Iowa Environmental Mesonet

Iowa State University Department of Agronomy

View current Iowa Road Conditions
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WFO: Warning Type: Tornado Svr T'storm Marine Flash Flood (2008+)
Hail Size: LSR Type: Tornado Svr T'storm Marine Flash Flood (2008+)

IEM Cow (NWS Storm Based Warning Verification)

Data presented here is unofficial and should be used for educational purposes only. This application allows you to view warnings and storm reports issued by a Weather Forecast Office (WFO) for a period of time of your choice. The application attempts to automatically provide verification numbers for the warnings issued.

This application works for dates after 8 June 2005.

Polygon Warnings?

Most of you are certainly familiar with traditional warnings issued on a per county basis. The National Weather Service has been experimenting with a new technology that generates warnings on a polygon basis. A polygon is simply a region much like a county. Storms don't follow county borders nicely, so many times warnings are issued for a county when only a small portion is affected.

The image shown here demonstrates the two types of warnings. You can see the traditional outline around the county which the warning is for. The white box is actually the polygon warning which often highlights the area of concern for a particular storm.

County based warnings will be around for a while. The polygon warnings highlight a latitude+longitude box which is hard for the public to understand. At some point, the polygon is translated into counties.

This application attempts to provide verification statistics for these polygon warnings. One of the motivations for polygons is to provide more accurate warnings to the public. This accuracy should be reflected in higher verification numbers.