Alert archive / Texas / Mesoscale Discussions in 2009

Mesoscale Discussion 515

April 18, 200916 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2009, 1:43 PM CDT for 16 counties in Texas. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Apr 18, 2009, 1:43 PM CDT (18:43 UTC)
Expired: Apr 18, 2009, 3:15 PM CDT
In force: 92 min
Issued by: the Storm Prediction Center

Counties Angelina County, TX, Austin County, TX, Brazoria County, TX, Chambers County, TX, Fort Bend County, TX, Galveston County, TX, Harris County, TX, Liberty County, TX, Matagorda County, TX, Montgomery County, TX, Nacogdoches County, TX, Polk County, TX, San Jacinto County, TX, Trinity County, TX, Waller County, TX, Wharton County, TX

The radar

The Houston radar (KHGX), 59 km from the middle of the area, began a volume at 18:43 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

Lake Charles Mun, LA (KLCH), launched 12:00Z, 6.7 hours before the alert went out and 218 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: 778 J/kg
Mixed-layer CIN: -108 J/kg
Mixed-layer LCL: 573 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 160 m²/s²
0-3 km storm-relative helicity: 499 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 8.3

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 17, 9:33 PM CDT	Mesoscale Discussion	SPC	Childress, Collingsworth, Cottle, Foard, Gray, Hansford and 13 more	27 min
Apr 17, 11:44 PM CDT	Mesoscale Discussion	SPC	Atascosa, La Salle, McMullen	61 min
Apr 18, 3:22 AM CDT	Mesoscale Discussion	SPC	Atascosa, Bandera, Bastrop, Bee, Bexar, Blanco and 34 more	113 min
Apr 18, 4:21 AM CDT	Severe Thunderstorm Watch	SPC	Aransas, Atascosa, Austin, Bandera, Bastrop, Bee and 43 more	7 hr
Apr 18, 6:32 AM CDT	Mesoscale Discussion	SPC	Atascosa, Bandera, Bastrop, Bexar, Caldwell, Comal and 17 more	118 min
Apr 18, 9:47 AM CDT	Mesoscale Discussion	SPC	Anderson, Angelina, Austin, Brazoria, Brazos, Chambers and 22 more	28 min
Apr 18, 9:53 AM CDT	Tornado Watch	SPC	Anderson, Angelina, Austin, Brazoria, Brazos, Burleson and 23 more	6 hr
Apr 18, 10:52 AM CDT	Mesoscale Discussion	SPC	Aransas, Atascosa, Bee, Calhoun, DeWitt, Duval and 15 more	53 min
Apr 18, 11:26 AM CDT	Mesoscale Discussion	SPC	Anderson, Angelina, Austin, Brazoria, Brazos, Burleson and 29 more	2 hr
Apr 18, 1:01 PM CDT	Tornado Watch	SPC	Hardin, Jasper, Jefferson, Newton, Orange, Sabine and 3 more	7 hr
Apr 18, 1:14 PM CDT	Mesoscale Discussion	SPC	Archer, Clay, Wichita	61 min
Apr 18, 3:11 PM CDT	Severe Thunderstorm Watch	SPC	Archer, Clay, Collin, Cooke, Dallas, Denton and 14 more	9 hr
Apr 18, 3:38 PM CDT	Mesoscale Discussion	SPC	Hardin, Jasper, Jefferson, Newton, Orange, Sabine and 3 more	97 min
Apr 18, 5:14 PM CDT	Mesoscale Discussion	SPC	Cooke, Denton, Grayson	91 min
Apr 18, 5:46 PM CDT	Mesoscale Discussion	SPC	Hardin, Jasper, Jefferson, Newton, Orange, Sabine and 3 more	59 min

Nearby

Mesoscale Discussions in Texas, 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.