07/05/05 -- TALK: Hurricane Dennis

[Owen Shieh]

As long as SST's are 26 degrees C or higher, there is no need to think of the water as any sort of hinderance on the intensification of the storm! This also goes for the oceanic heat content variable. Without any tremendous upwelling, the ocean heat content this time of year can sustain major hurricanes anywhere in the Gulf or Caribbean....given the right atmospheric conditions. Upwelling from major hurricanes is rare anyway, because most systems that stall out in one area are weak. This is because the physical imbalance that is present within an intense hurricane is such that the atmosphere simply will not allow it to stay in one place for so long! I believe Mitch and Isidore was the only exception in recent history. Right now, the thermocline is deep enough (which is directly related to the oceanic heat content) to support intensification. As long as the shear is low, there is a decent chance that Dennis will be cat. 3 or higher at landfall. However, I do not believe that a cat. 5 will materialize in the Gulf this weekend.

 

[MClarkson]

winds at keywest are sustained at 50 knots... not bad.

 

[Brandon Clement]

I'm guessing that Dennis will strengthen rapidly today and return to a strong cat 3 maybe even a category 4 by this evening. I think just before it comes back ashore it will encounter some shear just south of the Fl panhandle and weaken to a strong cat 2 or weak cat 3. By the look of the visible gulf satelite tops are pushing off to the northeast rapidly over the Fl, Al areas and I think it is going to cause Dennis to make more of a northern turn and make landfall on the eastern part of the cone. My best guess is going to be between Destin and Panama City.

 

[Owen Shieh]

Current radar and satellite images are showing some gradual intensification with the convection trying to regain the center. It has a very broad circulation (this is no Charley), so it will take a lot for rapid intensification. What is more likely is some gradual, but definite strengthning to cat. 3 or just barely cat. 4 by tonight or early tomorrow morning. There will be shear present on the coast, so it will either hold that intensity or weaken slightly.

A general rule of thumb is to use the 500 mb mean layer flow for the steering winds of a strong tropical cyclone. According to the GFS, the flow at that level is pretty strong from the southwest over Alabama and Georgia. However, it should weaken by the time Dennis reaches the coast, so the steering would probably me more induced by the ridge to the east and the low over Texas. However, the slightest weakness in the ridge would bump Dennis more towards landfall in the Florida panhandle.

 

[Thomas Loades]

The eye, largely filled in, is now visible on the Key West WSR — it's due W of the town. Gusts of hurricane force have been recorded there and at Sombrero Key. Though Dennis is weaker now, convection is starting to crank up around the eyewall again.

 

[Gabe Garfield]

Well, now that I am eating some tasty crow, I wanted to point out that Dennis appears to be rapidly intensifying now. The CDO is becoming more symmetrical with time, and the eye is becoming better defined every hour. Dvorak numbers are increasing rapidly, and judging from the NHC color scale (I'm not sure why they don't label the colors), appear to be in the Cat 3/low Cat 4 range currently in the front quads. This could be a doozy after all...starting to look scary for the US coast.

Gabe

 

[David Wolfson]

It's about to cross a very nice patch of hot (31C+) water. Should be interesting.

 

[Owen Shieh]

Dennis has done something incredibly unusual...
Most TC's that spend around 10 hours over land, no matter how flat it is, struggle desperately to regain its strength. This is seen even with the slightest brush of the Yucatan or the western tip of Cuba. However, with the core seemingly collapsing overnight, Dennis just seemed to trip, fall, and then jump right back up on its feet again. Radar presentation was really good this morning, even with the eye so far out from Key West. I'm doubtful about using the term "rapid intensification" just yet. However, constant, steady strengthening will be certain throughout the course of the day and night. IMO, we will definitely be looking at a landfalling major hurricane, but at the most, a cat. 4. Outflow is still a bit restricted to the west, but fair to good north and south. As per my analysis of the wind flow around 300 mb, there is evidence of some "cyclonic" upper-level flow, which is a bit odd in the western semicircle. This could be part of the reason that it is restricted there. IF outflow improves, then we will be looking at trouble.

 

[Owen Shieh]

Latest VORTEX: 958 mb

This thing is beginning to go.

 

[Owen Shieh]

WOW!! Look at the last 30 minutes of radar and satellite.....this thing is exploding. There is simply no way this storm is only a cat. 2 right now. If this isn't already a cat. 3, I don't know what is. Too bad there is a lack of surface data to verify the radar and satellite presentations. The last 30 minutes, the eye just cleared out almost completely! It's only a matter of time before recon finds winds in the cat. 3 range.

 

[Kevin Bowman]

WOW!! Look at the last 30 minutes of radar and satellite.....this thing is exploding. There is simply no way this storm is only a cat. 2 right now. If this isn't already a cat. 3, I don't know what is. Too bad there is a lack of surface data to verify the radar and satellite presentations. The last 30 minutes, the eye just cleared out almost completely! It's only a matter of time before recon finds winds in the cat. 3 range.

the pressure is crashing right now

at 3pm et it was 962mb, at the 5 update it was 955

 

[Owen Shieh]

speaking of crashing pressures....

Latest VORTEX message came in via wire:

It's 947 mb now!!!!!

It is not physically possible for winds to still be 105 mph. This thing is being underestimated by 15-20 kts!!



EDIT: 10 minutes later, just in via wire: NHC upped the winds to 115 mph.

 

[MClarkson]

and it looks like its going to make landfall tommorow durring the day.

It looks like I made the wrong desicion not to chase this one. Too bad its a 24 hour drive from where I am... and its too late to get on one of the last flights.

 

[MClarkson]

Since I will be staying home I will offer to nowcast the eye position based on radar to anyone who wants.

PM for my phone #.

 

[Owen Shieh]

Latest NHC forecast advisory update calls for 120 kts at landfall. If this verifies, this could get ugly really fast for all those in its path. Good luck to all of you out to chase this thing. I will be watching this constantly tonight and tomorrow.