IEM Daily Bulletin for Sep 23 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 23 September 2025

News

No news is good news

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Daily Feature

Equinox Driving Difficulty
Date: 22 Sep 05:50 AM
Votes: Good: 16   Bad: 1 Abstain: 0

This afternoon (1:19 PM) is the Autumn Equinox, which is the moment when the sun is directly over the equator and denotes the end of the astronomical summer season for the northern hemisphere. The sun will rise due east and set due west today, which has an important impact to vehicle travel as shown by the featured RWIS webcam image from last night near Adair. Since most of Iowa's roads are oriented either north/south or east/west, a good portion of them will experience difficult driving near sunrise and sunset with the sun directly in the line of the roadway. Of course, it isn't just today with these difficulties as the sun's rising and setting is only marginally different than due west and east for a number of weeks surrounding today.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 22 Sep 2025 - 12 AM 23 Sep 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	6	0	0	0	0	0	0	0
Svr Tstorm	119	20	8	0	9	17	2	1
Flash Flood	18	0	0	0	0	0	0	---

ARX = LaCrosse, WI DVN = Davenport, IA DMX = Des Moines, IA OAX = Omaha, NE FSD = Sioux Falls, SD

IEM Cow Report

SVR+TOR Warnings Issued: 124 Verified:  38 [30.6%]
Polygon Size Versus County Size            [21.0%]
Average Perimeter Ratio                    [31.0%]
Percentage of Warned Area Verified (15km)  [15.4%]
Average Storm Based Warning Size           [1307 sq km]
Probability of Detection(higher is better) [0.68]
False Alarm Ratio (lower is better)        [0.69]
Critical Success Index (higher is better)  [0.27]