Alert archive / Tennessee / Mesoscale Discussions in 2018

Mesoscale Discussion 817

June 21, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Jun 21, 2018, 8:30 PM CDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jun 21, 2018, 8:30 PM CDT (01:30 UTC)
Expired: Jun 21, 2018, 10:30 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 39 counties

Colbert County, AL, Franklin County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Crittenden County, AR, Cross County, AR, St. Francis County, AR, Alcorn County, MS, Benton County, MS, DeSoto County, MS, Lafayette County, MS, Marshall County, MS, Panola County, MS, Prentiss County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Chester County, TN, Decatur County, TN, Fayette County, TN, Giles County, TN, Hardeman County, TN, Hardin County, TN, Haywood County, TN, Henderson County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Madison County, TN, Marshall County, TN, McNairy County, TN, Moore County, TN, Perry County, TN, Shelby County, TN, Tipton County, TN, Wayne County, TN

The radar

The Memphis radar (KNQA), 122 km from the middle of the area, began a volume at 01:30 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

Little Rock, AR (KBYH), launched 00:00Z, 1.5 hours before the alert went out and 128 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: 293 J/kg
Mixed-layer CIN: -97 J/kg
Mixed-layer LCL: 2167 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 91 m²/s²
0-3 km storm-relative helicity: 218 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 22, 9:09 AM CDT	Mesoscale Discussion	SPC	Fayette, Franklin, Lamar, Marion, Pickens, Tuscaloosa and 2 more	96 min
Jun 22, 12:35 PM CDT	Mesoscale Discussion	SPC	Blount, Cherokee, Colbert, Cullman, DeKalb, Etowah and 15 more	85 min
Jun 22, 8:42 AM CDT	Mesoscale Discussion	SPC	Ashley, Bradley, Calhoun, Chicot, Columbia, Drew and 2 more	93 min
Jun 22, 10:55 AM CDT	Severe Thunderstorm Watch	SPC	Columbia, Union	10 hr
Jun 22, 3:03 PM CDT	Mesoscale Discussion	SPC	Ashley, Columbia, Union	87 min
Jun 22, 6:05 PM CDT	Mesoscale Discussion	SPC	Claiborne, Clarke, Copiah, Covington, Hinds, Issaquena and 14 more	115 min

Nearby

Mesoscale Discussions in Tennessee, 2018 Mesoscale Discussions in Mississippi, 2018 Mesoscale Discussions in Alabama, 2018 Every mesoscale discussion in 2018

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.