Alert archive / Texas / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 22, NWS Houston/Galveston, TX

April 18, 2020Grimes County, Montgomery County, Waller County, Texas

NWS Houston/Galveston, TX issued this severe thunderstorm warning at Apr 18, 2020, 3:40 PM CDT for Grimes County, Montgomery County, Waller County, Texas. It was in force for 35 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Apr 18, 2020, 3:40 PM CDT (20:40 UTC)
Expired
Apr 18, 2020, 4:15 PM CDT
In force
35 min
Issued by
NWS Houston/Galveston, TX
Area
Storm-based polygon
Hail
1.0 in
Wind
60.0 mph

Counties Grimes County, TX, Montgomery County, TX, Waller County, TX

The radar

The Houston radar (KHGX), 116 km from the middle of the area, began a volume at 20:40 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, 8.7 hours before the alert went out and 253 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-pSkew-T log-p diagram, Lake Charles Mun, LA at 12:00Z on 2020-04-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 334 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lake Charles Mun, LA at 12:00Z on 2020-04-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 39 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
334 J/kg
Mixed-layer CIN
-142 J/kg
Mixed-layer LCL
519 m above ground
0-6 km bulk shear
54 kt
0-1 km storm-relative helicity
39 m²/s²
0-3 km storm-relative helicity
171 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.9

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Houston/Galveston, TX wrote its last area forecast discussion before this severe thunderstorm warning went out at Apr 18, 3:40 PM CDT, 0 minutes earlier.

Area forecast discussion, Apr 18, 3:40 PM CDT, 0 minutes before
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In the hours before

Special weather statement, Apr 18, 2:50 PM CDT, 50 minutes before
Special Weather Statement
National Weather Service Houston/Galveston TX
250 PM CDT Sat Apr 18 2020

TXZ197-211-212-182015-
Washington TX-Waller TX-Austin TX-
250 PM CDT Sat Apr 18 2020

...SPECIAL WEATHER STATEMENT...

At 249 PM CDT, Doppler radar was tracking a strong thunderstorm over
Bellville, moving northeast at 35 mph.

Pea size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Hempstead, Prairie View, Bellville, Pine Island and Monaville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 2983 9626 2997 9642 3021 9614 3000 9591
TIME...MOT...LOC 1949Z 229DEG 32KT 2995 9629
Special weather statement, Apr 18, 3:22 PM CDT, 18 minutes before
<!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>

The office that day

Everything else NWS Houston/Galveston, TX issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 17, 7:18 PM CDTSpecial Marine WarningHGX42 min
Apr 17, 8:00 PM CDTSpecial Marine WarningHGX60 min
Apr 17, 9:02 PM CDTSpecial Marine WarningHGX28 min
Apr 17, 11:20 PM CDTSpecial Marine WarningHGX40 min
Apr 18, 2:50 PM CDTSpecial Weather StatementHGXAustin, Waller25 min
Apr 18, 3:22 PM CDTSpecial Weather StatementHGXWaller38 min
Apr 18, 3:35 PM CDTSevere Thunderstorm WarningHGXFort Bend, Harris, Waller25 min
Apr 18, 3:42 PM CDTSpecial Weather StatementHGXChambers48 min
Apr 18, 3:54 PM CDTSevere Thunderstorm WarningHGXHarris36 min
Apr 18, 4:06 PM CDTSevere Thunderstorm WarningHGXGrimes, Montgomery, Walker39 min
Apr 18, 4:35 PM CDTSevere Thunderstorm WarningHGXPolk, San Jacinto, Trinity, Walker55 min
Apr 18, 4:43 PM CDTSpecial Weather StatementHGXWashington47 min
Apr 18, 4:47 PM CDTSpecial Weather StatementHGXHarris43 min
Apr 18, 5:03 PM CDTAreal Flood AdvisoryHGXHarris, Montgomery57 min
Apr 18, 5:18 PM CDTSevere Thunderstorm WarningHGXHarris, Liberty, Montgomery30 min
Apr 18, 5:27 PM CDTSevere Thunderstorm WarningHGXChambers, Harris, Liberty33 min
Apr 18, 5:32 PM CDTSpecial Weather StatementHGXMontgomery28 min
Apr 18, 5:50 PM CDTSevere Thunderstorm WarningHGXLiberty40 min
Apr 18, 5:59 PM CDTSevere Thunderstorm WarningHGXLiberty, Montgomery, San Jacinto46 min
Apr 18, 6:31 PM CDTSpecial Weather StatementHGXLiberty44 min

Nearby

Severe Thunderstorm Warnings in Texas, 2020Every severe thunderstorm warning in 2020

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.