Tuesday, December 29, 2015   |   Case Studies, Critical Weather

Case Study: Mississippi Tornado – Dec. 23, 2015

On December 23, 2015, a long track tornado made its way through Mississippi and Tennessee causing significant damage in several areas. The initial time of touchdown was at 2:58 p.m., a few miles to the north of Shelby, Mississippi along US-61. This is visible in the images above and below. Around 2:35-2:37 p.m., a severe SCIT would have produced a “Dangerous Storm Approaching” alert for that area. At 2:43 p.m. the first Shear Marker was present from LZK radar, indicating the storm was quickly developing a circulation. The NWS in Memphis issued the first Severe Thunderstorm Warning at 2:53 p.m. for the storm.

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At 2:57 p.m. the first Shear SCIT associated with the storm appeared, sending out the initial “Twisting Storm Approaching” alert, which was just ahead of the time of the initial tornado touchdown. It should be noted that it appears Shear SCITs and “Twisting Storm Approaching” alerts were then present through the duration of the tornado. The NWS in Memphis issued its first Tornado Warning for the storm a few minutes later at 3 p.m. By 3:05 p.m. there was already a TDS marker with the storm coming from Memphis radar.

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Several videos online show the tornado crossing I-55 near Como, Mississippi just before 4 p.m., or about an hour after the tornado developed. At the time the tornado crossed the Interstate, reflectivity data showed a doughnut hole in the location of the tornado. The storm information box indicated it was moving NE at 56 mph with 104 mph of shear, along with a strong circulation noted in velocity data.

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There was a high amount of shear within the storm at this time, as well. The correlation coefficient showed only a small area with low values, indicating a small amount of lofted debris. This was verified in numerous videos of the tornado crossing the Interstate.

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A mosaic of the Baron Button shows the path of the tornado, which matches with the Shear Swath product.

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Holly Springs, Mississippi was probably hit the hardest by the tornado, and Baron products performed extremely well with the storm as it passed through the town.  Below is the TDS Swath product and the TDS Marker with a debris extent of nearly 2 miles.

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As the storm approached Holly Springs, over 200 mph of gate-to-gate shear was observed in De-Aliased Velocity data and minutes later a very well-defined hook echo was present in reflectivity data as it passed over the city.

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As the storm passed over Holly Springs, the Shear Rate product clearly showed the high amount of shear present within the storm. Very few hail reports were received with the storms in Mississippi, and the Reflectivity With Hail product shows only a small area of hail present within the storm.

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The town of Holly Springs sustained a lot of damage and Resampled RHO can give further proof of that. An area of lowered CC was present with the storm for many radar scans as it moved through north Mississippi. Minutes before hitting the town, the area of lowered CC was small in size with the lowest values of .575.  But after passing through the town, the area of lowered CC expanded in size with values lowering down to .465. This indicated an increased amount of lofted debris.

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Another area hit hard by the tornado was just north of Ashland, Mississippi—a high amount of damage occurred in this area. The TDS Swath product shows where the highest amount of tornado debris was detected within the storm.

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Numerous low-level shear markers, along with a Shear SCIT, were present with the storm as it rapidly moved to the NE. Velocity data showed a clearly defined and strong circulation with the storm.

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The Shear Rate product and the Baron Button clearly show where the strongest circulation was occurring.

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Lowered values of correlation coefficient immediately north of the town of Ashland gives additional confidence that damage was occurring with lofted debris in the area.

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The Shear Swath product clearly shows the path the tornado took through the northern tier of Mississippi.

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The supercell thunderstorm continued rapidly, moving NE through Tennessee and producing intermittent tornado damage. The storm produced a deadly tornado near Linden, Tennessee in the evening. At 6:02 p.m., roughly 14 minutes before the tornado would make another touch, Shear SCITs were present with the storm. This generated “Twisting Storms Approaching” alerts for the areas affected by the tornado. By 6:12 p.m., the storm was moving over the town of Linden.

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Velocity data shows a tight circulation at 6:12 p.m., minutes before the tornado would touch down. The Baron Button also helps highlight the location of the strongest rotation.

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The Reflectivity image at 6:23 p.m. indicates when the tornado was on the ground and causing damage. Velocity data is interesting in this case. We see only inbound returns, but still over 100 mph of shear. This is due to the incredibly fast movement of the storm to the NE at 70 mph. Using Storm Relative Velocity in the case would give the user a more typical velocity pattern.

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At 6:23 p.m., the Shear Rate product indicated a small area of higher shear, and in that exact location we see an area of lowered correlation coefficient indicating the potential for some lofted debris.

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The Shear Swath product depicts the location and path the tornado took around the town of Linden, Tennessee. Also, 1” hail was reported with the storm and the Hail Swath product shows areas most likely to be affected by hail.

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