Slide1: HOLLY, COLORADO TORNADO 28 MARCH 2007 Bill Eckrich DayWeather, Inc. Cheyenne, Wyoming


Overview of Holly, Colorado: Overview of Holly, Colorado Located in southeastern Colorado on U.S. Highway 50 in far eastern Prowers County, 28 miles east of Lamar and approximately 5 miles from the Kansas state line Population 1,048 (2000 U.S. Census)


Holly Tornado Statistics: Holly Tornado Statistics First touched down at 1957 MDT one mile south of Holly WFO PUB Tornado Warning issued at 2000 MDT Rated as high-end EF3 Moved just east of north across the entire town causing EF1 to low-end EF3 damage 2 fatalities, one within a day and another nearly a month later, with 10 injuries Path length 28 miles over a 25-30 minute period Damage width in Holly was 1000 feet wide


Holly Tornado Statistics: Holly Tornado Statistics 48 structures destroyed 100+ structures damaged Event occurred outside of both the SPC slight and moderate risk areas (12Z, 13Z, 1630Z, 20Z, 01Z) as well as the later-issued Tornado Watch #83 Colorado convection evolved from a retreating dryline possibly caused by stronger-than-forecast ageostrophic forcing from northward-propagating shortwave


SPC DAY1 OUTLOOK (20Z): SPC DAY1 OUTLOOK (20Z)


TORNADO WATCH #83: TORNADO WATCH #83 HOLLY


SYNOPTIC AND MESOSCALE ENVIRONMENT: SYNOPTIC AND MESOSCALE ENVIRONMENT INCLUDING RADAR AND SATELLITE DATA


00Z 29 March 300mb: 00Z 29 March 300mb NOSE OF JET STREAK


00Z 29 March 500mb: 00Z 29 March 500mb


00Z 29 March 700mb: 00Z 29 March 700mb


00Z 29 March 850mb: 00Z 29 March 850mb THERMAL RIDGE


Slide16: 2116Z 28 March


Slide17: 2316Z 28 March


Slide18: 0200Z 29 March


Slide19: IR SATELLITE 0100Z 29 MARCH


Slide20: VISIBLE SATELLITE 0130Z 29 MARCH


Slide21: 0153Z 29 MARCH


Slide22: 0157Z 29 MARCH


Slide23: 0157Z 29 MARCH


Slide24: 0202Z 29 MARCH


Slide25: 0202Z 29 MARCH


Slide26: HOLLY Prowers County Kiowa County Kansas


EF3 Damage in Holly: EF3 Damage in Holly WFO Pueblo


EF3 Damage in Holly: EF3 Damage in Holly WFO Pueblo


High-end EF3 Damage 12N of Holly: High-end EF3 Damage 12N of Holly WFO Pueblo


High-end EF3 Damage 12N of Holly: High-end EF3 Damage 12N of Holly WFO Pueblo


Slide32: Courtesy Ty Harmon - KLMR


Slide33: Courtesy Ty Harmon - KLMR


Slide34: Courtesy Ty Harmon - KLMR


Slide35: Courtesy Ty Harmon - KLMR


CONCLUSIONS: CONCLUSIONS Large and deep storm system over the central Rockies Large-scale ascent across eastern Colorado, southwestern Nebraska, western Kansas and the Oklahoma/Texas panhandles Surface winds ahead of the dryline backed with time as the shortwave/jet streak approached Dryline retreated SRH increased with backing winds relative to storm motion


CONCLUSIONS: CONCLUSIONS First tornado deaths in Colorado since June 27, 1960 Only the second killer tornado in Colorado since 1950 Earliest strong tornado in Colorado history Previous: 3/29/1910 in Sedgwick County Earliest killer tornado in Colorado history Previous: 4/30/1942 in Bent/Kiowa counties


CONCLUSIONS: CONCLUSIONS Prowers County has had only one prior significant tornado June 24, 1968 One injury Occurred within one mile of Holly