IEM Daily Bulletin for Jul 15 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 15 July 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jul 14 4:22 PM	iem-database,main	⬆️ Update precommits	Link
Jul 14 4:22 PM	iem-database,main	🎨 Add DEP views and tillage_direction to field	Link

Daily Feature

Ames to Des Moines
Date: 14 Jul 05:30 AM
Votes: Good: 13   Bad: 1 Abstain: 1

The past few mornings have featured strong "radiational cooling" events thanks to clear skies and calm winds. Such events often highlight micro-climate differences between weather stations, which was the case when you compare temperatures at the Ames airport vs Des Moines. Temperature differences between the two stations reached 8°F during the morning hours. A daily feature last week highlighted the Des Moines heat island, which tends to buoy temperatures at night time. So with the Ames station being much less urban, it stands to reason that large temperature differences could happen when the heat island effect is most pronounced. The featured chart takes a bit of a deep dive into air temperature differences between the two sites. The top left panel shows the raw values so far this July. The top right panel presents the frequency of Ames being warmer by hour and week of the year. The bottom left panel shows yearly aggregate statistics. The bottom right panel partitions the data by month of the year. Perhaps the most interesting sub-plot is the upper right, which shows two clear areas of increased frequency of Ames being warmer than Des Moines. The reason for these two likely has to do with increased humidity levels due to nearby cropping increasing morning temperatures during the growing season and then a sandier soil allowing for increased heating during the day vs Des Moines.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 14 Jul 2026 - 12 AM 15 Jul 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	1	0	0	0	0	0	0	0
Svr Tstorm	42	0	0	0	0	0	0	2
Flash Flood	44	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:  37 Verified:  12 [32.4%]
Polygon Size Versus County Size            [14.1%]
Average Perimeter Ratio                    [22.8%]
Percentage of Warned Area Verified (15km)  [17.7%]
Average Storm Based Warning Size           [1490 sq km]
Probability of Detection(higher is better) [0.79]
False Alarm Ratio (lower is better)        [0.68]
Critical Success Index (higher is better)  [0.30]

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