 days

Where is the link?
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138. Patrap 4:29 PM GMT on September 04, 2011    
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139. HCW 4:29 PM GMT on September 04, 2011    
Looks like Storm Chaser Vincent Webb found the TWC live trucks


Link
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140. BaltimoreBrian 4:29 PM GMT on September 04, 2011    
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141. aussiecold 4:30 PM GMT on September 04, 2011    
Quoting weatherjr:
Models are created using the scientific method, climatology, taking into account many atmospheric variables... and so on... BUT if you believe in the models at a long range you also believe in "crystal balls" as elements for prediction of future events... I mean, at long range global models are as good as "crystal balls"

Is that the reason that you said your failure in your prediction with Katia?
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142. TropicalAnalystwx13 4:30 PM GMT on September 04, 2011    
Quoting Patrap:

Kind of looks like Lee's center has tightened up since landfall.

Weird....
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143. RavensFan 4:31 PM GMT on September 04, 2011    
Quoting Tazmanian:




i like the NOGAPS @ 144 hours:

florida, why?
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144. scott39 4:32 PM GMT on September 04, 2011    
Taco, We are under a tornado watch right now, With Lee moving so slow, were going to have to keep one eye and ear open for at least the next 24 to 48 hours. Stay safe....
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145. Seastep 4:32 PM GMT on September 04, 2011    
127. P451 - She's working on it.

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146. Patrap 4:32 PM GMT on September 04, 2011    

Storm Relative 1km Geostationary Visible Imagery

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147. TropicalAnalystwx13 4:33 PM GMT on September 04, 2011    


MESOSCALE DISCUSSION 2120
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT SUN SEP 04 2011

AREAS AFFECTED...REMAINDER OF FL PNHDL INTO SWRN GA

CONCERNING...SEVERE POTENTIAL...WATCH NEEDED SOON

VALID 041627Z - 041700Z

RECENT OBSERVATIONAL DATA INDICATE THAT AIR MASS DESTABILIZATION IS
OCCURRING ALONG ERN ENVELOPE OF STRONGER LOW-LEVEL WIND FIELD
ASSOCIATED WITH T.S. LEE. THE RESULT IS ORGANIZING STORM STRUCTURES
INVOF TLH WHICH WILL HAVE THE POTENTIAL TO EVOLVE INTO SUPERCELLS
WITH AN ASSOCIATED TORNADO THREAT.

..MEAD.. 09/04/2011
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148. Melagoo 4:34 PM GMT on September 04, 2011    
Quoting P451:


Also showing a rather poor eye structure especially on the northern and northeastern sides. Seems rather thin and weak.



... yah I see that interesting to see if Katia can overcome that ... the fun of following Hurricane season :c)
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149. AussieStorm 4:35 PM GMT on September 04, 2011    
Quoting ackee:
katia seem to be going west if u look at the eye to me guess we see

I would say, just north or west.
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150. TexasHurricane 4:35 PM GMT on September 04, 2011    
I know this isn't written in stone but really.....sigh

"The GFS model predicts that a tropical depression could form in the southern Gulf of Mexico's Bay of Campeche by Friday or Saturday this week. Several other models give support to this idea, and predict such a storm would track northwards or north-northeastwards towards the northern Gulf Coast between Louisiana and the Florida Panhandle."
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151. trHUrrIXC5MMX 4:36 PM GMT on September 04, 2011    
Quoting Ameister12:
Looks to me like Katia is nearing major hurricane status.


totally!
A NHC special update could be issued to address the changes
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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.

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