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EF0 tornado in Cass County, Iowa

Tornado July 12, 2023 · Cass County, Iowa

EF0

Rating

3.6 mi

Whole path

50 yd

Path width

$5K

Damage as recorded

NOAA records this tornado county by county. Its path ran through Cass County → Cass County; the totals above are for the whole tornado.

EF0EF1EF2EF3EF4EF5Unrated

The path drawn at its surveyed width of 50 yards (0.03 mi) — zoom in and the swath grows to true scale. Other tornadoes recorded nearby that day are shown faint.

What EF0 means. On the Enhanced Fujita scale, EF0 is light damage: shingles and siding peeled, gutters torn, branches broken, consistent with estimated gusts of 65–85 mph. The rating comes from a survey of the worst damage after the storm, not from a wind measurement, so it says as much about what the tornado hit as about how strong it was.

What the National Weather Service wrote

Tornado was indicated by a Correlation Coefficient depression on radar and also verified through high resolution satellite imagery north of Marne. The tornado remained in mostly open cropland although some EF0 tree damage was done to a tree line along the edge of one of the fields.

The wider storm

Two rounds of convection moved across Iowa in quick succession beginning in the pre-dawn hours of July 12th. This first was an area of convection that developed along an elevated boundary into northwest Iowa. While this area of storms mainly remained sub-severe, severe hail did fall across central Iowa near 6 am. At the same time a MCS moved out of the Dakotas and into western Iowa, moving quickly and eventually merging with the first area of storms. This second round developed into a line of storms with winds gusting up to 70 mph, fueled by the low level jet. Orientation of 0-3 km shear was favorable for quick spin-ups and two weaker tornadoes did form in Cass county that morning. With deep warm cloud layers over 4000 meters and precipitable water nearing 2, areas that received rain in both rounds received two to four inches by the time storms ended late in the morning. An isolated pocket of four to six inches fell in Greene and Boone counties, creating flash flooding in the area.

Began near Marne (41.4798, -95.1291).

Source: NOAA Storm Events Database, event 1108464. Narratives are written by the National Weather Service forecast office that issued the report.

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