The Randolph Iowa Tornado of 1990

The line of isolated storms formed from our northwest to east-northeast and only one became tornadic. We watched the cells and picked one to our northeast as the one to chase. This decision was based on totally visual observations, and put us on the storm late for the first tornado. Our biggest problem was crossing the Missouri River which was done at Nebraska City, NE. We observed the first tornado in progress as we crossed the river and got initial first photography after getting into Iowa. The tornado was located behind a line of hills that parallel the river on the Iowa side.

The first tornado of the day continued on the ground as we proceeded east on US-2 into Iowa. The cell at that time was close to being a low precipitation storm as very little rain fell near the updraft region of the storm. This allowed us an excellent view on the tornado minus the problem with the hills of course. As we navigated around the hills the tornado dissipated. That was dissipointing, but it was still early and we had a good position for any new tornadic decelopment.

The second tornado took much longer to form and the storm continued to rotate, pushing the mesocyclone far to the north, then northwest of the main precipitation core. Another rain area developed behind the mesocyclone and eventually got entrained into the circulation, obscuring the tornado. Our positon allowd us to view the funnel formaing and dissipating through the rain curtains that were circulating around the funnel.

This tornado was the slowest to form of any we have witnessed. During this time the rain slow increased around the outer circulation of the funnel until a curtain of striated rain surrounded the vortex. We began to see dirt and debris rise from the ground under the tip of the funnel a the circulation on the ground slowly increased. The path on the ground from the large funnel was only 65 yards wide but 11 miles long. The tornado did F-2 damage to structures.

During this time the storm traveled slowly to the east. About 20 minutes later the tornado dissipated and another mesocyclone formed spinning up dirt vortex's on the ground, but no more tornadoes. The lightning activity, which had been infrequent, increased dramatically after the tornado dissipated. My chase partner was able to nail a bolt hitting a radio tower to our north. The storm persisted into the night but we left as we lost photography light. We didn't know about the damage the tornado caused until we read about it in the next mornings paper.