IEM Daily Feature
Monday, 17 July 2023

Intense Ames Rainfall

Posted: 17 Jul 2023 05:30 AM

Wednesday morning, the 12th of July, last week featured an intense rainfall event during the morning hours. The one minute interval data from the Ames Airport is now available and the featured chart presents some metrics from the event. The blue bars represent an extrapolated hourly rate base on the single minute observations. The tan line represents an extrapolated hourly rate based on fifteen minute interval observations and the red line represents the actual accumulation over the trailing 60 minutes of time. Of course, instantaneous and intense precipitation rates are very difficult to sustain locally over long periods of time as the atmosphere needs to have a source that can replenish/generate rain water at that local location. Storms generally need to keep moving to be able to maintain intense rainfall rates. Sometimes mountains (not a mechanism for Iowa) or the "low level jet" (common for Iowa) can help feed a storm and allow it to not move much and maintain an intense rate over a limited area for a significant period of time. So for this event and for Ames, the precipitation came in three waves and actual rates never got too out of control, so flash flooding was limited. A bit further west of Ames, rates were higher with larger accumulations, so flash flooding was more an issue there.

Good = 12
Bad = 0