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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701. ackee 7:56 PM GMT on September 04, 2011    
katia dont really looks like a major thow but I a, in mo postion to know that for sure if NHC upgrdae this to cat 3 would be making the headlines I am very ssuprise that up to now the NHC has not send recon into katia
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702. Levi32 7:56 PM GMT on September 04, 2011    
Quoting Tropicsweatherpr:
Levi,the NE Caribbean still may have threats during the rest of September with the pattern eluded by 23 and you earlier?


Definitely, especially while we're still in September and the Cape Verde season is still in session. The risk starts lessening in October when tropical waves start to become less vigorous.
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704. atmoaggie 7:57 PM GMT on September 04, 2011    
Any substantial wind in the next few days will result in more of this:

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705. 7544 7:57 PM GMT on September 04, 2011    
Quoting Hhunter:


ukmet shows Katia very south just north of cuba..a scary position indeed..it is the south outlier with Navy nogaps and a couple of other models more in the northern bahamas...but, interesting stuff...


can i get that link plzz tia
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707. PensacolaDoug 7:58 PM GMT on September 04, 2011    
Quoting oceanblues32:
So it looks like florida may have dodged another hurricane season they all seem to be turning up and out to see.



Where do you get these ideas from?
It's only the 1st week of September.
Either a troll or just clueless.
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708. BahaHurican 7:58 PM GMT on September 04, 2011    
Quoting tiggeriffic:


hey ya Baha...lookin at Katia?
That, yeah, and the EAtl wave that's looking fairly interesting right now. Katia I still feel pretty hopeful about, at least in the 3-day forecast, anyway. Dunno what's going to happen with it and Lee, though.

The EATL Twave could be of much greater interest to me, at least in the 10 day range...
Member Since: October 25, 2005 Posts: 19 Comments: 17631
711. atmoaggie 7:59 PM GMT on September 04, 2011    
Quoting emcf30:


Interesting pics. Do you know the time difference between the two photos?
Those 2 were taken yesterday and today, respectively. (Or, knee height on the Jeep the day before shoulder height.)

Prolly about 24 hours apart, but that is a guess.
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713. BahaHurican 7:59 PM GMT on September 04, 2011    
Thought this might be interesting to those looking at the EATL and CATL features...

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714. 7544 7:59 PM GMT on September 04, 2011    
i think by now we all can s guess how strong katia will be the million dollar question is where she will be going get your rulers and compasses out and for these next few days you are or will be the hurricane authority
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715. EYEStoSEA 8:00 PM GMT on September 04, 2011    
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716. tiggeriffic 8:00 PM GMT on September 04, 2011    
Quoting BahaHurican:
That, yeah, and the EAtl wave that's looking fairly interesting right now. Katia I still feel pretty hopeful about, at least in the 3-day forecast, anyway. Dunno what's going to happen with it and Lee, though.

The EATL Twave could be of much greater interest to me, at least in the 10 day range...


so then 12-14 for me then huh? oh yay...more storms... thought they said nadda for a few weeks... oh well...this the season to watch the tropics, fa la la la la...la la la la
Member Since: September 16, 2007 Posts: 0 Comments: 3592
717. nash28 8:00 PM GMT on September 04, 2011    
Quoting thechanger:
that model will change dont worry


Until it doesn't...

No one is worrying. Just noting the models are having a tough time with the evolving synoptic pattern. They're back and forth from run to run. Yesterday, they were all out to sea. Then the next run they all bended hard left. Now we're out to sea again...

No consistency. Yet...
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718. Tazmanian 8:00 PM GMT on September 04, 2011    
Quoting thechanger:
looks like the models have a good handle on 95 and 96 we will just have to wait and see again



we dont have 95 and 96L yet for the time being there being called per 95 and 96L
Member Since: May 21, 2006 Posts: 5088 Comments: 111341
719. ackee 8:00 PM GMT on September 04, 2011    
Quoting Tazmanian:
i think we could see 95L and 96L soon

per 95L will be the one with the close low and per 96L would be the one with the wave moveing W

agree THINK ONE TO S WILL be 95L probaly be first storm to tack fully west this seasons guess we see I betting that maria will come from the GULF while this will be NATE just gut feeling thow
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722. TropicalAnalystwx13 8:02 PM GMT on September 04, 2011    
96/183 COMPLETE

Just past 50% done with the 2011 Atlantic hurricane season.
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723. Tazmanian 8:02 PM GMT on September 04, 2011    
Quoting ackee:
agree THINK ONE TO S WILL be 95L probaly be first storm to tack fully west this seasons guess we see I betting that maria will come from the GULF while this will be NATE just gut feeling thow




will see
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724. GetReal 8:02 PM GMT on September 04, 2011    
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725. Levi32 8:03 PM GMT on September 04, 2011    
Again, seeing this kind of cold come into the southeastern U.S. for the next week or two means we have to really watch out in the areas of the NW Caribbean, southern gulf, and Bahamas during the 3rd week of September, near and after the 15th. Sea-level pressures have been so low over the eastern U.S. lately that the Caribbean has been quiet. That will change as the air cools, becoming denser and allowing pressures to rise. With the eastern Pacific completely dead right now and the monsoon trough displaced north, a tropical wave from the east should try to spark a storm in that region 10-15 days from now. The track would be either up north into the eastern gulf/Florida/Bahamas area or west into central America/Mexico.

GFS ensemble mean temperature anomalies for Week 1:

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727. emcf30 8:04 PM GMT on September 04, 2011    
Deleted

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728. BahaHurican 8:04 PM GMT on September 04, 2011    
BTW, thanks 2 atmoaggie for the pics from LA... proof that it doesn't take a major to cause damage to people's homes / livelihoods.

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729. TropicalAnalystwx13 8:04 PM GMT on September 04, 2011    
Quoting Levi32:
Again, seeing this kind of cold come into the southeastern U.S. for the next week or two means we have to really watch out in the areas of the NW Caribbean, southern gulf, and Bahamas during the 3rd week of September, near and after the 15th. Sea-level pressures have been so low over the eastern U.S. lately that the Caribbean has been quiet. That will change as the air cools, becoming denser and allowing pressures to rise. With the eastern Pacific completely dead right now and the monsoon trough displaced north, a tropical wave from the east should try to spark a storm in that region 10-15 days from now.

GFS ensemble mean temperature anomalies for Week 1:



Think it will be Ophelia...What about you?

j/k, lol.
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732. Levi32 8:05 PM GMT on September 04, 2011    
Quoting TropicalAnalystwx13:


Think it will be Ophelia...What about you?

j/k, lol.


Are you making fun of me today? Lol.
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733. GetReal 8:05 PM GMT on September 04, 2011    
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734. Tropicsweatherpr 8:06 PM GMT on September 04, 2011    
Levi, what do the 12z Euro ensembles show?
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735. Levi32 8:06 PM GMT on September 04, 2011    
Quoting Tropicsweatherpr:
Levi, what do the 12z Euro ensembles show?


They will be out soon.
Member Since: November 24, 2005 Posts: 586 Comments: 25445
737. emcf30 8:06 PM GMT on September 04, 2011    
Quoting atmoaggie:
Those 2 were taken yesterday and today, respectively. (Or, knee height on the Jeep the day before shoulder height.)

Prolly about 24 hours apart, but that is a guess.


Thanks. That is a excellent representation of what a lot of people overlook, which is the water and surges that come with these systems. Even the week ones. It not always about the winds...
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738. TropicalAnalystwx13 8:07 PM GMT on September 04, 2011    
Quoting Levi32:


Are you making fun of me today? Lol.


Just messing, haha.
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740. GetReal 8:07 PM GMT on September 04, 2011    


NAM picking up on CMC storm forming in BOC.
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741. Ameister12 8:07 PM GMT on September 04, 2011    
What are the chances that we see a category 5 hurricane this season?
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742. nofailsafe 8:07 PM GMT on September 04, 2011    
Quoting thechanger:
im gonna get ready to track 95


At the very beginning of the season I printed off a chart of the atlantic basin on 8 sheets of printer paper, taped them up together, and penciled in the first positions for 92L. Unfortunately it was too small to put all the data I wanted on there, wind, pressure, day, time, name, etc. so I had to scrap it. I was hoping to have this great big chart with all of the storms, invests and otherwise by the end of the season. Oh well. It was fun for the first month :P
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743. Tazmanian 8:08 PM GMT on September 04, 2011    
Quoting Ameister12:
What are the chances that we see a category 5 hurricane this season?



ch are still vary good but wish storm will it be
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744. BahaHurican 8:08 PM GMT on September 04, 2011    
Don't you hate when pple tell you "don't worry", and all u r doing is just watching the storm with interest and scientific curiosity? Like they are dumbing your natural desire to know down to simple fear...
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745. atmoaggie 8:08 PM GMT on September 04, 2011    
Quoting BahaHurican:
BTW, thanks 2 atmoaggie for the pics from LA... proof that it doesn't take a major to cause damage to people's homes / livelihoods.

Well, what damage there is, is indeed isolated, but widespread.

There are some cases of water in houses and businesses well inland due to river flooding. The odd tree down here and there, though in a one hour interstate drive, I only saw ~10 pines down. I saw a few pics of trees on houses or carports and a couple of pics of homes damaged by wind.
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746. HoustonTxGal 8:08 PM GMT on September 04, 2011    
I am still getting some pretty good wind gusts here in North Houston. My power has been going off and on since yesterday. Trees limbs fall and take out power lines..ugh. Our trees are so dry you can bump a tree and limbs will fall off..LOL
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747. BioWeather 8:08 PM GMT on September 04, 2011    
Quoting Altestic2012:

125 miles per hour is 6 less than Cat 4 strength. So yeah, I'd say that's pretty darn close...


I lived in Jupiter, FL at the time (east coast). She got knocked down a bit by the time she hit us. But it was still bad. I don't want another experience like that. Now, I moved to NC 2 years ago and all the action has followed me. lol I don't want Katia anywhere near NC. Drought or no drought.
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749. tiggeriffic 8:09 PM GMT on September 04, 2011    
Quoting BahaHurican:
Don't you hate when pple tell you "don't worry", and all u r doing is just watching the storm with interest and scientific curiosity? Like they are dumbing your natural desire to know down to simple fear...


giving you post of the decade on this one :)
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751. Sfloridacat5 8:10 PM GMT on September 04, 2011    
Very few homes can withstand a true cat 4 (sustained winds over 130 mph with gust in the 150 mph range).

Most homes start to have major issues at 90-100 mph or so. Windows blow in, roofs begin to lift off, garage doors blow in, etc.

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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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