April 12 Severe Event

[yoda]

 

[audioguy3107]

Hmmmmm, "historic" wording from FFC is, needless to say, extremely unusual.  Haven't heard them honk this much since April 2011 and along with everyone else, hard to see something like that verifying.  Wonder what their thinking is, especially since ATL is further east (as usual) from the greatest threat area.

[boo radley]

  On 4/11/2020 at 6:01 PM, yoda said:

 

Expand  

Isn’t Atlanta pretty far east for tornado threat?

[audioguy3107]

  On 4/11/2020 at 6:04 PM, Wmsptwx said:

Isn’t Atlanta pretty far east for tornado threat?

Expand  

The Atlanta metro is definitely in play for the chance of significant severe including a tornado or two, but as it happens almost 100% of the time with these setups, the instability and threat for major severe always diminishes the further east, especially as you go into the overnight hours.  We call it the north Georgia storm shield.

[ingyball]

Atlanta and the western parts of Georgia are under the 10% hatched, perhaps it may be a tad overboard, but they're very much on the eastern edge of the tornado threat for right now. 

[jpeters3]

  On 4/11/2020 at 6:12 PM, ingyball said:

Atlanta and the western parts of Georgia are under the 10% hatched, perhaps it may be a tad overboard, but they're very much on the eastern edge of the tornado threat for right now. 

Expand  

The 12 UTC 3km NAM sends an UH track right over downtown ATL...

[Upper Level LOL]

  On 4/11/2020 at 6:15 PM, jpeters3 said:

The 12 UTC 3km NAM sends an UH track right over downtown ATL...

Expand  

UH tracks =\= tornados, that's a pretty crude way to interpret that

 

 

[ingyball]

  On 4/11/2020 at 6:29 PM, Upper Level LOL said:

UH tracks =\= tornados, that's a pretty crude way to interpret that

 

 

Expand  

Sure, you use it like you'd use any other parameter. If you go blindly using any one parameter you'll get burnt. The important thing to take from it is that the model does have a storm there that could otherwise take advantage of an atmosphere capable of strong tornadoes. Perhaps it's in the form of a QLCS, but it's been stated before that even a QLCS can produce a strong tornado in some of these atmospheric conditions. 

[Upper Level LOL]

  On 4/11/2020 at 6:38 PM, ingyball said:

Sure, you use it like you'd use any other parameter. If you go blindly using any one parameter you'll get burnt. The important thing to take from it is that the model does have a storm there that could otherwise take advantage of an atmosphere capable of strong tornadoes. Perhaps it's in the form of a QLCS, but it's been stated before that even a QLCS can produce a strong tornado in some of these atmospheric conditions. 

Expand  

Yeah a prolific nighttime QLCS is a definite possibility with this setup

[Quincy]

  On 4/11/2020 at 5:56 PM, jojo762 said:

The discussion text is literally the same from the 06z update, word for word, while the graphics are different. I suspect this is an error, and would anticipate them fixing this soon.

Expand  

Sometimes for continuity they use the same text and only tweak some wording details. I’ve noticed it a bit more lately. 

[jpeters3]

  On 4/11/2020 at 6:29 PM, Upper Level LOL said:

UH tracks =\= tornados, that's a pretty crude way to interpret that

 

 

Expand  

You don't have to patronize with statements like this.  Obviously UH tracks are not a direct indicator of a tornado.  UH tracks in an environment that can support tornadoes suggest the possibility.  Take a look at the models before posting.

Below is a forecast sounding just west of ATL just before the UH track was produced.  A low-shear very high CAPE type of scenario, but could certainly support a strong QLCS and/or embedded supercell related tornado threat.  

 

[goldsborosnow]

How useful is this model product? Its showing a 75% contour over Central NC Monday afternoon 

[jojo762]

  On 4/11/2020 at 6:43 PM, Quincy said:

Sometimes for continuity they use the same text and only tweak some wording details. I’ve noticed it a bit more lately. 

Expand  

I've just never seen them do it for such an anticipated event, especially for the D2 outlook. I mean, I suppose not enough changed between the 00z CAMs and the 12z CAMs to talk about much more, i'm just surprised that the forecaster would not want to provide their own forecast.

[Quincy]

  On 4/11/2020 at 6:59 PM, goldsborosnow said:

How useful is this model product? Its showing a 75% contour over Central NC Monday afternoon 

Expand  

It has some utility, but not always. It gives you a good idea of where the background environment would favor tornadoes, but it doesn’t really distinguish between storm mode (supercell vs. QLCS for example).

Usually it exaggerates the threat between 06-12z due to the LCL and 0-1km terms skewing during that time frame, however I think this situation is a outlier, where nighttime and morning tornadoes could be fairly widespread. 

[shaggy]

  On 4/11/2020 at 7:06 PM, Quincy said:

It has some utility, but not always. It gives you a good idea of where the background environment would favor tornadoes, but it doesn’t really distinguish between storm mode (supercell vs. QLCS for example).

Usually it exaggerates the threat between 06-12z due to the LCL and 0-1km terms skewing during that time frame, however I think this situation is a outlier, where nighttime and morning tornadoes could be fairly widespread. 

Expand  

I'm in greenville NC and pulled this sounding just as the storms hit here.  Ot sure I've ever seen SRH levels above 500 m2 s2 here.

 

[Solak]

New day 3

 

[joshwx2003]

  On 4/11/2020 at 7:26 PM, Solak said:

New day 3

 

Expand  

This will be interesting for me to experience as I live in SE NC

[jojo762]

Everyone's favorite dooms day model, the HRRR, added to the complexity of the forecast with the 18z run. I know the HRRR has a reputation for running hot when it comes to blowing up convection, but it *really* blows up lots of storms throughout the afternoon in most of Mississippi and Alabama, should be noted that this does stand relatively in contrast with the 12z CAMs. With this run there is a possibility that there could be tornadoes given the impressive low-level wind field, but honestly looks more like a heavy rain and damaging wind threat to me than a tornado threat. Some potential for supercells to form behind the blobs of rain, or within, but do not think that they'd be very intense storms.

[boo radley]

  On 4/11/2020 at 7:51 PM, jojo762 said:

Everyone's favorite dooms day model, the HRRR, added to the complexity of the forecast with the 18z run. I know the HRRR has a reputation for running hot when it comes to blowing up convection, but it *really* blows up lots of storms throughout the afternoon in most of Mississippi and Alabama, should be noted that this does stand relatively in contrast with the 12z CAMs. With this run there is a possibility that there could be tornadoes given the impressive low-level wind field, but honestly looks more like a heavy rain and damaging wind threat to me than a tornado threat. Some potential for supercells to form behind the blobs of rain, or within, but do not think that they'd be very intense storms.

Expand  

Saw that...was a bit of a mess. Definitely not a high risk look on HRRR.

[gman]

Received this e-mail from Duke Energy.

High winds and heavy rains could bring significant damage and outages. Here’s how we’re preparing. 

Severe weather is forecast for the Carolinas later this weekend and into Monday, including high winds, heavy rains and an increased risk of tornadoes. These conditions could also bring significant damage to trees, power lines and other electrical equipment. 

We recognize that this is already an extremely challenging time in our community. And the possibility of storm damage or power outages on top of everything else is hard to hear. That’s why we’re doing everything we can to prepare for this approaching weather and to restore any resulting outages as quickly as possible. 

We also encourage you to take whatever steps you can to prepare for the incoming weather conditions. See our website for helpful tips and information. You can also help protect your perishable foods with this helpful guidance from the U.S. Food and Drug Administration.

If you do lose power, you can report your outage online or by texting OUT to 57801. While you’re on our website, you can also check our maps for any available updates. You can also sign up for outage restoration alertsand learn more about our power restoration process. 

 

 

Safety Reminders 

• Stay away from power lines that have fallen or are sagging. Consider all lines energized as well as trees, limbs or anything in contact with lines.
• If a power line falls across a car that you’re in, stay in the car. If you MUST get out of the car due to a fire or other immediate life-threatening situation, do your best to jump clear of the car and land on both feet. Be sure that no part of your body is touching the car when your feet touch the ground.  
• Charge cellphones, computers and other electronic devices in advance of the storm to stay connected to important safety and response information. Consider purchasing portable chargers and make sure they are fully charged as well.

Thank you in advance for your patience as we all work together to get through this latest challenge. We hope no one’s power is affected by these storms – but if yours is, we’ll be hard at work, doing everything possible to repair the damage and get you back up and running as quickly as possible. 

[Radtechwxman]

18z HRRR continues a very messy evolution of tomorrow. Multiple waves of storms. Still could see significant severe esp with anything interacting with the warm front

[jpeters3]

  On 4/11/2020 at 8:01 PM, Wmsptwx said:

Saw that...was a bit of a mess. Definitely not a high risk look on HRRR.

Expand  

I don't know - one could argue that a lot of these are discrete cells, and there are A LOT of UH tracks.  This could indicate an outbreak.

[Windspeed]

  On 4/11/2020 at 8:32 PM, jpeters3 said:

I don't know - one could argue that a lot of these are discrete cells, and there are A LOT of UH tracks.  This could indicate an outbreak.

The coverage in the warm sector is large. People are expecting a string of pearls, however, these may very well be scattered cells in close proximity over a wide coverage area. The initial explosive convection in the warm sector that would be suspect and tornadic doesn't look particularly linear to me.

 

Edit: RE :18z HRRR. I should add that the convection on the backside of that warm sector does take on a more linear look, but not until after plenty of intial suspiciously discrete convection has already moved NE into the upper TN Valley.

[jpeters3]

FYI, my former PHD advisor's group at CSU runs a 4 km WRF that uses GFS as LBCs.  The simulated radar reflectivity loop can be found here:

 

http://schumacher.atmos.colostate.edu/weather/real_time_wrf/radar_1km_4km/anim.php

 

UH tracks:

 

[DanLarsen34]

  On 4/11/2020 at 9:30 PM, jpeters3 said:

FYI, my former PHD advisor's group at CSU runs a 4 km WRF that uses GFS as LBCs.  The simulated radar reflectivity loop can be found here:

 

http://schumacher.atmos.colostate.edu/weather/real_time_wrf/radar_1km_4km/anim.php

 

UH tracks:

 

Expand  

That paints a volatile scenario for tomorrow. Loop towards the middle showed several discrete/semi-discrete cells breaking out across Mississippi. 

[Indystorm]

And that loop also shows the initial WAA storms getting out of the way and off to the north.

[DanLarsen34]

 

[Amped]

  On 4/11/2020 at 9:35 PM, DanLarsen34 said:

That paints a volatile scenario for tomorrow. Loop towards the middle showed several discrete/semi-discrete cells breaking out across Mississippi. 

Expand  

And it goes nuts overnight tomorrow. I don't know if that's a NAM thing or a legit threat.

[SnowGoose69]

  On 4/11/2020 at 9:46 PM, DanLarsen34 said:

 

Expand  

There has been so many events where wildfire smoke was involved it’s hard to really come to any conclusion.  The May 3 1999 outbreak in Oklahoma had widespread smoke from Mexico fires 

[Amped]

Are there any recons doing extra soundings in the gulf tonight?