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Tropical Depression Dorian

phil882

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AvantHiatus

AvantHiatus

Posted
Posted

12Z GFS using the new super computer takes Dorian into Hispaniola.

 

:axe:

Bermuda ridge from hell builds in from the north, essentially right over Dorian. Track looks somewhat similar to Hurricane Ike. GFS Full Resolution reveals that Dorian is not very weak, the southward movement is associated with changes in the steering pattern.

 

gfsfull_pres_pcpn_atltropics_33.png

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Ground Scouring

Ground Scouring

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I would argue there has been quite a significant change to the overall structure. Dorian looks like its about to go on life support. 

Climatologically, this fits in with what others have been saying: that a storm forming as far N and E as Dorian tends to be closer to the subtropical high and to be centered over the cooler, more stable boundary layer that exists N of 15°N and E of 55°W. (It is a fact that most late-July systems that have formed so far NE tended not to last very long.) First, you have the stable boundary layer being ingested by Dorian on its north side. This is significant as the cyclone is beginning to lose its moisture influx from the ITCZ, as a building mid-level ridge to the SE cuts off the southerly inflow. This places Dorian entirely at the mercy of the strong easterly trade belt in which it is embedded. Given its small size and the legacy of climatology, I think that Dorian is about to struggle significantly over the next 48 hours, much more than suggested by the GFS and certainly more than many people may expect. This will allow it to be carried much farther S and W over the next three days due to the enhanced low-level easterlies, which, along with the decoupling of the LLC from the MLC / +PVA (convection) currently seen on satellite, will hinder Dorian from reorganizing. Thus this makes the faster, farther-S ECMWF and GEM solutions more probable over the next three days, bringing Dorian into the Leeward Islands in about 72 hours. This makes interaction with Hispaniola more probable and could even kill Dorian as it would have enough time to reorganize and feel the mid-level weakness in the ridge. This means it is more likely to plow into Hispaniola rather than pass N of the Greater Antilles. Overall, the people who are going gangbusters on a FL threat (or a U.S. landfall for that matter) are going to look ridiculous in another 48-72 hours.

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Ground Scouring

Ground Scouring

Posted
Posted

12Z GFS using the new super computer takes Dorian into Hispaniola.

I disagree with the strong intensity, but the Debbie-like track makes perfect sense based upon the environment in which Dorian is centered. It takes better account into the likely structural changes over the next few days, making Dorian a shallower system prone to decapitation by the fast easterlies.

 

By the way, I made my previous post before seeing the latest GFS, so I was prescient.  :violin:

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wxtrackercody

wxtrackercody

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Should be interesting to see how Dorian fares. It has overcome the coolest of SSTs along most of its path, but its connection with the ITCZ is going to be cut. To counteract that though is the fact that it's entering increasingly warmer waters, which may be able to keep convection persistent despite the dry air. Dissipation seems unlikely.

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GaWx

GaWx

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July-August CV storm climo based on satellite era stats:

 

~45% chance for recurvature E of US (including Canadian hits)

~25% chance of US hit

~25% chance of dissipation in open water or over Hispaniola

~5% chance for landfall in MX or Central America

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Eskimo Joe

Eskimo Joe

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July-August CV storm climo based on satellite era stats:

 

~45% chance for recurvature E of US (including Canadian hits)

~25% chance of US hit

~25% chance of dissipation in open water or over Hispaniola

~5% chance for landfall in MX or Central America

Where did you get those percentages from?

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Superstorm93

Superstorm93

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Recon is scheduled for Sunday...if Dorian is still alive. 

 

 

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT THU 25 JULY 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 26/1100Z TO 27/1100Z JULY 2013
TCPOD NUMBER.....12-055

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
3. ADDITIONAL DAY OUTLOOK: BEGIN 6-HRLY FIXES FOR TROPICAL
STORM DORIAN AT 28/1200Z NEAR 19.8N 57.0W.

 

 

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CUmet

CUmet

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After staring at the 1km storm-relative visible, it appears to me that the vortex is already tilting with the lower part outrunning the upper part.  It really becomes apparent if you run the loop super-fast by using the keyboard arrows...there's the low-level cloud swirl to the SW, and there's a swirl in the convective clouds aloft that's perhaps more obvious to the NE.  This has occurred earlier than I expected, and this may well be the beginning of a very difficult few days ahead for Dorian.

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GaWx

GaWx

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Where did you get those percentages from?

 

 I looked at the tracks years by year, analyzed only CV storms (per my def., which is any storm which 1st became at least a TD east of 50W and south of 20N), and crunched the numbers to come up with the %'s.

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gulfcane

gulfcane

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GFS became #1 for me after Debby last year. ECMWF had a hurricane into Houston, GFS had a tropical storm into FL. Since that time, the GFS has consistently performed better and it continues today. Last time I checked the ECMWF was never showing a 60mph tropical storm on any of its runs last week. And just because the GFS is an outlier on intensity does not mean its solution is incorrect. When you're the best model, you tend to be an outlier until the laggers catch up.

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phil882

phil882

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After staring at the 1km storm-relative visible, it appears to me that the vortex is already tilting with the lower part outrunning the upper part.  It really becomes apparent if you run the loop super-fast by using the keyboard arrows...there's the low-level cloud swirl to the SW, and there's a swirl in the convective clouds aloft that's perhaps more obvious to the NE.  This has occurred earlier than I expected, and this may well be the beginning of a very difficult few days ahead for Dorian.

 

Yep, the storm has already become tilted due to the variation in flow (faster low-level easterly flow, slower easterly upper-level flow). The big thing to watch is how quickly (if at all) the centers become completely decoupled. Right now the mid-level vortex is still in close enough proximity that it could attempt to pull the llc back into the convection and attempt to realign. In fact thats more or less what the GFS wants to do with Dorian the next 3-5 days. However, the ECMWF has a much swifter fate where the llc and mid-level vortex completely separate within 24 hours. If that happens, its game over and its unlike that Dorian survives to make it to the Lesser Antilles. 

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Derecho!

Derecho!

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 I think that Dorian is about to struggle significantly over the next 48 hours, much more than suggested by the GFS and certainly more than many people may expect...Overall, the people who are going gangbusters on a FL threat (or a U.S. landfall for that matter) are going to look ridiculous in another 48-72 hours.

 

What "people who are going gangbusters on a FL threat?" You mean elsewhere (S2K, etc)? Certainly not here...if you mean here, you're creating a strawman. 

 

Heck, people here who fairly mildly argue that it isn't going to weaken, or may intensify, sometimes feel compelled to apologize for seeming like a weenie in their own posts.

 

People here have been mostly anti-weenie-ing this thing into oblivion using an armada of sophisticated arguements since it was a wave over Africa, and it's consistently been STRONGER "than many people may expect" up until now. Of course, this doesn't mean it DOESN'T weaken or dissipate over the next few hours or days; I just don't see where the predominance of opinion on Dorian has been some sort of ill-informed weenie hype.

 

American (and Eastern) are a lot different than they were years ago. I actually think there's more bias and inaccuracy now from people trying to be "cooler than thou" by proclaiming the bust or demise of (insert TC/outbreak/snowstorm here) than from over-excited weenies. And it's actually a bit more insidious in some respects because the former is more likely to come from Red taggers, and at least SEEM more informed and well argued, than the latter.

 

People almost feel compelled to invent weenie strawmen so they can look cool debunking them.

 

 

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phil882

phil882

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Hey Phil what's a good site to look at in regards to what you're referring to. I have a ton of different sites but perhaps you have a really good one that I am unaware of. You seem to know your stuff so you're my go to guy. Thanks!

 

http://www.tropicaltidbits.com/analysis/models/gfsfull/2013072512/gfsfull_ir_atltropics.html

 

While low resolution, you can see the pulsing nature of the convection that takes place with Dorian. The difference between the GFS and the ECMWF at this point is the size of the convective plume and hence amount of moisture in proximity to Dorian. The GFS you can see builds huge bursts of convection from time to time which keeps the in-situ environment somewhat moist. The ECMWF on the other hand has all the convection collapsing soon after the centers decouple which leads to dry air completely wrapping into the low-level circulation and choking off additional convective opportunities.

 

The funny thing is synoptically the GFS and ECMWF have nearly identical synoptic patterns at 500 hPa 36 hours out. The big difference appears to be strength of mid-level vortex, where the ECMWF doesn't have a discrete center currently while the GFS has a robust vortex co-located with the center.

 

GFSvsECMWF.gif

 

CIMMS analysis gives support towards the GFS, but I have no idea how accurate the CIMMS 500 hPa vorticity product is. 

 

wg8vor2Z.GIF

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Mike.Ventrice

Mike.Ventrice

Posted
Posted

Bermuda ridge from hell builds in from the north, essentially right over Dorian. Track looks somewhat similar to Hurricane Ike. GFS Full Resolution reveals that Dorian is not very weak, the southward movement is associated with changes in the steering pattern.

 

gfsfull_pres_pcpn_atltropics_33.png

 

Hi guys,

 

Where can I find the new GFS-ran super comp stuff?

 

Thanks in advance!

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Eskimo Joe

Eskimo Joe

Posted
Posted

 I looked at the tracks years by year, analyzed only CV storms (per my def., which is any storm which 1st became at least a TD east of 50W and south of 20N), and crunched the numbers to come up with the %'s.

Awesome thanks.  Wasn't questioning the validity of the data, just wondering about your methodology is all.

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