Alert archive / Oklahoma / Severe Thunderstorm Warnings in 1999

Severe Thunderstorm Warning 331, NWS Norman, OK

May 20, 1999Harper County, Oklahoma

NWS Norman, OK issued this severe thunderstorm warning at May 20, 1999, 6:22 PM CDT for Harper County, Oklahoma. It was in force for 38 min. 1 report came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: May 20, 1999, 6:22 PM CDT (23:22 UTC)
Expired: May 20, 1999, 7:00 PM CDT
In force: 38 min
Issued by: NWS Norman, OK
Area: Whole counties; the outline is the Mesonet’s reconstruction

County Harper County, OK

The radar

The Dodge City radar (KDDC), 111 km from the middle of the area, began a volume at 23:25 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.

What was reported inside it

Time	Report	Where	Remark
May 20, 6:55 PM CDT	Hail 0.75	Laverne, OK

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
May 20, 3:15 PM CDT	Tornado Watch	SPC	6 hr

The nearest sounding before it

Dodge City, (KDDC), launched 12:00Z, 11.4 hours before the alert went out and 111 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: 857 J/kg
Mixed-layer CIN: -97 J/kg
Mixed-layer LCL: 828 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 171 m²/s²
0-3 km storm-relative helicity: 180 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

Open this sounding in Storm Lab

The text

The text of this product is not in the archive. The NWS text archive before 2002 is incomplete.

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 Norman, OK wrote its last area forecast discussion before this severe thunderstorm warning went out at May 20, 2:00 PM CDT, 4 hours 22 minutes earlier.

Area forecast discussion, May 20, 2:00 PM CDT, 4 hours 22 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
200 PM CDT THU MAY 20 1999

STRONG SOUTH WINDS WILL PERSIST IN THE BOUNDARY LAYER OVER WESTERN
OKLAHOMA TONIGHT AS A DRYLINE APPROACHES FROM THE WEST AND A COLD
FRONT FROM THE NORTH. THUNDERSTORMS ARE LIKELY LATER THIS EVENING
AND TONIGHT ACROSS THE NORTHWEST HALF OF OKLAHOMA. THERE IS SOME
RISK OF HEAVY RAIN IN PARTS OF NORTH CENTRAL OKLAHOMA WHERE ABUNDANT
MOISTURE WILL CONTINUE MOVING INTO THE FRONTAL ZONE HOWEVER, THE
HEAVIER RAINFALL IS LIKELY TO BE IN KANSAS.

WITH THE HELP OF KANSAS RAINS TONIGHT, THE FRONT WILL CONTINUE INTO
CENTRAL OKLAHOMA BY SUNRISE. A LINE OF STORMS IS LIKELY TO FORM
ALONG THIS FRONT OVERNIGHT AS A WEAK MID-LEVEL WAVE WILL MOVE OUT OF
COLORADO AND INTO THE SOUTHERN PLAINS RIDGE.

SKIES SHOULD BE MOSTLY CLOUDY WITH SHOWERS FOR SEVERAL HOURS AFTER
THE FRONT PASSES ACROSS THE NORTHERN HALF OF OKLAHOMA LATE TONIGHT
AND FRIDAY MORNING. THE FRONT WILL PROVIDE FOCUS FOR SHOWERS AND
THUNDERSTORMS FRIDAY AFTERNOON AND EVENING ACROSS THE SOUTH.

AFTER ANOTHER TRANSIENT MID-LEVEL WAVE FRIDAY NIGHT OR SATURDAY
MORNING ACROSS THE NORTH BRINGS A CHANCE FOR STORMS AND SHOWERS, THE
REST OF SATURDAY SHOULD BE LARGELY RAIN-FREE BEFORE A CHANCE OF RAIN
RETURNS LATER IN THE WEEKEND WITH A STRONGER COLD FRONT ON SUNDAY.

FCSTID = 9
OKC   64  77  61  80 /  70  40  20   0
HBR   65  82  63  84 /  40  40  20   0
SPS   66  82  64  83 /  40  60  20  20
GAG   58  76  57  81 /  70  30  30  20
PNC   64  75  60  79 /  80  30  30   0
DUA   67  81  64  81 /  40  60  30  20

.OUN...
OK...NONE.
TX...NONE.

In the hours before

Special weather statement, May 20, 12:30 PM CDT, 5 hours 52 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>

Special weather statement, May 20, 12:30 PM CDT, 5 hours 52 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>

Local storm report, May 20, 3:32 PM CDT, 2 hours 50 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>

Local storm report, May 20, 3:32 PM CDT, 2 hours 50 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 Norman, OK issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 6:59 PM CDT	Severe Thunderstorm Warning	OUN	Ellis, Harper	46 min

Nearby

Severe Thunderstorm Warnings in Oklahoma, 1999 Every severe thunderstorm warning in 1999

Sources

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