IEM Daily Bulletin for May 29 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 29 May 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
May 28 12:56 PM	iem,main	🐛 Correct download start year to 2000	Link
May 28 1:38 PM	iem,main	♻️ Refactor to function	Link
May 28 1:51 PM	iem,main	🎨 Rollup bootstrap5 + php fixes	Link
May 28 1:51 PM	iem,main	⬆️ Update ruff precommit	Link
May 28 2:01 PM	iem,main	💚 Address codereview	Link
May 28 12:42 PM	pywwa,main	➕ Add CKC3 to pireps	Link
May 28 12:43 PM	pywwa,main	⬆️ Update ruff precommit	Link

Daily Feature

Lenticular Clouds
Date: 28 May 05:30 AM
Votes: Good: 17   Bad: 0 Abstain: 0

Cloud watchers over central Iowa were treated to Lenticular Clouds on Wednesday afternoon. While this type of cloud is often observed on the leeward side of mountains, it takes a special environment to produce them in the absence of significant topography. In this case, a northeasterly propagating gravity wave into flow going in the opposite direction likely combined to produce a "standing wave" environment necessary for these clouds to form. You can find a satellite lapse showing the gravity wave interaction. The clouds have a smooth appearance as the flow sculpts the cloud stuck in the crest of the standing wave. A time lapse from ISU was captured and available on YouTube that shows the stationary nature of the clouds. Again, you'll find plenty of much fancier and more dramatic examples of these clouds near mountains on the Internet, but such displays on the plains are rare! Hope you were able to see them.

NWS Watch/Warning Summary for 12 AM 28 May 2026 - 12 AM 29 May 2026 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	77	0	0	0	0	0	0	2
Flash Flood	35	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:  73 Verified:  22 [30.1%]
Polygon Size Versus County Size            [10.3%]
Average Perimeter Ratio                    [18.2%]
Percentage of Warned Area Verified (15km)  [11.2%]
Average Storm Based Warning Size           [1616 sq km]
Probability of Detection(higher is better) [0.62]
False Alarm Ratio (lower is better)        [0.70]
Critical Success Index (higher is better)  [0.25]

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): 2,072
• Mastodon / Fediverse: 12
• Slack: 76
• Twitter/X: 7,719
• HTTP Webhooks: 149
• Weather.IM Jabber Chatrooms: 10,294