Overview
A very robust storm system produced a nearly 24-hour long severe weather event in our area that lasted from late morning on May 8th until the morning of May 9th. There were numerous reports of damaging winds and large hail with some of these reports being very significant and fairly rare in our forecast area. Several places saw extreme straight line winds estimated to be in excess of 90 mph in some places. One fatality also resulted in Claiborne County due to a tree that fell on a car. One EF-1 tornado was confirmed in Cherokee County, NC. There were also several reports of flash flooding, especially by the morning of May 9th with many places receiving in excess of 3" of rain.
Tornadoes:
Tornado - 4 E of Murphy to 5 SSE of Marble
Track Map
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The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:
EF0 Weak 65-85 mph |
EF1 Moderate 86-110 mph |
EF2 Significant 111-135 mph |
EF3 Severe 136-165 mph |
EF4 Extreme 166-200 mph |
EF5 Catastrophic 200+ mph |
Wind & Hail Photos:
Wind
Significant damage occurred as a result of extreme straight line winds that were estimated to be in excess of 90 mph and to the same level as the EF-1 tornado that occurred in eastern Cherokee County, NC. Many other places saw less intense severe winds, but the photos below show the most significant winds from the event.
Straight line winds in association with a severe supercell thunderstorm rated at 88 mph snapped several trees within the Hamblen Memorial Gardens. | Several trees were snapped after winds up to 93 mph occurred during a severe supercell thunderstorm in eastern Hamblen County between Morristown and Russellville | Straight line winds up to 95 mph in association with a tornadic thunderstorm felled several large trees along the right flank of the tornado path in eastern Cherokee County, NC |
Hail
Several instances of large hail occurred across the area with the ones shown below near the size of a baseball. Hail to this size is very rare in our region.
Large hail fell in Bean Station and west to Rutledge, with the largest hailstones approaching 2.5 inches in diameter! Photo used with permission: Anna B. Bean Station, TN. | Large hail fell in Bean Station and west to Rutledge, with the largest hailstones approaching 2.5 inches in diameter! Photo used with permission: Anna B. Bean Station, TN. |
Tornado Damage Photos
An EF-1 Tornado felled a few large hardwood and softwood trees along a 2.5 mile long path with winds estimated up to 95 mph. | A very large tree uprooted along the same path |
Radar
*All images in this section are from May 8th
Animation of Base Reflectivity, Base Velocity, Storm Relative Velocity, and Correlation Coefficient |
A supercell thunderstorm tracked from the northern Cumberland Plateau through Morristown and east to Greeneville during the morning hours of May 8. This animation shows the period when the storm was at its strongest, between Rutledge and Mosheim. It is rare to have such a strong and well-defined supercell storm move so close to the Morristown radar, and may interesting features were detected by our radar. The storm produced very large hail, damaging wind, and a funnel cloud, but a tornado did not reach the ground.
4-Panel of Base Reflectivity, Storm Relative Velocity, Base Velocity, and Correlation Coefficient at 10:12 AM EDT |
The lower right panel of this image shows base velocity, with the bright green colors indicating strong winds moving toward the radar (labeled KMRX in the lower right of all panels). The maximum wind speed detected by the radar is 70 mph near Washburn. A few minutes after this image, the Severe Thunderstorm Warning was updated to indicate that this was a destructive storm with 80 mph winds possible. There was some extensive wind damage reported near Rutledge and Bean Station as the storm continued east. Notice that there is a narrow line where radar data are missing, aligned from southwest to northeast between Washburn and Rutledge. This is where the radar beam is encountering the top of the Clinch Mountains.
Base Reflectivity Tilts at 10:15 AM EDT |
This image shows reflectivity at different levels of the storm. The upper left panel is the lowest slice, then the upper right shows a higher slice, followed by the lower left and the lower right. The highest slice in the lower right panel shows very high reflectivity (pink to violet colors). The radar sends out a beam of energy, which encounters objects in the atmosphere, and a portion of that energy gets reflected back to the radar. A large object reflects more energy than a small object, so the high reflectivity values here indicate very large hail in this storm. Another interesting feature in this image is the low reflectivity (gray colors) located behind the storm, west of Tazewell. This feature is called a Three Body Scatter Spike (TBSS). It appears when part of the radar’s energy beam reflects off hail toward the ground, reflects off the ground and back to the hail, and then reflects off the hail to the radar. The extra time that it takes this energy to travel (only a fraction of a millisecond) results in the radar plotting this returned energy behind the storm. A TBSS as large as this one indicates very large hail in the storm, and 2.5-inch diameter hail was observed in Rutledge about 5 minutes after the time of this image.
Base Reflectivity Cross-Section at 10:18 AM EDT |
This image is a cross section through the storm when it was over Rutledge, looking from the radar toward the northwest. The vertical scale is thousands of feet, and since the storm is so close to the radar, we can only see the storm up to around 20,000 ft. The interesting feature to note is the column of weak reflectivity (green colors) from just below 10,000 ft to 20,000 ft, surrounded by very high reflectivity (pink, violet, and white colors) on either side. This feature is called a Bounded Weak Echo Region. It is caused by a very strong, rotating updraft. The updraft is a rising column of air that suspends precipitation high in the storm, and prevents it from falling in this area. The rising, rotating column of air pushes hail higher in the storm and outside of the updraft area. This is a key feature of supercell thunderstorms, because it allows the updraft to persist by separating the rising air from the descending air.
4-Panel of Base Reflectivity, Storm Relative Velocity, Base Velocity, and Correlation Coefficient at 10:25 AM EDT |
A Tornado Warning was issued around the time of this image for Grainger and Hamblen counties. As the storm crossed the Clinch Mountains, it developed a hook echo (seen in the reflectivity in the upper left panel) and counter-clockwise rotation (seen in the storm-relative velocity image in the upper right panel, southeast of Rutledge). Sometimes, as storms move past ridges and downslope, rotation can intensify due to winds strengthening as they move down the side of a mountain. That appears to be what occurred with this storm, and although there was some scattered wind damage southeast of Rutledge, there was no tornado on the ground. The damage was likely caused by straight-line winds from a downdraft, which can be seen by the strong winds moving toward the radar (bright green colors) in the lower right panel.
4-Panel of Base Reflectivity, Storm Relative Velocity, Base Velocity, and Correlation Coefficient at 10:48 AM EDT |
Around the time of this radar image, there were reports and videos of a rotating funnel cloud on the east side of Morristown. The reflectivity image in the upper left panel shows a well-defined hook echo where the funnel cloud was spotted, but the storm-relative velocity image in the upper right panel shows only very weak rotation. A storm damage survey confirmed that there was no tornado on the ground. The wind damage that occurred around Russellville Elementary School and the Morristown Memorial Gardens Mausoleum was determined to be caused by straight-line winds.
4-Panel of Base Reflectivity, Storm Relative Velocity, Base Velocity, and Correlation Coefficient at 11:39 PM EDT |
In contrast to the storm that crossed Grainger and Hamblen counties, this storm was far from the radar, in Cherokee County, NC. At that distance, due to the earth’s curvature, the lowest that the radar can detect is around 5,500 feet above the ground. The radar beam also gets wider as it gets farther from the radar, so resolution is reduced. In this image, the reflectivity shown in the upper left panel does not show a pretty hook echo, but it does exhibit a “L”shape. The storm-relative velocity in the upper right shows strong rotation (bright green next to red) east of Murphy, but this is occurring 5,500 ft above the ground. This rotation indicates a mesocyclone, or a rotating updraft within the storm, but it is not detecting the actual tornado near the ground. Sometimes, rotation aloft precedes a tornado on the ground, but not always. Because of this rotation signature, a Tornado Warning was issued near the time of this image, and a tornado touched down a few minutes later in the Peachtree community east of Murphy.
Storm Reports
W - Wind
H - Hail
T - Tornado
Public Information Statement National Weather Service Morristown TN 432 PM EDT Wed May 8 2024 /332 PM CDT Wed May 8 2024/ ...Hamblen County Tennessee Damage Survey Results from 5/8/2024... The NWS Morristown office surveyed the damage that occurred late this morning in Russellville, Tennessee. It was determined to be caused by a downburst centered near East Andrew Johnson Highway, Bethesda and Old Kentucky Road. The winds were estimated to be 80 to 90 mph. Radar estimates show this occurred just before 11 am EDT. Significant roof damage occurred to the Russellville Elementary and subsequent water intrusion into several classrooms and gymnasium. Other structural roof damage occurred to some homes and several tree trunks were snapped with just a few trees uprooted. The Morristown Memorial Gardens Mausoleum also sustained roof damage. The Bethesda Cemetery sustained numerous trees snapped. The total area affected was roughly two square miles.
Public Information Statement National Weather Service Morristown TN 1154 AM EDT Fri May 10 2024 /1054 AM CDT Fri May 10 2024/ ...NWS Damage Survey for 05/08/24 Tornado Event - Update #2... .Update...Additional information was analyzed and the path width and length have been updated. ..Cherokee North Carolina Tornado near Peachtree... Rating: EF1 Estimated Peak Wind: 95 mph Path Length /statute/: 2.42 miles Path Width /maximum/: 40 yards Fatalities: 0 Injuries: 0 Start Date: 05/08/2024 Start Time: 11:41 PM EDT Start Location: 4 E Murphy / Cherokee County / NC Start Lat/Lon: 35.0918 / -83.9532 End Date: 05/08/2024 End Time: 11:42 PM EDT End Location: 5 SSE Marble / Cherokee County / NC End Lat/Lon: 35.1043 / -83.9149 Survey Summary: Pockets of extensive tree damage were noted near and around the Peachtree community. The tornado likely developed near Greenlawn Cemetery Road and Memory Lane. It continued east across Upper Peachtree Road causing some tree damage on Lizzie Elliot Road. The tornado took a slight northeast jog and was non-continuous throughout its life cycle. It crossed Sky Trek Drive and Shadow Pond Road. The tornado lifted before crossing Upper Peachtree Road again. Numerous trees were either uprooted or snapped along the path. It was noted that large limbs were also downed. Other significant tree damage was found where Upper Peachtree Road turns north just past Trinity Drive close to Boyd Ridge Drive. However, this damage was associated with straightline winds in excess of 70 mph. && EF Scale: The Enhanced Fujita Scale classifies tornadoes into the following categories: EF0.....65 to 85 mph EF1.....86 to 110 mph EF2.....111 to 135 mph EF3.....136 to 165 mph EF4.....166 to 200 mph EF5.....>200 mph NOTE: The information in this statement is preliminary and subject to change pending final review of the event and publication in NWS Storm Data. ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 0750 AM Flash Flood Oakdale 35.99N 84.56W 05/09/2024 Morgan TN 911 Call Center Car partially submerged in the Oakdale City Park parking lot. 0745 AM Flash Flood 2 SW Elgin 36.31N 84.63W 05/09/2024 Scott TN 911 Call Center Highway 27 in Glenmary is flooded; mudslide on River Road near Helenwood. 0650 AM Flash Flood Dunlap 35.37N 85.39W 05/09/2024 Sequatchie TN 911 Call Center Numerous reports of flooding. 0615 AM Tstm Wnd Dmg 2 NNE Flint Springs 35.06N 84.90W 05/09/2024 Bradley TN Broadcast Media Several trees down across the southern portion of the county. Relayed to us by amateur radio operator from public radio. 0610 AM Tstm Wnd Dmg 2 W Charleston 35.28N 84.80W 05/09/2024 Bradley TN Dept of Highways Trees down. 0550 AM Tstm Wnd Dmg 4 WSW Middle Valley 35.16N 85.25W 05/09/2024 Hamilton TN Public Several large trees have been blown down with multiple power outages in the area. 0530 AM Tstm Wnd Dmg Dunlap 35.37N 85.39W 05/09/2024 Sequatchie TN 911 Call Center Numerous reports of trees down across the county. Time estimated by radar. 1145 PM Tstm Wnd Dmg Marble 35.18N 83.92W 05/08/2024 Cherokee NC 911 Call Center Reports of trees and powerlines down across the county. Also, an amateur radio operator reported a wind gust to 50 mph in the Marble area.
1141 PM Tornado 4 E Murphy 35.09N 83.96W 05/08/2024 Cherokee NC NWS Storm Survey A survey found EF-1 tornado damage, with peak winds of 95 mph. Path length was 2.42 miles, path width was 40 yards. Pockets of extensive tree damage were noted near and around the Peachtree community. The tornado likely developed near Greenlawn Cemetery Road and Memory Lane. It continued east across Upper Peachtree Road causing some tree damage on Lizzie Elliot Road. The tornado took a slight northeast jog and was non-continuous throughout its life cycle. It crossed Sky Trek Drive and Shadow Pond Road. The tornado lifted before crossing Upper Peachtree Road again. Numerous trees were either uprooted or snapped along the path. It was noted that large limbs were also downed. Other significant tree damage was found where Upper Peachtree Road turns north just past Trinity Drive close to Boyd Ridge Drive. However, this damage was associated with straight line winds in excess of 70 mph.
1125 PM Tstm Wnd Dmg 3 SW Marble 35.14N 83.98W 05/08/2024 Cherokee NC 911 Call Center Trees down county-wide with time estimated from radar. 1105 PM Tstm Wnd Dmg 2 WSW Jefferson City 36.11N 83.52W 05/08/2024 Jefferson TN NWS Employee Couple of trees blown down on either side of New Market, TN. Time estimated by radar. 1055 PM Tstm Wnd Dmg 4 NE Bullet Creek 35.32N 84.37W 05/08/2024 Monroe TN 911 Call Center One tree down. 1045 PM Tstm Wnd Dmg 1 NE Maryville 35.76N 83.96W 05/08/2024 Blount TN 911 Call Center Trees and powerlines down across the county. Much of downtown Maryville is without power. Also, a tree caught on fire due to downed powerlines. 1030 PM Tstm Wnd Dmg Haletown (guild) 35.03N 85.54W 05/08/2024 Marion TN Dept of Highways Trees down. 1030 PM Tstm Wnd Dmg 1 E Friendsville 35.76N 84.11W 05/08/2024 Blount TN 911 Call Center Trees and powerlines down along Vinegar Valley Road. 1025 PM Tstm Wnd Dmg 4 NW Oldfort 35.07N 84.78W 05/08/2024 Bradley TN Dept of Highways Trees down. 1025 PM Hail South Pittsburg 35.02N 85.71W 05/08/2024 E1.50 Inch Marion TN Public 1015 PM Tstm Wnd Dmg 3 NE Palio 35.50N 85.29W 05/08/2024 Bledsoe TN 911 Call Center Trees down across the county with time estimated from radar. 1015 PM Flash Flood 2 NE Palio 35.49N 85.29W 05/08/2024 Bledsoe TN 911 Call Center Flooding along U.S. 127 in multiple different locations in Bledsoe County. 1011 PM Hail 3 SE South Pittsburg 34.99N 85.68W 05/08/2024 E1.00 Inch Marion TN Public Report from mPING: Quarter (1.00 in.). 1010 PM Tstm Wnd Dmg 1 E Mcdonald 35.11N 84.96W 05/08/2024 Bradley TN Dept of Highways Trees down. 1010 PM Tstm Wnd Dmg Athens 35.45N 84.61W 05/08/2024 McMinn TN 911 Call Center Trees down close to Athens. Location approximate. Time estimated by radar. 1010 PM Rain 5 SE Decatur 35.48N 84.73W 05/08/2024 M4.30 Inch McMinn TN Public Reported by Trained Spotter. Rainfall measured by WX station in Idlewild, TN area so far today. 1000 PM Tstm Wnd Dmg Kingston 35.87N 84.51W 05/08/2024 Roane TN 911 Call Center Trees and powerlines down county-wide. 0955 PM Hail Orme 35.01N 85.81W 05/08/2024 M1.00 Inch Marion TN Trained Spotter Emergency manager reported hail from a trained spotter. 0950 PM Tstm Wnd Dmg 1 N Hopewell 35.25N 84.90W 05/08/2024 Bradley TN Dept of Highways Trees down. 0950 PM Tstm Wnd Dmg 2 NE Harriman 35.95N 84.53W 05/08/2024 Roane TN 911 Call Center Trees down on Highway 61. Time estimated by radar. 0943 PM Hail 3 S Palio 35.43N 85.33W 05/08/2024 E3.00 Inch Bledsoe TN Public Report from mPING: Tea Cup (3.00 in.). 0915 PM Tstm Wnd Dmg 2 WSW Elgin 36.32N 84.64W 05/08/2024 Scott TN 911 Call Center Trees down on Nydeck Trail that have resulted in powerlines being knocked down. Location approximate and timing based on radar. 0240 PM Flash Flood Paint Rock 35.74N 84.52W 05/08/2024 Roane TN Trained Spotter . 1210 PM Tstm Wnd Dmg 3 NNW Newport 36.00N 83.21W 05/08/2024 Cocke TN 911 Call Center Few trees down. 1148 AM Hail 2 ENE Liberty 36.15N 82.59W 05/08/2024 M1.25 Inch Washington TN Public 1115 AM Hail Mosheim 36.19N 82.96W 05/08/2024 M1.50 Inch Greene TN Emergency Mngr 1055 AM Tstm Wnd Dmg Russellville 36.26N 83.20W 05/08/2024 Hamblen TN Amateur Radio Roof, window, and other structural damage to Russellville Intermediate School. 1045 AM Tstm Wnd Dmg Russellville 36.26N 83.20W 05/08/2024 Hamblen TN NWS Employee Large Trees Down. 1045 AM Tstm Wnd Dmg 2 NE Morristown 36.24N 83.27W 05/08/2024 Hamblen TN 911 Call Center Tree on house on Old Liberty Hill Rd. 1045 AM Tstm Wnd Dmg 2 NE Morristown 36.24N 83.27W 05/08/2024 Hamblen TN Amateur Radio Tree down on home on Quillen Drive. 1044 AM Hail Morristown 36.22N 83.30W 05/08/2024 M1.00 Inch Hamblen TN NWS Employee 1035 AM Hail Bean Station 36.34N 83.29W 05/08/2024 E1.50 Inch Grainger TN Public 1025 AM Tstm Wnd Dmg Bean Station 36.34N 83.29W 05/08/2024 Grainger TN 911 Call Center Trees and power lines down countywide. 1020 AM Hail Rutledge 36.28N 83.52W 05/08/2024 E2.50 Inch Grainger TN Broadcast Media 0955 AM Tstm Wnd Dmg 1 WSW Russellville 36.25N 83.22W 05/08/2024 Hamblen TN Emergency Mngr Roof damage to the mausoleum at Hamblen Memory Gardens. 0955 AM Tstm Wnd Dmg 1 ENE Lone Mountain 36.39N 83.58W 05/08/2024 Claiborne TN Emergency Mngr *** 1 FATAL *** Trees down. Home destroyed. Tree fell on car killing the occupant at the intersection of Lone Mountain Rd, and Jennings Lane. 0950 AM Tstm Wnd Dmg Sunbright 36.24N 84.67W 05/08/2024 Morgan TN 911 Call Center Trees down. 0855 AM Tstm Wnd Dmg Winfield 36.56N 84.45W 05/08/2024 Scott TN Dept of Highways Trees down.
Environment
An upper level jet across from the southern Plains to the Ohio and Tennessee valleys was dominated by strong west to southwest flow aloft with a series of jet streaks (short-waves) moving quickly across the region. These waves produced a series of thunderstorm complexes that moved across the Tennessee valley from the morning of May 8th until the morning of May 9th.
Each upper level jet streak produced large-scale forcing over the Tennessee valley into the southern Appalachians with the 300mb analysis showed divergence aloft which aided in the development of storms.
The upper forcing enhanced the boundary layer jet over the Mississippi and Tennessee valleys with southwest winds increasing to 30-40 kts. This low level jet pulled abundant moisture and instability northward into the region.
Figure 1: 300mb Heights, Divergence, and Winds at 1800 UTC, 08 May 2024 |
Figure 2: 500mb Heights, Temperature, and Winds at 1800 UTC, 08 May 2024 | Figure 3: 850mb Heights, Temperature, and Winds at 1800 UTC, 08 May 2024 |
The surface analysis from 1500 UTC, 08 May 2024 to 0800 UTC, 09 May 2024 depicted an outflow boundary from a series of storm complexes. Initially this boundary was located in close proximity from the northern Plateau to near Morristown Tennessee. Warm and moist air mass ahead of this boundary produced a series of severe storms the morning of May 8th 2024 that produced very large hail and damaging winds. A funnel cloud was observed near Morristown Tennessee.
This boundary continued to move slowly south during the day and became nearly stationary across middle Tennessee to extreme southeast Tennessee and southwest North Carolina into the night. Warm and moist conditions continued to pull northward into this boundary producing rounds of thunderstorm complexes.
Figure 4: Surface Station Plot at 1500 UTC, 08 May 2024 | Figure 5: Surface Station Plot at 2300 UTC, 08 May 2024 | Figure 6: Surface Station Plot at 0400 UTC, 09 May 2024 |
Figure 7: Surface Station Plot at 0800 UTC, 09 May 2024 |
The SPC mesoanalysis depicted an unstable environment with MLCAPES of 1000-2000 J/Kg. As noted above the 0-3 km MLCAPE was quite high with values of 100-150.
Hail CAPES of 700-900 J/Kg and effective storm scale shear in the 50s produced an environment favorable for large hail growth and resident time for severe hail. These environmental factors during the morning of May 8th 2024 produced hail in excess of baseball size across Grainger and Hamblen counties in Tennessee.
The Supercell Composite Parameter (SCP) and Significant Tornado Parameter depicted an overall favorable environment for rotating storms across northern Tennessee in the morning of May 8th and southeast Tennessee and southwest North Carolina early morning hours of May 9th. The main question was the location of the southward moving boundary across the region. These boundaries are often the focus for tornadogenesis.
Besides the severe storm potential, there were several factors that contributed to the potential of heavy rainfall and flash flooding. The Precipitable Water values increased to 1.8 inches or more across parts of the area which is near the maximum ever recorded across the area for early May. The unseasonably high moisture content of the air mass combined with strong moisture transport into the Tennessee valley set the stage for heavy rainfall. The thunderstorms with torrential rains trained along this nearly stationary boundary produced flash flooding.
Figure 8: RAP Initialization Sounding at KMOR (Morristown, TN) at 1400 UTC, 08 May 2024 | Figure 9: RAP Initialization Sounding at KCHA (Chattanooga, TN) at 0900 UTC, 09 May 2024 | Figure 10: MLCAPE and CIN at 1500 UTC, 08 May 2024 |
Figure 11: MLCAPE and CIN at 2300 UTC, 08 May 2024 | Figure 12: MLCAPE and CIN at 0800 UTC, 09 May 2024 | Figure 13: 0-3 km MLCAPE and Surface Vorticity at 1500 UTC, 08 May 2024 |
Figure 14: 0-3 km MLCAPE and Surface Vorticity at 0500 UTC, 09 May 2024 | Figure 15: CAPE (-10 to -30 C), Freezing Level, and 0-6 km Shear at 1500 UTC, 08 May 2024 | Figure 16: Effective Shear at 1500 UTC, 08 May 2024 |
Figure 17: Effective Shear at 0400 UTC, 09 May 2024 | Figure 18: 0-1 km Shear at 1500 UTC, 08 May 2024 | Figure 19: 0-1 km Shear at 0600 UTC, 09 May 2024 |
Figure 20: Supercell Composite Parameter (SCP) (effective layer with muCIN) and Bunkers Storm Motion at 1500 UTC, 08 May 2024 | Figure 21: Supercell Composite Parameter (SCP) (effective layer with muCIN) and Bunkers Storm Motion at 0500 UTC, 09 May 2024 | Figure 22: Significant Tornado Parameter (effective layer) and MLCIN at 1500 UTC, 08 May 2024 |
Figure 23: Significant Tornado Parameter (effective layer) and MLCIN at 0500 UTC, 09 May 2024 | Figure 24: Precipitable Water (inches) at 0500 UTC, 09 May 2024 | Figure 25: 850mb Moisture Transport (fill and vector), height (black), and theta-e (dashed green) at 0800 UTC, 09 May 2024 |
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