Hail — Hardin, Iowa

2009-08-09 · near Eldora, Hardin, Iowa

Event narrative

Large hail brok windows out of a residence and caused considerable crop damage.

Wider weather episode

A very warm, moist, and unstable airmass was in place over Iowa from 8th into the 9th. Surface temperatures on the 8th warmed into the upper 80s and 90s, with dew point readings in the 70s. A weak cold front moved into the state during the evening of the 8th and early morning of the 9th. There was little thunderstorm development initially as the airmass was capped. Temperatures at the 700 mb level were +14 to +17 C. During the early morning hours of the 9th, a short wave lifted northeast out of the southern Rockies. This resulted in cooling of the mid levels of the atmosphere, thus destabilizing the airmass. The cold front stall out during the morning of the 9th as a second short wave lifted northast. Eventually, the front moved south of the state on the night of the 9th. Overall lifted indices were in the -6 to -10 C range with CAPE values in the 3000 to 4000 J/kg range. Downdraft CAPE was in the 800 to 1400 J/kg range with 30 to 50 kts of shear available. CAOE available in the -10 to -30 C layer of the atmosphere was between 300 and 700 J/kg, with a freezing level of 14,000 to 14,500 feet. The LCL was relatively high across the area ranging from just below 1000 meters to about 1250 meters. Plenty of moisture was available with precipitable water values between 1.75 and 2.25 inches. Thunderstorms developed initially over Nebraska and tracked east-northeast into Iowa shortly after sunrise. One supercell continued to track across the state and produced a swath of wind and hail damage from Sac County east to Black Hawk County. Additional thunderstorms formed along the cold frontal boundary by mid morning and progressed into the state. The storms remained below severe levels for several hours, but did become severe by mid afternoon. A broken like of storms formed with two primary areas tracking east across central and southern Iowa. These two areas featured mini bow echoes. The predominant mode of severe weather in the afternoon was high winds. Several of the storms produced hail, but the hail was sub-severe. A long lived supercell Thunderstorm tracked across northern Iowa Sunday morning with the Highway 20 corridor receiving the brunt of the damage. Reports of quarter to golf ball sized hail were common with some hail stones reported to be in excess of two inches approaching the size of a tennis ball. The hail was wind blown as well, at speeds of 50 to 70 mph, making it extremely damaging and dangerous striping siding off houses and knocking out windows. A measured wind speed of 68 mph was recorded at a KCCI TV SchoolNet site near Jewell in Hamilton County. Significant hail damage was received all along the track with areas near Otho, Callender, Radcliffe, Eldora and Grundy Center hit particularly hard. In Eldora, many homes had windows broken out and tree and power line damage left the city without power. Winds of over 100 MPH toppled a communication tower in Eldora. A short time before the winds hit Eldora, a 102 MPH wind gust was recorded at the landfill northwest of town. Wind driven hail of 2 to 3 inches in diameter broke all siding and windows out on the north and west walls of most homes, with hail stones reported landing inside of houses. Damage in the town of Eldora was expected to be greater than the damage done in the town of Parkersburg by the EF5 tornado a year earlier. A 150 square mile area of crops was affected in Hardin County. Total losses were reported on 45,000 acres, with 60% or greater loss on another 55,000 acres. Hail damage in the Otho to Callender areas was described as the worst seen in 20 years. MODIS satellite pictures of the crop damage area included in this report. Estimates of crop damage from this one supercell were over $175,000,000. Governor Culver declared Hardin County a state disaster area within a day or two of the storm, and declared Webster County a disaster area about a week later. Formal paperwork was turned in to make 8 Iowa counties federal disaster areas, They were Calhoun, Grundy, Hamilton, Hardin, Ida, Sac, Webster, and Woodbury. Following the storms, a shelter was set up for those who felt they should not stay in their homes. Luckily the evening round of storms tracked south. Campers at nearby Pine Lake State Park, gathered for an archery event, were bruised by hail. There were 22 reports of injuries in Hardin County, 11 serious enough for people to be taken to hospital, but there are no known life threatening injuries. A second round of severe weather rolled roughly along I-80 between 1630 and 1800 CST, producing a lot of tree and power line damage but apparently little structural damage. As the storms moved through the metropolitan Des Moines area, winds damaged power lines and knocked out power to 12,000 homes. One storm produced a wet microburst in Union County. The winds took the roof and shingles off of a two story brick building near Afton. The afternoon round of storms produced some hail, but most of the hail was not severe as mentioned above, and was pea size or smaller. During the morning round of storms, lightning struck a building in Waverly. The lightning struck an antenna on the building and melted screws all the way down the side of the building, starting a small fire and blowing hole in the wall.

View location on OpenStreetMap → (42.3600, -93.1000)

Source: NOAA Storm Events Database, event_id 178602. Narrative written by the NWS forecast office that issued the report.