Alert archive / Oklahoma / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 487, NWS Norman, OK

September 17, 2021Harper County, Oklahoma

NWS Norman, OK issued this severe thunderstorm warning at Sep 17, 2021, 7:28 PM CDT for Harper County, Oklahoma. It was in force for 47 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Sep 17, 2021, 7:28 PM CDT (00:28 UTC)
Expired: Sep 17, 2021, 8:15 PM CDT
In force: 47 min
Issued by: NWS Norman, OK
Area: Storm-based polygon
Damage threat: Considerable
Hail: 1.0 in
Wind: 70.0 mph

County Harper County, OK

What was reported inside it

Time	Report	Where	Remark
Sep 17, 7:40 PM CDT	TSTM WND GST 72	1 N Laverne, OK

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Dodge City, (KDDC), launched 00:00Z, 0.5 hours before the alert went out and 117 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: 1092 J/kg
Mixed-layer CIN: -21 J/kg
Mixed-layer LCL: 1639 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 25 m²/s²
0-3 km storm-relative helicity: 142 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.4

Open this sounding in Storm Lab

The text

As transmitted.

937 
WUUS54 KOUN 180028
SVROUN
OKC059-180115-
/O.NEW.KOUN.SV.W.0487.210918T0028Z-210918T0115Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Norman OK
728 PM CDT Fri Sep 17 2021

The National Weather Service in Norman has issued a

* Severe Thunderstorm Warning for...
  Southwestern Harper County in northwestern Oklahoma...

* Until 815 PM CDT.

* At 727 PM CDT, a severe thunderstorm was located near Laverne,
  moving southeast at 15 mph.

  HAZARD...70 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect considerable 
           tree damage. Wind damage is also likely to mobile homes, 
           roofs, and outbuildings.

* Locations impacted include...
  Laverne.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3677 9997 3685 9982 3671 9957 3663 9971
      3660 9986
TIME...MOT...LOC 0027Z 316DEG 12KT 3674 9985 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

JP

1 follow-up statement

914 
WWUS54 KOUN 180044
SVSOUN

Severe Weather Statement
National Weather Service Norman OK
744 PM CDT Fri Sep 17 2021

OKC059-180115-
/O.CON.KOUN.SV.W.0487.000000T0000Z-210918T0115Z/
Harper OK-
744 PM CDT Fri Sep 17 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM CDT
FOR SOUTHWESTERN HARPER COUNTY...

At 740 PM CDT, a 72 mph wind gust was measured just north of Laverne 
from a severe thunderstorm located 4 miles northwest of May, moving 
southeast at 15 mph.

HAZARD...70 mph wind gusts and quarter size hail.

SOURCE...Public.

IMPACT...Hail damage to vehicles is expected. Expect considerable 
         tree damage. Wind damage is also likely to mobile homes, 
         roofs, and outbuildings.

Locations impacted include...
Laverne and areas north of May.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3677 9997 3685 9982 3671 9957 3663 9971
      3660 9986
TIME...MOT...LOC 0042Z 322DEG 14KT 3666 9981 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...OBSERVED
MAX WIND GUST...70 MPH

$$

TL

The office that day

Everything else NWS Norman, OK issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 17, 7:34 PM CDT	Areal Flood Advisory	OUN	Harper	3 hr
Sep 17, 7:48 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OUN	Ellis, Harper	42 min
Sep 17, 8:04 PM CDT	Severe Thunderstorm Warning Destructive damage threat	OUN	Ellis, Harper, Woodward	41 min
Sep 17, 8:46 PM CDT	Special Weather Statement	OUN	Ellis	29 min
Sep 17, 8:48 PM CDT	Special Weather Statement	OUN	Ellis	27 min
Sep 17, 9:21 PM CDT	Special Weather Statement	OUN	Ellis	24 min
Sep 17, 9:54 PM CDT	Special Weather Statement	OUN	Roger Mills	36 min

Nearby

Severe Thunderstorm Warnings in Oklahoma, 2021 Every severe thunderstorm warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive.