Tornado in Story County, Iowa

Tornado continued from Boone County into Story County, remaining in cropland. Satellite imagery and drone imagery provided by emergency management helped to refine the path. No damage occurred to damage indicators, thus the unknown rating.

A shortwave passed across the area the previous evening with a trailing boundary that dove south across the area through the early morning hours of July 19th. Strong theta e advection in the warm sector ahead of the boundary created an unstable environment with 1000-2000 J/kg of MUCAPE with 30-40 kts of 0-6 km shear. Storms developed along this boundary across northern Iowa and quickly pushed south through sunrise, fueled by the low level jet. Wind was the primary hazard with the line of storms and in most cases it remained sub severe, however acceleration in central Iowa near sunrise resulted in gusts of 60 to 70 mph. At the same time a cell merger occurred along the leading edge of storms. This merger resulted in a brief enhancement with tornadogenesis. This tornado developed in Boone county and tracked through cropland, crossing into Story county before dissipating just before reaching the community of Gilbert. Despite the tornado dissipating, straight line winds remained strong and resulted in some damage within Gilbert.