Alert archive / Oklahoma / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 139
The Storm Prediction Center issued this severe thunderstorm watch at May 4, 2021, 12:47 AM CDT for 9 counties in Oklahoma. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 12:47 AM CDT (05:47 UTC)
- Expired
- May 4, 2021, 3:05 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Atoka County, OK, Bryan County, OK, Carter County, OK, Coal County, OK, Johnston County, OK, Love County, OK, Marshall County, OK, Murray County, OK, Pontotoc County, OK
The radar
The Norman radar (KTLX), 120 km from the middle of the area, began a volume at 05:48 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 SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 40%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 1:23 AM CDT | Severe Thunderstorm Warning | OUN | Johnston, Murray, Pontotoc | 52 min |
| May 4, 1:55 AM CDT | Severe Thunderstorm Warning | OUN | Coal, Johnston, Pontotoc | 50 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Fort Worth, TX (KFWD), launched 00:00Z, 5.8 hours before the alert went out and 171 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.
- Mixed-layer CAPE
- 3299 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 1213 m above ground
- 0-6 km bulk shear
- 58 kt
- 0-1 km storm-relative helicity
- 150 m²/s²
- 0-3 km storm-relative helicity
- 143 m²/s²
- Significant tornado parameter
- 2.6
- Supercell composite
- 13.9
The text
As transmitted.
746
WWUS20 KWNS 040543
SEL9
SPC WW 040543
OKZ000-041000-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 139
NWS Storm Prediction Center Norman OK
1245 AM CDT Tue May 4 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southern Oklahoma
* Effective this Tuesday morning from 1245 AM until 500 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
SUMMARY...Scattered severe thunderstorms will continue eastward
overnight across southern Oklahoma, with large hail and damaging
winds a possibility mainly across south-central toward southeast
Oklahoma.
The severe thunderstorm watch area is approximately along and 30
statute miles north and south of a line from 30 miles west of
Ardmore OK to 40 miles east northeast of Durant OK. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU9).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 137...WW 138...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 450. Mean storm motion vector
27025.
...GuyerSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 3, 7:38 PM CDT | Mesoscale Discussion | SPC | Atoka, Bryan, Choctaw, Coal, Haskell, Hughes and 7 more | 97 min |
| May 3, 8:38 PM CDT | Mesoscale Discussion | SPC | McCurtain | 2 hr |
| May 3, 9:10 PM CDT | Severe Thunderstorm Watch | SPC | McCurtain | 7 hr |
| May 3, 11:34 PM CDT | Mesoscale Discussion | SPC | McCurtain | 86 min |
| May 4, 1:07 AM CDT | Mesoscale Discussion | SPC | Atoka, Bryan, Carter, Choctaw, Coal, Garvin and 7 more | 83 min |
Nearby
Severe Thunderstorm Watches in Oklahoma, 2021Every severe thunderstorm watch 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.