Rich B
British Meteorologist
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Ok, so Dean looks quite good on satellite, with a decent , but no visible eye as yet - despite his intensity as a Strong Cat 1. Recon are now sending back obs so will be good to see what they find as they get closer to the centre. Looks as if Dean will pass probably to the north of Barbados, very near to St Lucia or Martinique, as a strong Cat 2 or possibly a low-end Cat 3 on Friday. The general consensus is for a motion towards the Yucatan, possibly with a side swipe at the Caymans. It looks like most of the greater antilles islands will miss the worst of the system though at present.
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Rich B
SkyWarn UK
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stormchazer
Storm Tracker
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Loc: Central Florida
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nl,
I see what you are saying with the Upper Level Low or Trough is digging deep into the High, but you also can see it showing signs of pressing to the left with the High starting to move it towards Florida. This is what the models are seeing to showing it moving West in tandem with Dean.
Things can and likely will change somewhat, but right now, things look as forecast.
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Jara
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MikeC
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Recon's already finding 90MPH winds and it just entered the system, looks like pressure is down to 970mb. Dean is a bit stronger than the advisory indicated.
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Kevin
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There was an obvious time constraint involved with releasing the 2PM intermediate.
I would expect an update if it appears that Dean is approaching category 3 status before the islands.
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Kal
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Loc: Space Coast
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The is sticking to its guns in the latest run . It still turns Dean NW between Cuba and the Yucatan, and focuses attention on the West-Central Gulf Coast. As is often repeated, you can't trust model guidance beyond three days, but the apparently doesn't mind its "outlier" status with regards to its prediction for a NW turn.
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dem05
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I think there is little question on the importance of the Gulfstream IV upper level wind sampling that will be occurring. This information is going to paint a much better picture of what is going on and should help the future model runs out quite a bit. I think the importance of this upper air mission is adequately stated by the , as they have made reference to this flight in the last 3 or 4 Hurricane Dean Advisory Discussions.
Lots of talk on the evolution of the high, the Cut off low, and other features that may affect Dean. In looking at the current models, I also share concern that the models may be making the overall atmosheric dynamics too straight forward. With respect to the , this is one the most reliable hurricane forecasting models and this model always gets very heavy weigh in on forcast tracks. With that said, I think last nights was weakening Dean during the forecast period, as it was seeing a system that would head into the Cutoff low and experience shear. As for todays model runs so far, the seems to have recognized that Dean is more formidable than the weaker tropical counterparts. As a result, the now sees an interaction with the cutoff low that moves it NWward, versus lasts nights representation that moved Dean under the cutoff and into a sheared environment.
Now, back to the Upper Low, the high pressure ridge and possible steering consequences. I'm gonna dive into the Water Vapor here, and I'd only like to base my interpertations on how the steering flow may change over the next 24 hours. Tomorrow, I will likely post a similar post looking at the next 24 hour period.
The View across the Atlantic: http://www.ssd.noaa.gov/goes/east/tatl/loop-wv.html
- The cutoff low does not appear to be weakening, it is moving to the west very slowly,but probably not as fast as one would expect based on the models...This could be an implication, since Dean is making some headway on the cutoff low.
- There is indeed a trough affiliated with the cutoff low, and the trough does extend pretty far into the Carribean.
- True, the Ridge of High Pressure is moving westward and placing some pressire on the southern extent of the Cut-off low/trough. However, I am somewhat concerned about the cutoff low that is also moving westward and centered around around 30N, 46W. The reason for concern is that the interaction of the Bahama'slow and this low may change the orientation of the ridge...instead of the ridge being oriented E-W as forcasts indicate, the ridge may become oriented in a N-S direction. This may hinder the westward progress of the Bahama's low in the coming day or so. It may also hinder the continued westward advancement of the ridge that the models want to depict.
- Finally, I notice a weak (albiet Small) upper level low trying to form ahead of Dean along the South American Coast. (Around 10N and 62.5W). This would have little impact on Dean from a shearing prospective...But as this kink in the upper level winds continues to prog westward, it will be curious to see if this links up with the Bahama's Cutoff Low and increases the southerly flow.
The View across the : http://www.ssd.noaa.gov/goes/east/nwatl/loop-wv.html
- AT this point, the jet stream looks fairly zonal...no real troughs or ridges...so nothing to really move the high over the Missippi Valley/Georgia area too much (considering the ULL over the Bahama's). However, in looking downstream, the ridge over the MissValley/GA also extends into the Northern Gulf and western Gulf States (On the western side of the ULL. So even though the Atlantic Ridge is pushing on the Baham's Low from the east, the High over the Southeast is pushing on the Cutoff low from the west. Talk about mother nature's power play...
In sum, I do not expect the upper level low over the Bahama's to make as much westward progess as was expected during the next 24 hours and the bottom line is this...Dean is making faster forward progress to the west than the Baham's low. Dean and it's anticipated 200MB ridge will push back on the ULL when they get a little closer to one another, but if the Upper Low does not fade away in the next 72 hours, I would not be surprised to see Dean on a more NWerly or Nerly route in days 4-5. That Gulfstream Jet Data is gonna be very important to the upcoming forecasts. I will not be surprised to see the models shift to a little more northerly route over time...much like the is starting to do now. Mean time...In another 24 hours...it will be interesting to look again and post on what is expected with the upper level dynamics through Saturday...
Edited by dem05 (Thu Aug 16 2007 07:02 PM)
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WeatherNLU
Meteorologist
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Loc: New Orleans, LA
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Not only the track on the , but the intesity. It has it as high as 159KT!
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I survived Hurricane Katrina, but nothing I owned did!
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Lee-Delray
Weather Master
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On the last run, the has moved further west. It hasn't joined the "group" yet, but has jumped hundreds of miles?
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danielw
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Two quick notes on the outlier model.
The last two runs of this model were outliers in respect to turning Dean toward the NW.
The 06Z run began the turn at 96hours 20.2N/ 82.0W
The 12Z run begins the turn at 90hours 19.5N/ 81.8W
(the difference is only 6 hours and that is the difference in the times of the model runs.)
So the is now the right hand side of the Cone of uncertainty...roughly.
One other note. The CLP5 model has shifted from the Bahamas at 120 hours, to a FL Straits/ N Coast of Cuba at 120 hours. In other words it seems to be following the trrend of the . shifts to the right...CLP5 shifts to the left.
http://flhurricane.com/modelanimator.php?storm=4&year=2007
Gulfstream NOAA aircraft is now airborne enroute to Dean.
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stormchazer
Storm Tracker
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Loc: Central Florida
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Quote:
On the last run, the has moved further west. It hasn't joined the "group" yet, but has jumped hundreds of miles?
Can you post a link to that run because I know there was some issues with Penn State's Model Board where it was showing and older run. I understood that the last GDFL was close to the previous run. I certainly could be misunderstanding though  .
You can get these at http://moe.met.fsu.edu/tcgengifs -- or straight from the source at http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/hur_nested/storm_1/00/index_hur_nestedpage.shtml -- Clark
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Jara
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Edited by Clark (Thu Aug 16 2007 08:44 PM)
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Lee-Delray
Weather Master
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The shift I saw in the GFL was in the 12Z run. I've noticed that the CLP5 has usually been to the right of the other models.
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mikethewreck
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Loc: Treasure Coast FL
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I think the Hurricane Center is also well aware of the possibility that the high may not build up and block Dean from the GOM. Throughout their discussions they have been incessantly saying that we all should be watching this storm. I think they are pinning their hopes that the NOAA G-IV will give them the data they need to either confirm the scenario or correct the model runs. Until they can confirm the GOM is a strong possibility for Dean, it would be imprudent to alarm the already shaken Louisiana and Mississippi folks. Not to minimize the potential human cost of the Dean GOM scenario, but the financial markets are already taking a beating with the mortgage companies. Imagine the prospect of a Cat 5 storm plowing again through the GOM oil fields and refineries.
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Earliest memory Hurricane Cleo!
Went under Hurricane Gloria!
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Steve
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Loc: Metairie, LA
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Hey All,
Just watching and waiting to see what happens with the models since Dean isn't even to the islands yet. 12Z Euro appears to be a southern outlier (often happens with that model). Lots of flooding in the Houston metro based on some training from Erin with some reports of 6"/hour rainfall rates (not substantiated by me).
GFDL's 12Z run really makes things look bad for the Houston metro again. I have no way to know if it's going to verify (doubt it), but it, along with the other models, should change a few more times during the next few days. Everyone from the islands, to the Yuctan to the US Gulf Coast needs to be paying close attention. If the 12Z scenario appears like it's going to pan out, you might want to gas up your vehicles/generators/spare tanks sooner rather than later. Gas prices will go up in response. And all we can do is speculate beyond that if it actually verifies what's going to happen with them. 
As for the question on the difference between daytime heating thunderstorms and diurnal maximums, the source moisture and synoptics are different. Clark, Ed, HF, Jason or one of the pro mets could probably put it better layman's terms than I could.
Steve
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MF'n Super Bowl Champions
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Ron Basso
Storm Tracker
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Quote:
Two quick notes on the outlier model.
The last two runs of this model were outliers in respect to turning Dean toward the NW.
The 06Z run began the turn at 96hours 20.2N/ 82.0W
The 12Z run begins the turn at 90hours 19.5N/ 81.8W
(the difference is only 6 hours and that is the difference in the times of the model runs.)
So the is now the right hand side of the Cone of uncertainty...roughly.
One other note. The CLP5 model has shifted from the Bahamas at 120 hours, to a FL Straits/ N Coast of Cuba at 120 hours. In other words it seems to be following the trrend of the . shifts to the right...CLP5 shifts to the left.
http://flhurricane.com/modelanimator.php?storm=4&year=2007
Gulfstream NOAA aircraft is now airborne enroute to Dean.
Daniel, the CLP5 is a statistical model - it's based on historical climatology of storm tracks that are located at the position of the storm you are tracking - it will shift as the storm moves. The 12Z , 12Z HWRF, and 12Z UKMET have all shifted northward today in contrast to the and the Euro. This is likely due to the speed and interaction of an ULL (300 mb) that migrates from the Bahamas to the GOM over the next three days. This ULL weakens the upper level ridge enough to allow a more NW movement into the GOM. The two intensity/track models, both the HWRF and , bring the storm to a CAT 5 in the western caribbean. When a storm reaches that intensity, the upper levels (300 mb) become more of a factor in their steering than the mid-levels (500 mb). This may be one reason why the globals such as & the Euro, which cannot discretize the intensity of the storm well, may be reflecting more of a southward bias at the moment. Just a theory at the moment. Clark may want to weigh into this situation in more detail.
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RJB
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Clark
Meteorologist
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Actually, I don't have much more to add to that, Ron -- that's the jist of it.
Couple of other quick comments...
1) : 100mph at 5pm, forecast for 140mph in the Caribbean. That's pretty reasonable.
2) Very good points made by dem05 about the Gulfstream aircraft and what it means to the track forecast. Don't have anything to add to it.
3) Most of the "early" 18Z models did come a little north in the Gulf in the 4-5 day time frame, but not as far as the was earlier. I wouldn't put much stock in exact locations that far out even today.
4) Saw something from Steve about daytime convection versus the diurnal maximum -- at night in the tropics, the upper levels of the atmosphere cool off, enhancing the sea surface to upper level (truly outflow level) temperature gradient. This is known to enhance convection in general and enhance the efficiency of tropical systems in particular. There are other factors at play, but that's another part of it. Over land, heating during the day drives convection (the standard "CAPE" or available energy arguments) since the landmasses cool off much more significantly than bodies of water at night, counteracting any upper level cooling that may help enhance temperature gradients.
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Current Tropical Model Output Plots
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LisaC
Weather Watcher
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5 pm... status quo on movement. Strengthening but we knew that.
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aboz56
Registered User
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Loc: Louisville, KY
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What effect, if any, do you expect Dean to have on the Destin, Florida area? I'm heading there on Saturday for vacation and am trying to plan ahead as well as possible.
Use the PM feature for questions like this, not the Main Page.
Edited by Storm Cooper (Thu Aug 16 2007 08:45 PM)
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Steve
Senior Storm Chaser
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Loc: Metairie, LA
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>>What effect, if any, do you expect Dean to have on the Destin, Florida area?
Probably will be some elevated surf and maybe rip currents to watch out for. Otherwise, Destin is probably east of any future affects not directly tied to the Gulf Water. It's a waiting game now, but enjoy your vacation. If Dean passes as far south as it is progged to do, you'll proabably have some hot sunny beach days to look forward to IMHO.
But stay tuned anyway.
Steve
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MF'n Super Bowl Champions
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aboz56
Registered User
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Loc: Louisville, KY
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Quote:
>>What effect, if any, do you expect Dean to have on the Destin, Florida area?
Probably will be some elevated surf and maybe rip currents to watch out for. Otherwise, Destin is probably east of any future affects not directly tied to the Gulf Water. It's a waiting game now, but enjoy your vacation. If Dean passes as far south as it is progged to do, you'll proabably have some hot sunny beach days to look forward to IMHO.
But stay tuned anyway.
Steve
Will do, Steve, thanks.
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neospaceblue
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Loc: Newport News, VA
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When the tropical update came on at 4:50, they put Dean's pressure at 920 mb and the guy up there had said 920 mb too. But when the 5:00 update came up it was corrected.
If Dean really was at that low pressure, we'd be screwed big time.
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I survived: Hurricane Bonnie (1998), Hurricane Dennis (1999), Hurricane Floyd (1999), Hurricane Isabel (2003), Tropical Storm Ernesto (2006)
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