A subtle 500-mb shortwave trough brought enough instability to pair with 60-70 kts of 0-6 km bulk shear to create some potent storms last night and early this morning. The Storm Prediction Center had issued a slight risk of storms, including tornadoes, for the mid-Mississippi Valley at 2000 UTC yesterday.
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| Fig. 1: SPC 2000Z categorical outlook with preliminary verification. |
The severe storm activity began with one isolated storm that formed in southeast Missouri and traveled through Cairo, IL and southern Kentucky, dropping large hail.
NOAA/CIMSS ProbSevere highlighted this storm early on, aided by a "strong" satellite growth rate from GOES-16 and a quickly-increasing total lightning flash rate, from
ENTLN. The storm exhibited robust radar signatures by the time it was first warned.
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| Fig. 2: ProbSevere (contour) with MRMS MergedReflectivity and NWS severe thunderstorm warning (yellow polygon). |
Below, we see the rapid increase in ProbHail and ProbWind around 22:00 UTC, while ProbTor increased much later in the storm's life (and produced a tornado report). You can see the ProbSevere predictor time series for this storm
here.
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| Fig. 3: Time series of ProbSevere models' probabilities for an isolated storm in MO/IL/KY. |
Numerous large hail reports (and several tornado reports, later on), were a result of convective storms in southeast Missouri.
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| Fig. 4: ProbSevere contours (outer contours are colored by the ProbTor value, present if ≥ 15%), MRMS MergedReflectivity, and NWS severe weather warnings. |
Another storm formed in western Tennessee and was quickly warned by the NWS. This storm spawned
several damaging and deadly tornadoes in Nashville and Cookeville, as well as hail up to the size of baseballs. ProbTor probabilities ramped up in response to increasing MRMS azimuthal (i.e., rotational) shear and total lightning density in an environment characterized by 40 kts of effective bulk shear, 50 kts of 1-3km AGL mean wind, and 400 J/kg of 0-1km AGL storm-relative helicity. More time series plots of ProbSevere predictors are saved
here and
here.
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| Fig. 5: ProbSevere contours (outer contours are colored by the ProbTor value; present if ≥ 15%), MRMS MergedReflectivity, and NWS severe weather warnings. |
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| Fig. 6: Time series of ProbSevere models' probabilities for a long-lived, deadly storm in Tennessee. |
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| Fig. 7: Time series of ProbTor probabilities and constituent predictors for the long-lived, deadly storm in Tennessee. |
