07/05/05 -- TALK: Hurricane Dennis

hurr. dennis

in the last few satelite images dennis has developed a visible eye and continues to look more and more organized. anybody else thinking that this thing just might become a major hurricane before hitting jamaica?
 
I think it's very probable we'll have something AOA 100mph by the time it hits Jamaica, though I'll want to watch the look of it over the next few hours... the next six or so are critical. Rapid intensification looks like it may be getting underway as dry air was entrained earlier.

I am concerned with how much people may base their preparedness over what happens in the next 24 hours or so. It's been clear from history that intensity forecasts are not reliable past 72 hours. However, there's plenty of attention on this storm by the media at present. The current landfall intensity (if it hits the middle gulf coast) is about 115mph. Is this a "bad" storm in the layman's eyes after last year's activity in Florida? I would say a Cat 3 is a hurricane that you need to evacuate from. I am just concerned after what happened with Ivan that folks will not treat this seriously if the forecast remains a Cat 3 or lower.

Was hoping for more rain in TX after seeing the Euro ensembles last night.

(ADD: Since we're in Talk at this point... how well does the Orleans area handle rain like we saw last night with Cindy. The thing stalled for a period of time. I assume flooded areas return to normal quickly. Might come up as a point later if Dennis gets close to that area.)
 
Originally posted by Morgan Palmer
I am just concerned after what happened with Ivan that folks will not treat this seriously if the forecast remains a Cat 3 or lower.
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I don't get your thinking here. Ivan did quite a bit of damage. There is still extensive damage to coastal areas and there was quite a bit of damage well inland from Ivan as well. I have talked to a lot of people in the area. I think they will be prepared to evacuate.

I think that Dennis may be a minimal cat4 at least by US lanfall somewhere just west of Mobile bay.
 
I guess the bigger problem is that some people over-reacted with Arlene earlier in June. No winds were sustained over 37 kts or so, even though the storm was labeled a strong tropcial storm. But overall, I think most people understand what a hurricane can do, and they should listen to evacuation orders. I guess the fact that public safety officials themselves leave when winds approach strong tropical storm force, leaving anyone who dials 911 helpless, would act to convince some of the skeptics to leave.
 
Originally posted by cedwards
I think that Dennis may be a minimal cat4 at least by US lanfall somewhere just west of Mobile bay.
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IMO Dennis will be a Cat 3 or a strong Cat 2. Though many weather fanatics think this will be a Cat 4 (or even a Cat 5 by one account), we must be realistic here, not wishful (if you hope that it will be strong). (BTW, I know that you do not truly wish for a Cat 5 Dennis directly hitting New Orleans, but I do know that some others do.)

GOM waters are still fairly cool, and though Cindy and Arlene have little upwelling impact, any will hamper Dennis. Now, look at Lili and Ivan. Both were strong but suddenly weakened as they approached the shallow waters of the Gulf Coast. Shear will be increasing as Dennis will approach the coast, and TPC indicates this. In addition, TPC usually underestimates the weakening when a major hurricane weakens near the coast (look at Isabel, Frances, Lili, and Ivan).

TPC usually underestimates the intensification of strong TC's (possibly on purpose to prevent the public from panicking), so I do fully expect Dennis to reach Cat 4 strength. After all, the pressure is rapidly decreasing, SST's are extremely warm, and shear will be low for the next few days.

On the other hand, right now, though Dennis is trying its hardest to form an eye, based on hurricane hunter reports, the eye is still open in the south and west quadrants. Dry air is still being entrained in the western quadrant, based on satellite images. And land interaction from Hispaniola, Jamaica, and Cuba won't help it either.

P.S. Shouldn't the title be changed from "Tropical Storm Dennis" to "Hurricane Dennis"?
 
Well, I think it's time the forum name was changed to HURRICANE Dennis, since it's been almost 8 hours since he was named one. :lol:
The satellite presentation shows Dennis intensifying fairly rapidly. The last scan of the Infrared satellite loop I believe I saw the eye beginning to open up and break through the high level clouds. I would not be surprised at all if Dennis is at 85 knots, possibly as high as 95 knots as he passes over or just to the north of Jamaica. I also believe that Jamaica won't have too much effect on Dennis; it may lower windspeeds five knots or so, but with the abnormally warm SST's Dennis will recover and recover quickly from almost any of the land masses he could possibly encounter on his rampage towards the Gulf of Mexico (save Central Cuba, which he will most likely avoid; the eye looks to cross between Havana and the western tip of Cuba at this time. That is flat terrain there and Dennis won't sustain any lasting damage from that crossing.)
After that it's wide open all the way to the Gulf Coast, as we well know. The media is currently trying to downplay the situation by saying that Dennis is only forecast to be a Cat 3 when he makes landfall. They are just trying to avoid starting a panic along the Gulf Coast. And after last year's hurricane hullabaloo, they may be making a wise choice.
My current predictions are that hurricane wary residents will begin leaving Friday and Saturday in small numbers, and then late Saturday and Sunday especially depending on the track, speed and strength of Dennis (likely at least high end Cat 3/minimal Cat 4, making landfall between New Orleans and Pensacola) the evacuations will begin. It will be a massive evacuation whichever way it heads, but if it makes a beeline for New Orleans we could potentially have the largest 'cane evacuation in history on our hands. The storm surge will be at least as bad as Ivan's, if not more on a scale closer to Camille's(God forbid). All around it looks like Monday afternoon and evening the eye of Dennis will roar onto the central Gulf Coast somewhere along that 200 mile stretch of coastline with winds between 105 and 125 knots and 12 to 20 foot storm surge. It will be devastating, even if it is just a Cat 3; we all know what Ivan did to Pensacola. :shock: I know I'll be praying for the residents of coastal Louisiana, Missisppi, Alabama and the Florida Panhandle the next couple nights. They'll need it. :(
 
Originally posted by cedwards
Ivan did quite a bit of damage. There is still extensive damage to coastal areas and there was quite a bit of damage well inland from Ivan as well. I have talked to a lot of people in the area. I think they will be prepared to evacuate.
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Absolutely... Gulf Shores to Pensacola took a beating. Perdido Key is still a ghost town.

Many places here are already sold out of generators..... the tropics are now being taken very seriously in the area.

The weather weenie/chaser part of me hopes this storm comes right at me much like Ivan, Arlene and Cindy did, but the John Q. Public side of me, having many friends in this area as well as interests of my own here (particularly fishing), hopes this goes somewhere else. But hopefully not New Orleans. All my family is in LA.

If Pensacola/GulfShores gets hit again by a Cat 3 or greater, I really dont see the area rebuilding into the tourism/vacation focal point that it once was. People will be too discouraged, bankrupt, and gun-shy to try and rebuild.
 
In the current "hurricane culture," there always seems to be a lot of emphasis on warm SST's as the deciding factor of whether or not a hurricane will intensify. Research has indicated that this is not the case. Yes, 26 degree C water at over 100 m depth is needed for genesis of a tropical cyclone, BUT it is not what will dictate intensification! The most important thing is to make sure the synoptic setup is prime for intensification. If everything is good, then the cyclone-scale setup comes next. Afterwards, the convective scale comes into play. If all three things are good, THEN it is important to look at SST's. Otherwise, it doesn't matter if the water is 150 degrees. If the synoptic pattern is subsident, and wind shear is dominant at the cyclone scale, then the thing isn't going to intensify! SST's are important as a heat source. That's simply that. But what really drives a hurricane? Latent heat! So warm SST's provide the sensible heat, and latent heat has to be transformed from the sensible heat in order to drive the entire cyclone. And the only way for latent heat to build up is if the cyclone-scale and synoptic-scale environments are in sync. Otherwise, the storm simply cannot use the heat that it's given! If all the latent heat blows away, then it doesn't matter how warm the SST's are. Imagine sitting on a swing in a playground. No matter how strong you are, you will never be able to "pump" and raise yourself higher if there is another force acting against you (such as friction).

So basically, SST's should only come into play if all other atmospheric conditions are prime for intensification. Examples of hurricanes either weakening over warm water or intensifying over cold water: Lili, Opal, Floyd, Gaston, Alex, Jeanne, Frances, Isabel, the list goes on and on. Opal is often cited as the storm that rapidly intensified overnight while traveling over a warm Gulf eddie, then weakening right before landfall as it moved away from the eddie. Well, this widely publicized assumption turned out to be false. The reason Opal intensified was because of a trough that dug in to the northwest the night before landfall. It enhanced the outflow to the north, thereby causing a rapid pressure fall and subsequent intensity burst. Then, as the trough came too close to the storm, it began to shear it, thereby causing weakening. Dr. Krishnamurti at Florida State, the guy who wrote the FSU Superensemble model, proved this by simulating the Opal situation in a computer model. He removed the warm Gulf eddie variable, and the same intensity change occurred! He put it back in, and there was still the same intensity change. It showed that the synoptic forcing was more important than the SST's in this case and in many others. I can elaborate on each of the above hurricanes, but that would take a while.
 
You are absolutely right, Owen. SST's are most definitely not the ONLY factor to consider when evaluating a tropical system. I myself have been guilty of that little oversight even in this forum. Thanks for bringing us back down to Earth. That is quite a sound theory you have on Opal; I imagine it holds true for most landfalling U.S. hurricane intensity fluctuations immediately prior to landfall. Besides the SST's(which have been beaten into the ground by now) Dennis will encounter very little shear until he gets within two hundred or so miles of the coast line, where it is predicted he will encounter southwesterly shear. Even then, it isn't currently forecast to be particuarly strong shear, so it shouldn't disrupt the circulation too badly.
Latest satellite images show a definite eye has formed. It is rather small in diameter at the moment. Latest pressure as of 2 a.m. advisory is 975 millibars, which shows that Dennis is continuing to strengthen, with a pattern emerging of a pressure drop of 5-8 millibars every advisory. I predict he will be a Category 2 in 6 to 12 hours, and have at least sustained winds of 100 miles an hour and pressure readings in the vicinity of high 950/low 960 millibars when he comes ashore over Kingston, Jamaica. Then he'll likely drop back to high end Cat 1 tomorrow afternoon/evening after his encounter with Jamaica, which will likely only last about 6-12 hours before he restrengthens back into a Cat 2 and possibly be a mid level Cat 3 when he makes a slight turn between the Isle of Youth and the mainland, making what looks to be a direct hit on Havana Friday night. Looking back to last August, when Charley hit, the damage was pretty extensive and at the time he was just a mid level Cat 2. I imagine there will be considerably greater damage from Dennis if he tracks over that city as a Cat 3, likely doing quite a number on the many shantytowns, old wooden apartment buildings and well kept 1950's American automobiles of the soaring fin and chrome-by-the-acre era that define that city.
Just guesscasting here, after reviewing the models and watching the satellite loops. Well I'm off to bed now, I will rejoin you gentleman bright and early around 6 AM Mountain Time. C ya. :D
 
it looks like the models are in pretty good agreement of shear developing over the northern gulf in the next few days.... remember how quickely lili fell apart as she moved onshore?

should be fun in jamaica and cuba though...

edit: im trying to remember how much shear ivan had forecasted over the northern gulf last year. Was it 20 knots?
 
Since we're in Talk at this point... how well does the Orleans area handle rain like we saw last night with Cindy. The thing stalled for a period of time. I assume flooded areas return to normal quickly. Might come up as a point later if Dennis gets close to that area
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New Orleans deals with minor and brief street flooding anytime there is a significant thunderstorm. However, it takes a long heavy downpoor for major flooding to occur. The pumping system and canals in place are pretty effective. The only time major flooding occurs in New Orleans is when they have huge rainfall totals in a short period and the flooding can last for quite a while. The historic floods usually are caused by a squall line stalling and training over New Orleans. I remember May 8th 1995, I was in high school and there were reports of 24"+ in and around the NO metro.
http://www.srh.noaa.gov/lix/html/top10.htm

I agree with Owen, once the water temps in the gulf gets into the 80's it is all on the upper level winds. The upwelling feature is not too significant. When their is very little shear in the carribean and Western Atlantic it is not unusual to see back to back hurricanes that do well. Just look at the last two years.

Dennis is now cat. 2 and I would not be the least bit surprised to see a rapid intensification happen during the day today. It looks as though it is primed to really blossom and become a classic looking storm by this afternoon. I would not be the least bit surprised to see a cat. 4 in the gulf and I do not rely on long term forecasts for strength or shear so it could really do just about anything. My dad called yesterday and was packing valuables into his RV and telling me he was coming up here this weekend. He lives on the north side of lake ponchatrain and usually does not over react so....I think people are taking this seriously. I told him to calm down and wait to see what it does and make up his mind on Sat. morning. It is much more difficult to get excited about these storms after all of the damage from last year, but I am getting ready.
 
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