Hurricane Dean

[rdale]

So of the four hurricanes that the GFS developed in the last 5 days, one TD has developed... Not bad!

 

[MClarkson]

I like the lastest HWRF run... sub 900mb by day 5. Obviously thats not likely to happen, but I said the same thing when the GFDL progged wilma to sub 900 last year as well when it was still a baby. The lastest GFDL is a bit more modest at ~975 for Dean. Regardless, what the storm does intensity wise 1000 miles from the US isnt particularly relevant to our chasing prospects, as long as it stays alive. I'll keep my fingers crossed for a track closer to me, if it nears the US at all.

 

[John Peters]

gfs, hwrf, and gfdl now seem to agree on the westerly path into the Caribbean and across Jamaica. If I'm not mistaken, isn't the Caribbean less climatologically favorable at this point in the season as apposed to later on? Ocean temps appear to be in the 83-85 degree range... i find it highly unlikely that we will have a sub-900mb monster on our hands until the storm nears at least the western Caribbean and/or gulf (where temps are in the 85-87 degree range).

 

[MClarkson]

the GFS has been developing pretty solid poleward outflow, and I would like to see the SSTs up higher but solid outflow can make up for that. A track further north runs into slightly higher SSTs(according to unisys analysis) and maybe better outflow, which probably accounts for the more northerly HWRF being stronger than the GFDL.

 

[HAltschule]

"Dean" is the tropical system that the GFS had pegged as a major hurricane in the 12-14 day range...before it even existed as a blob moving off the African coast. THAT is impressive. As I mentioned previously, when the GFS has such strong signals and such a strong appearance in the model, there is a very good bet there will be something forming. Good job by the GFS and to those forecasters who nailed it early on!! And for the non-believers who dismiss everything tropical on the GFS as a bias, I don't know what to say except "told ya so".

 

[Justin E. Reed]

I judt got back into JAX from vacation to see familty in TN. Hmm, I predict a landfall between Louisiana and NC, wide swath, but Im seriously thinkin this could be the start of the season. Most of us agreed this would be a late-bloomer season. I hope it rides the FL east coast, get me outta here again! J/K, but I hope it hits the CTRL GULF COAST. As bad as that sounds, it'd be about the ONLY way to get some rain into TN,AL,GA,MS and several other states. Its horribly bad there, lets hope and pray, yet, I see a major landfall.

 

[John Peters]

New runs for GFDL, HWRF, and GFS in. Looks like GFS and HWRF pretty much agree on something between an "Allen" and "Gilbert" type path that takes the storm across Jamaica at 918 mb (HWRF) and just north of the tip of the Yucatan into the gulf (possibly briefly onshore). GFDL has resolved an even more southerly path and continues to project more conservative strength estimates. GFS develops very nice outflow in the western Caribbean near the Yucatan, which would suggest further strengthening as the storm leaves Jamaica (corresponds to higher SSTs inthe western Caribbean).

As stated above, higher SSTs in the northern Caribbean probably explain the strength disagreement between GFDL and HWRF. Even with the northern track, i wouldn't expect a 918 mb cat 4 or 5 by Jamaica (GFS strengthens outflow and pressure gradient after Jamaica), though i could easily see a strong Cat 4/5 come ashore on the northern Yucatan.

This is my first season attempting to make use of computer models, so feel free to make any comments and/or correct any wrongful assumptions i have made.


Addition:
As of 11:00 AM AST pressure is down to 997 mb, sustained winds are up to 60 mph, and CDO is looking much more organized than earlier. We could very well be dealing with hurricane dean by the end of the day.

 

[rdale]

"Dean" is the tropical system that the GFS had pegged as a major hurricane in the 12-14 day range...before it even existed as a blob moving off the African coast. THAT is impressive.

It will be impressive if it happens - don't think you can verify a forecast before the event ;>

 

[cedwards]

Im seriously thinking this could be the start of the season. Most of us agreed this would be a late-bloomer season.

I don't think this is the start, OR a "late-bloomer season". We already have the "D" storm and possibly the "E" storm today, and it is only Mid-August. The peek of the season is a month away. typically, you will just be starting off now with the "A" storm.

I do think that Dean could pose a significant threat to the US, It is too early to tell where. The best of all possibilities (For the US) appears to be that it goes over Hispaniola and Cuba, weakens then hits Florida before it has time to re-strengthen. If it misses the islands, it could pose a significant threat to the Gulf coast.

 

[Jeff Piotrowski]

Dean

I would like to point out that if Dean reaches the Western Caribbean at 120 hrs based on HWRF and other models.
http://moe.met.fsu.edu/cgi-bin/hwrftc2.cgi?time=2007081506-dean04l&field=Sea+Level+Pressure&hour=Animation
This area has some of the deepest 26C water over 100-150 meters in that region.
]http://www.aoml.noaa.gov/phod/dataphod1/work/HHP/NEW/2007226d26.png
This depth of the warm water can supper charge the hurricane as it moves into that region. The area from Jamaica, Grand Cayman, and Cancun will likely have to deal with a major hurricane next week.

 

[Matthew Crowther]

The chances of a U.S. landfall have lessened considerably- the strong ridge in the States combined with the ridge over the Atlantic should keep Dean on a WNW track quite close to Gilbert's path back in 1988. So if you want to chase this one, I suggest looking into tickets to the Yucutan...Jim L?

 

[Gregg Gallina]

On a side note...
Very interesting set up for potential volcanic eruption as well here with Dean. Soufriere Hills volcano, located on the Southern end of Montserrat is extremely unstable at the moment. Hvy rainfall events have lead to prior dome collapses in the past and with the forecast track, currently south of Mont. but already busted a bit north...who knows...this is about as good as you get to predicting a volcanic eruption though I would never wish to do that forecast

Additionally, Volcano vs. TC Volcano wins, as proof, Mt. Pinatubo blew apart all circulation to TC Yunya in 1991. Though the scale of that eruption would dwarf anything by SH.

 

[John Massura]

Interesting, it's been awhile since I've heard mention of Soufriere Hills. Hi Gregg!

 

[John Peters]

On a side note...
Very interesting set up for potential volcanic eruption as well here with Dean. Soufriere Hills volcano, located on the Southern end of Montserrat is extremely unstable at the moment. Hvy rainfall events have lead to prior dome collapses in the past and with the forecast track, currently south of Mont. but already busted a bit north...who knows...this is about as good as you get to predicting a volcanic eruption though I would never wish to do that forecast

Additionally, Volcano vs. TC Volcano wins, as proof, Mt. Pinatubo blew apart all circulation to TC Yunya in 1991. Though the scale of that eruption would dwarf anything by SH.

I think pinatubo ejected something like 6-8 cubic km of ash during it's 1991 eruption (compared to 1 cubic km in st. helens' 1980 eruption). It was the second largest volcanic eruption of the 20th century (1912 Novarupta eruption in Alaska was #1). Soufriere hills probably only belches out a few hundred thousand cubic meters when it goes off (most of which is probably in the form of pyroclastic flows).

I find it an amazing coincidence that pinatubo entered it's climactic phase while a typhone was making landfall.

Also, the ash column produced by pinatubo's eruption reached heights of 34km (over 110,000 feet!). Obviously that is much higher than any convection produced by tropical cyclones (or any weather phenomena for that matter)

Edit: HWRF and GFDL have backed down significantly on their strength estimates (mentioned in recent nhc forecast discussion). Any ideas on why this may be?

 

[MClarkson]

well the 18z GFDL doesnt appear much different than the previous model concensus, gradually taking the storm to ~950mb, probably a cat 3. It seems to be a bit too weak in the short term.


the 18z HWRF... I dont know why it possibly flip flopped like that and now refuses to develop the storm at all. The poleward outflow on day 4+ will be gone, but overall shear isnt bad. Considering on IR that the storm looks pretty decent, and might allready be a hurricane, I would toss this run. The 00z run is almost available... see if that changes.


EDIT: well the 00z hurricane runs are in and... there is no significant change from the 18z. The GFDL still keeps the storm a little weaker at first and then ~955mb for a yucatan landfall. HWRF still dissipates the system in the central carib. The GFDL seems to be resolving a front of sorts to the southwest of the storm which could be throwing off its internal dynamics and intensity for day ~2. Then again it might be on to something. We will see. The HWRF... just looks wrong. SHIPS model hasnt changed much either and still progs a very powerful storm.