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Severe WX Severe Weather Threat 3/14-3/16

KevinH said:
You are going to end up eating your words :)

Super Outbreaks only happening once every 35-40 years is no longer the case. Not saying this weekend will be a Super Outbreak, but we will see one well before 2040 :(
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Was it ever the case? I think it depends on how you define Super Outbreak but, honestly, there wasn't THAT much separating Palm Sunday 65 and 74 in terms of raw violence, granted that one was broader (But Palm Sunday had violent tornadoes from Iowa to Eastern Ohio!) and had more tornadoes overall. They were only 9 years apart

Point being, truly upper echelon outbreaks aren't necessarily an every two generations event in any era
 
Aaron Rider said:
Was it ever the case? I think it depends on how you define Super Outbreak but, honestly, there wasn't THAT much separating Palm Sunday 65 and 74 in terms of raw violence, granted that one was broader (But Palm Sunday had violent tornadoes from Iowa to Eastern Ohio!) and had more tornadoes overall. They were only 9 years apart

Point being, truly upper echelon outbreaks aren't necessarily an every two generations event in any era
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The "generational" terminology is very popular and widespread, but remember that what it's referring to is statistical frequency, not real frequency. On average, "generational" outbreaks may happen every 40-50 years or so, but that is an average. 2 such outbreaks could occur 3 weeks apart, nothing keeps that from happening, it's merely that in any given period, there is an average of 1 such event.
 
Clancy said:
The "generational" terminology is very popular and widespread, but remember that what it's referring to is statistical frequency, not real frequency. On average, "generational" outbreaks may happen every 40-50 years or so, but that is an average. 2 such outbreaks could occur 3 weeks apart, nothing keeps that from happening, it's merely that in any given period, there is an average of 1 such event.
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This is key in understanding how statistics work. Just because something typically occurs once every 100ish years or so doesn’t mean it will happen every 100 years - it is not outside of the realm of possibility for another super outbreak to occur only a couple months apart, or literally weeks apart. It’s just statistically extremely unlikely to occur. In a March pattern like this one, it is not outside the realm of possibility for this to verify as a truly upper echelon outbreak IMO. If things continue to display as they are I honestly don’t see any way to sugar coat this; tell it like it is.
 
So I decided to try ChatGPT seemed pretty cool. I used the same box sounding that was used earlier. And asked wether the sounding indicated storms would be sheared apart.

*Based on the provided sounding and hodograph, storms are unlikely to be sheared apart in this environment. The hodograph shows strong deep-layer shear (notably, 0-6 km shear exceeding 50 knots), which is favorable for organized convection, including supercells.

Additionally, low-level shear (0-1 km shear and SRH) is also strong, supporting storm rotation and potential tornadoes rather than storm disruption. The presence of a curved hodograph and significant helicity values suggest an environment supportive of sustained, rotating updrafts.

Rather than storms being sheared apart, this setup favors organized severe storms, including supercells with potential tornadoes. The presence of a "PDS TOR" (Particularly Dangerous Situation Tornado) label further supports th
is.*
 
slenker said:
This is key in understanding how statistics work. Just because something typically occurs once every 100ish years or so doesn’t mean it will happen every 100 years - it is not outside of the realm of possibility for another super outbreak to occur only a couple months apart, or literally weeks apart. It’s just statistically extremely unlikely to occur. In a March pattern like this one, it is not outside the realm of possibility for this to verify as a truly upper echelon outbreak IMO. If things continue to display as they are I honestly don’t see any way to sugar coat this; tell it like it is.
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Yeah this is kind of why I dislike the term "generational", because, let's face it, the mathematical literacy of the average non-weather-weenie probably isn't that high, and they're not going to understand that calling an outbreak "generational" is a probabilistic statement and there's no physical reason you couldn't have another "generational" outbreak next month, it's just statistically very unlikely.
 
wx_guy said:
This is from Chat GPT so please...take it with grains of salt! That being said, it's very obvious AI is making leaps and bounds and can interpret this sounding pretty effectively. This is its response to my box sounding encompassing all of eastern MS and all of western AL at 21z on Saturday. Thoughts?



This box sounding from the 18z GFS valid for Saturday (March 15, 21z) over eastern Mississippi and western Alabama suggests a highly volatile severe weather environment with strong tornado potential.

Thermodynamics:​

  • MLCAPE: ~1700 J/kg, with SBCAPE slightly higher at ~1900 J/kg. These values indicate moderate instability, sufficient for sustained deep convection.
  • LCL (Lifted Condensation Level): ~745m AGL – very low, suggesting strong low-level buoyancy and efficient stretching of updrafts.
  • LFC (Level of Free Convection): ~1.1 km – also quite low, which supports quick storm development and low CINH.
  • EL (Equilibrium Level): ~12.5 km, meaning strong updrafts will have room to grow deep into the troposphere.
  • Steep lapse rates: The 700-500mb lapse rate is 7.0°C/km, which is favorable for robust convection.

Kinematics (Shear & Hodograph Analysis):​

  • 0-1km SRH: 517 m²/s² and 0-3km SRH: 597 m²/s² – These values are highly supportive of tornadic supercells, especially in a low LCL environment.
  • Bulk shear:
    • 0-6km shear: ~80 knots – extremely strong, ensuring strong storm organization.
    • Effective inflow shear: 64 knots – indicating supercell support.
  • Critical Angle: 56° – Favorable for effective streamwise vorticity ingestion.
  • Hodograph: Displays a large, curved shape in the lowest 1-3 km, with substantial veering and elongation – highly favorable for tornado development.

Significant Tornado Potential:​

  • Supercell Composite Parameter (SCP): 16.6 – very high, strongly supportive of discrete supercells.
  • Significant Tornado Parameter (STP):
    • Effective-layer STP: 3.6 (without CIN) and 1.1 (with CIN). This is supportive of strong tornadoes, though CINH may need to erode for storm initiation.
  • SARS Analog Matches:
    • 77% match to a past violent tornado case (TOR PDS)
    • 50% significant hail match
  • PDS Tornado Threat Classification – This highlights the strong risk of EF2+ tornadoes given convective initiation.

Storm Mode & Hazards:​

  • Storm motions: Right-moving supercells expected with a 220°/55kt mean vector – fast-moving storms.
  • Low-Level Shear (LLS): ~200 m²/s² – highly supportive of tornadogenesis.
  • EBWD (Effective Bulk Wind Difference): 64 knots, reinforcing the supercell threat.

Conclusion:​

This box sounding strongly suggests a dangerous severe weather event with the potential for significant, long-track tornadoes. If convection initiates and remains discrete, any storm developing in this environment will likely become tornadic quickly. The combination of low LCLs, extreme low-level shear, and strong instability makes this a classic high-end tornadic setup for the Deep South. If this forecast holds, this would warrant a moderate or higher risk outlook from SPC.
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Thanks for posting this. Very helpful for someone like me who doesn't understand everything that I'm looking at.
 
Clancy said:
The "generational" terminology is very popular and widespread, but remember that what it's referring to is statistical frequency, not real frequency. On average, "generational" outbreaks may happen every 40-50 years or so, but that is an average. 2 such outbreaks could occur 3 weeks apart, nothing keeps that from happening, it's merely that in any given period, there is an average of 1 such event.
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Agreed. 4/15/11 isn’t considered generational, because of the lack of violent tornadoes, but 45 tornadoes in a state on one day is pretty generational. Especially when the next closest numbers up to that point were 36 and 23…one of which was a tropical tornado episode.
 
NorthGaWeather said:
Agreed. 4/15/11 isn’t considered generational, because of the lack of violent tornadoes, but 45 tornadoes in a state on one day is pretty generational. Especially when the next closest numbers up to that point were 36 and 23…one of which was a tropical tornado episode.
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Wasn't it the state's biggest tornado total for a single outbreak until 4/27?
 
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