Alert archive / Iowa / Mesoscale Discussions in 2004

Mesoscale Discussion 772

May 20, 20047 counties in Illinois; 43 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at May 20, 2004, 11:31 AM CDT for 7 counties in Illinois; 43 counties in Iowa. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 20, 2004, 11:31 AM CDT (16:31 UTC)
Expired: May 20, 2004, 2:00 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 50 counties

Adair County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Buchanan County, IA, Cedar County, IA, Clarke County, IA, Clinton County, IA, Dallas County, IA, Delaware County, IA, Des Moines County, IA, Dubuque County, IA, Greene County, IA, Grundy County, IA, Hamilton County, IA, Hardin County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jasper County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Linn County, IA, Louisa County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Muscatine County, IA, Polk County, IA, Poweshiek County, IA, Scott County, IA, Story County, IA, Tama County, IA, Union County, IA, Van Buren County, IA, Wapello County, IA, Warren County, IA, Washington County, IA, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Knox County, IL, Mercer County, IL, Rock Island County, IL, Warren County, IL

The radar

The Des Moines radar (KDMX), 116 km from the middle of the area, began a volume at 16:34 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 4.5 hours before the alert went out and 153 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1924 J/kg
Mixed-layer CIN: -45 J/kg
Mixed-layer LCL: 689 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 209 m²/s²
0-3 km storm-relative helicity: 197 m²/s²
Significant tornado parameter: 1.6
Supercell composite: 9.4

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 3:35 PM CDT	Severe Thunderstorm Watch	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 23 more	6 hr
May 19, 7:12 PM CDT	Mesoscale Discussion	SPC	Audubon, Calhoun, Carroll, Emmet, Floyd, Franklin and 15 more	2 hr
May 20, 4:54 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Appanoose, Audubon, Boone, Cass and 33 more	96 min
May 20, 5:00 PM CDT	Tornado Watch	SPC	Adair, Adams, Appanoose, Audubon, Cass, Clarke and 23 more	5 hr

Nearby

Mesoscale Discussions in Iowa, 2004 Mesoscale Discussions in Illinois, 2004 Every mesoscale discussion in 2004

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.