IEM Daily Bulletin for Jul 9 2026

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 09 July 2026

News

No news is good news

IEM Code Pushes <repo,branch> on Github

Timestamp	Repository	Message	Link
Jul 8 7:39 AM	iem,main	🎨 Misc improvements to HRRR processing	Link
Jul 8 8:59 AM	iem,main	🎨 Cleanup some idep/profit references	Link
Jul 9 6:44 AM	iem,main	💚 Address codereview	Link
Jul 8 8:27 AM	iemone,main	🐛 Fix and refactor time handling whilst in RT mode fixes #92	Link
Jul 8 8:37 AM	iemone,main	💚 Address codereview	Link

Daily Feature

Des Moines Heat Island
Date: 08 Jul 05:30 AM
Votes: Good: 11   Bad: 0 Abstain: 0

With a low temperature of 70°F on Tuesday, the Des Moines airport weather station was the warmest within Iowa among airport based weather stations. This situation happens frequently for the site due to the urban heat island effect being the strongest for the most urban airport weather sensor within Iowa. The featured chart illustrates this by computing the average low temperature percentile for Des Moines vs the rest of the long term climate stations within Iowa. Please note that there was no spatial weighting done, it is just a simple comparison. The bottom panel shows the bias between the Des Moines average value vs the rest of the state. The increasing impact of the heat island is readily apparent, but you may wonder what is happening during the early period prior to ~1940. This was approximately when the station moved from downtown to the present location, which was more rural at the time. Additionally, observation techniques changed with most of the rest of the state reporting 24 hour values during the afternoon hours, which tends to bias low temperatures warmer.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 8 Jul 2026 - 12 AM 9 Jul 2026 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	4	2	1	0	0	1	0	0
Svr Tstorm	138	22	7	0	3	14	3	3
Flash Flood	34	3	3	0	1	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: 137 Verified:  48 [35.0%]
Polygon Size Versus County Size            [13.4%]
Average Perimeter Ratio                    [21.6%]
Percentage of Warned Area Verified (15km)  [19.9%]
Average Storm Based Warning Size           [1060 sq km]
Probability of Detection(higher is better) [0.65]
False Alarm Ratio (lower is better)        [0.65]
Critical Success Index (higher is better)  [0.29]

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