While Frances has weakened significantly (and surprisingly) during the past 24 hours while interacting with the Bahamian islands, please don't take this hurricane lightly.
There is a long history of south Florida hurricanes explosively deepening just before landfall....just as we witnessed with Charley three weeks ago. The infamous 1935 "Labor Day hurricane" deepened from a 60-70 mph tropical storm to category five hurricane in only 30 hours while passing slowly over the warm Gulf Stream between Andros Island and the Florida Keys.
As hurricane Andrew passed over the Gulf Stream in 1992, the central pressure fell 19 mb (941 to 922 mb) in only five hours.
Those are only three of many hurricanes that went from weak to intense in only a few hours.....those warm waters are what makes any hurricane approaching southern Florida potentially very dangerous.
While I've backed off somewhat on my landfall intensity forecast, I'm still concerned Frances will bomb similar to Charley and Andrew.....and am forecasting a 120 kt (135 mph) cat-4 at landfall near Palm Beach tomorrow night. If the inner core doesn't come together soon enough, it will be less intense...but still IMO a major hurricane at landfall. With the central pressure already in the 959-960 mb range, it won't take deepening much over the Gulf Stream for the sustained winds to come back up to 115-120 mph or more. If the core wraps sooner than I expect, OR hurricane Frances moves more slowly than forecast over the very warm Gulf Stream...then 145 mph or higher is still possible.
You can read my latest track/ intensity forecast and evening analysis here:
http://community-2.webtv.net/vortex4000
To everyone in the hurricane warning area.....my prayers and the prayers of my family are with you.
Please stay safe...
Perry
Frances forecast analysis FRI 9/3/04 - 9:45 p.m.
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SouthernWx
Frances forecast analysis FRI 9/3/04 - 9:45 p.m.
Last edited by SouthernWx on Fri Sep 03, 2004 8:53 pm, edited 1 time in total.
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SouthernWx
Congrats, Perry, on your location forecast and for your evening posts on this storm. Intensity forecasts are historically much more difficult to predict, but climatology should teach us never to dismiss a hurricane approaching the Gulf stream at a speed of four miles per hour as our Hurricane Frances is currently doing.
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simplykristi
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SouthernWx
JtSmarts wrote:Hi Perry I have enjoyed reading your thoughts dating back to last year, do you think the dry air and sheer will continue to limit Frances?
Thanks
I know shear and dry air was a factor in Frances weakening, but also the interaction with the Bahama Islands the hurricane passed over/ near. I noted the eyewall began unwinding about the time Frances "bounced off" Rum Cay toward San Salvador. Those islands may be low, but if a hurricane runs over or parallel to them, it will bring down the intensity...
The concern I have is people hear if went from cat-4 to cat-2....and assume "it's dying". I hope and pray no one who hasn't evacuated yet doesn't decide to stay just because the hurricane weakened some. The central pressure is still low....960 mb or so, and that's normally a 100-105 kt cat-3.
Once the core of Frances gets away from Abaco and moves south of Freeport over those 86-87° sst, I expect to see intensification begin, then accelerate as the hurricane passes over the Gulf Stream. If Frances only deepens 20 mb in 24 hours before landfall, we're talking a 940 mb hurricane...and probably at least 120-125 mph.
The projected slow movement of Frances while crossing the Gulf Stream also concerns me....it the shear lets up (as I expect), we could see the central pressure fall 3 mb or more per hour up to landfall...even if deepening begins only 4 hours before landfall, we have a 945-950 mb hurricane (likely cat-3).
This isn't North Carolina and this hurricane isn't Floyd or Isabel approaching land. The waters this hurricane will encounter the next 24-30 hours before landfall are among the warmest in the hurricane belt....and south Florida's hurricane history warrants deep concern.
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