IEM Daily Bulletin for Sep 13 2023

[daryl herzmann]

Iowa Environmental Mesonet Daily Bulletin for 13 September 2023

News

No news is good news

IEM Code Pushes <to branch> on Github

• Sep 12 8:52 AM <main> fix: database update whackamole
  refs akrherz/pyIEM#754
• Sep 12 9:01 AM <main> Merge pull request #517 from akrherz/230910-2
  fix: database update whackamole
• Sep 12 9:44 AM <main> fix: misc cleanups
• Sep 12 9:52 AM <main> Merge pull request #518 from akrherz/230912
  fix: misc cleanups
• Sep 12 6:57 PM <main> mnt: psycopg 3 issues whackamole
• Sep 12 11:10 PM <main> mnt: psycopg 3 whackamole
• Sep 13 5:23 AM <main> Merge pull request #519 from akrherz/230912-2
  mnt: psycopg 3 issues whackamole

Daily Feature

Change in 90 Day SPI
Date: 12 Sep 12:01 AM
Votes: Good: 11   Bad: 2 Abstain: 0

The seven day total precipitation ending this morning around 7 AM is considered for the weekly update to the US Drought Monitor issued on Thursday. This period has seen a couple of rounds of rainfalls hitting various parts of the state. The focus of today's daily feature is assessing if any of it was enough to move the drought needle? While there is no one-to-one association of drought classification to any precipitation index, a commonly consulted value is trailing 90 day standardized precipitation index (SPI). The left hand map shows the most recent US Drought Monitor depiction along with long term climate sites drought classification based on 90 day SPI. The top right panel shows the weekly change in 90 day SPI over the past seven days with the arrow showing the direction of change over that period. The bottom right shows a count of stations meeting various before and after SPI values. The first thing that may catch your eye are the very negative red lines in th! e upper right panel. These can be explained by the fact that the trailing 90 day window dropped some heavy rainfall events from 3 months ago as the window slid forward. This is a huge caveat when looking at a given number of day SPI value as the big rainfall events can introduce noise as they come in and leave the time window. Another caveat is that replacing a week of June with a week of September lowers the climatological accumulation, which is effectively a positive addition to SPI without it even raining! So getting back to the original question, the last week of rain didn't do too much to erase any of the drought that continues to plague the state.

The featured media can be generated on-demand here

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NWS Watch/Warning Summary for 12 AM 12 Sep 2023 - 12 AM 13 Sep 2023 CDT

	Summary		By WFO					Watches
Type	US	IA	ARX	DVN	DMX	OAX	FSD	US
Tornado	2	0	0	0	0	0	0	0
Svr Tstorm	53	0	0	0	0	0	0	0
Flash Flood	14	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:  51 Verified:  23 [45.1%]
Polygon Size Versus County Size            [8.5%]
Average Perimeter Ratio                    [14.4%]
Percentage of Warned Area Verified (15km)  [28.7%]
Average Storm Based Warning Size           [992 sq km]
Probability of Detection(higher is better) [0.76]
False Alarm Ratio (lower is better)        [0.55]
Critical Success Index (higher is better)  [0.39]