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Saturday, July 09, 2005 |
| ..131 knots in the northeast quadrant, do the usual 10% deduction and convert to mph and you get 136 mph. Ladies and gentleman we have a category four hurricane in the Gulf of Mexico in July. Insane. 2005 Hurricane Season, Weather comment []11:55:17 PM  trackback []
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| At 10 PM CDT the center of dangerous Hurricane Dennis was at 26.6 North, 85.3 West, 250 miles south of Panama City Florida. Movement is to the northwest at 14 mph with a turn to the north-northwest expected overnight. Maximum sustained winds are 125 mph and pressure is 941 millibars. Dennis is forecast to become a category four hurricane overnight. Hurricane force winds extend 40 miles from the center and tropical storm force winds extend outward up to 230 miles away. For details specific to your area, check with your local National Weather Service Office. NWS offices covering the area under hurricane warning are: National Weather Service Office New Orleans National Weather Service Office Mobile National Weather Service Office Tallahassee For evacuation turn to your local media. I link websites of NBC affiliates along the warning area as I find that they tend to have consistently high quality websites: NBC New Orleans NBC Jackson NBC Pensacola/Mobile NBC Panama City Once again, a highly quotable opening sentence for the discussion: AFTER DEEPENING AT A RATE THAT BORDERED ON INSANE DURING THE closing this post so that I can get it out there... more to follow very soon... BRIEFLY LATER: Dennis continues to spin up tornadoes. NWS Jacksonville put up a warning for Live Oak that verified (i.e. there was an actual confirmed touchdown). NWS Tallahasse also put up a warning earlier this evening. It would be unsurprising for this trend to continue westward along the Gulf Coast and associated inland counties, so people need to maintain awareness of the weather situation in their immediate area. It has been a couple of hours since the northeast quadrant has been sampled. Because the hurricane hunter samples the entire windfield and since the windfield overall is so big, the time between complete passes is substantial. The pressure observation was taking at about 9:30 this evening. The trend since the rapid deepening has been 1-2 millibars per hour, so the pressure probably is down to 940 millibars now, assuming that another quick intensification round has not started. I concur with the NHC's expectation for Dennis to get up to 140 mph or so. I am less sure of their forecast for it to hold at that speed; I think there will be slight weakening tomorrow morning. However, in practical terms, that weakening will not be meaningful. Dennis will be a dangerous and destructive hurricane at landfall. I close with the plea that if you are under evacuation orders, please heed them at the soonest opportunity. If you know someone that may be under evacuation orders and they have not complied with them, please give them a call first thing tomorrow morning and talk some sense into them. Dennis will be destructive, that is for sure. However, it need not be deadly to residents of the Gulf Coast. 2005 Hurricane Season, Weather comment []11:20:22 PM trackback []
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| At 9 PM CDT the center of Hurricane Dennis was at 26.3 North 85.1 West, 275 miles south of Panama City and moving to the northwest at 13 miles per hour with a turn to the north-northwest expected overnight. Maximum sustained winds are up to 125 mph and pressure is down to 942 millibars (27.82"). Hurricane force winds extend 40 miles from the center and tropical storm force winds extend 175 miles. The pressure fall wasn't as steep this time, but the trend, of course, is still that of a strengthening storm. As I mentioned earlier, Sea Surface Temperature Analyses suggest that the temperatures on the course of Dennis start to drop slightly north of 27/28 degrees latitude; that may help flatten the strengthening trend. Dennis still has a few hours before it reaches that enviroment. Unfortunately, there are some analyses (that indicate a warm eddy right in front of Dennis path, before it gets to 28 North. That may bring one last quick intensification round. 2005 Hurricane Season, Weather comment []9:18:39 PM trackback []
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| Recon found pressure of 942 millibars when they entered the eye for the first time on the current mission. The strengthening trend continues... New advisory soon... 2005 Hurricane Season, Weather comment []8:41:56 PM trackback []
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| ... on the Gulf Coast, especially between Mobile and Pensacola (make that Fort Walton Beach) and saying, "Well, I stuck around for Ivan and made it through fine, so I'm sticking this one out". Please, please, for the love of God, reconsider. Ivan made landfall with winds 105 knots... Dennis is stronger than that now and the National Hurricane Center forecast brings Ivan in with wind speeds of 120 knots. Point being, this storm is not Ivan, it is going to be worse for whatever area has the misfortune of being the arrival point for Dennis. There is still time to leave tonight... conditions are going to go downhill fast tomorrow, so please do not procrastinate... 2005 Hurricane Season, Weather comment []8:22:09 PM trackback []
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| Right now, I am in nowcasting (vice forecasting) mode, and I suspect that to some extent the National Hurricane Center forecasters are too. They had scheduled an intermediate advisory for 7 PM, but it looks like they have pushed it back to 8 PM, possibly to get a better grip on the rapid change pressure... no new pressure ob from the recon plane yet, but it looks like they are finding flight level winds that would equate to 120-125 mph at the surface. Dennis certainly has a fierce appearance on satellite right now. Scary. More in a bit... A FEW MINUTES LATER OK, they got out a 7 PM advisory... a bit late, but here are the highlights At 7 PM EDT the center of Hurricane Dennis was at 26.1 North 89.4 West, 285 miles south of Panama City, Florida. Movement is to the northwest at 14 miles per hour with a turn toward the north-northwest expected overnight. Winds are up to 115 mph and pressure is down to 947 millibars. First line of discussion WHAT A DIFFERENCE 2 HOURS MAKES! No time for a forecast of my own at the moment... my forecast on Friday (which I backed down 5 mph the next day) brought Dennis up to 145 and then dropping to 135. I have not had the time to look at why NHC is not forecasting any weakening prior to landfall. More in a bit... .... oh, by the way, welcome Irish Trojan readers. Good thing there aren't public phone boothes around anymore else residents of South Bend would be treated to the site of the mild mannered law student Brendan Loy dashing to a phone booth to change into his Max Mayfield (National Hurricane Center director) costume or something... 2005 Hurricane Season, Weather comment []7:34:27 PM trackback []
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| On the basis of the observation I mentioned at the end of my previous post the National Hurricane Center has upgraded Dennis to category three status, making it a major hurricane once again. If this deepening trend were to continue, Dennis would jump to category four status later tonight. More in a bit... 2005 Hurricane Season, Weather comment []6:22:54 PM trackback []
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| At 5 PM EDT the center of Hurricane Dennis was at 25.7 North 84.6 West, 320 miles south-southeast of Panama City and moving to the northwest at 14 mph. Pressure has dropped to 955 millibars and winds are up to 105 mph. Have to quote the discussion directly for a moment: WHAT A DIFFERENCE 6 HOURS MAKES! I am late posting this update because I am watching reports come in from the Hurricane Hunters. An observation taken about twenty minutes ago show that the minimum central pressure is already significantly lower... now down to 947 millibars. That is a perilous crash. If winds follow the pressure fall we are going to see a significantly stronger storm shortly... more in a bit... 2005 Hurricane Season, Weather comment []5:47:50 PM trackback []
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| The entire western Gulf Coast of Florida and adjacent inland counties is under Tornado Watch 628. NWS Tampa has already put out a couple of tornado warnings this afternoon. 2005 Hurricane Season, Weather comment []4:20:55 PM trackback []
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| Unlike last year, hitherto I have not had the time to look at what people in affected areas have been blogging. A Cool Change , however, fills the gap nicely. Oh, and to answer the question left on the my 932 millibar post: Andrew's mimimum central pressure at landfall was 922 millibars. 2005 Hurricane Season, Weather comment []4:00:45 PM trackback []
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| At 3 PM EDT the center of Hurricane Dennis was at 25.5 North 82.4 W, 295 miles south of Apalachicola, Florida. Movement is to the northwest at 14 mph. Maximum sustained winds are 100 miles per hour and minimum central pressure is 962 mph. The Hurricane Hunter observations indicate that the pressure is falling at a modest rate of 1-2 millibars per hour. Dennis continues to be in a low shear / warm sea surface temperature enviroment favorable for strengthening. Dennis has the potential to get up to low-mid category three status (115-125 mph winds) in the next few hours. Sea Surface Temperatures start to drop at 27/28 North, and at that latitude, Dennis northern half will become exposed to a bit more shear (SST analysis / shear analysis ). For those reasons, Dennis' intensity should max out at that time (8-10 hours from now on its present course). The morning forecast model runs were in close agreement, most bringing landfall between Mobile and Pensacola, with NOGAPS putting Dennis a little bit further west, into Mississippi. It continues to appear that NOGAPS is under-representing the southwest-northeast flow that currently exists over Louisana and Mississippi that would preclude a landfall in that area. My personal forecast continues to be more concerned with an earlier curve to the north-northeast than expected, which would cause a landfall slightly further east than currently forecast. As such, my unofficial landfall warning area continues to extend from Mobile to Appalachicola (granted Appalachicola is an unlikely spot for landfall given that Dennis is now due south of there, but I will still manitain that as an eastern point for a bit longer). Residents west of Mobile to New Orleans should be mindful of the prospect that Dennis manages to slide a bit further west than forecast, bringing hurricane force winds to their area. The usual reminder: A hurricane is not a point, but a large area of high winds. Currently hurricane force winds extend 35 miles from the center and tropical storm force winds extend 175 miles. An example worth remembering is from Tallahassee last year. The highest winds recorded during the season came in a squall line from Frances when Frances was about twelve hours away from its closest point of approach to Tallahassee. Please check your local National Weather Service Office to see what winds are being forecast for your area. Something to keep in mind for people watching the satellite loops of Dennis (storm floater 1). Please be careful in not getting obsessed over the movement of the storm in the last hour or two. Storms are not so kind as to travel in the straight lines that we use to plot our forecasts. It is more accurate to look at the several hours of motion as a whole. I like to do this by stopping the loop on the first frame and placing the bottom right corner of a piece of paper where the center is at. Then, I advance to the last frame and rotate the paper so that the paper connects its corner with the center of the storm. (The satellite loop provided on that link is almost too short; RAP/UCAR satellite imagery is not storm centered; however, one can look at the Gulf of Mexico loop for a duration of up to twelve hours). 2005 Hurricane Season, Weather comment []3:47:04 PM trackback []
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| At 11 AM EDT, the center of Hurricane Dennis was at 24.7 North 83.8 West, 125 miles west of Key West, FL. Movement is to the northwest at 14 miles per hour. Winds are 100 mph and pressure is 967 millibars (28.56"). Dennis has slowly become better organized this morning. Pressure has slowly dropped, but the recon flights are not finding the increases in wind that should be accompanying that drop. The wind speed is based on a mixture of satellite data and observations from the Hurricane Hunters. Satellite imagery indicate that a key feature in the Gulf of Mexico, southwest to northeast flow, is a bit stronger than yesterday evening's forecast models were indicating. This stronger flow is expected to cause the forecast models to shift their track to the right (east) on their morning runs. Dennis is currently over a small area of cool water, which inhibits his development. However, temperatures are warmer once Dennis gets out of that area. Conditions are favorable for Dennis to get back up to Category Thre strength, however, the forecast brings Dennis just short of category three status. This morning, the National Hurricane Center upgraded their watches on the northeast Gulf coast to warnings. The hurricane warning extends from the LA/MS state line to the northeastern corner of the Gulf of Mexico. A Tropical Storm warning covers southeastern Louisana. I was awake when the first observations came in from the Hurricane Hunter came in . They found a pressure that would indicate a hurricane, but really couldn't find hurricane force winds. Cuba took quite a bit more out of Dennis than had been expected. The advisories yesterday evening used a particular Doppler radar product to estimate the winds in Dennis. The evening discussion warned that "there is a large margin of error for both the winds and the minimum central pressure". Their estimate of pressure was not that bad, but their wind estimate was horrendously off. I suspect that the radar just wasn't designed for accurately depicting wind speeds of something 100+ miles away; I am not sure why the NHC resorted to it. More in a little bit as I catch up on the situation.... 2005 Hurricane Season, Weather comment []12:31:48 PM trackback []
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© Copyright
2005
Charles Fenwick
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Last update: 8/2/2005; 2:00:35 PM .
Last update: 8/2/2005; 2:00:35 PM .
