Alert archive / Louisiana / Mesoscale Discussions in 2009

Mesoscale Discussion 613

April 27, 200914 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2009, 9:09 PM CDT for 14 parishes in Louisiana. It was in force for 36 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2009, 9:09 PM CDT (02:09 UTC)
Expired: Apr 27, 2009, 9:45 PM CDT
In force: 36 min
Issued by: the Storm Prediction Center

Counties Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Rapides Parish, LA, Saint Landry Parish, LA, Vermilion Parish, LA, Vernon Parish, LA

The radar

The Lake Charles radar (KLCH), 62 km from the middle of the area, began a volume at 02:09 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 204Apr 27, 9:10 PM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 2.2 hours before the alert went out and 61 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: 1808 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 657 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 107 m²/s²
0-3 km storm-relative helicity: 130 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 4.1

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, 7:08 PM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Caldwell, Catahoula, Claiborne and 14 more	67 min
Apr 27, 9:17 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 7 more	4 hr
Apr 27, 11:06 PM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Cameron, Evangeline, Iberia and 12 more	84 min

Nearby

Mesoscale Discussions in Louisiana, 2009 Every mesoscale discussion in 2009

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.