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Posted: Fri Aug 17, 2007 10:11 am
Dean has moved into the eastern Caribbean Sea. Highest gust recorded was 87 mph on Fort-de-France, Martinique. Dean's intensity was probably over-forecast a bit. With winds 100 mph sustained, you should find a gust somewhere around 120 mph.
The problem with forecasting revealed: lack of data. The hurricane center at 5 am stated that a special mission to investigate upper air was completed and the models responded by showing a weaker ridge to the north - and a slight shift in some of the models to the north.
Dean appears to have strengthened over the past few hours and at the 11 am advisory is 105 mph. That is probably close as pressure has now dropped to 964 mb. It is very possible that Dean will be the monster cat 4 or 5 by the time it gets to the western Caribbean as it faces little shear and lots of warm water.
The offical 11am track takes Dean directly over Jamaica (like Gilbert in 1988). Dean eventually moves over Cancan/Cozumel then toward northest Mexico near the Texas border. This track is nearly the same as the GFS. The new GFS should be out in a few hours and the European after that.
The high to the north and upper air low is the focus of the forecast. If the high stays strong, the U.S. is ok for the exception of maybe south Texas. It the high weakens as the special upper air mission suggested then a more northward turn will be possible.
Posted: Fri Aug 17, 2007 12:42 pm
Latest GFS from this morning looking more like the European. Farther south....Landfall possible in Jamaica, then the Yucatan, then Mexico on the west side of the bay of Campeche.
Posted: Fri Aug 17, 2007 4:15 pm
5pm NHC advisory has Dean at 125 mph. This seems reasonable. The pressure continues to drop and the satellite presentation is looking much more impressive with a solid central dense overcast (CDO) now. The official NHC track has the pathway over Jamaica then to Cancun then to northeast Mexico. This also seems reasonable with the model split at this time.
The GFDL has more of a curve into the Gulf through the Yucatan channel.
The GFS is close to the NHC solution and the European is still holding to its guns keeping Dean farther south across the bay of Campeche. NHC noted the GFDL but did not go with it. I know that they must be a bit nervous with the farther north solution.
The high to the north of Dean is the controlling influence. The Euro has the high weakening allowing for a pass just south of Cuba then restrengthens the high pushing Dean westerward into the Yucatan then into the bay of Campeche. The 12z run of the GFS is now fairly close to the Euro solution.
So, three good models - Euro and GFS have the farther south route and the GFDL the mid Gulf solution. The NHC track - a split down the middle.
Probably a good way to go now until another day or two when we know what model is doing the best.
Posted: Sat Aug 18, 2007 12:39 am
Dean has undergone impressive development into this evening with a pressure of 935 mb as of 11 pm friday night. For the next few days, only internal hurricane changes will allow for strengthening or weakening. There is little wind shear observed and plenty of warm water to travel over. Dean also will weaken some if it goes over a land mass such as Jamaica or the Yucatan. I may add though, hurricane Gilbert rolled straight over Jamaica in 1988 and actually strengthened while doing so!
It is quite possible that Dean will become a cat 5 somewhere over the central or western Caribbean.
The european model has been very consistent with taking Dean over the Yucatan, then across the bay of Campeche into Mexico again 2 or 3 hundred miles south of Texas. The GFS did a flip - flop. It was consistently showing a track over the Yucatan then farther north into Mexico just south of the border. The afternoon Friday run took Dean much farther south. Guess what. The late evening run has it back to where it was before....just south of the border. Status quo.
Next update will be sometime Saturday morning...
BTW, at this time it looks like Dean is going through a slight weakening phase. The cloud tops have warmed, especially on the western side.
Posted: Sat Aug 18, 2007 9:36 am
Saturday late AM
Satellite imagery and recon information showing that Dean is getting into a rare class. Recon from earlier had a flight level wind of 177 mph. Flight level was way up at 700 mb. They set the surface extimate at 150 mph. As they mentioned, that may have been conservative. Latest pressure from the recon 928 mb. Satellite presentation looks very impressive with the strong side of the hurricane on the east side at this time.
Models staying consistent which is a relief! European has been rock solid with its prediction of Near Jamaica, Yucatan, across bay of Campeche into Mexico again. Last night's GFS still going with near Jamaica, Cozumel/Cancun then Northeast Mexico south of Texas.
Time line for eye to pass over: Jamaica - Sunday, The Caymans - Early Monday, Yucatan - Monday night, northeast Mexico - Wednesday.
New GFS and NHC advisory coming out soon so I will update in about another hour or less.
Posted: Sat Aug 18, 2007 10:59 am
Latest satellite shows more of an elongation of the central cloud structure. This usually is a sign of some (temporary) weakening. The 929 mb pressure from the previous advisory was not actually the lowest measured. A 924 mb pressure was found earlier, so the slight weakening trend has been going on for two or three hours. Dean has a chance to be a cat 5 any time between now and when it hits the Yucatan.
The morning run of the GFS is in. It appears to have bounced just a bit farther south again. Overall no changes in forecast track.
Posted: Sat Aug 18, 2007 4:08 pm
todays european just slightly north. European and GFS coming to a consensus....NHC track is on this line. Little change in strength of Dean today.
A more detailed update later this evening.
Posted: Sat Aug 18, 2007 9:01 pm
Dean is becoming a catastrophic hurricane...
Satellite imagery this evening has shown impressive organization of Dean's central dense overcast (cdo). Cloud tops have cooled indicating eyewall development. Dean will very likely be upgraded to a cat 5 soon. It would not surprise me if winds aren't raised to 160 mph at the 11pm advisory. Pressure has dropped to 918 mb.
The models are in good agreement. The forecast is unchanged again. Dean should move near Jamaica then near The Caymans to the Yucatan across the bay of Campeche or southwestern Gulf into Mexico 100-200 miles south of the Texas border.
It is possible that the eye may pass just to the south of Jamaica and the Caymans. It should still be close enough for very strong winds even if that scenario unfolds.
Posted: Sat Aug 18, 2007 10:12 pm
OK, NHC baffled me on the 11pm update. They actually droped the winds 5 mph. They stated a double eye wall structure was the reason. Many times a hurricane will take a break in intensification when this occurs.
It doesn't jive with their earlier reasoning though. Dean has been up to 150 mph all day. The pressure fell from 930 mb to 918 mb this evening. That is a substantial drop and should signify strengthening. They even admitted that the recon may not have sampled the strongest winds.
next update will be Sunday morning.
Posted: Sun Aug 19, 2007 7:44 am
Overnight it appears that Dean has weakened a touch. Recon pressure is up just a bit, but the satellite impression doesn't looks quite a good as last night. The eye appears larger and not as well defined as yesterday.
With that being said, Dean is still a powerful hurricane and will likely move near or just south of Jamaica today. The forecast track is nearly unchanged and has been remarkable consistent over the past two or three days now, especially the European. Dean will continue past Jamaica and just south of the Caymans tonight and tomorrow morning. Beyond that, Dean will pass just south of Cozumel Monday evening into Monday night. Eventually over the bay of Campeche to Mexico again.
If this track does eventually verify, the European will have been the best model. The highly acclaimed GFDL which is usually good will get a poor grade for insisting on turning Dean into the western and central Gulf.
Dean may still become a cat 5 before before the Yucatan.
Posted: Sun Aug 19, 2007 6:42 pm
Dean has been raking Jamaica today, especially the southern half of the island. At last check the pressure is holding at 930 mb. The maximum flight level wind found recently was 166 mph. Kingston, Jamaica reported a wind gust to 138 mph not long ago.
Recent GFS is almost total agreement with what the European has been saying for days now. It looks like Dean is going to pass south of the Caymans into the Yucatan. It is possible that Dean will be a cat 5 somewhere in the western Caribbean Sea. Latest track keeps it a bit farther south of Cozumel and closer to Belize. Eventually Dean moves across the bay of campeche into Mexico again.
next update later this evening
Posted: Sun Aug 19, 2007 8:56 pm
Dean's eye appears to be getting smaller again indicating that strengthening will commence. Cloud tops are cooling on the southern eyewall and after all influences of Jamaica's terrain are behind. This will be Dean's run at trying to offically hit cat 5 before the second landfall on the Yucatan Monday night.
Posted: Mon Aug 20, 2007 6:04 am
Dean is passing a little over 100 miles south of the Caymans today. Great news for them! The worst of the hurricane will miss them.
Top sustained winds are back up to 150 as the anticipated strengthening has started. Pressure is now back down to 926 mb.
The track still remains unchanged and Dean is moving a little north of due west which will take it into the Yucatan south of Cozumel and Cancun. The eye will probaby be closer on its present course to Chetumal. Belize will also be effected as the hurricane approaches today and makes landfall tonight.
Posted: Mon Aug 20, 2007 11:43 am
Satellite image appears more impressive. It's possible that Dean will be a cat 5 just before landfall. Since NHC is predicting a 140 kt hurricane this evening there is a good chance that it will be a cat 5.
Remember - there is little difference between a strong cat 4 and a minimal cat 5.
Posted: Mon Aug 20, 2007 4:19 pm
Late Afternoon Monday
NHC has decided to keep Dean at 150 mph for the 5pm advisory. Pressure has dropped to 918 mb again and a flight level wind of 173 mph was observed.
I'm a bit surprised that the wind wasn't bumped up to 155. NHC has wording that Dean probably will be a cat 5 before landfall, so I expect that they will up the winds sometime this evening. It really doesn't matter much because there is little difference between a strong cat 4 and a minimal cat 5.
Satellite suggests that the forecast track is still on line. The worst will pass a little south of Cancun and Cozumel into northern Belize.