April 12 Severe Event

[METALSTORM]

18 minutes ago, AmericanWxFreak said:

Is tornado chasing essential? 

 

If it's you and 1 or 2 others it should be fine. Just bring alcohol wipes or Chlorox wipes and sanitizer. Pack your own food. At the rate these storms will be moving it will be more of a quick intercept rather than following and staying with it.

[eyewall]

I chased in NC the other day and was in my car in a rural area with nobody else around. As long as you don't make contact with people it should be fine.

[Santa Clause]

Looking like we stay moderate until tomorrow and then wait and see if upgrade is needed depending on real time conditions tomorrow.

 

[jpeters3]

Just now, Wmsptwx said:

Looking like we stay moderate until tomorrow and then wait and see if upgrade is needed depending on real time conditions tomorrow.

 

This seems like the responsible decision given the lingering uncertainty. 

[eyewall]

2 minutes ago, Wmsptwx said:

Looking like we stay moderate until tomorrow and then wait and see if upgrade is needed depending on real time conditions tomorrow.

 

Yeah I don't think we will see a high today. During the April, 16 2011 outbreak in NC the high wasn't issued until the morning of the event.

[jojo762]

12z CAMs generally showed less blobs and less elevated WAA convection, but also don’t necessarily show a solution that would scream tornado outbreak either. Moderate risk will probably be maintained at 1730z, pretty cut and dry right now to me that CAM solutions wouldn’t support a high risk.

FWIW, most of them do like the idea of a long-tracking supercell or two.. probably on the tail end of the initial east Texas convection. Seems to me right now that the most probably type of day would be 4/24/10, where we essentially got one monster, memorable supercell (See Tallulah-Yazoo city-Durant tornado) plus another one that was decent.

[Santa Clause]

10 minutes ago, jojo762 said:

12z CAMs generally showed less blobs and less elevated WAA convection, but also don’t necessarily show a solution that would scream tornado outbreak either. Moderate risk will probably be maintained at 1730z, pretty cut and dry right now to me that CAM solutions wouldn’t support a high risk.

FWIW, most of them do like the idea of a long-tracking supercell or two.. probably on the tail end of the initial east Texas convection. Seems to me right now that the most probably type of day would be 4/24/10, where we essentially got one monster, memorable supercell (See Tallulah-Yazoo city-Durant tornado) plus another one that was decent.

Even 4/24 may be higher end than this one, but a lot remains to be seen.

[Radtechwxman]

1 hour ago, jojo762 said:

12z CAMs generally showed less blobs and less elevated WAA convection, but also don’t necessarily show a solution that would scream tornado outbreak either. Moderate risk will probably be maintained at 1730z, pretty cut and dry right now to me that CAM solutions wouldn’t support a high risk.

FWIW, most of them do like the idea of a long-tracking supercell or two.. probably on the tail end of the initial east Texas convection. Seems to me right now that the most probably type of day would be 4/24/10, where we essentially got one monster, memorable supercell (See Tallulah-Yazoo city-Durant tornado) plus another one that was decent.

I totally agree with this. I think there's going to be a lot of morning convection like the Yazoo City day. I think we will see somewhat of a lull by early afternoon with some destabilization occurring from increasing waa south of wf and maybe some peaks of sun. I think the main event will be a mixed mode of supercells and lines of storms. The wind shear should allow a storm or two to advantage of this environment with a few significant tornadoes. I'm honestly more worried about AL for an overnight threat. Overall for now I'm not seeing a major tornado outbreak happening but it is also not out of the cards. This will come down to fine mesoscale details in the morning. However, it only takes one significant tornado hitting a community to make for a bad day

[shaggy]

1 hour ago, eyewall said:

Yeah I don't think we will see a high today. During the April, 16 2011 outbreak in NC the high wasn't issued until the morning of the event.

I'm off on Monday and with us having a slightly later in the morning event I may chase near home If it's safe and my home isn't threatened. Not sure we see enough discrete cells here for any major tornado outbreak but it might not take much to get a few out of this setup.

[joshwx2003]

Anyone else anxiously awaiting the 1730z outlook?

[Santa Clause]

6 minutes ago, StormChaser4Life said:

I totally agree with this. I think there's going to be a lot of morning convection like the Yazoo City day. I think we will see somewhat of a lull by early afternoon with some destabilization occurring from increasing waa south of wf and maybe some peaks of sun. I think the main event will be a mixed mode of supercells and lines of storms. The wind shear should allow a storm or two to advantage of this environment with a few significant tornadoes. I'm honestly more worried about AL for an overnight threat. Overall for now I'm not seeing a major tornado outbreak happening but it is also not out of the cards. This will come down to fine mesoscale details in the morning. However, it only takes one significant tornado hitting a community to make for a bad day

Yeah nothing is looking like outbreak from what I see at least(admittedly more amateur than most) or anything that screams upgrade to high risk...borderline tomorrow in real time.

[MUWX]

1 minute ago, joshwx2003 said:

Anyone else anxiously awaiting the 1730z outlook?

I don’t see any reason that there would be many differences from the prior update. 

[Santa Clause]

2 minutes ago, joshwx2003 said:

Anyone else anxiously awaiting the 1730z outlook?

It will stay MOD I’m certain.

[jojo762]

14 minutes ago, joshwx2003 said:

Anyone else anxiously awaiting the 1730z outlook?

SPC has surprised some of us in the past when we were convinced that there would be no changes. A lot of it henges on who the forecaster writing the outlook is... but I doubt this is one of those instances where they surprise us and choose to upgrade, unless they feel that the solutions showing one or two long-tracking significant supercells across the risk area warrants an upgrade.

[a5ehren]

I would expect some geographical shifts (MDT extended west, maybe a hatched area for winds added somewhere?), but can't see a HIGH justified from the new runs in the last 12 hours.

[ILMRoss]

We really don’t know if the high ceiling will be realized until this time tomorrow. Every CAM has a different technique on how they render boundary layer mixing, which dictates how warm it gets at the surface. 3km NAM still displays a “mild” solution, in this case meh surface temperatures never get past the mid 70s and rising parcels don’t really have a ton of difference between their temp and the background temp until they rise to about 700 MB, according to this sounding I pulled. If the 3km is right, expect to see a lot of shallow, ‘baby’ supercells that struggle to stay alive amongst the strong low level shear. This solution would keep the SPC from slapping a high risk onto things.

Once again, all about boundary layer with this limiter, and other models (looking at you HRRR) will scare a lot of people because they have a tendency to overdue temps and therefore, CAPE.

[MUWX]

They seem to be running a little late with the update 

[jpeters3]

5 minutes ago, ILMRoss said:

We really don’t know if the high ceiling will be realized until this time tomorrow. Every CAM has a different technique on how they render boundary layer mixing, which dictates how warm it gets at the surface. 3km NAM still displays a “mild” solution, in this case meh surface temperatures never get past the mid 70s and rising parcels don’t really have a ton of difference between their temp and the background temp until they rise to about 700 MB, according to this sounding I pulled. If the 3km is right, expect to see a lot of shallow, ‘baby’ supercells that struggle to stay alive amongst the strong low level shear. This solution would keep the SPC from slapping a high risk onto things.

Once again, all about boundary layer with this limiter, and other models (looking at you HRRR) will scare a lot of people because they have a tendency to overdue temps and therefore, CAPE.

I would be cautious in interpreting these soundings from tropical tidbits.  Strictly speaking, one should compare the virtual temperature of a lifted parcel to the virtual temperature of the background environment to assess lifted parcel buoyancy and CAPE, but their soundings use actual temperature.  So this plot is misleading - the dashed line is probably a bit more to the right than indicated on here.  Note that there is no MLCIN.  This is actually a pretty good looking thermodynamic profile.

Attached is a similar sounding from the same approximate location and time, plotted correctly from dupage.  You can see that there is actually quite a bit of low-level buoyancy for a lifted parcel.

 

 

[jojo762]

Seems to be an error of some sort with the 1730z update. It updated at 12:35pm on the COD SPC website, but the discussion text is exactly the same as the 06z D2 update.

[SmokeEater]

They may be going high risk, 45% wind contour is added.

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[METALSTORM]

Just now, MUWX said:

They seem to be running a little late with the update 

I kind of expected it to. Probably some heated discussions and maybe out and out arguing. Or revising the written disco.

[yoda]

Just now, SmokeEater said:

They may be going high risk, 45% wind contour is added.

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I think 60% wind is needed for high risk 

[a5ehren]

Just now, yoda said:

I think 60% wind is needed for high risk 

https://www.spc.noaa.gov/misc/SPC_probotlk_info.html

Yeah, 60% hatched to go HIGH for wind. 30% hatched for HIGH on tornadoes.

[SmokeEater]

I think 60% wind is needed for high risk 

Yea it wouldn't be for wind, just judging where it is, either the mod is gonna shift, or it's high. I'm furiously refreshing, lmfao.

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[SmokeEater]

Stays moderate, mod just got slightly larger.

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[SmokeEater]

.

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[jpeters3]

Good call on the Mod risk, IMO.  

[MUWX]

Mentioned increasing wind probs. But unless they hatch, it won’t be a wind driven high risk. 

[jojo762]

Just now, MUWX said:

Mentioned increasing wind probs. But unless they hatch, it won’t be a wind driven high risk. 

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.

[ILMRoss]

I would be cautious in interpreting these soundings from tropical tidbits.  Strictly speaking, one should compare the virtual temperature of a lifted parcel to the virtual temperature of the background environment to assess lifted parcel buoyancy and CAPE, but their soundings use actual temperature.  So this plot is misleading - the dashed line is probably a bit more to the right than indicated on here.  Note that there is no MLCIN.  This is actually a pretty good looking thermodynamic profile.

Attached is a similar sounding from the same approximate location and time, plotted correctly from dupage.  You can see that there is actually quite a bit of low-level buoyancy for a lifted parcel.
 
 

Ok, thank you, it’s been too long since I’ve taken thermo and my old textbook is an an attic somewhere so I’m in not much of a position to rebut. That dents my argument, although I’m still weary of low level buoyancy issues (that was a better-than-the-median sounding of the ones I glanced at)