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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1201. DeMango 9:03 PM GMT on September 03, 2011
Quoting jrweatherman: do we have to keep post the radar every 2 minutes? We get it, it's raining in Louisiana. +1! Member Since: September 11, 2008 Posts: 0 Comments: 12

1202. ncstorm 9:03 PM GMT on September 03, 2011
Member Since: August 19, 2006 Posts: 7 Comments: 8408

1204. pcola57 9:03 PM GMT on September 03, 2011
Quoting MiamiHurricanes09: Soggy Lee...lol. LOL! Like Stagger Lee,I get it.. Member Since: August 13, 2009 Posts: 13 Comments: 3814

1205. TropicalAnalystwx13 9:03 PM GMT on September 03, 2011
Rob Lightbown has done good with his landfall areas so far this season...He has the NC/SC coasts, the Bahamas, central/southern Florida, the Greater Antilles, the Yucatan peninsula, and the coasts of LA/MS/FL panhandle. There is a little area in SE Texas, we'll see if it plays out... Bahamas: Bret, Emily, Irene Yucatan peninsula: Don, Harvey LA/MS/FL: Lee NC/SC/FL: Irene Greater Antilles: Emily, Irene Member Since: July 6, 2010 Posts: 89 Comments: 25274

1206. Patrap 9:03 PM GMT on September 03, 2011
.."been a long time since we Rock and Rolled".. Member Since: July 3, 2005 Posts: 370 Comments: 111297

1207. RitaEvac 9:04 PM GMT on September 03, 2011
Just came in from watering the back yard, lol, while the rain is so close bet yet so far Member Since: July 14, 2008 Posts: 1 Comments: 8894

1208. earthlydragonfly 9:05 PM GMT on September 03, 2011
Quoting tropicfreak: She spawned a few tornadoes in the Richmond VA metro area, one passed 2 miles to my NW. A very small vortex passed in my backyard that knocked down a shed twisted a couple of branches of a tree and flipped over my push mower... Here in Central Fl. Member Since: July 1, 2005 Posts: 10 Comments: 1649

1209. treehuggingsister 9:06 PM GMT on September 03, 2011
Quoting Patrap: .."been a long time since we Rock and Rolled".. A long lonely, lonely, lonely, lonely time... Member Since: August 18, 2006 Posts: 0 Comments: 188

1210. pcola57 9:06 PM GMT on September 03, 2011
Quoting Patrap: .."been a long time since we Rock and Rolled".. "Zepplin" Member Since: August 13, 2009 Posts: 13 Comments: 3814

1211. 69Viking 9:06 PM GMT on September 03, 2011
Quoting DeMango: +1! Guess what it's raining in Florida too! Member Since: August 25, 2006 Posts: 0 Comments: 2247

1212. hahaguy 9:06 PM GMT on September 03, 2011
Quoting TropicalAnalystwx13: Rob Lightbown has done good with his landfall areas so far this season...He has the NC/SC coasts, the Bahamas, central/southern Florida, the Greater Antilles, the Yucatan peninsula, and the coasts of LA/MS/FL panhandle. There is a little area in SE Texas, we'll see if it plays out... Bahamas: Bret, Emily, Irene Yucatan peninsula: Don, Harvey LA/MS/FL: Lee NC/SC/FL: Irene Greater Antilles: Emily, Irene Irene didn't really affect us here in south florida. So I wouldn't count us as being affected. Member Since: August 12, 2007 Posts: 2 Comments: 2838

1214. ncstorm 9:07 PM GMT on September 03, 2011
Look at the white line..is every area that is impacted by a landfall this season have a 1-2 punch? Member Since: August 19, 2006 Posts: 7 Comments: 8408

1216. BaltimoreBrian 9:07 PM GMT on September 03, 2011
Yes tropicfreak, really. Lee doesn't look like a hurricane to me with that big dry sector. No CDO, no eye. However, pressure is continuing to fall at the Fresh Water Canal Locks station, to 988.0 mb / 29.18". Lee may tighten up as he moves ashore the way Cindy did, although I think hurricane strength is very unlikely. Member Since: August 9, 2011 Posts: 25 Comments: 3311

1217. EYEStoSEA 9:07 PM GMT on September 03, 2011
WNerdPr....you seem to have your own little system there in PR :P Member Since: September 16, 2010 Posts: 0 Comments: 1491

1219. TropicalAnalystwx13 9:08 PM GMT on September 03, 2011
Watch out Houston/Galveston, looks like you guys MAY see some rainfall over the next few hours...So close, but to them, so far away... Member Since: July 6, 2010 Posts: 89 Comments: 25274

1221. Walshy 9:08 PM GMT on September 03, 2011
The NWS has issued 56 Tornado Warnings since Tropical Storm Lee approached the coast yesterday! - Jessee Ferrel from Accuweather Member Since: May 17, 2009 Posts: 2 Comments: 618

1222. Levi32 9:08 PM GMT on September 03, 2011
Quoting TropicalAnalystwx13: Rob Lightbown has done good with his landfall areas so far this season...He has the NC/SC coasts, the Bahamas, central/southern Florida, the Greater Antilles, the Yucatan peninsula, and the coasts of LA/MS/FL panhandle. There is a little area in SE Texas, we'll see if it plays out... Bahamas: Bret, Emily, Irene Yucatan peninsula: Don, Harvey LA/MS/FL: Lee NC/SC/FL: Irene Greater Antilles: Emily, Irene Well no offense but he might as well have just said there would be increased landfall potential in the SW Atlantic basin this year....which is basically what I said in my pre-season ideas. He essentially colored the entire map there in the areas that climatologically get hit anyway. Member Since: November 24, 2005 Posts: 586 Comments: 25443

1224. RitaEvac 9:09 PM GMT on September 03, 2011
Good Lee, keep sucking that dry air outta TX, suck it out so much that you will change the pattern and buckle the atmosphere for our premier flooding event that is gonna have to take place Member Since: July 14, 2008 Posts: 1 Comments: 8894

1225. Patrap 9:09 PM GMT on September 03, 2011
Quoting Walshy: The NWS has issued 56 Tornado Warnings since Tropical Storm Lee approached the coast yesterday! - Jessee Ferrel from Accuweather One predict yesterday morn was 55 t0 65 from one forecaster who does that. Via Angela Fritz on Twitter Member Since: July 3, 2005 Posts: 370 Comments: 111297

1226. jascott1967 9:09 PM GMT on September 03, 2011
A little wind here in Kemah, TX, no rain today but the winds have not been too severe so that is good. With all the dead and dying trees, the last thing we need is a lot of strong gusts. So thank you Lee for that! Member Since: August 16, 2007 Posts: 0 Comments: 516

1228. tropicfreak 9:09 PM GMT on September 03, 2011
Quoting trackawaytosea: WHERE WILL THEY SAY THAT KATIA WILL MAKE LANDFALL ? A) south florida B) central east coast florida C) north florida D) south georgia E) north georgia F) s. carolina G) n.casrolina H) virginia I) delaware J) new jersey K) new york as another cat 3 L) iceland M) or ALL OF THE ABOVE ON DIFFERENT DAYS? N: Banned. Member Since: September 2, 2006 Posts: 110 Comments: 6566

1229. wareaglesprinkle2 9:09 PM GMT on September 03, 2011
Quoting TropicalAnalystwx13: Rob Lightbown has done good with his landfall areas so far this season...He has the NC/SC coasts, the Bahamas, central/southern Florida, the Greater Antilles, the Yucatan peninsula, and the coasts of LA/MS/FL panhandle. There is a little area in SE Texas, we'll see if it plays out... Bahamas: Bret, Emily, Irene Yucatan peninsula: Don, Harvey LA/MS/FL: Lee NC/SC/FL: Irene Greater Antilles: Emily, Irene Member Since: July 27, 2011 Posts: 0 Comments: 2

1230. pcola57 9:09 PM GMT on September 03, 2011
Quoting trackawaytosea: WHERE WILL THEY SAY THAT KATIA WILL MAKE LANDFALL ? A) south florida B) central east coast florida C) north florida D) south georgia E) north georgia F) s. carolina G) n.casrolina H) virginia I) delaware J) new jersey K) new york as another cat 3 L) iceland M) or ALL OF THE ABOVE ON DIFFERENT DAYS? P hate to say it,but you forgot Canada...I'm just guessing but I'll vote for Canada... Member Since: August 13, 2009 Posts: 13 Comments: 3814

1233. CaribBoy 9:11 PM GMT on September 03, 2011
...KATIA SPARRING WITH STRONG UPPER-LEVEL WINDS...KNOCKED DOWN TO A TROPICAL STORM FOR THE SECOND TIME... ...SOGGY LEE LUMBERING NORTHWARD TOWARD SOUTHERN LOUISIANA... TROPICAL STORM WARNING EXTENDED EASTWARD... INSPIRED NHC Member Since: October 6, 2007 Posts: 0 Comments: 2846

1234. BaltimoreBrian 9:11 PM GMT on September 03, 2011
Pressure down some more. 987.7 mb. 29.17". I wonder how accurately this sensor is calibrated. Anyway this is the station to watch. Member Since: August 9, 2011 Posts: 25 Comments: 3311

1236. ncstorm 9:11 PM GMT on September 03, 2011
Quoting Levi32: Well no offense but he might as well have just said there would be increased landfall potential in the SW Atlantic basin this year....which is basically what I said in my pre-season ideas. He essentially colored the entire map there in the areas that climatologically get hit anyway. yep pretty much..but his actual text forecasts called for about everything to go into the GOM.. Member Since: August 19, 2006 Posts: 7 Comments: 8408

1237. cruzinstephie 9:12 PM GMT on September 03, 2011
Quoting TropicalAnalystwx13: Rob Lightbown has done good with his landfall areas so far this season...He has the NC/SC coasts, the Bahamas, central/southern Florida, the Greater Antilles, the Yucatan peninsula, and the coasts of LA/MS/FL panhandle. There is a little area in SE Texas, we'll see if it plays out... Bahamas: Bret, Emily, Irene Yucatan peninsula: Don, Harvey LA/MS/FL: Lee NC/SC/FL: Irene Greater Antilles: Emily, Irene There is a red line on at least part of every hurricane prone area on the CONUS and Caribbean. Of course he has done "good." He would be right no matter where a tropical system went. Member Since: August 31, 2008 Posts: 0 Comments: 23

1238. canehater1 9:12 PM GMT on September 03, 2011
Ok Lee youve earned your own theme song... Link Member Since: September 8, 2008 Posts: 1 Comments: 675

1241. pcola57 9:13 PM GMT on September 03, 2011
Quoting P451: It's just another reason to put thought into the chance that Lee is just not a purely tropical system anymore. (Myself, I don't think it is, and hasn't been for some time, and heading further away as well) These are the storms that we know so little about...not that we know much about tropical storms either..studying nature can be a very humbling experience...JMO Member Since: August 13, 2009 Posts: 13 Comments: 3814

1242. tropicfreak 9:13 PM GMT on September 03, 2011
Admin please get rid of trackawaytosea! Member Since: September 2, 2006 Posts: 110 Comments: 6566

1243. KEEPEROFTHEGATE (Mod) 9:13 PM GMT on September 03, 2011
Member Since: July 15, 2006 Posts: 143 Comments: 40474

1244. Walshy 9:13 PM GMT on September 03, 2011
(1985 Danny)Still like 2005 Cindy Analog Better.. Member Since: May 17, 2009 Posts: 2 Comments: 618

1245. jascott1967 9:13 PM GMT on September 03, 2011
Quoting Walshy: The NWS has issued 56 Tornado Warnings since Tropical Storm Lee approached the coast yesterday! - Jessee Ferrel from Accuweather A tornado from a hurricane is more likely going to be an EF0 or EF1. They are almost always weak and short-lived. Member Since: August 16, 2007 Posts: 0 Comments: 516

1247. KEEPEROFTHEGATE (Mod) 9:13 PM GMT on September 03, 2011
Member Since: July 15, 2006 Posts: 143 Comments: 40474

1248. freeroam 9:14 PM GMT on September 03, 2011
Quoting Patrap: One predict yesterday morn was 55 t0 65 from one forecaster who does that. Via Angela Fritz on Twitter Pat, what ya think? http://raleighwx.americanwx.com/models/nam/18znam5 00mbHGHTNANAMLoop.html Member Since: September 1, 2007 Posts: 0 Comments: 245

1249. BaltimoreBrian 9:14 PM GMT on September 03, 2011
Tropical storm wind probabilities kissing over Georgia. Member Since: August 9, 2011 Posts: 25 Comments: 3311

1250. Hou77083 9:14 PM GMT on September 03, 2011
Quoting TropicalAnalystwx13: Watch out Houston/Galveston, looks like you guys MAY see some rainfall over the next few hours...So close, but to them, so far away... Don't tease us, You know we need the rain bad! Member Since: July 5, 2010 Posts: 0 Comments: 86

1251. TexasMariner 9:14 PM GMT on September 03, 2011
Looking like lee has ended up further eastward than it is supposed to be Going to see some high winds and maybe some much needed rain here in Galveston tonight. Member Since: August 25, 2011 Posts: 0 Comments: 54

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