Dr. Jeff Masters' WunderBlog

Tropical Storm Lee moving ashore; Katia continues northwest
Posted by: Dr. Jeff Masters, 1:53 PM GMT on September 03, 2011 +19
Tropical Storm Lee is marching steadily northwards towards landfall in Louisiana, and continues to slowly intensify. The storm's central pressure is now down to 993 mb, as measured by an Air Force hurricane hunter aircraft at 7am CDT. However, the center of Lee is now very close to the coast, and the storm doesn't have much time to intensify further before the center moves over land. The main impact from the storm on the coast thus far has been heavy rains. At New Orleans Lakefront Airport, 5.88" inches of rain had fallen from Lee as of 8 am CDT this morning. Top winds were 35 mph, gusting to 55 mph. Though Lee's top winds are rated as being 60 mph, it is difficult to find any land stations that have reported sustained winds of tropical storm force, 39 mph or greater. One station that has is at the tip of the Mississippi River Delta, where Southwest Pass measured sustained winds of 40 mph, gusting to 58 mph, at 7:03 am CDT. Upper-level winds out of the southwest are creating a moderate 10 - 20 knots of wind shear over Lee, keeping the storm's heavy thunderstorms pushed to the east side of the storm. Latest satelllite loops show Lee is becoming increasingly organized.


Figure 1. Radar-estimated rainfall from Lee from the New Orleans radar. Lee has dumped a large region of 4 - 8 inches so far (orange colors.)


Figure 2. Predicted rainfall for the 5-day period ending at 8 am EDT Thursday Sep 8, 2011. Lee is expected to bring a large swath of 4+ inches of rain all the way to New England. Image credit: NOAA/HPC.

Forecast for Lee
Lee'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 make Lee look a lot like a subtropical storm on satellite imagery, with a broad center and the majority of the heavy thunderstorms in a broad band well removed from the center. Subtropical storms can undergo only relatively modest rates of intensification, and Lee is unlikely to become a hurricane. Also tending to slow intensification will be the fact that much of its circulation is over land. Damages from Lee are likely to be less than $100 - $200 million, with the greatest threats being fresh water flooding from heavy rains. Given that much of the region Lee will traverse over the next few days is under moderate to severe drought, the storm's rains may cause more economic benefit than damage. Since Texas is on the dry side of the storm, that state will see very little rainfall from Lee, except very close to the border with Louisiana. The rains from Lee appear to have mostly ended across extreme southern Louisiana, so the feared 10 - 15 inches of rain does not look like it will materialize there. One possible concern for Lee's rains will be the mid-Atlantic and Northeast, where recovery efforts from the devastating flooding due to Hurricane Irene may be hampered by the additional 2 - 4 inches that may fall from Lee's remnants by the middle of the week.Tornadoes from Lee are 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 8 am CDT.

Lee is the 12th named storm this year, and came eight days before the half-way point of the Atlantic hurricane season. Climatologically, September 10 marks the half-way point. A typical hurricane season has just 10 - 11 named storms, so we've already had more than a whole season's worth of storms before reaching the half-way point. At this rate, 2011 will see 24 - 26 named storms, making it the 2nd busiest season on record, behind 2005. Lee's formation date of September 2 puts 2011 in 5th place for earliest date of arrival of the season's 12th storm. Only 2005, 1995, 1936, and 1933 had an earlier 12th storm.

Hurricane Katia
The latest set of model runs show very little change in the outlook for Hurricane Katia. Katia will continue its long trek across the Atlantic Ocean, and will not pose a danger to any land areas over the next five days. Katia is still struggling with dry air and wind shear that has risen to a high 20 - 25 knots. Latest satellite loops show a lopsided hurricane that is suffering from the impacts of dry air and wind shear on its southwest side.

The models now agree that the upper-level trough of low pressure bringing the wind shear to Katia will move away by Sunday, putting Katia in an environment with low to moderate wind shear. At the same time, ocean temperatures will warm to 29°C, a full 0.5°C over what Katia is experiencing today. These effects should allow Katia to intensify to a Category 2 hurricane by Monday. It is still unclear how much of a threat Katia may pose to the U.S., as this depends on the strength and timing of a trough of low pressure predicted to move off the U.S. East Coast 5 - 7 days from now. Our models do not have enough skill to predict how the steering currents will behave that far into the future. As I mentioned in yesterday's post, part of the problem is due to the inability of the computer models to agree on what will happen to Tropical Storm Talas in the Western Pacific. Talas hit Japan early on Saturday as a strong tropical storm, and is racing northwestwards towards Alaska. Talas is expected to transition into a powerful extratropical storm in the waters south of Alaska early next week. This extratropical storm will create a ripple effect downstream in the jet stream, all the way to North America, affecting the trough of low pressure off the U.S. East Coast expected to potentially recurve Katia when it approaches the U.S. The computer models are not very good at handling these sorts of interactions, leading to more than the usual amount of uncertainty in the long-range outlook for Katia. It will probably be another two days before the models will converge on a solution for the long-term fate of Katia. It's a good bet that locations on the U.S. coast south of North Carolina are in the clear, but residents from North Carolina to New England need to watch Katia. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have a 15% chance of hitting North Carolina, a 22% chance of hitting Canada, a 12% chance of hitting New England, and a 58% 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.


Figure 3. Satellite image of Tropical Storm Talas taken September 2, 2011, as the storm approached Japan. Image credit: NASA.

Jeff Masters
So far 4 (minou)
We're in a Lee-lull at the moment but winds have been strong and gusty this morning with blowing rain at times. I had to don my gullashes and wander around the overhang!
So far 4
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851. WetBankGuy 7:23 PM GMT on September 03, 2011    
Lee still interesting for LA. Stalled at 1 PM CDT, with that massive feeder band that stretches south of the lattitude of Brownsville. Here in NOLA hoping it jobs east a bit (sorry Mississippi). Looks to be simultaneously entraining dry air from the west but also popping up convection just SW of the center as if trying to close off.

What do you think, Pat?
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852. beell 7:23 PM GMT on September 03, 2011    
Quoting Levi32:


True, it does look like the GFS shows the upper low being left behind to an extent, albeit a lot farther east than the Euro.


At 120 hrs, models are a suggestion of synoptics. Actual results may vary!
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854. Levi32 7:24 PM GMT on September 03, 2011    
Quoting TropicalWeatherGrl88:


Levi, the ridge you talked about that Lee would create from his outflow. If that ridge were to be in place south of Florida(some modes show this). How long would that ridge stay for? Thank you for your time.


Well that specific piece of the ridge will probably stick around until Lee and his associated upper trough leave the area. Even after that though we might see the Atlantic ridge build westward in the wake of Katia and extend into the Florida area, so it may look like ridging never left.
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855. Patrap 7:24 PM GMT on September 03, 2011    
Member Since: July 3, 2005 Posts: 377 Comments: 112983
857. Walshy 7:25 PM GMT on September 03, 2011    
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858. WeatherNerdPR 7:25 PM GMT on September 03, 2011    
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860. redwagon 7:25 PM GMT on September 03, 2011    
Quoting RitaEvac:
Ticking time bomb in TX as winds are gonna get stronger with Lee to our east and cool front coming in, everything dead, and ready to burn, gonna get ugly real fast in TX

Maybe our neighboring states will understand what we're talking about when blowback and smoke from our wildfires force them to stay inside for a month.

Beel already lost power this AM from the firewinds knocking a dead tree over a power line.
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861. CaribBoy 7:25 PM GMT on September 03, 2011    
Quoting Levi32:
Yup. The 12z Euro does have something in the long-range in the Caribbean, like the GFS. I dealt with that idea in my blog this morning. There's actually some interesting things going on that support the idea of a storm in the Caribbean near or after the 15th of September.



Cool, we need action (wind, rain, thunder... but not too much lol). It's too boring right now!
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862. Col15thTex 7:25 PM GMT on September 03, 2011    
863. jpsb 7:26 PM GMT on September 03, 2011    
Quoting Altestic2012:

Are you crazy? None of the models expect any significant rain in TX through September.
i think is talking about fires, they have been bad this year.
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864. Levi32 7:26 PM GMT on September 03, 2011    
Quoting Altestic2012:
So in other words Levi, no Katrina/Rita tracks this year.


Katrina and Rita developed in our back yard. Those could still happen, but the long-trackers that get named east of 60W, pass north of the Caribbean, and then get all the way to Florida seem unlikely in the overall pattern. However, again, we take it week by week because the overall pattern isn't what exists day by day, because it is always fluctuating. Any track can happen in any year. All we can try to do is get a grasp of what tracks will tend to do.
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865. Patrap 7:26 PM GMT on September 03, 2011    
Quoting WetBankGuy:
Lee still interesting for LA. Stalled at 1 PM CDT, with that massive feeder band that stretches south of the lattitude of Brownsville. Here in NOLA hoping it jobs east a bit (sorry Mississippi). Looks to be simultaneously entraining dry air from the west but also popping up convection just SW of the center as if trying to close off.

What do you think, Pat?


I think Lee is going to be with us like Mickey Rooney,,real late and real early thru Monday.
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866. Orcasystems 7:26 PM GMT on September 03, 2011    
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867. aislinnpaps 7:26 PM GMT on September 03, 2011    
Power back on. Hopefully it'll stay that way.
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868. jpsb 7:26 PM GMT on September 03, 2011    
Quoting Patrap:
You post the most interesting graphics, i only wish I knew what they meant.
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869. GTcooliebai 7:27 PM GMT on September 03, 2011    
Quoting washingtonian115:
Not to mention Florida can still get hit in October.Especially wit the Trofs becoming more common(Wilma)
Lets not forget the 1921 Hurricane, just for Tampa residents that have become complacent over the years.
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870. HurricaneVSafety 7:27 PM GMT on September 03, 2011    
Quoting CybrTeddy:


Statements like these just deserve a massive facepalm.

Florida isn't safe at all. Do you need a geography lesson? Florida sticks out like a sore thumb away from the USA.

Its TIMING that matters. If you get a storm into the Caribbean with the conditions that are in place, a strong one at that too, like a Category 2, it will be picked up and head into the Gulf. That's just the facts.


CybrTeddy,

On average Florida gets hit by a Hurricane every 4 years and a Tropical storm every 2 years.

If you go by statistical averages.. then yes Florida is the Hurricane Capital of the US.
however, this year there is nothing to suggest that Florida will ever be affected... This year
The majority of the storms have been to the east and pulled northward away from you folks down there.

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871. brazocane 7:27 PM GMT on September 03, 2011    
Rain creeping ever so closer to Houston/Galveston:

Link

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873. CaribBoy 7:28 PM GMT on September 03, 2011    


Nice turning in the EATL. Looks like IRENE when she has her large scale turning with very little convection.
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874. Patrap 7:28 PM GMT on September 03, 2011    
Quoting jpsb:
You post the most interesting graphics, i only wish I knew what they meant.


Me too most the time jpsb.
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875. GTcooliebai 7:28 PM GMT on September 03, 2011    
Quoting HurricaneVSafety:


CybrTeddy,

On average Florida gets hit by a Hurricane every 4 years and a Tropical storm every 2 years.

If you go by statistical averages.. then yes Florida is the Hurricane Capital of the US.
however, this year there is nothing to suggest that Florida will ever be affected... This year
The majority of the storms have been to the east and pulled northward away from you folks down there.

Yes, but a good analog to this year is 1999, and Irene came from the Caribbean and hit southwest FL. that year.
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876. washingtonian115 7:28 PM GMT on September 03, 2011    
Quoting TropicalAnalystwx13:


That's a big no-no...

Bleh.That's nasty.
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877. CybrTeddy 7:29 PM GMT on September 03, 2011    
Quoting HurricaneVSafety:


CybrTeddy,

On average Florida gets hit by a Hurricane every 4 years and a Tropical storm every 2 years.

If you go by statistical averages.. then yes Florida is the Hurricane Capital of the US.
however, this year there is nothing to suggest that Florida will ever be affected... This year
The majority of the storms have been to the east and pulled northward away from you folks down there.



Statistics are moot.

Majority of storms go out to sea that are hurricanes.

Its not Florida, its every state.

NYC got hit, that's rare. That's something that is a once-in-a-20 year event.

But to say something like 'Florida is the safest state' is ridiculous.
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878. baytwntx11 7:29 PM GMT on September 03, 2011    
YIPPEE!!!! Raining here now..... Just east of Baytown, TX.
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880. TropicalWeatherGrl88 7:29 PM GMT on September 03, 2011    
Quoting Levi32:


Well that specific piece of the ridge will probably stick around until Lee and his associated upper trough leave the area. Even after that though we might see the Atlantic ridge build westward in the wake of Katia and extend into the Florida area, so it may look like ridging never left.


And that ridge would stay until the next trough came down? As long as it was deep enough to force it out of the way that is...
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882. washingtonian115 7:31 PM GMT on September 03, 2011    
Quoting GTcooliebai:
Lets not forget the 1921 Hurricane, just for Tampa residents that have become complacent over the years.
Tampa residents nowadays think they are safe from a hurricane.I have to SMH at those people.
Member Since: August 14, 2010 Posts: 5 Comments: 11200
884. GetReal 7:31 PM GMT on September 03, 2011    
Well the weather had improved here the past few hours, but over the last 45 minutes the conditions are changing again. The dry air that we were experiencing has departed and the heavy tropical air mass is back, and the cloiud deck is lowering and thickening again. I can see an approaching squall from the south.
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885. jpsb 7:31 PM GMT on September 03, 2011    
Beer time, see yall later come on rain!
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886. Levi32 7:31 PM GMT on September 03, 2011    
Quoting Altestic2012:

Interesting, but didn't Katrina began as a long-tracking TW/TD that probably would have been a fish storm if it had developed earlier (like Irene), and Rita developed at around 65W just NNE of Puerto Rico. Not exactly in our back yard...(i.e., the Bahamas). Both of them had time to develop into minimal hurricanes before hitting Florida, and then on in to the Gulf as Cat 5's.



Um the Bahamas are the United States' back yard lol.
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887. oddspeed 7:31 PM GMT on September 03, 2011    
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888. TropicalAnalystwx13 7:32 PM GMT on September 03, 2011    
Quoting Altestic2012:

Interesting, but didn't Katrina begin as a long-tracking TW/TD that probably would have been a fish storm if it had developed earlier (like Irene), and Rita developed at around 65W just NNE of Puerto Rico. Not exactly in our back yard...(i.e., the Bahamas). Both of them had time to develop into minimal hurricanes before hitting Florida, and then on in to the Gulf as Cat 5's.



Ummm, the Bahamas ARE our backyard...
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889. Col15thTex 7:32 PM GMT on September 03, 2011    
Quoting TxGrandma:
Is that the island that was created with dredgings from the channel into Bayport? (I've heard it called Fisherman's Island, but not sure....)


Red Fish Reef has been there since at least the early 1800's. Jean Lafitte used to anchor off the island.
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890. Levi32 7:33 PM GMT on September 03, 2011    
Quoting TropicalWeatherGrl88:


And that ridge would stay until the next trough came down? As long as it was deep enough to force it out of the way that is...


Probably, yes. You should hope it stays there for a while, because if we do get something in the western-central Caribbean in 10-15 days, its only alleyway into the United States would be via the eastern Gulf of Mexico, which would only be open if there is no strong ridge over Florida.
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891. WeatherNerdPR 7:33 PM GMT on September 03, 2011    
Quoting GTcooliebai:
Yes, but a good analog to this year is 1999, and Irene came from the Caribbean and hit southwest FL. that year.

This year's Irene was bigger and stronger, so it felt the through earlier and wrecked New England instead of Florida.
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892. Some1Has2BtheRookie 7:33 PM GMT on September 03, 2011    
Quoting baytwntx11:
YIPPEE!!!! Raining here now..... Just east of Baytown, TX.


Old and Lost rivers or Mont Belveiu? Fan some a liitle further west, please.
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894. Marou 7:33 PM GMT on September 03, 2011    
hi evertbody, do you think we can still see a long tracker cap verdian, this year ?
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895. PlashIslandResident 7:33 PM GMT on September 03, 2011    
Windy, heavy rain and rough surf in Gulf Shores.
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896. washingtonian115 7:34 PM GMT on September 03, 2011    
We all know that Trackawaytosea is a troll.Lol.
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897. HurricaneVSafety 7:35 PM GMT on September 03, 2011    
Quoting CybrTeddy:


Statistics are moot.

Majority of storms go out to sea that are hurricanes.

Its not Florida, its every state.

NYC got hit, that's rare. That's something that is a once-in-a-20 year event.

But to say something like 'Florida is the safest state' is ridiculous.


Why do you think this season is any different than the last 6 since Wilma...

My folks live in Fort Myers.

For the past 6 years since then .. they have been told ever year to prepare .. to buy hurricane supplies for each season. And nothing ever came...

I doubt a system will affect my folks this year.
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898. Levi32 7:35 PM GMT on September 03, 2011    
Quoting Altestic2012:

That's my point lol, neither Katrina nor Rita formed in the US back yard (i.e. the Bahamas). They formed well east of there. I can't believe y'all would misinterpret my statement like that.


Recent hurricane history 101:



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899. WaterWitch11 7:35 PM GMT on September 03, 2011    
Quoting Patrap:
You post the most interesting graphics, i only wish I knew what they meant.

love this
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900. ConnecticutWXGuy 7:35 PM GMT on September 03, 2011    
why do 8 year-olds always think typing in all caps makes them more noticed?
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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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