ATL: DORIAN - Post-Tropical - Discussion

[Cainer]

Just curious, what is it that causes the statistical and dynamical models to vary so much in situations like this?

[SFLcane]

Which local Miami station is "zoom radar" affiliated with again?

CBS4 works with David bernard

[chaser1]

Got it, thanks

[SapphireSea]

Just curious, what is it that causes the statistical and dynamical models to vary so much in situations like this?

Statistical models don't account for size or storm structure or changes in structure due to other factors aside from shear/SST, and I believe CAPE. They can't account for mid-level dry air, or shear between smaller layers, hostile upper level systems that can cut off outflow, but cause low shear, so all this makes them buff up a storm more than normal. The short explaination, all they do is run hypothetical numbers and see what a storm might do under those conditions.

Dynamical are similar to statisticals, but they factor in different layers, vorticity and generally have better resolution in synoptic scale. I believe these definitely factor in possible CAPE values and other variables adjusting in tandem with future synoptics and is fed into intensity forecast.

End-in-End intensity and cyclogenesis forecasts are made through assistance of all models and a manual evaluation of conditions. The dynamicals have improved to the point that surprises are rare now-a-days, also Pro-Met judgement has been vastly improved in all areas, especially tropics in the last 10 years.

[bamajammer4eva]

I've noticed that the NHC mentions the LGEM and Ships models a lot and GFDL/HWRF very little so one would think that it has a pretty good chance.

[boca]

There only might be a mid level circulation but its vigorous.

http://www.ssd.noaa.gov/PS/TROP/floater ... -long.html

[chaser1]

Though this makes sense to me (and perhaps to most), am not to sure of the significance. Ultimately a LLC will have to form "somewhere" prior to Dorian being upgraded and that is not going to happen immediately (given lack of present convection and verified low level circulation center). So is this solely relevant with regards to where models initialize the system center?

If the feature on satellite is indeed the center, then 91L is well on its way to becoming Dorian again...much closer than others thought it was. The fact that thunderstorms have constantly developed over this feature today makes me believe we have a well-defined low-level center there.[/quote]

Am not sure I understand your point. A number of us (myself included) have anticipated that this center point on Satellite where convection has been popping is where the MLC and eventually a LLC would likely form. There is no doubt in my eyes that Dorian may be getting close to T.D. status again, however that and $2.00 won't buy you a cup of coffee (well, not at Starbucks anyway LOL). Regardless if NHC puts an "X" on the right spot or not, there must eventually be pressure/winds to substantiate an upgrade. Until such a time, it will remain classified as a wave. When the ASCT did a pass earlier in the day, there was not substantiating winds to fully close off a center. So my question is........ simply because the NHC has chosen to move the "appearant" LLC eastward to a position under what would appear to be the MLC, why is this significant if many of us had already come to that conclusion (or assumption) anyway??

[gatorcane]

Latest Rainbow frame from floater showing convection continuing to build right around the MLC (20.5N, 61W):

[cycloneye]

Up to 50%

A TROUGH OF LOW PRESSURE...ASSOCIATED WITH THE REMNANTS OF DORIAN...
IS PRODUCING A SMALL BUT CONCENTRATED AREA OF SHOWERS AND
THUNDERSTORMS...AS WELL AS GALE-FORCE WINDS...A FEW HUNDRED MILES
NORTH-NORTHEAST OF THE LEEWARD ISLANDS. ALTHOUGH THERE ARE
CURRENTLY NO INDICATIONS OF A CLOSED LOW-LEVEL CIRCULATION AND A
WELL-DEFINED CENTER...ONLY A SMALL INCREASE IN ORGANIZED
THUNDERSTORM ACTIVITY COULD LEAD TO THE REFORMATION OF A TROPICAL
CYCLONE. ENVIRONMENTAL CONDITIONS ARE MARGINALLY CONDUCIVE FOR
REGENERATION...AND THIS SYSTEM HAS A MEDIUM CHANCE...50 PERCENT...
OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WESTWARD TO WEST-NORTHWESTWARD AT 15 TO 20 MPH. THIS DISTURBANCE IS
EXPECTED TO PASS WELL TO THE NORTH OF THE LEEWARD ISLANDS AND
PUERTO RICO TONIGHT AND MONDAY...AND MOVE OVER THE TURKS AND CAICOS
ISLANDS AND THE SOUTHEASTERN BAHAMAS ON TUESDAY.

[SapphireSea]

I've noticed that the NHC mentions the LGEM and Ships models a lot and GFDL/HWRF very little so one would think that it has a pretty good chance.

Well SHIPS and LGEM are actually statistical-dynamical. So my previous statement about intensity view was half-wrong. I believe the GFDX models are Intopolated so they extrapolate conditions around dynamically from a few points. The SHIPS models use the data at low res and don't guess. I believe I need a model expert or pro-met to explain the intensity models proper.

[tolakram]

Live IR: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... umframes=5

Live IR with map: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... umframes=5

WV: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=15

[SFLcane]

Stacy!! 8pm TWO 50%

[cycloneye]

Stacy!! 8pm TWO 50%

There are the results of that CBS4 tweet.

[gatorcane]

What a comeback by Dorian. Declared dead 24 hours ago. Now just a little bit of convection away from coming back!

[northjaxpro]

I have to say this is the best this system has looked in four days. Outflow has established itself over ex-Dorian quite nicely and now new convection is flaring up near where a possible new LLC may be forming. I stress may be forming!

If convection can hold together and maintain later tonight, I suspect we may be seeing the revival of this system on tomorrow.

[SFLcane]

Stacy!! 8pm TWO 50%

There are the results of that CBS4 tweet.

I spoke to Stacy early today Luis and he seemed rather concerned with ex Dorian once it slows to less the 10kts in the Bahamas he mentioned the very deep Gulf Stream waters. Recon later 1030 correct? should be interesting especially if they relocated the possible developing llc were storms are currently fireing.

[chaser1]

50%? Sounds about right. Right now, i'd say its all about the dry air that it's continually ingesting into it's mid level circulation and thus choking off the needed convergence and thus preventing the mid level center from working its way down to the surface. Last night into this a.m. i'd say it got close, but the disrupted convection possibly allowed what was a low level center forming, to be pushed faster to the west by the quicker surface layer flow.

Its interesting how naturally each of us might prefer different sites for model data, and of course different resolutions for satellite presentation. Not a new one yet I think useful at night, check out the Shortwave IR -http://www.ssd.noaa.gov/PS/TROP/floaters/91L/flash-swir-short.html
Is looking quite "skeletal" at the moment, but no doubt there's turning at some level.

[Bocadude85]

Not much to see on the 18z GFS

[bahamaswx]

Held his own through DMIN today. Beautiful structure. I don't see any real noteworthy convection yet, but if/when deep reds start appearing on IR it's game on.

[cycloneye]

Stacy!! 8pm TWO 50%

There are the results of that CBS4 tweet.

I spoke to Stacy early today Luis and he seemed rather concerned with ex Dorian once it slows to less the 10kts in the Bahamas he mentioned the very deep Gulf Stream waters. Recon later 1030 correct? should be interesting especially if they relocated the possible developing llc were storms are currently fireing.

Well,he didn't mentioned the recon mission but is planned for 10:30 PM.