Tropical Storm Lee moving ashore; Katia continues northwest

By: Dr. Jeff Masters , 1:53 PM GMT on September 03, 2011

Share this Blog
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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1421 - 1371

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43Blog Index

Hi everyone from a still dry North Houston. Any new info on Lee?
Member Since: Posts: Comments:
Quoting hurricanerunaway:


What is that coming straight towards the Bahamas and Florida on Tues in this loop?


K storm
Member Since: Posts: Comments:
1419. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting JLPR2:
Looks like Katia is making a comeback.


I agree, within an hour of a downgrade , katia is probably a hurricane again!
Member Since: Posts: Comments:
Quoting sarahjola:
can someone post the latest pressure readings for lee? thanks!


The lowest pressure has been 987.0 mb at Canal Locks station. The center is passing to the SW and the pressure there has just begun to rise.
Member Since: Posts: Comments:
Wind Shear lowering in front of Katia...Meanwhile, what is going on in the Eastern Pacific? Seriously, lol.

Member Since: Posts: Comments:
Quoting RitaEvac:


What is that coming straight towards the Bahamas and Florida on Tues in this loop?
Member Since: Posts: Comments:
1413. BEENE
Quoting SETexas74:


It looks like it's moving NNw


SETexas74 just spoke to my friend who lives in Center, TX - said they are getting heavy rain right now.
Member Since: Posts: Comments:
Quoting polarcane:


East side of Baytown


My cousin lives over there, just wondering. I spent every summer in Winnie when I was a kid.
Member Since: Posts: Comments:
1409. Patrap
....ummmmmmmmm, pie
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Birds are out and chirping now. Hope it stays this way!
Member Since: Posts: Comments:
1406. scott39
Quoting sarahjola:
can someone post the latest pressure readings for lee? thanks!
989mb
Member Since: Posts: Comments:
Pressure up some more at Canal Locks to 987.3 mb. Wind bending more to the south.
Member Since: Posts: Comments:
1404. will40
Quoting sarahjola:
can someone post the latest pressure readings for lee? thanks!



989 at 5 eastern
Member Since: September 19, 2005 Posts: 2 Comments: 4266
1403. Walshy
Quoting Patrap:
Is there Pie involved atmo?



Link
Member Since: Posts: Comments:
Quoting wxobsvps:
One thing of interest with the NAM...

We have mentioned here that the convection plume to the SE of the LLC, out over the central GoM, seems disjointed from Lee.

When you look at the NAM solution, it does just that... separates that energy, sending it up over the FL panhandle and NEwrd, while Lee comes back into the West Central GoM


Actually makes sense to do that, with a left behind low pressure lingering, until the next trough comes down to get it next week
Member Since: Posts: Comments:
Quoting Tazmanian:




oh made here made was it here boy friend lee?



any one else noted that whit little dot


LOL ROTFLMAO!!!
Member Since: Posts: Comments:
1400. Patrap
NAM-O-Doom
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting P451:


It looks to be pushing -85 to -87 there. Impressive.

I wonder if it could sustain itself. I think it might just follow the other convective bursts it's gone through due to the dry air problems around it.

But that is pretty amazing. Katia is a bit scary in how resilient she is. A lesser developed storm would be a pretty bad shape given that environment. There has always just been something about Katia that has been so well developed that it's been able to fight off a poor environment.



And conditions MAY improve over the coming days...

SHEAR (KT) 21 19 18 16 20 13 12 7 3 6 3 3 5

700-500 MB RH 54 52 51 49 48 47 50 50 52 54 59 60 57
Member Since: Posts: Comments:
I did an extreme closeup of the visible satellite for Lee and it looks like the low center I've been observing at Canal Locks is a meso-sized feature scooting WNW along the central Louisiana coast, almost paralleling the shore. Mostly a low cloud swirl.
Member Since: Posts: Comments:
can someone post the latest pressure readings for lee? thanks!
Member Since: Posts: Comments:
1396. Patrap
Is there Pie involved atmo?

Member Since: July 3, 2005 Posts: 426 Comments: 129093
1394. scott39
The debates are fun to watch on here. Im trying to learn when to take the bait and...... when not to. LOL
Member Since: Posts: Comments:
i wish we had a recon for the K storm
Member Since: May 21, 2006 Posts: 5091 Comments: 115362
1392. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129093
The local weather thing at the top says Alaska...I think Jeff lives in Ann Arbor, and if that is the case, they are getting some pretty bad storms right now.

Trees down.
Member Since: Posts: Comments:
Quoting Tazmanian:
a recon for a are K storm will be vary help full


Sure would, if they were stationed in St Croix.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:



the sun starting too set
Member Since: May 21, 2006 Posts: 5091 Comments: 115362
Quoting atmoaggie:
Well, the system is degrading and the strongest winds were never on the side BR-metro is and will be getting.

West, offshore and for long enough *could* bring you some stronger winds, but honestly, your strongest gusts will come from the odd cell that moves through. Very much like Gustav, but half the intensity, for the area.

(Howdy from Central...visiting fam there.)


Howdy, Thanks for the info
Member Since: Posts: Comments:
1387. KEEPEROFTHEGATE (Mod)
013L/TS/L/CX
MARK
29.98N/92.68W
Member Since: Posts: Comments:
1386. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Thanks RitaEvac
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: Posts: Comments:
1380. Walshy
Sarcasm Flag (ON)


Lee continues to edge north strengthening from the source of the Mississippi River.
Member Since: Posts: Comments:
Quoting Termite3344:


asking the experts, Zachary is North of Baton Rouge, but the way the satellite looks, if it does turn NE, we are still in the clear, and if it goes N, same, looks like only thing that would get worse would be due W, I am new that's why I ask you, want to learn,,
Well, the system is degrading and the strongest winds were never on the side BR-metro is and will be getting.

West, offshore and for long enough *could* bring you some stronger winds, but honestly, your strongest gusts will come from the odd cell that moves through. Very much like Gustav, but half the intensity, for the area.

(Howdy from Central...visiting fam there.)
Member Since: Posts: Comments:
How cool! These stations are 11 miles apart. KVNP is reporting WNW winds, while Canal Locks is reporting ESE winds.

The pressure at Canal Locks was 987.0 mb for 3 observations and has risen now to 987.1 mb. The center is between the two locations.
Member Since: Posts: Comments:
1377. KEEPEROFTHEGATE (Mod)
012L/TS/K/CX
MARK
19.88N/57.38W
Member Since: Posts: Comments:
Can someone provide a link to the NAM?
Member Since: Posts: Comments:
I wouldn't have downgraded Katia anyway...Has the classic hurricane look now, lol...

Member Since: Posts: Comments:
Quoting Walshy:


Some parts of the east coast really need water.

Western North Carolina needs 9-12inches to end the drought. I think Georgia needs rain too.

I understand that there are a lot of places that need rain, I guess my concern is the areas that have already received some and the storms to come.
Member Since: Posts: Comments:
Quoting Termite3344:
Here in Zachary La, the sun is out, can see some blue skies, High clouds are not moving, lower clouds are racing, wind is picking up. It's kinda is miss leading, any comments,,,

I am also concerned after viewing the NAM.
As someone said this would change the end result for Katia as well.
Member Since: September 1, 2007 Posts: 0 Comments: 249
Member Since: Posts: Comments:

Viewing: 1421 - 1371

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
59 °F
Overcast