Historic Hailstorm - April 10th 2001

Overview: During the afternoon and evening hours of April 10, 2001, a long-lived high precipitation (HP) supercell thunderstorm traversed portions of Missouri and southwest Illinois producing catastrophic hail damage. The HP supercell produced a swath of large hail approximately 245 miles (395 km) in length and up to 22 miles (35 km) in width as it moved east through the highly populated Interstate 70 corridor from southeast of Kansas City through St. Louis. Most of the hail ranged in size from 1.00-3.00 inches in diameter, however south of the largest hail, marginally severe hail (0.75-1.00 inch) also caused considerable damage as it was propelled by 70+ mph downburst (rear flank downdraft) winds. This storm has been named the “Tristate Hailstorm” by Changnon and Burroughs (2003), and is considered the most costly hailstorm in U.S. History with insured losses of $1.5 billion. (see the authors note below). Known Missouri insurance claims consist of 120,000 home claims, 65,000 auto claims, and 8,000 commercial claims. It is believed nearly every home and business in northern St. Louis County suffered hail damage. All of the SUVs parked outside at the Ford Motor Company assembly plant in Hazelwood were damaged (hundreds), while in the adjacent community of Florissant, every home was estimated to have received damage. Twenty-four commercial and military aircraft at Lambert St. Louis International Airport were also damaged. Uninsured losses are unknown. Largely overshadowed by the devastating hail were the tornadoes produced by the HP supercell. This single storm produced a total of 9 weak tornadoes (6 - F1, 3 - F0) with path lengths ranging from 1-10 miles (1.6-16.0 km). The F1 tornado which struck Fulton (southeast of Columbia) destroyed a mobile home producing the first tornado fatality in Missouri since 1994. With $12 million damage reported from the tornadoes, the total damage from the tornadoes paled in comparison to the hail damage. Careful and detailed radar analysis (some of which is briefly presented in this event review) reveals that the “Tristate Hailstorm” hailswath as defined by Changnon and Burroughs (2003) was actually the cumulative impact of three distinctly different supercell thunderstorms, rather than one exceptionally long-lived classic supercell. The HP supercell documented in this event review produced the largest hailswath of the three storms, and nearly all of the catastrophic damage. If you have questions about this event, or have any photos of the hail or damage that you would be willing to share, please email Lead Forecaster Fred Glass.


Tornado Damage Pictures

Observations SPECI KSZL 102248Z 28036G73KT 220V310 1/4SM +TSRA OVC004 20/18 A2966 RMK TS OHD MOV NE OCNL LTGICCGCC SPECI KCOU 110014Z 31046G59KT 3/4SM +TSRA BR SQ BKN012 BKN042 OVC080 17/17 A2971 RMK A02 PK WND 33059/0010 WSHFT 2354 RAB08 PRESRR P0030 SPECI KSTL 110220Z 30011G37KT 270V340 1SM R30R/1200VP6000FT +TSRA SCT017 SCT046CB BKN050 18/17 A2975 RMK A02 PK WND 30037/0214 WSHFT 0202 TSE14B19RAB14 LTGICCGCAIC TS OHD MOV E GR2 P0050 Radar Data