IEM Daily Bulletin for May 19 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 19 May 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
May 18 10:20 AM	iem,main	🚚 Replace homepage precip map with MRMS	Link

Daily Feature

Return of Humidity
Date: 18 May 05:30 AM
Votes: Good: 11   Bad: 0 Abstain: 0

The featured chart presents a time series of hourly dew point temperatures for Ames since 25 April. The lack of humidity during the month of May has dramatically reversed over this past weekend with even a 70°F dew point observation on Sunday. The return of humidity has certainly helped the return of spring time thunderstorms and severe weather with more of both expected on Monday.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 18 May 2026 - 12 AM 19 May 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	60	12	0	0	7	15	0	5
Svr Tstorm	238	21	0	1	4	29	3	5
Flash Flood	20	3	0	0	1	2	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: 288 Verified: 136 [47.2%]
Polygon Size Versus County Size            [38.3%]
Average Perimeter Ratio                    [41.3%]
Percentage of Warned Area Verified (15km)  [26.1%]
Average Storm Based Warning Size           [1805 sq km]
Probability of Detection(higher is better) [0.86]
False Alarm Ratio (lower is better)        [0.53]
Critical Success Index (higher is better)  [0.44]

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