IEM Daily Bulletin for May 18 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 18 May 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
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Daily Feature

No feature posted

NWS Watch/Warning Summary for 12 AM 17 May 2026 - 12 AM 18 May 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	63	29	3	1	12	12	14	5
Svr Tstorm	196	45	7	0	9	35	17	2
Flash Flood	7	3	0	0	0	2	2	---

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

IEM Cow Report

SVR+TOR Warnings Issued: 254 Verified: 116 [45.7%]
Polygon Size Versus County Size            [33.6%]
Average Perimeter Ratio                    [34.5%]
Percentage of Warned Area Verified (15km)  [23.6%]
Average Storm Based Warning Size           [1775 sq km]
Probability of Detection(higher is better) [0.89]
False Alarm Ratio (lower is better)        [0.54]
Critical Success Index (higher is better)  [0.43]

IEMBot Social Media Posts

IEMBot can be configured to post messages to a number of social media services. More details: IEMBot Homepage.

Posts yesterday per supported service:

• ATMosphere (bluesky only attm): 2,073
• Mastodon / Fediverse: 25
• Slack: 144
• Twitter/X: 10,402
• HTTP Webhooks: 206
• Weather.IM Jabber Chatrooms: 15,795