Alert archive / Alabama / Mesoscale Discussions in 2013

Mesoscale Discussion 571

April 27, 201318 counties in Alabama; 4 counties in Georgia

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2013, 8:56 PM CDT for 18 counties in Alabama; 4 counties in Georgia. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2013, 8:56 PM CDT (01:56 UTC)
Expired: Apr 27, 2013, 10:00 PM CDT
In force: 64 min
Issued by: the Storm Prediction Center

All 22 counties

Blount County, AL, Calhoun County, AL, Cherokee County, AL, Cleburne County, AL, Colbert County, AL, Cullman County, AL, DeKalb County, AL, Etowah County, AL, Franklin County, AL, Jackson County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marshall County, AL, Morgan County, AL, St. Clair County, AL, Winston County, AL, Catoosa County, GA, Chattooga County, GA, Dade County, GA, Walker County, GA

The radar

The Northeast Alabama radar (KHTX), 74 km from the middle of the area, began a volume at 02:00 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

Nashville Metro, TN (KBNA), launched 00:00Z, 1.9 hours before the alert went out and 202 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: 108 J/kg
Mixed-layer CIN: -100 J/kg
Mixed-layer LCL: 579 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 170 m²/s²
0-3 km storm-relative helicity: 244 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.7

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
Apr 27, 10:25 PM CDT	Mesoscale Discussion	SPC	Colbert, Lauderdale	2 hr
Apr 28, 12:37 PM CDT	Mesoscale Discussion	SPC	Barbour, Bullock, Butler, Chambers, Conecuh, Crenshaw and 10 more	83 min
Apr 28, 5:09 PM CDT	Mesoscale Discussion	SPC	Baldwin, Bibb, Bleckley, Burke, Butts, Columbia and 32 more	66 min

Nearby

Mesoscale Discussions in Alabama, 2013 Mesoscale Discussions in Georgia, 2013 Every mesoscale discussion in 2013

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.