ATL: NESTOR - Post-Tropical - Discussion

[northjaxpro]

It looks like the CoC is moving more E-NE than Northeast the.past couple of hours. You aldo see the shesr pushing away the vonvection from the CoC this hour. The CoC looks to pass just south of Apalachicola and move into position to come ashore a little farther eastward in the Big Bend region, probably around St. Marks .

The punch of cool, and stable air from the west kept the CoC to not intensify which I had thought would happen. The reliable EURO, GFS and UKMET as late as late yesterday all had Nestor's CoC intensifying on approach to landfall this morning. Right now pressure is at 998 mb with the center, but has not dropped any lower than that to this juncture. So unless it intensifies in the next 2-3 hours or so, Nestor has peaked in intensity in all likelihood

It appears the models were a bit too agreessive on the intensity of the system. I too was of the thought that the cyclone could "wall off" the cooler punch up to landfall, but that did not occur. This is why intensity forecasts with cyclones is among yhe toughest challenges in forecasting. Also, you could make a case of Nestor being subtropical right now due to the strongest wind and heavy weather well removed to the south and east of the CoC and the cooler and stable drier air advecting in from the west.

57 earlier called it correctly late yesterday observing how effectively that cool air behind the front at the coast would eventually halt any potential of further intensification of the CoC.

There are still storm surge concerns as always when either cyclones or other significant west or southwesterly wind flow events occurs in Apalachee Bay. We will have to see later today just how that will evolve, especially in Cedar Key, and Steinhatchee. Also Horseshoe Beach is another locale prone to surge.

Also, there waa some tornado activity which occured last night down in Pinellas County and that is not surprising with the strong helecity values indicated and favoranle profiles conducive
for these quick, small scaled tornadoes to spin-up and touchdown from these super cells. This is always probable to see this occur with any landfalling cyclone and we potentially could see a few more of these super cells to occur across the region later this morning into the early afternoon. Lots of much needed rainfall is soaking a good vast amount of the peninsula from the Big Bend region and points east and southeast. Should see good rain.amounts in the 2-4 inch range for most with this event with Nestor.

[GCANE]

Looks like a cell headed for Metro Tampa with the possibility of a tornado developing.

[GCANE]

 https://twitter.com/BeauWTSP/status/1185427758807162880




 https://twitter.com/LuisSantana/status/1185416183400587264

[GCANE]

Cell is intensifying on approach to Tampa Metro

[bamajammer4eva]

I'm kinda surprised there's no tornado risk across S AL, S GA, FL Panhandle areas when the risk is always greatest NORTH as well as east of the storm center and track. East is covered by Tornado watch for peninsula but why no risk to the North?

Radar

[caneman]

NHC at 5 said the center is now I'll defined but it looks like whatever is left is coming onshore between Cedar Key and Cross city to me. Significant damage to a school in the Tampa bay area (Lakeland) and some mobile homes (Seminole). Calling for 5ft storm surge. We will see how that pans out.

[GCANE]

MD 2075

https://www.spc.noaa.gov/products/md/md ... um=twitter



Mesoscale Discussion 2075
NWS Storm Prediction Center Norman OK
0401 AM CDT Sat Oct 19 2019

Areas affected...Central/northern FL Peninsula

Concerning...Tornado Watch 675...

Valid 190901Z - 191030Z

The severe weather threat for Tornado Watch 675 continues.

SUMMARY...Threat for a few tornadoes and locally strong wind gusts
will continue this morning.

DISCUSSION...At 0845Z, the strongest convection in/near WW 675 is
ongoing off of the FL East Coast, and also across portions of the
west-central Peninsula. Persistent rotating cells east of Cape
Canaveral will continue to pose a threat of waterspouts, but this
threat is expected to remain generally offshore for the next few
hours.

Further west, a cluster of convection that developed earlier over
southwest FL is moving north-northeastward. Weak rotation has
occasionally been noted with convective elements within this
cluster. As this cluster approaches the diffuse warm-frontal zone
across the central/northern Peninsula, some uptick in the tornado
threat is possible, given 0-1 km SRH values of 200-300 m2/s2 noted
in the TBW VWP and recent objective mesoanalyses.

As T.S. Nestor continues to move north-northeastward toward the FL
Panhandle, offshore convection will gradually spread into western
portions of the FL Peninsula through mid morning. Some tornado
threat will persist with this round of convection as well,
especially with cells interacting with the effective warm front,
which is expected to gradually move northward with time through the
morning.

..Dean.. 10/19/2019

[bamajammer4eva]

Channel 7 seems to agree with Panhandle/AL risk and are tracking the storms


 https://twitter.com/RyanMichaelsWX/status/1185486452383199233

[lando]

Closest I’ve ever come to a tornado was tonight at less than 2 miles! Crazy stuff, especially when your at work and It’s not only your life to worry about haha

[Frank2]

Glad I stuck to my first take on this system despite some who thought "the Gulf will do its magic" - 50 Kts of shear does not make a viable system. Its easy to hear the frustraton of the NHC forecaster in the latest discussion. That is why the system was not named initially and should never had been named, because it was never a distinct tropical system. -removed- or trigger-finger forecasting only confuses everyone and should never be allowed. The old days of forecasting did not allow this or rarely were errors made. Today thanks to the pressures of social media they are made too frequently. I wonder what my old forecaster coworkers think of so-called Nestor...

[NDG]

Shear and dry air won over the system, but when you have the usual very trust worthy Euro on its 12z run yesterday forecasting it to become a 980mb storm is hard not to go ahead and name it. Is the good old damn if you do or damn if you don't, they are always going to get crap from both extreme sides
Perhaps it should had been named Subtropical Storm Nestor, it did qualified for that, proof me otherwise that it did not deserved to be named.

Edit: I just read the latest NHC discussion, I don't see the frustration in the forecaster that you are talking about, other than "it is rapidly loosing the few tropical characteristics that it once had".

[northjaxpro]

I'm kinda surprised there's no tornado risk across S AL, S GA, FL Panhandle areas when the risk is always greatest NORTH as well as east of the storm center and track. East is covered by Tornado watch for peninsula but why no risk to the North?

Radar

https://i.imgur.com/B2TPixS.jpg

The reason in this particular instance and situation:

A cool and stable airmass in.place NORTH of Nestor. Dew points are currently well down into the 40s and 50s all across much of Georgia and the Carolinas with a very cool, northeast flow in.place. This situation is similar to a CAD situation.up that way during winter. So, the dynamics are just lacking and.are simply not in place or not sufficient for the development of tornadoes north of Nestor right now.

Now, as the front moves back north as a warm front later today, the warm, moist air will move over the cooler, stable airmass, which will promote a very significant overrunning (isentrophic lifting) event across much of Georgia and the Carolinas later today. They are in for quite a heavy rain event, especally the Carolinas. BTW, the Florida Gators play at noon today in Columbia SC to play the SC Gamecocks and that will be a quagmire as heavy rain will occur all during that game.

So, as Nestor moves away to the northeast, then instability and dew points will increase along the immediate Southeast U.S. coast up to NC , which may allow a chance of a few isolated tornadoes to develop later today. But, that window for this possibility to happen will be very narrow as Nestor.moves rapidly through the region.

[NDG]

The only reason why I think Nestor did not strengthened as much as yesterday's 12z Euro showed is because the shortwave passed over Nestor faster than what it was forecasting it, like the latest NHC mentions, and can clearly seen on water vapor how the convection around Nestor's CoC collapsed after the passage of the shortwave.

[northjaxpro]

:uarrow: Shear and dry air won over the system, but when you have the usual very trust worthy Euro on its 12z run yesterday forecasting it to become a 980mb storm is hard not to go ahead and name it. Is the good old damn if you do or damn if you don't, they are always going to get crap from both extreme sides
Perhaps it should had been named Subtropical Storm Nestor, it did qualified for that, proof me otherwise that it did not deserved to be named.

Edit: I just read the latest NHC discussion, I don't see the frustration in the forecaster that you are talking about, other than "it is rapidly loosing the few tropical characteristics that it once had".

Yeah when I saw that 12Z EURO run yesterday getting Nestor down to 980 mb by landfall, I also let that influence my thinking , like I am sure many did as well. All of the Big 3 Reliables, The EURO, GFS and the UKMET had all showed Nestor intensifying right up to approach of landfall. It just did not happen this time around. Cool and stable air from the north and west, along with strong shear really ctippled the CoC and the models were too aggressive strengthening it. That' s the beauty of the tropics and weather in general. Forecasting intensity with cyclones is the toughest task, no doubt about it.

[AJC3]

I'm kinda surprised there's no tornado risk across S AL, S GA, FL Panhandle areas when the risk is always greatest NORTH as well as east of the storm center and track. East is covered by Tornado watch for peninsula but why no risk to the North?

Radar

https://i.imgur.com/B2TPixS.jpg

Zero surface-based instability. Current surface temperatures there are in the lower 60s. You can have all the helicity on the planet, however if the air mass isn't unstable/buoyant, you won't get deep convection, let alone tornadoes.



The eastern panhandle is under a MRGL risk early today though...

[NDG]

Another video as the tornado in Polk County crossed I-4

 https://twitter.com/IreneSans/status/1185420066956943361

[northjaxpro]

The only reason why I think Nestor did not strengthened as much as yesterday's 12z Euro showed is because the shortwave passed over Nestor faster than what it was forecasting it, like the latest NHC mentions, and can clearly seen on water vapor how the convection around Nestor's CoC collapsed after the passage of the shortwave.

Yeah, I agree with you NDG about this as well. That shortwave came through faster than anticipated and that in turn was a chief contributor to kill the convergence around Nestor's CoC.

[wxman57]

So far have not seen any severe weather in Panama City but you can definitely tell this system is tropical in nature. Our temperature went from 59 at 5pm to 68.5 currently. The pressure here is down to 1004mb, highest wind gust at my house 28mph and highest I have seen in our area 44mph at St. George Island.

What you observed was the warm front pushing back inland across the Panhandle. That doesn't mean Nestor is tropical.

[wxman57]

Plenty of surface obs across the NE Gulf to analyze Nestor's intensity. Max wind I could find was one brief 35kt report from a buoy south of Apalachicola as a squall went by. Nestor appears to be a frontal low with 30-40 mph winds. Mostly, winds are in the 20-30 mph range.

[N2FSU]

Per 8am NHC update discussion, "center" has reformed about 50 miles further west.


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