Katrina falters, does not intensify overnight

By: Dr. Jeff Masters , 12:04 PM GMT on August 25, 2005

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The chances for Katrina undergoing a major rapid intensification and reaching Category 2 or Category 3 status now appear very dim. Katrina faltered overnight, and increased only slightly in intensity. Dry air on the west side continued to prevent convection from wrapping all the way around the storm, and some shearing also appeared to be occurring on the storm's west side.

However, Katrina is still expected to intensify today and reach Category 1 hurricane status by tonight or early Friday morning, when it makes landfall over South Florida. The storm slowed in forward speed some, giving it more time today over the very warm (31C) waters of the Gulf Stream. Other than the small amount of shear noted on her west side overnight, Katrina is in a low-shear environment, and the shear may decrease today. The combination of low shear and warm water may allow Katrina to strenthen rapidly into a Category 1 hurricane just before landfall. The Miami radar loop shows an increase in low-level banding during the past two hours, and an eye-like feature trying to form. Katrina is getting more organized. Upper level outflow looks pretty ragged on satellite imagery, but appears to be improving and slowing expanding.

The major threat to South Florida from Katrina is freshwater flooding from her rains. Rainfall amounts of 6 - 10 inches are expected from this slow-moving storm. For comparison, Hurricane Irene of 1999, which hit South Florida as a Category 1 hurricane, dumped 10 - 20 inches of rain. Damage from Irene was over $800 million in Florida. Damage from Katrina will probably be much lower, in the $30 - $100 million range, since Katrina's rainfall will be half of what Irene's was.

Once Katrina makes landfall early Friday morning, the storm will cross over the Florida Peninsula and re-emerge into the Gulf of Mexico. If her path in the Gulf allows her to remain over water for at least a day, Katrina could easily strengthen to a Category 1 or 2 hurricane before making her second landfall.

I'll make several updates today as new Hurricane Hunter data becomes available; I was unable to make many updates yesterday, as I was travelling.

For observations of what's happening now in South Florida, we have several bloggers writing today. If you're in South Florida and are blogging today, let me know where you are at so I can add you to this list:

turtlehurricane (Weston, Broward County)

sngalla (Fort Lauderdale)

MrJ76 (Okeechobee)

Zeenster (Cape Coral, SW Florida)

evolution (Charlotte Harbor, SW Florida)

Dr. Jeff Masters

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386. WPBHurricane05
1:45 AM GMT on August 24, 2008
StormTop nailed it LMAO!
Member Since: July 31, 2006 Posts: 56 Comments: 8112
385. sSnack
7:38 PM GMT on August 25, 2005
It's Officialy Hurricane Katrina (according to NHC)
384. txweather
6:25 PM GMT on August 25, 2005
Also my I add a suggestion. I read that some gas stations are pricegouging. In most states this is ILLEGAL. Call your authorities or at least document this gouging. These are the lowest of creatures to take advantage of a natural disaster.
383. txweather
6:16 PM GMT on August 25, 2005
Colasc, I don't agree with Stormtop. I personally think it will hit the panhandle. But, a New Orleans landfall can't be ruled out. Some models are trneding that way and with that Warm eddy out there it could be a disaster. Its doubtful, but can't be ruled out.
382. txweather
6:10 PM GMT on August 25, 2005
Well good news the press isn't dropping any, but with that pressure in these conditions it could get to 70/75 without anyfurth pressure drop.
381. IceSlater
6:10 PM GMT on August 25, 2005
http://www.weatherunderground.com/tropical/tracking/at200512_model.html Thats the link
Member Since: July 6, 2005 Posts: 0 Comments: 417
380. IceSlater
6:06 PM GMT on August 25, 2005
Look at the computer models... All together for 12 hours... Show a south motion... Just where though.
Member Since: July 6, 2005 Posts: 0 Comments: 417
379. COLASC
6:06 PM GMT on August 25, 2005
HERE GOES STORMFLOP AGAIN--- JUST REVERSE WHAT HE SAYS AND IT WILL PROBABLY BE RIGHT. I'M WAITING ON MY 300.00 THAT YOU WAGERED YESTERDAY!!! IT IS NOT GOING TO HIT NO!!
378. txweather
6:03 PM GMT on August 25, 2005
Actually in all seriousness it seems on the verge of actually getting its act together and will simply run out of time. But it could well get to cat1 but it will be really close.
377. JaxAdjuster
6:01 PM GMT on August 25, 2005
Thanks TX. Your last sentence helped explain the formula. I understand why velocity would be included in the equation. I can see how latitude will also have an impact since the effect changes as you go north or south. Now I have to do a little research on how latitude and longitude came about. I am sure that will help me understand why a sin of the latitude is used. I know a triangle is in there somewhere and the sin is used for a magnitude. The latitude must be an angle based off the equator. But I will figure that out.


Thanks for the equation. It helped a lot! According to this equation, the further north a storm moves, the greater the effect, even with a slower wind speed. Does this mean that the eye wall would likely get tighter as a storm moves north? Or, conversly, the eye wall could grow and the velocity go down?

Somehow this all plays out and it is fascinating. No wonder meteorologist need to be good at physics.

WOW! Thanks again! Well, I'm off for a while. I'm going fishing. I'll check back in later.

I really appreciate the tutoring lessons.
376. txweather
6:00 PM GMT on August 25, 2005
Well txweather giveth and tx weather taketh. I've taken Katrina off the eye list. It doesn't have an eye by any stretch of the imagination. But this could change. Sorry I couldn't resist doing at least one joke on the 2000 election.
375. IceSlater
5:57 PM GMT on August 25, 2005
Lefty,

The new eye is forming south of the word Ft. Lauderdale... what do u think
Member Since: July 6, 2005 Posts: 0 Comments: 417
374. txweather
5:38 PM GMT on August 25, 2005
Jax,
Coriolis = 2*(Omega)*velocity*Sin(latitude)
Omega is the Angular Speed of Rotaion of Earth and is constant so the only variable in the eq are Latitude and Velocity.

Thus the faster you go the greater effect and the further north you are the greater the effect(since Sine goes from 0-1 in the North hemisphere)

Note Corilis work perpendicular to the motion so if you are heading e it deflects to the south.
373. JaxAdjuster
5:34 PM GMT on August 25, 2005
LOL! This blog has gone down the toilet. That was a funny line. Thanks again for all the help folks. I have learned a tremendous amount the last couple of days.
372. weatherguy03
5:33 PM GMT on August 25, 2005
I think she does. I am thinking she will come into the Big Bend area of Florida. But also I am alittle skeptical, where it may turn NE towards the end, and come in more towards Appalachia Bay to Cedar Key area. But it should have time to reintensify to CAT2, tough one to call for West Coast of Fl...I will see ya all later..i am at wok..busy today..
Member Since: July 5, 2005 Posts: 590 Comments: 29698
371. 53rdWeatherRECON
5:33 PM GMT on August 25, 2005
Link RAPID INTENSIFICATION OCCURING. Forget the radar. It is only showing you the rain drops.
Member Since: August 5, 2005 Posts: 2 Comments: 80
370. icebear7
5:33 PM GMT on August 25, 2005
gee.... Caps Lock Boy seems awfully confident about this....and i seem to have developed a headache suddenly
Member Since: August 20, 2005 Posts: 0 Comments: 5
369. StormJunkie
5:32 PM GMT on August 25, 2005
Moving to new blog?
Member Since: August 17, 2005 Posts: 26 Comments: 15644
368. stormydee
5:31 PM GMT on August 25, 2005
oh no, I chkd the wave below katrina, I think I see a spin maybe around 21 & 69...can someone check and see if I am seeing correctly?
Member Since: August 25, 2005 Posts: 39 Comments: 517
367. StormJunkie
5:31 PM GMT on August 25, 2005
Icebear-pay the 5$ to become a wunderground memeber. No adds and you can get a much longer radar loop. Just set the frames to 40 for the miami radar. It is well worth it. I do not think I will use a NOAA radar again for a long while.
Member Since: August 17, 2005 Posts: 26 Comments: 15644
366. FLCrackerGirl
5:31 PM GMT on August 25, 2005
dr masters new post is up
Member Since: August 12, 2004 Posts: 47 Comments: 597
365. leftyy420
5:31 PM GMT on August 25, 2005
wow storm top thats a out there forcast. i see cat 3 but don;t think she could make it past that due to the 12 reorginisation she will undergo after she gets back over water followed by a 3-6 lull, so i dunno know bout that
Member Since: August 24, 2005 Posts: 35 Comments: 1987
364. willdd1979
5:29 PM GMT on August 25, 2005
bigdrvr your question about the lakes impact on Katrina I can answer it by saying that because it's shallow but it's also water that it would keep Katrina from loosing strength too rapidly. I am in NC and Fran came over Fayetteville (my city) and the week before we had flooding rains well Fran intensified (just a little) when it moved over flooded fayetteville.
363. StormJunkie
5:28 PM GMT on August 25, 2005
Weatherguy what is your take on what happens when and if she gets in the gulf. Does she make it far enough off prior to the turn to pick up a full head of steam?
Member Since: August 17, 2005 Posts: 26 Comments: 15644
362. STORMTOP
5:28 PM GMT on August 25, 2005
Posted By: STORMTOP at 12:NOON CDT on August 25, 2005.
STORMTOPS NWS BULLETIN

OBSERVATIONS TODAY HAS SEEN KATRINA DEEPENING IN HER PRESSURE FROM LAST NIGHT AND HAS BEEN GAINING STRENGTH SLOWLY..KATRINA IN THE NEXT 4 HOURS WILL HAVE AND EXPLOSIVE DEVELOPMENT..THE WINDS SHOULD BE 95 MPH BEFORE WINDING DOWN EARLY TOMORROW..THE MOST IMPORTANT THING IS KATRINA WILL NOT STALL THE HIGH PRESSURE GUIDING IT IS QUITE STRONG AND AS KATRINA APPROACHES I WOULD NOT AT ALL BE SURPRISED TO SEE A WSW OR SW MOTION TOWARDS MIAMI..SO HEADS UP MIAMI AND THE KEYS YOU ARE FOR FROM BEING OUT THE WOODS WITH KATRINA.. KATRINA HAS BEEN MOVING ON A STRAIGHT WEST HEADING BUT LIKE I SAID THAT COULD CHANGE IN THE NEXT 4 HOURS AS THE HIGH BECOMES MORE OF A AFFECT AND THE STRENGTHNING PROCESS BEGINS..LET ME EXPLAIN WHY I FEEL THIS WAY..KATRINA HAS ALREADY BEEN UNDER THE INFLUENCE OF THIS VERY STRONG EAST TO WEST HIGH PRESSURE SYSTEM WHICH I PERSONALLY THINK THE NHC DOES NOT REALLY KNOW HOW STRONG THIS HIGH WILL BE...I THINK KATRINA WILL START MOVING WSW LATER IN THE 48 HOUR PERIOD COMING OFF SHORE IN THE SOUTHESATERN GULF SOMEWHERE IN THE MIDDLE KEYS AS A CAT 1...I EXPECT THE WINDS TO BE 70 MPH BY 1PM TODAY AND A FULL FLEDGED HURRICANE AT 80MPH BY 3PM AND 95MPH WHEN KATRINA SUCKS UP THE WARM GULSTREM JUST BEFORE HITTING SOUTHERN FLORIDA..AFTER THAT KATRINA WILL NOT SLOW DOWN AS EVERYONE IS EXPECTING IT WILL CONTINUE TO MOVE IN A WEST DIRECTION AT 6 TO 8 MPH UNTIL 85 DEGRESS THEN MAKE ITS TURN TOWARDS THE WNW SATURDAY NIGHT AS KATRINA STRENGTHENS INTO A DANGEROUS CAT 3 HURRICANE WITH WINDS APPROACHING 115MPH...ON SUNDAY A COOL FRONT WILL DROP DOWN FROM THE ROCKIES AND WEAKEN THE HIGH THAT IS NOW OVER LA MS ALABAMA..THE HIGH WILL RETREAT BACK INTO TEXAS AND THIS WILL CAUSE KATRINA TO MAKE THE FINAL TURN TOWARDS THE NW AS THE HIGH IS PUSHED WESTWARD INTO TEXAS...SUNDAY MORNING A HURRICANE WATCH WILL BE ISSUED FROM MOUTH OF THE MISS TO PENSECOLA FLORIDA..KATRINA BY THIS TIME WILL BE A CAT 4 WITH WINDS APPROACHING 145MPH BY SUNDAY NIGHT AS SHE NEARS A LANDFALL...THE GREATEST THREAT FOR HURRICANE WARNINGS WILL BE FROM PASS CHRISTIAN TO PENSECOLA FLORIDA.....MY PREDICTION KATRINA MOVES ON SHORE MONDAY NIGHT WITH WINDS OF 170MPH NEAR PASS CHRISTIAN MISS...THIS IS A SERIOUS SITUATION FOR BOTH MISS,LA,ALABAMA, AND THE FLORIDA PANHANDLE..A CAT 5 COULD BRING 15 TO 20 INCHES OF RAIN TO THE NORTH AND NE GULF COAST WITH CATOSTROPHIC WINDS AND NOT TO MENTION THE TIDAL SURGE WHERE EVER THE STORM CROSSES THE COAST....THATS THE LATEST THINKING RIGHT NOW ILL BE BACK WITH ANOTHER UPDATE ABOUT 11PM TONIGHT AFTER I READ MORE NEW DATA COMING IN...FOLKS I CANT STRESS THIS ENOUGH WHEN KATRINA GETS OVER THE GULF SHE WILL BE OVER IT FOR 2 WHOLE DAYS IN 89-95 DEGREE TEMPS..PLEASE TAKE ALL NECESSARY PRECAUTIONS AGAINST THIS RECORD BREAKING HURRICANE....KATRINA WILL BE ONE TO REMEMBER...
361. leftyy420
5:27 PM GMT on August 25, 2005
yeah i see no drop less than 40 mph unless she stalls and with a well defined circulation she would have no trouble reorginising over thet sizziling gulf
Member Since: August 24, 2005 Posts: 35 Comments: 1987
360. icebear7
5:27 PM GMT on August 25, 2005
this is the map thingie i have been staring at Link
Member Since: August 20, 2005 Posts: 0 Comments: 5
359. stormydee
5:27 PM GMT on August 25, 2005
that dry air has been lingering all morning, it is not killing it, only slowing down intesification...if it weren't there, she'd probably be at least 85mph by now...
Member Since: August 25, 2005 Posts: 39 Comments: 517
358. IceSlater
5:27 PM GMT on August 25, 2005
Yep, looks like the eye is closing!
Member Since: July 6, 2005 Posts: 0 Comments: 417
357. weatherguy03
5:26 PM GMT on August 25, 2005
Lefty is correct on movement..It is still due west..Also if you look at WV it looks like the High to the north as made its final southern push, now starting to exit to the east. I would doubt this would move much farther south anymore. By the time landfall occurs we may start to see a slight WNW motion, but again slow mover, so may be erratic.
Member Since: July 5, 2005 Posts: 590 Comments: 29698
356. icebear7
5:26 PM GMT on August 25, 2005
that gap of air is getting bigger, between the west palm beach and ft lauterdale words
Member Since: August 20, 2005 Posts: 0 Comments: 5
355. StormJunkie
5:25 PM GMT on August 25, 2005
I do not think she will drop below 40 to 50 mph winds period. Lake or no Lake. Lots of warm water all around her and the only verticle height is the trees.
Member Since: August 17, 2005 Posts: 26 Comments: 15644
354. leftyy420
5:25 PM GMT on August 25, 2005
here is a couple links to the 4winds site so you can see real time wind data. most of you migth have something like this but this is what i use during landfalls i ma not chasing

Link

Link
Member Since: August 24, 2005 Posts: 35 Comments: 1987
353. icebear7
5:23 PM GMT on August 25, 2005
it does look like it is closing
Member Since: August 20, 2005 Posts: 0 Comments: 5
352. raindancer
5:23 PM GMT on August 25, 2005
In the last few frames - the so-called eye has filled - dry air on the north side is killing it. We may not get a hurricane yet.
Member Since: September 14, 2001 Posts: 0 Comments: 79
351. leftyy420
5:23 PM GMT on August 25, 2005
hard to say what impact the lake would have but would def help maintain the strength but not by much. i see the wobble south and it seems the whole storm is with this wobble this time but i am wating for another hour or 2 of movement befor i say for sure if she is moving southward
Member Since: August 24, 2005 Posts: 35 Comments: 1987
350. StormJunkie
5:22 PM GMT on August 25, 2005
Ice, 5 frames at 5 to 8 miles per hours shows no real movement. Radar frames are not seperated by more than about 5 minutes. That is less than 8 miles of movement if she is moving at 8mph. Hence the reason I wanted longer radar loops which the 5$ to wunderground gave me.
Member Since: August 17, 2005 Posts: 26 Comments: 15644
349. stormydee
5:22 PM GMT on August 25, 2005
look again Ice..the wall is caving in on ft lauderdale name, poss reforming and strengthening...
Member Since: August 25, 2005 Posts: 39 Comments: 517
348. icebear7
5:21 PM GMT on August 25, 2005
is that it, right on the "E" and "R" ?
Member Since: August 20, 2005 Posts: 0 Comments: 5
347. bigdrvr
5:21 PM GMT on August 25, 2005
A question I had thought about is what if the center of Katrina were to go inland and move slowly over Lake Okeechobee...Obviously the lake is a shallow one, but its waters are pretty warm..Would it have the heat content needed to maintian it as a tropical storm?
346. leftyy420
5:21 PM GMT on August 25, 2005
thats really hard to say cause the storms speed will determine when she feel that weakness. i think she will not turn till in the gulf and i feel a pnhandle second landfall is likly but we have to watch
Member Since: August 24, 2005 Posts: 35 Comments: 1987
345. stormydee
5:19 PM GMT on August 25, 2005
lefty, you got things pegged so far today...when do you think it will go north?
Member Since: August 25, 2005 Posts: 39 Comments: 517
344. IceSlater
5:19 PM GMT on August 25, 2005
Lefty,

That eye is about to go under the word Ft. Lauderdale on the radar...
Member Since: July 6, 2005 Posts: 0 Comments: 417
343. leftyy420
5:19 PM GMT on August 25, 2005
movment is based on a 3hr consensus when it comes to traking puposes
Member Since: August 24, 2005 Posts: 35 Comments: 1987
342. StormJunkie
5:19 PM GMT on August 25, 2005
Also-How much will she weaken over the swamp lands with very hot gulf on E and hot Atlantic on W?
Member Since: August 17, 2005 Posts: 26 Comments: 15644
341. IceSlater
5:18 PM GMT on August 25, 2005
111pm image shows a bit south again... Please let me know if you see this... I mean, you keep saying wobble... but doesn't five wobbles make a move?
Member Since: July 6, 2005 Posts: 0 Comments: 417
340. leftyy420
5:17 PM GMT on August 25, 2005
eyes in visible form at 60-65mph so a visible eye is not a good indication of strength, but due to the depper wall intensity i could see here getting close to that 74mph threshhold
Member Since: August 24, 2005 Posts: 35 Comments: 1987
339. stormydee
5:17 PM GMT on August 25, 2005
my fear is it won't make it across the state before it starts back north. this slowness bothers me...doesn't look like its going south yet or if it will at all..watching it follow the ft lauderdale name on the miami doppler...and the deeper convection is continueing to wrap around the center...
Member Since: August 25, 2005 Posts: 39 Comments: 517
338. StormJunkie
5:17 PM GMT on August 25, 2005
WHat is everyones take on the models shifting W before making the N/NNE turn? This could be real bad if it does get a 100+ miles into the gulf before turning.
Member Since: August 17, 2005 Posts: 26 Comments: 15644
337. icebear7
5:16 PM GMT on August 25, 2005
think the winds will pick up rapidly from now on ?
Member Since: August 20, 2005 Posts: 0 Comments: 5
336. Cavin Rawlins
5:15 PM GMT on August 25, 2005
I can see an eye forming why isnt it a hurricane yet. Is there a plane put the storm.
Member Since: July 24, 2005 Posts: 407 Comments: 19076

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