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!

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701. Beachfoxx 6:49 PM GMT on September 03, 2011
Viking, I've got a weather station... never used it. Quoting 69Viking: Hello everybody! Pretty blustery in Fort Walton Beach, up to 3.5" of rain since it started early this morning. These feeder bands have some surprisingly gusty winds, wish I had a way to measure the gusts! Member Since: July 10, 2005 Posts: 153 Comments: 29285

702. Patrap 6:49 PM GMT on September 03, 2011
366 WFUS54 KLIX 031846 TORLIX LAC063-095-105-031915- /O.NEW.KLIX.TO.W.0121.110903T1846Z-110903T1915Z/ BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE NEW ORLEANS LA 146 PM CDT SAT SEP 3 2011 THE NATIONAL WEATHER SERVICE IN NEW ORLEANS HAS ISSUED A * TORNADO WARNING FOR... NORTHEASTERN LIVINGSTON PARISH IN SOUTHEAST LOUISIANA... EXTREME NORTHEASTERN ST. JOHN THE BAPTIST PARISH IN SOUTHEAST LOUISIANA... SOUTHERN TANGIPAHOA PARISH IN SOUTHEAST LOUISIANA... THIS INCLUDES THE CITY OF HAMMOND... * UNTIL 215 PM CDT * AT 143 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A STRONG RAIN SQUALL CAPABLE OF PRODUCING A TORNADO 14 MILES SOUTHEAST OF PONCHATOULA...OR 14 MILES SOUTHWEST OF MANDEVILLE... MOVING NORTHWEST AT 40 MPH. * OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO SPRINGFIELD AND INDEPENDENCE PRECAUTIONARY/PREPAREDNESS ACTIONS... HEAVY RAINFALL MAY OBSCURE THIS TORNADO. TAKE COVER NOW! IF YOU WAIT TO SEE OR HEAR IT COMING...IT MAY BE TOO LATE TO GET TO A SAFE PLACE. THE SAFEST PLACE TO BE DURING A TORNADO IS UNDER A WORKBENCH OR OTHER PIECE OF STURDY FURNITURE. SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN AN INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO COVER YOUR BODY AND ALWAYS STAY AWAY FROM WINDOWS. IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A SUBSTANTIAL SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS. A TORNADO WATCH REMAINS IN EFFECT UNTIL 1000 PM CDT SATURDAY EVENING FOR SOUTHEAST LOUISIANA AND SOUTHERN MISSISSIPPI. LAT...LON 3068 9054 3036 9023 3030 9029 3022 9037 3026 9043 3028 9041 3030 9044 3031 9043 3034 9048 3032 9050 3053 9073 TIME...MOT...LOC 1846Z 138DEG 36KT 3030 9032 CLICK HERE TO GO TO PREVIOUS BULLETINS. Member Since: July 3, 2005 Posts: 372 Comments: 111626

703. Patrap 6:50 PM GMT on September 03, 2011
Member Since: July 3, 2005 Posts: 372 Comments: 111626

704. jlp09550 6:50 PM GMT on September 03, 2011
Yay for a nice blue sky over head right now--but pressures nearing 990mb here. Member Since: February 21, 2008 Posts: 1 Comments: 340

705. cat6band 6:51 PM GMT on September 03, 2011
Levi....does Lee appear to be trying to form an eye south of it's current location? Local mets are considering the option...what's your thoughts? Member Since: May 11, 2011 Posts: 0 Comments: 151

706. WeatherNerdPR 6:51 PM GMT on September 03, 2011
Member Since: July 7, 2010 Posts: 0 Comments: 5464

707. Drakoen 6:51 PM GMT on September 03, 2011
Quoting Bluestorm5: So, ECMWF is predicting SUPER sharp curve? At the very least it'll be Hatteras scrapper and a hit to New England again like Irene. With a positively titled trough that's what you would expect. If the trough can tilt negative then we would have a different story. Member Since: October 28, 2006 Posts: 57 Comments: 29010

709. Patrap 6:52 PM GMT on September 03, 2011
Member Since: July 3, 2005 Posts: 372 Comments: 111626

710. Levi32 6:52 PM GMT on September 03, 2011
Quoting wxobsvps: Can you explain more about the hybrid appearance? It looks like a comma, a signature typically taken by developing baroclinic low pressure systems. It doesn't look like a typical tropical cyclone, and thus has a "hybrid" appearance. Member Since: November 24, 2005 Posts: 586 Comments: 25459

711. GTcooliebai 6:52 PM GMT on September 03, 2011
Anybody got the latest run of the NOGAPS & UKMET models? Member Since: August 31, 2009 Posts: 0 Comments: 5203

715. Patrap 6:53 PM GMT on September 03, 2011
On the Porch I can see thru the Low Scud racing by east to west and see the Tops and curved row of T-Storms in that eastern Feeder in NOLA east. Member Since: July 3, 2005 Posts: 372 Comments: 111626

716. freeroam 6:53 PM GMT on September 03, 2011
Out of lurk mode to say...THANK U PAT! Member Since: September 1, 2007 Posts: 0 Comments: 245

717. HurricaneVSafety 6:53 PM GMT on September 03, 2011
So... The carolina's have been hit this year.... New York has been hit this year.... New Orleans has been hit this year... Waiting for a Hurricane/Tropical Storm to hit Miami,Fl or Houston,TX. I think Florida will not get hit this year. Member Since: August 27, 2011 Posts: 0 Comments: 43

718. Levi32 6:54 PM GMT on September 03, 2011
The 12z ECMWF is radically different from the previous runs because it keeps Lee and his associated upper low/trough stranded over the center of the country instead of phasing northeastward towards New England. I don't immediately see any other model agreeing with this, so this run bringing Katia so close to Cape Hatteras may be an outlier. Regardless, she still turns out as I think she should, but into the Canadian Maritimes which would be a bad storm for them. Day 6: Member Since: November 24, 2005 Posts: 586 Comments: 25459

719. TxGrandma 6:54 PM GMT on September 03, 2011
Quoting jpsb: Hmmm, we have a couple of crazy sailors anchored up at red fish island in the middle of Galveston bay. Right now there are in a lee, but if the water comes up a few more feet the island goes away and the ship waves are gonna be hell there. I don't think the iron genie is going to be able to maintain steering in 50mph winds and 4-5' chop. Guess I will have to keep en eye on them in case things get real bad. Anchored out in a strong T.S. is not my idea of how to spend labor day weekend. 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....) Member Since: August 29, 2008 Posts: 0 Comments: 29

720. Drakoen 6:54 PM GMT on September 03, 2011
UKMET model shifted northward. I wonder what's going on with that model. Member Since: October 28, 2006 Posts: 57 Comments: 29010

721. RobertM320 6:55 PM GMT on September 03, 2011
Quoting P451: If you are so upset about what occurs in a public forum where people share ideas may I suggest refraining from visiting the blog and consulting only the NHC statements when they come out? Seems like they may be more what you are looking for. Your opinion of my posting style is a misguided one and absurd description of them. I will post what I see and my opinions on them as things come. Just as anyone else. Because you don't share my views this disturbs you and has caused you to lay personal attacks in your replies. What you need to do is either accept the dynamic of a public forum or remove yourself from it if it upsets you so. +1 NHC statements are for info blogs are for sharing and discussing ideas and topics Member Since: September 27, 2007 Posts: 0 Comments: 111

722. WeatherNerdPR 6:55 PM GMT on September 03, 2011
Quoting P451: It's still active? I'm impressed. Can't possibly see it doing anything after early yesterday's brief window of opportunity. Looks good-ish. Not sure if it's still active, as that center fix is way outdated. Member Since: July 7, 2010 Posts: 0 Comments: 5464

724. Tazmanian 6:55 PM GMT on September 03, 2011
Quoting Levi32: The 12z ECMWF is radically different from the previous runs because it keeps Lee and his associated upper low/trough stranded over the center of the country instead of phasing northeastward towards New England. Day 7: now now now Levi your showing us a black box so your not showing us nothing thye no longer hot link from that site Member Since: May 21, 2006 Posts: 5088 Comments: 111360

725. Patrap 6:55 PM GMT on September 03, 2011
The Carburetor looks like its Giving it the Gas to me. TS Lee Floater - Rainbow Color Infrared Loop Member Since: July 3, 2005 Posts: 372 Comments: 111626

727. MississippiWx 6:56 PM GMT on September 03, 2011
Lee has recently been developing convection near the center. Will be interesting to see if it can continue. The 990mb pressure is interesting as well. Member Since: July 15, 2006 Posts: 14 Comments: 8651

728. Tazmanian 6:57 PM GMT on September 03, 2011
Quoting WeatherNerdPR: Looks good-ish. Not sure if it's still active, as that center fix is way outdated. invest_DEACTIVATE_al942011.ren has of 9/3/5:38PM Member Since: May 21, 2006 Posts: 5088 Comments: 111360

729. Levi32 6:57 PM GMT on September 03, 2011
Quoting Drakoen: UKMET model shifted northward. I wonder what's going on with that model. I'm rather disappointed with its performance on Irene and Katia...it's going to degrade my confidence in it for future central Atlantic storms this season. Member Since: November 24, 2005 Posts: 586 Comments: 25459

730. GTcooliebai 6:57 PM GMT on September 03, 2011
12Z CMC in line with 12Z Euro on Katia scraping the OBX & the CMC shows Lee spending at least another 2 days over NOLA before lifting out. Member Since: August 31, 2009 Posts: 0 Comments: 5203

731. Levi32 6:57 PM GMT on September 03, 2011
Quoting Tazmanian: now now now Levi your showing us a black box so your not showing us nothing thye no longer hot link from that site My bad...keep forgetting that lol. I fixed it. I wonder why he changed it back. Member Since: November 24, 2005 Posts: 586 Comments: 25459

732. WeatherNerdPR 6:57 PM GMT on September 03, 2011
Quoting trackawaytosea: could be 6 years without a hit in florida ThunderFart Bonnie ring a bell? Or are you talking hurricanes? lol Member Since: July 7, 2010 Posts: 0 Comments: 5464

733. EYEStoSEA 6:57 PM GMT on September 03, 2011
Member Since: September 16, 2010 Posts: 0 Comments: 1491

735. carcar1967 6:57 PM GMT on September 03, 2011
Quoting Termite3344: Howdy,, Going to take a Bud-Lite Break Hi neighbors, north of DS off of Hwy 1025 Member Since: June 9, 2011 Posts: 0 Comments: 99

736. redwagon 6:58 PM GMT on September 03, 2011
Firewinds in Austin now gusting to 25mph. Birds in treetops (I'm in a lake treehouse) not liking it. Member Since: August 4, 2007 Posts: 0 Comments: 1444

737. WeatherNerdPR 6:58 PM GMT on September 03, 2011
Quoting Tazmanian: invest_DEACTIVATE_al942011.ren has of 9/3/5:38PM Thanks Taz. :P Member Since: July 7, 2010 Posts: 0 Comments: 5464

738. Tazmanian 6:58 PM GMT on September 03, 2011
Quoting Levi32: My bad...keep forgetting that lol. I wonder why he changed it back. not sure that some in you have too ask him about Member Since: May 21, 2006 Posts: 5088 Comments: 111360

740. freeroam 6:58 PM GMT on September 03, 2011
Quoting Patrap: The Carburetor looks like its Giving it the Gas to me. TS Lee Floater - Rainbow Color Infrared Loop Ok, where is the dry air going there? Member Since: September 1, 2007 Posts: 0 Comments: 245

741. GTcooliebai 6:59 PM GMT on September 03, 2011
Quoting Drakoen: UKMET model shifted northward. I wonder what's going on with that model. Where do you have a link, raleighwx hasn't updated that model nor the NOGAPS model? Member Since: August 31, 2009 Posts: 0 Comments: 5203

742. Tazmanian 6:59 PM GMT on September 03, 2011
Quoting WeatherNerdPR: Thanks Taz. :P your welcome Member Since: May 21, 2006 Posts: 5088 Comments: 111360

744. Tazmanian 7:00 PM GMT on September 03, 2011
AL, 13, 2011090318, , BEST, 0, 292N, 921W, 50, 989, TS Member Since: May 21, 2006 Posts: 5088 Comments: 111360

745. Levi32 7:00 PM GMT on September 03, 2011
The 12z ECMWF and UKMET keep Lee very close to the Louisiana coast for the next 48 hours, allowing the storm to largely maintain its intensity and dump even more rain on the area. Member Since: November 24, 2005 Posts: 586 Comments: 25459

746. MiamiHurricanes09 7:00 PM GMT on September 03, 2011
Quoting Drakoen: UKMET model shifted northward. I wonder what's going on with that model. Looks like it. In pretty good agreement with the 12z NOGAPS. Member Since: September 2, 2009 Posts: 129 Comments: 19976

747. CCkid00 7:00 PM GMT on September 03, 2011
Quoting carcar1967: Hi neighbors, north of DS off of Hwy 1025 hi there.....off of Juban Road!! Member Since: August 22, 2008 Posts: 0 Comments: 266

748. will40 7:00 PM GMT on September 03, 2011
Quoting Tazmanian: now now now Levi your showing us a black box so your not showing us nothing thye no longer hot link from that site i see the image Taz Member Since: September 19, 2005 Posts: 2 Comments: 3439

749. Tazmanian 7:00 PM GMT on September 03, 2011
AL, 12, 2011090318, , BEST, 0, 196N, 564W, 60, 993, TS, Member Since: May 21, 2006 Posts: 5088 Comments: 111360

750. Drakoen 7:01 PM GMT on September 03, 2011
Quoting GTcooliebai: Where do you have a link, raleighwx hasn't updated that model nor the NOGAPS model? Just using the sfwmd hurricane plot page Link Member Since: October 28, 2006 Posts: 57 Comments: 29010

751. pcola57 7:01 PM GMT on September 03, 2011
Quoting wxobsvps: 12Z Euro looks like it may have a b Quoting Patrap: ...LEE STALLS JUST SOUTH OF LOUISIANA...HEAVY RAINS CONTINUE OVER SOUTHERN PORTIONS OF LOUISIANA...MISSISSIPPI...AND ALABAMA... 1:00 PM CDT Sat Sep 3 Location: 29.3°N 91.8°W Max sustained: 60 mph Moving: Stationary Min pressure: 991 mb Thats a fairly low pressure Pat.Makes my ears pop just thinking about it. Member Since: August 13, 2009 Posts: 13 Comments: 3867

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