Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 12:52 AM GMT on July 11, 2005
Posted: 8pm EDT Sunday July 10
Here's the official word from NHC:
Radar observations indicate that Hurricane Dennis made landfall at 225 PM CDT on Santa Rosa Island between Navarre Beach and Pensacola Beach Florida. Data from the stepped frequency microwave radiometer on board the NOAA hurricane hunter aircraft, as well as flight-level observations from NOAA and Air Force Reserve aircraft indicate that the landfall intensity of Dennis was 115 to 120 mph--a Category 3 on the Saffir-Simpson hurricane scale.
And my comments:
Dennis is still a serious hurricane. A storm surge of 9-10 feet was reported up to 175 miles east of where Dennis made landfall, in the coastal areas just south of Talahassee. Major storm surge flooding is still occurring all along the Florida Panhandle. Water has pushed across Route 98 near Apalachicola and there has been structural damage there similar to what was observed in 1985 with hurricanes Kate and Elena. Saint Marks, Florida--200 miles east of Pensacola--is flooded. Inland flooding worse than Ivan's is occurring throughout Alabama in Florida in areas soaked last week by Tropical Storm Cindy with six inches of rain. Already, Dennis has dumped an addtional 4-8 inches. There have been several reports of tornadoes in both Alabama and Florida, and these tornadoes could very well turn out to be the major killers for this storm. Another area of concern is inland flooding over the Tennessee Valley later in the week--model forecasts show Dennis stalling out over southern Illinois, creating a potential serious flooding event there. Dennis will be a menace for many days to come.
Don't even look out east of the Leeward Islands, where a powerful tropical wave is already spinning and gathering some impressive deep convection around it. And don't look at the calendar, which says July 10, and think about what happens two months from now, on September 10--the peak of hurricane season.
Dr. Jeff Masters
Posted: 3pm EDT Sunday July 10
Dennis is finally coming ashore, just east of Pensacola, and about 30 miles east of where Ivan struck. The central pressure measured by the hurricane hunters has risen to 943 mb, and the strongest winds measured at 10,000 feet have fallen considerably. Dennis will probably be classified as Category 3 with 125-130 mph winds at landfall.
The eye has maintained its tiny 8 mile diameter, and the most extreme damage will be confined to a smaller area than Ivan. I wouldn't be surprised to see Dennis carve a channel straight through Santa Rosa Island, the barrier island offshore from Pensacola. The worst storm surge damage will occur in the East Bay of Pensacola Bay, where a storm surge of 15 feet could occur. Extreme wind damage will miss Pensacola's downtown, but will severely impact Milton, a town of 7,000 people just east of Pensacola. Whiting Field Naval Air Station, just 15 miles inland, will also suffer heavy damage.
Posted: 11am EDT Sunday July 10
Dennis finally peaked in intensity. The hurricane hunters found no further drop in pressure, and the winds have eased off a bit to 140 mph. The eye is a very tight 8 miles in diameter, which a hurricane cannot maintain for very long. This eyewall could start to collapse in the next few hours, which would probably reduce the peak winds at landfall down into the Cat 3 range. Add to that the fact that Dennis is now travelling over cooler 29 - 30C water, and I arrive at the conclusion that this storm will hit as a strong Cat 3/weak Cat 4. High tide is around noon today, so Dennis will not be hitting at the worst time possible. It could have been worse--but not much. Mobile looks likely to barely escape (again) having a huge storm surge roll up Mobile Bay, but Pensacola will receive another punishing blow from a major hurricane worse than last year's Ivan.
Posted: 7am EDT Sunday July 10
Latest hurricane recon showed a pressure drop to 931 mb, 1 mb lower than two hours ago. If Dennis comes ashore with that pressure, it would be the 7th most intense hurricane ever to strike the U.S. An additional pressure fall to 927 mb would rank it number four, behind only Camille, the 1935 Labor Day storm, and Andrew.
Dennis still looks on track for a an exact duplicate landfall where Hurricane Ivan hit along the Florida-Alabama border, just west of Pensacola. The storm surge from Dennis will be one the highest ever for the U.S., up to 15 feet in some locations. The all-time record is Hurricane Camilles's 24.6 feet (image credit: NOAA Photo Library). Expect extensive damage to the weakened dunes and beaches, new cuts opened all the way through barrier islands, and of course near-total destruction of all buildings where the 10-15 foot storm surge values occur. The tourist industry will take a very long time to recover in Pensacola.
Posted: 11pm EDT Saturday July 9
Dennis has slowed down its rapid intensification, and is probably near its lowest pressure. The last recco flight found only a 1 mb drop in 1.5 hours, compared to 5 mb over the previous 2.7 hours and 11 mb in the 1.5 hours before that. Dennis is still traversing a warm pool of 32C waters, so may continue to drop in central pressure until about 3am, when it passes into cooler 30C waters. The winds will continue to increase to Category 4 strength until perhaps 6am, peaking out at 145 mph or so. From 3am until landfall, Dennis will be traversing 28 - 30C waters, which are about what it was seeing earlier today near Cuba. At this time, a slow weakening trend may result as it undergoes an eyewall replacement cycle.
If you're thinking of evacuating now, it may be too late. It's better to be riding out the storm at home than caught in a traffic jam on the expressways.
Posted: 9pm EDT Saturday July 9
Dennis continues its impressive intensification; the pressure dropped 16 mb in 3 hours, which matches the rapid deepening seen in Hurricane Charley last year shortly before it made landfall. Dennis's intensification is probably in part due to the fact it is traversing a narrow pool of 32C (90F) water. The eye has shrunk another 2 miles in diameter to 10 miles, and likely will shrink a little more then break apart like it did before hitting Cuba. I expect Dennis's winds will continue to increase to about 145 - 150 mph to bring it in equilibrium with its new pressure.
Dennis continues to break the rules for what is usual for a hurricane. In my previous blog entry, I wrote that it is very unusual for a major hurricane to regain its former intensity after a long crossing over land. However, Dennis is poised to do just that.
Aircraft recon just measured a central pressure of 947 mb at 5:15pm, an 11 mb drop in 90 minutes--a rarely observed rate of intensification. The eyewall shrank from 15 miles in diameter to 12 miles, and the satellite presentation confirms that the storm is undergoing explosive deepening. Dennis will surely be a strong Category 4 storm in about 6 hours, when the winds have time to catch up to the pressure falls, and Category 5 is not out of the question. Satellite imagery shows an outer wind maximum is probably forming, meaning Dennis will enter another eyewall replacement cycle tonight after this phase of explosive deepening is over.
The current track of the storm is more WNW than NW, and is likely a temporary wobble similar to two others this storm has already done. I expect Dennis will shortly resume its previous northwest track. The most recent wobble occurred as the storm was doing its previous rapid intensification cycle just before it hit Cuba. The current wobble is enough to probably spare Panama City the worst of the hurricane, but increases the danger to Mobile. A direct hit by Dennis just west of Mobile could easily challenge Hurricane Andrew as the most expensive hurricane in history. Dennis's storm surge of 15-20 feet would push into Mobile Bay and cause tens of billions in destruction. Even if Dennis hits further east near Pensacola, as I still expect, the damage will surpass Ivan's $13 billion and Charley's $14 billion to make Dennis the second costliest hurricane on record.
If you want to watch live windows media player feeds, check out:
CBS WFOR MIAMI FL.:
CBSNEWS.COM FEED 1
mms://eyenet.wm.llnwd.net/eyenet_livenews1 (Showing the same as above)
CBS WKRG MOBILE AL:
CBS WIAT PANAMA CITY:
http://www.weatherserver.net/livevideo.htm will show all 3 feeds will at once. Thanks to Jason@Weatherserver.net, who posted this info on the WX-TALK@LISTSERV.UIUC.EDU email list.
Entry from 10am EDT
Cuba did the U.S. an enormous favor by absorbing Dennis' worst punch. It's pretty rare for a major hurricane to regain its former intensity after a long land crossing, and Dennis has only until Sunday evening to regroup. While I do believe Dennis will reintensify to a Category 3 hurricane-- which will be plenty bad for the storm-weary residents of the Florida Panhandle, Alabama, and Mississippi--a return to the Cat 4 monster that ravaged Cuba is pretty unlikely. A search back into the hurricane archives for similar storms reveals the case of Hurricane Georges, a strong 1998 Category 3 hurricane that smashed the Dominican Republic. After traveling down the length of Cuba, Georges popped off Cuba as a Category 1 hurricane about the same place Dennis did. Gerorges gradually intensified to a borderline Category 2/3 hurricane with a 12-foot storm surge and 110 mph winds before it hit Mississippi, and did about $5 billion in damage to the U.S. mainland. I'm betting Dennis will have a very similar impact.
It takes at least 12-24 hours for a hurricane to re-establish its inner core eyewall structure after a major disruption like Dennis suffered, which doesn't give it much time before landfall. I give Dennis a 10% chance of hitting as a Category 4, 50% as a Category 3, 30% as a Category 2, and 10% as a Category 1 or weaker. As for landfall location, the computer models are now in pretty unanimous agreement about a Mobile/Pensacola landfall, now that the distraction of dealing with the Cuba interaction is over. When the models all come together like this, it's usually a pretty sure bet that landfall will be within 50 miles of the target.
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