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Post Tropical Cyclone Debby


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Good money is on Debby drifting northeast into Florida until it makes landfall like the GFS shows, NHC has been way too committed to the western track forecast for no good reason. Yesterday even when Debby was moving northeast they kept saying it was stalled and would eventually start going west, so now a good bit of Florida is getting a "surprise" tropical storm. Woops.

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It does seem like the very deep convection that formed last night had some influence on the motion of the system. It has moved substantially further north and east than expected. Now there is little chance for the mid-level ridge to be able to capture the system with the system gaining too much latitude, so the most likely solution at this point is a continued north or northeast drift till landfall at the Florida coastline. From there the deepening upper level trough in the Eastern US should be able to capture the system fully and take it out to sea, per the GFS. Its amazing how easy it is for large systems such as this to be affected by small weaknesses in the flow.

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Latest 12z spc 4km wrf has Debby plowing right into Florida kind of like the GFS looks like a MAJOR bust for the euro if this verified. This shows why model hugging like the NHC did does not work and is a bad forecasting tactic.

http://www.emc.ncep.noaa.gov/mmb/mpyle/spcprod/12/nmmwrf.pcp_animate_1h.html

Well, hold on there. They didn't "hug" the Euro-- they selected that solution out of other possible ones and they offered decent reasoning for doing so. I mean, maybe you can criticize them for sticking on the W solution for too long, but I think "model hugging" isn't a fair charge here.

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Well, hold on there. They didn't "hug" the Euro-- they selected that solution out of other possible ones and they offered decent reasoning for doing so. I mean, maybe you can criticize them for sticking on the W solution for too long, but I think "model hugging" isn't a fair charge here.

+1 and to just add to this a bit is the fact that it is impossible to truly model "hug" when the ensambles resemble the "squashed spider" look for multiple consecutive runs. NHC knew they were taking a chance with one direction vs. another. I'm sure if they had a choice they would have put the the TX/LA border to The big bend of FL under a tropical storm watch or warning. Unfortunately that is unreasonable given the large sum of money that decision is worth in activating EOC's, shelters, Emergency Services overtime pay etc....

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Well, hold on there. They didn't "hug" the Euro-- they selected that solution out of other possible ones and they offered decent reasoning for doing so. I mean, maybe you can criticize them for sticking on the W solution for too long, but I think "model hugging" isn't a fair charge here.

I love everyone coming out of the woodworks today (not just here) to swipe at NHC. Like anyone else had a real clue as of yesterday themselves.

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Well, hold on there. They didn't "hug" the Euro-- they selected that solution out of other possible ones and they offered decent reasoning for doing so. I mean, maybe you can criticize them for sticking on the W solution for too long, but I think "model hugging" isn't a fair charge here.

I hear what you are saying but they did use the Euro out of deference for its past success. That could be construed as hugging a model when no clear consensus had been reached and when other VIABLE solutions were still in play. A better play by the NHC maybe would have been to have it meander for three days and not shown a five day due to uncertainty.

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I hear what you are saying but they did use the Euro out of deference for its past success. That could be construed as hugging a model when no clear consensus had been reached and when other VIABLE solutions were still in play. A better play by the NHC maybe would have been to have it meander for three days and not shown a five day due to uncertainty.

have they ever not shown a 5 day on a named storm since it's been part of the package?

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can't tell if she's looking better or worse as per visible satellite. it looks like convection is wrapping around the center more but then it looks like there's dry air wrapping in toward the center on the east side of the LLC.

The last few frames from visible do show the cluster of storms to her north being drawn down to the center -as opposed to being jettisoned- for the first time in Debbys short, miserable life.

Thinking the lower and mid-level circulations are becoming better aligned and the shear is relaxing.

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have they ever not shown a 5 day on a named storm since it's been part of the package?

I can't recall them not doing it, but to me is a better option when so much uncertainty is in play. From moment one of this storm the west vs east has been playing out, and the solution was unknown for a period of time. I think it would be prudent to not have a five day solution, which is in itself a solution of sorts. That would certainly let people know to stay tuned.

Certainly not bashing the NHC, but I believe it is fair game to discuss alternative ways to express uncertainty.

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000

URNT12 KNHC 241742

VORTEX DATA MESSAGE AL042012

A. 24/17:30:30Z

B. 28 deg 20 min N

085 deg 59 min W

C. 850 mb 1356 m

D. 53 kt

E. 347 deg 62 nm

F. 053 deg 70 kt

G. 349 deg 78 nm

H. 993 mb

I. 11 C / 1832 m

J. 18 C / 1827 m

K. NA / NA

L. NA

M. NA

N. 1345 / 08

O. 0.02 / 1 nm

P. AF302 0204A DEBBY OB 23

MAX FL WIND 78 KT N QUAD 17:05:00Z

;

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*yawn*...now everyone is an expert tropical forecaster...just not sure how many ways for days on end that the folks that were forecasting this slopgyre kept repeating "This Is A Low Confidence Forecast"...but I digress...

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Even though Debby has a sheared look, it's obviously still slowly strengthening based on the latest vortex message. I'm not sure if I buy the 78 knot FL winds as it could just be convective contamination with the band close to shore, but the pressure is still slowly falling. Assuming it doesn't make landfall this evening, tonight could be interesting.

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*yawn*...now everyone is an expert tropical forecaster...just not sure how many ways for days on end that the folks that were forecasting this slopgyre kept repeating "This Is A Low Confidence Forecast"...but I digress...

you are right. Every discussion I read from the NWS / NHC the past few days ended with obvious mention of significant uncertainty or low confidence.

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It does seem like the very deep convection that formed last night had some influence on the motion of the system. It has moved substantially further north and east than expected. Now there is little chance for the mid-level ridge to be able to capture the system with the system gaining too much latitude, so the most likely solution at this point is a continued north or northeast drift till landfall at the Florida coastline. From there the deepening upper level trough in the Eastern US should be able to capture the system fully and take it out to sea, per the GFS. Its amazing how easy it is for large systems such as this to be affected by small weaknesses in the flow.

That's pretty much the forecast I just put out on my blog. Even though the models are still in a squashed spider pattern, more of them are clustering towards the eastern solution. Makes alot of sense due to the cold front that is pushing through my area at the moment. This cold front is much stronger than usual for summer btw, expected to get down into the 40s the next couple of mornings around southern Wisconsin! Not to mention the fact the GFS shows cooler 850s reaching all the way down to the Gulf coast within 3 days.

post-645-0-16440700-1340560498_thumb.gif

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*yawn*...now everyone is an expert tropical forecaster...just not sure how many ways for days on end that the folks that were forecasting this slopgyre kept repeating "This Is A Low Confidence Forecast"...but I digress...

agree completely, but Joe Public likes pretty pictures, and believes what they see implicitly. Those pictures show something into TX. Only us weather nerds read the fine print. I don't blame the NHC for what they forecasted, as it was a viable solution, but with so much uncertainty, there may be better options with regard to what picture you show the public.

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This one was more challenging than most to try to forecast.  It almost seemed like there was no in between...it was either way west or way east.  And when you have multiple models starting to go toward one solution (west as of a few days ago) it's hard to go against that.

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Tutt is collapsing south, convection is trying to expand SW on the NW FL radar. However the structure so craopy that organization ay take days. It's almost better off shedding the first band and starting over from scratch.

Edit: UK folds GFS wins.

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I certainly Give the NHC a lot of credit for there hard work but I think maybe they could of tried to take more of a blend of the models then a one sided solution. I personally though thus storm would effect Louisiana more but as of this morning I really have my doubts of that verrfiying now given this looks to be taking bigger path towards Florida. what happens next I guess we just wait and see. This is one of those storms that has and will continue to hold surprises.

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NHC criticism is warranted in this case and rightfully so.

Just read the disco by Stewart only a few hours before everything collapsed from a modeling and actual storm movement standpoint. He took the GFS to the woodshed and in less than six hours that entire forecast was toast.

I'll back up the NHC in a heartbeat. Not here.....

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