Hurricane Dean

[crimsone]

As long as the shear doesn't kill it, it should

I'd say the shear isn't going to kill it... that's my bet anyway

[Cookie]

it would be a shear waste of time if it did! ( sorry couldnt resit)

[crimsone]

45kt to start the morning... and forecast track has again slipped slightly further to the south.

000

WTNT44 KNHC 150254

TCDAT4

TROPICAL STORM DEAN DISCUSSION NUMBER 7

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007

1100 PM EDT TUE AUG 14 2007

AFTER THE CONVECTION WANED THIS AFTERNOON...A NEW BURST HAS

REDEVELOPED OVER THE CENTER DURING THE PAST FEW HOURS. DESPITE THE

SOMEWHAT RAGGED SATELLITE APPEARANCE AROUND 2100 UTC...A QUIKSCAT

PASS AT THAT TIME DETECTED A RATHER WELL DEFINED CIRCULATION WITH

BELIEVABLE 45-50 KT WINDS. WITH A NOD TO THE SATELLITE

PRESENTATION...THE INITIAL INTENSITY IS SET AT A POSSIBLY

CONSERVATIVE 45 KT. RECENT MICROWAVE IMAGERY AND THE QUIKSCAT DATA

SUGGEST THAT THE CENTER IS SLIGHTLY NORTH OF THE EARLIER ESTIMATES.

THE INITIAL MOTION IS 270/16...A LITTLE SLOWER THAN THE PREVIOUS

ADVISORY. THE FORECAST PHILOSOPHY REMAINS UNCHANGED AS DEAN IS

EXPECTED TO BE STEERED WEST TO WEST-NORTHWESTWARD DURING THE NEXT

FEW DAYS...SOUTH OF A DEEP-LAYER RIDGE. THE MODEL GUIDANCE

GENERALLY AGREES ON THIS SCENARIO BUT WITH SOMEWHAT VARYING FORWARD

SPEEDS. THE OFFICIAL TRACK FORECAST REMAINS FASTER THAN THE NOGAPS

AND ECMWF SOLUTIONS...WHICH CONTINUE TO STRUGGLE INITIALIZING THE

FORWARD MOTION OF DEAN. THE NEW TRACK FORECAST IS CLOSER TO THE

CONSENSUS OF THE GFDL...HWRF AND GFS MODELS THROUGH 72 HOURS...BUT

IS A LITTLE SLOWER THAN THESE MODELS AT DAYS 4 AND 5.

IT APPEARS THAT THE EASTERLY SHEAR THAT HAS BEEN AFFECTING DEAN IS

BEGINNING TO DECREASE. THE GLOBAL MODELS FORECAST A FAVORABLE

ENVIRONMENT FOR STEADY STRENGTHENING AND THE AVAILABLE INTENSITY

GUIDANCE BRINGS DEAN TO A HURRICANE IN 36-48 HOURS...AND NEAR THE

MAJOR HURRICANE THRESHOLD BY DAY 5.

THE WIND RADII WERE ADJUSTED BASED ON THE QUIKSCAT DATA.

FORECAST POSITIONS AND MAX WINDS

INITIAL 15/0300Z 12.0N 42.3W 45 KT

12HR VT 15/1200Z 12.2N 44.8W 50 KT

24HR VT 16/0000Z 12.4N 48.2W 55 KT

36HR VT 16/1200Z 12.8N 51.7W 60 KT

48HR VT 17/0000Z 13.4N 55.2W 70 KT

72HR VT 18/0000Z 14.5N 61.0W 80 KT

96HR VT 19/0000Z 16.0N 66.5W 90 KT

120HR VT 20/0000Z 17.5N 71.5W 100 KT

Edited August 15, 2007 by crimsone

[Iceberg]

There is no doubt that Dean is going to do very well, it's a lot smaller and compact though than yesterday (tightening might well be occuring).

As to the NHC's conservative 45Kt, This seems rather strange to me, If they can see that on this QuikScat then they've got much better eye's than me.

[Iceberg]

Dvorak currently 2.0 supporting a 35Kt or 40Kt TS.

[Iceberg]

The above should have been 2.5 not 2, recently updated and still 2.5 which does not support 45Kt winds.

[kold weather]

To be fair the higher resolution version does show the odd 40-45kt barb here and there:

http://manati.orbit.nesdis.noaa.gov/dataim...ms/WMBds112.png

As for Dean, i actually think its starting to band quite nicely right now and interestingly the northern quadrant seems to be filled now with more convection then yesterday and starting to take on a more typical shape then it had yesterday which indicates maye the shear has eased off overnight somewhat and given its now starting to enter much warmer waters I wouldn't be too surprised to see it strengthening a little quicker given its got a deecnt sturcture right now. I don't think its going to rapidly deepen given its current set-up but its slowly adjusting its inner core and once this is done steady development looks the order of the day till just before the Windward/Leeward Isalnds, when it could begin a faster deepen phase with winds upto 85-100mph IMO.

Right now it looks like a 45-50kt tropical storm to me.

Now the track is still uncertain beyond day 4-5. The models keep adjusting southwards based on the foward speed and the powerful high that is still set-up over the SE states. Models are indicating Dean to head pretty much due west for quite a while, indeed the ECM takes it due west...into Mexico!!!

A track into the Caribbean seems the most likely option right now given its current latitude and I think the models are onto something with its track into the caribbean. The ECM is probably a little too far south beyond then, nearly all the models have the upper high over the states decaying quite readily by about day 7 hence why the GFS lifts the system into the gulf. The key of cours eis just how quickly the upper high weakens as to when it heads NW. The models have slowly been shunting that time further away but I suspect the GFS 0z probably isn't al lthat far away from the truth. It also should be noted the models do have a westerly bias outside of 120hrs which may wlel have an impact on some of those more southerly runs...however I will most certainly not rule out the ECM trac kas the UKMO/GFDL are also not too different to the ECM run upto 126-144hrs.

Right now best track to watch is hurricane Allen from 1980, looks the closest to me which tracked through the caribbean hitting then going on to skim the Yucatan and hit S.Texas. I susepct the last part of the track wil lbe bent more to the NW then Allen.

Still can't rule out a Mexico hit based on this morning's models though that would requite quite an exceptional ridge for it to gain so little lattiude between now and then...

IF it does take a track like some of the models are expecting no reason why it can't get upto cat-4/5 in the central/western Caribbean, HWRF still takes this down to some impressive low pressure, down to 929mbs on this run. Even a track further north skimming Cuba would likely still result in a pretty powerful hurricane though obviously land interaction would be higher. Odds are very high for a major hurricane at the moment unles its hit by some unexpected shear and if it reaches western Caribbean, unless EWRC timings are out, it could well reach high end cat-4, maybe even a cat-5, heat content easily supports it...

The track it takes has been taken by several cat-5, Emily, Gilbert, sort of Ivan and Allen to name some but not all.

Edited August 15, 2007 by kold weather

[kold weather]

Decent look on the Vis. imagery now as well, this does look like a strong tropical storm IMO given the obviously banding and under much better atmopsheric condtions this could be a hurricane n the next 18hrs IMO, I'd be surprised if they don't up the winds to 50-55kts come the next advisory. anyway here is our little beauty this afternoon:

Nothing in the near future that suggests Dean couldn't be a strong hurricane in the Caribbean.

06z GFS hits Mexico...06z GFDl would hit Belize and I'll let you see what the HWRF thinks...

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...rf_pcp_120s.gif

Edited August 15, 2007 by kold weather

[Iceberg]

I'd go with an increase to 50Kt, He does seem tight now, with a good outflow channel forming. More flip flopping from the models, although any Florida hit is now looking unlikely.

What is very consistant as you point at Kold is the very sharp intensification set to occur.

All models I believe now show strengthening to anywhere between a 3 and a 5.

[kold weather]

Quikscat is showing numerous 50-55kt barb with some as high as 60kt now on the latest, will probably up it to a 'conservative' 50kts but given its present structure it wouldn't be all that surprising if they go as high as 55kts given the current organisation it has.

One thing is certain, this is currently the best looking tropical cyclone of the season so far, not that that was hard to be honest!

Given its structure its not hard to see why some models go for a very powerful system in the Caribbean, the HWRF gets down to 970mbs just before the Leeward Islands.

[Iceberg]

At what point to we think an eye will start to form then ?.

He really is going for it today, I'll give him that.

Dvorak has increased to 3.0 or 45Kt....

Edited August 15, 2007 by Iceberg

[kold weather]

Yep the NHC have upped Dean to a 50kt tropical storm. I think it may well be on its way to a hurricane right now though looking at its impressive banding and I really wouldn't be al lthat surprised to see some fairly good strengthening at this rate. Note its a small system as well right now and once it gets even further west that could lead to some pretty rapid tightening of the pressure gradient as it hits the area of higher heat content (around 50-55W), can't rule out a major hurricane before the Caribbean at this moment as well which would be the strongest hit for the Lesser Antilles since Ivan 04 hit as a major.

As for an eye, might see the first indications of one overnight tonight but a true probably not for another 36hrs I suspect.

As it is such a small system any time over land could well weaken it quite a lot but equally these small systems can deepen rapidly as well. People in the Lesser Antilles should be preparing for a hurricane and maybe a major one, i sure feel sorry for the people who may get hit by this system.

(ps, finally back in the swing of thing in terms of hurricanes, happy to see it ramp up today like I said it would last weekend!)

(EDIT 15.45----Dean's position is 0.6N further north then was forecasted 24hrs by the NHC, if this type of motion continues for the enxt 12-24hrs it may mean the models slightly adjusting back northwards, esp the very southerly tracking models lie GFDL..though interestingly the GFDL is one of the only models to show this northerly movement but soon starts to shunt it back slight S. of west by 84hrs and hits Houndras as I said before.)

Edited August 15, 2007 by kold weather

[tcc]

I'm keeping a very close eye on this to see where it lands. I'm meant to be going to Puerto Morelos (30 mins south of Cancun) on the 8th Sept so if it does hit the area in the next few days, I might need to change my plans if my hotel is destroyed!

[kold weather]

Hi Tcc, well I (and no doubts soon many others) will be watching it, generally people sit and notice when these becomes hurricanes.

Anyway you have every right to be wathcing as the Yucatan region is a typical landfalling site of system that are trakcing wes tin that way. The latest NHC graphics show a generally close to WNW track. Its stil ltoo early to read to omuch into the longer term track right now tohugh it should be said that some of the models have been taking it close to that region and I suspect on its track there is a chance that the Ne of the Yucatan could be hit but this far out there are so many things that could alter. Worth keeping a close eye on it and also systems behind it, 8th September is prime time hurriane development but there is no need to be too worried yet.

Hope it clears off to the north or keep on the very southerly track. The fact its north of its current forecast track is a good thing for you though right now.

Edited August 15, 2007 by kold weather

[crimsone]

What I'm wondering, is that even though the system is small now, could the higher SSTs (and thus the increased convection) add to the strength and significantly add to the size of this storm?... and with the latter (size), would it require a slowing of the forward speed?

Edited August 15, 2007 by crimsone

[kold weather]

It wouldn't increase the core of the hurricane force winds but I suppose higher heat content would mean stronger convection so maybe it might lead to a slightly larger convective coverage. The most likely way though that Dean is going to get larger is via Eyewall replacement cycles which would expand the inner core each time it undertakes one and thus increase the size of the high wind radii.

Dean still looking good on Vis.satellite imagery right now, NHC have upper the winds to 50kts--or 60mph if converted (NHC misses out 55mph.)

Edited August 15, 2007 by kold weather

[tcc]

Hi Tcc, well I (and no doubts soon many others) will be watching it, generally people sit and notice when these becomes hurricanes.

Anyway you have every right to be wathcing as the Yucatan region is a typical landfalling site of system that are trakcing wes tin that way. The latest NHC graphics show a generally close to WNW track. Its stil ltoo early to read to omuch into the longer term track right now tohugh it should be said that some of the models have been taking it close to that region and I suspect on its track there is a chance that the Ne of the Yucatan could be hit but this far out there are so many things that could alter. Worth keeping a close eye on it and also systems behind it, 8th September is prime time hurriane development but there is no need to be too worried yet.

Hope it clears off to the north or keep on the very southerly track. The fact its north of its current forecast track is a good thing for you though right now.

Cheers Kold, I guess the only concern would be a direct hit, otherwise I should imagine the hotel will be up and running by then. But like you say I am in prime hurricane time, I guess I have to ask myself whether I feel lucky or not! :lol:

[kold weather]

Dean looking very good now, it has an ever improving look the system has right now. Note the dimple in the cloud structure on the western side of the convection. This may well be the first developing signs of an eye trying to form. importantly the IR also shows the cloud tops are warming in that spot which suggests as we can see the cloud tops are dropping in height which is a good sign of an eye forming:

12z GFS is tracking slightly further south in the caribbean then on the 06z run though in the first 48hrs it is further north then the 06z hitting Dominca and surrounding Leeward Isalnds. given the strength that quite a few now expect it to be at any island that is hit could suffer a similar fate to what Grenada had when it was smashed by Ivan in 2004, I suspect we will be looking at a cat-2/3 by that point given its current strengthening rate and alsi its small size. By 114hrs it starts to pull up in lattiude moving around WNW/NW towards the Yucatan landfalling aobut 100 miles south of Cancun heading it seems NW towards the Bay of Campeche and goes on to hit N.Mexico.

Edited August 15, 2007 by kold weather

[kold weather]

Just a few signs of dry air being injested into the SW quadrant right now but Dean is moderating it quite well, so will probably hold strength till early tomorrow during the D-Max that will take place which will really power up convection and drive it IMO to hurricane status.

Now the track remains interesting. The GFS/UKMO/ECM all take it through the Caribbean and hit the NE Yucatan before hitting Mexico on its second landfall. However some models are trending further north, the HWRF and Nogaps as well as the deep member of the BAM's are much further north heading towards the gulf. Now given that al lthe big models forecast it to head one way that I'd favor them...however maybe not so clear cut this time. All three only take Dean down to about 990mbs in the Caribbean which is obviously an utter fallacy and so will be guided by the middle level steering current sof the atmosphere. In this case the BAMM shows it heading broadly just north of west on a similar track to the models mentioned. However the BAMD take sit much further north and if you were to use one statistical model in this case it would be this one because I think its pretty obvious this system will become a hurricane and probably quite a deep one.

Now of course its probably too early to tel lwhere its going exactly in 5-7 days time however I'd like to also draw your attention to the fact that Dean is already as far north as was forecast for 1am tonight and its motion. i suspect that this could be explained by any numbe rof reasons, maybe its stronger then expected causing the Beta effect and causing Dean to head more polewards, maybe the ridge isn;t as strong as forecat and maybe even the upper level torugh diving down close tothe Bahamas is giving some lift. Either way Dean is tonight picking up some lattiude and is currently according tothe NHC heading at 285 degrees. Thw models have a good grip on this upto 36hrs then bend back west though given the way the models have been constantly adjusting for a longer WNW track over the last 4 runs this trend may continue. We will get a better grip once the gulfstream planes investigate tomorrow the surrounding region condtions.

Finally the system has now dropped to 994mbs given the better Sat.presentation and despite injesting some slight dry air it still has some very good banding present with some good convection, esp on the eastern side and while it may not deepn quite as readily today the diurnal maximum should keep convection readily bursting and keep the CDO intact ready for hurricane tomorrow morning IMO. This will probably be my last post on Dean tonight, will see what its like tomorrow morning!

[Iceberg]

DEAN CONTINUES TO ORGANIZE THIS AFTERNOON. ALTHOUGH THE CLOUD TOPS

HAVE WARMED RECENTLY...THE LAST FEW VISIBLE SATELLITE PICTURES

INDICATE A TIGHTLY CURVED BAND WRAPPING AROUND THE CENTER. AMSU AND

TRMM MICROWAVE IMAGES HAVE ALSO SUGGESTED THE FORMATION OF A

PARTIAL EYEWALL.

70% chance according to NHC that he will be hurricane in 12 hrs.

HWRF give Jamaica a real taste of something nasty, lets hope GFDL is right and it goes further south.

[kold weather]

Ah well one quick last post can't hurt...yep the NHC track is much faster then the previous and also slightly further north at the start and slightly further south at the end. Given the current trend for the system to be a touch further N. the nthe NHC forecast points, one has to think that Jamaica could be hammered by a system, indeed Gilbert went over it nearly 20 years ago and didn't weaken one bit.

Finally the NHC forecast cat-4 in the W.caribbean but history tells us that many beasts have gone through there, Emily, wilma, mitch, Gilbert, Allan, Ivan, Janet and Hattie all became category-5's in the W.Caribbean and given the upper atmosphere is forecasted to be pretty damn good for development with a upper anticyclone present heat content could well be high enough for a cat-5...

[crimsone]

BASED ON WHAT WE THINK WE KNOW ABOUT INTENSITY CHANGE...THERE DO NOT

SEEM TO BE TOO MANY INHIBITING FACTORS TO A FUTURE INTENSIFICATION

OF DEAN.

<snip>

FORECAST POSITIONS AND MAX WINDS

INITIAL 15/2100Z 13.1N 47.9W 55 KT

12HR VT 16/0600Z 13.5N 50.8W 65 KT

24HR VT 16/1800Z 14.1N 54.7W 70 KT

36HR VT 17/0600Z 14.6N 58.6W 75 KT

48HR VT 17/1800Z 15.1N 62.3W 85 KT

72HR VT 18/1800Z 16.0N 69.5W 95 KT

96HR VT 19/1800Z 17.0N 76.0W 105 KT

120HR VT 20/1800Z 18.5N 83.0W 115 KT

$$

FORECASTER BLAKE

That kinda says it all for anybody in the path of this storm really. I kind of infers "get out of the way if you can."

Blake seems to be a little less than certain that they know it all though.

Edited August 15, 2007 by crimsone

[SMU]

Dean-

Hurricane potential CAT 5!!

During the last couple of days i have been monitoring the progression of the waves of Africa, & the birth of dean-

Development was slow at first, however once past 35 & 40 w the easterly sheer has all but dissipated leaving favourable enviromental conditions for development-

As we stand now the satelite loop shows Excelllent banding & strong outflow indicating the presence of a developing system-

http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

The key to Deans intensity is track- more so- the time spent over water rather than land based-

Im expecting the status to be upgraded to Hurricane tomorrow ( cat 1) & for continued development there after-

The Leeward islands will be the Marker for an update on the model spread of Tracks- so whilst we have the current NHC track there is still room for movement-

http://flhurricane.com/cyclone/stormspotli...007&storm=4

Because the system remains to the South & on a Westerly vector islands like Puerto rico & Haiti may probably miss the WORST of the hurricane- although being on the Northern flank exposure to the outerbands & maybe the Northern Inner bands will ensure they wont escape totally-

Its here approaching Jamaica that we will need to wait with baited breath for the rapid intensification-

Highlighted below is the cyclonic heat potential for the GOM & Caribbean-

As you can see- West of Jamaica & South of Cuba intense energy can be sourced from the ocean water with a decent thermocline-

This is where we may see a sub 920 Mb system & one approaching cat 5- ANY southern track JUST south of Jamaica willsee this sort of development-

Obviously an early curve ( like the canadian model suggests) will pull it through haiti & into the Northern Islands- where it wont be as devestating..

After this depending on the Strength of the 500MB high to the North will dictate the time of recurve northwards- (if any-) which poses the threat ( all be it small) of a recurve through the ocean gap between Cuba & the yucatan penninsula- Although at this stage a track slightly south west of this passage looks likely-

& in that case rapid de-intensification will happen -

for now- I am certain of the cat 1 status tomorrow & then onto cat 2 3 towards the weekend- Cat 4 & 5- well the optimium track for 5 is highlighted above & is quite possible-

The optimum track for a Gulf coast strike will require a recurve through the gap & onto the GOM- possible over the gulf loop current & we all know what could happen there....

S

PS After dean watch out for the next wave off Africa- soon to be named felix!!!!

Edited August 16, 2007 by Steve Murr

[Iceberg]

Morning All, I agree there is the potential for a CAT 5 hear, it all depends on the internal dynamics, although he looks to be good.

A Cancun hit seems pretty likely, but I doubt we will see a hit any futher north than the Texas border.

Dean will be named a Hurricane at approx 9.45am today (I think it's a cert). Below is the side of an eye wall IM limited O.

Good banding still and structure.

The models seem to be alot less keen generally on the 00Z, probably down to missing obs maybe, with HWRF killing it off in the Carib. I don't believe that for a moment.

Lots of Real aircraft data today would should confirm a few things.

[Blackie]

I hope for the sake of Cancun that they don't get another direct hit. They are only just getting over the last hurricane. Cancun is hosting the International Golf Travel Market in early December, which I am attending. Fingers crossed Dean will pass by and not hit any heavily-populated areas - either in Mexico or the US.