11HPC Eckrich

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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

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2116Z 28 March

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2316Z 28 March

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0200Z 29 March

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IR SATELLITE 0100Z 29 MARCH

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VISIBLE SATELLITE 0130Z 29 MARCH

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0153Z 29 MARCH

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0157Z 29 MARCH

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0157Z 29 MARCH

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0202Z 29 MARCH

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0202Z 29 MARCH

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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

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Courtesy Ty Harmon - KLMR

Slide33: 

Courtesy Ty Harmon - KLMR

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Courtesy Ty Harmon - KLMR

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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