IEM Daily Bulletin for Sep 4 2025

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 04 September 2025

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Sep 3 10:43 AM	iem,main	🐛 Try again to get IEMRE daily wind_speed right	Link
Sep 3 12:07 PM	iem,main	✏️ Fix typo	Link

Daily Feature

31 Years of RADAR Imagery
Date: 03 Sep 05:26 AM
Votes: Good: 14   Bad: 0 Abstain: 0

Way back in 2003, the IEM started generating NWS NEXRAD Mosaics for the contiguous US. Over the years, the archive was back-filled using data from NCEI to the start of 1995. The featured plot presents the mosaic product valid 5 AM each 3 September since 1995. These plots and certainly the mosaic itself is not necessarily meant to be a scientifically rigorous product, but something that can be used as a quick screening and assessment tool. These days there are much more advanced mosaics available, including NOAA MRMS and GridRad. Here's to the next 31 years of generating this product by the IEM!

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 3 Sep 2025 - 12 AM 4 Sep 2025 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	0	0	0	0	0	0	0	0
Svr Tstorm	46	2	0	0	2	0	0	1
Flash Flood	14	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:  41 Verified:  19 [46.3%]
Polygon Size Versus County Size            [15.1%]
Average Perimeter Ratio                    [33.1%]
Percentage of Warned Area Verified (15km)  [36.2%]
Average Storm Based Warning Size           [1007 sq km]
Probability of Detection(higher is better) [0.95]
False Alarm Ratio (lower is better)        [0.54]
Critical Success Index (higher is better)  [0.45]