Alert archive / Tennessee / Mesoscale Discussions in 2017

Mesoscale Discussion 614

April 30, 20174 states

The Storm Prediction Center issued this mesoscale discussion at Apr 30, 2017, 1:21 PM CDT for 4 states. It was in force for 54 min.

The area

The outline as issued.

The facts

Issued
Apr 30, 2017, 1:21 PM CDT (18:21 UTC)
Expired
Apr 30, 2017, 2:15 PM CDT
In force
54 min
Issued by
the Storm Prediction Center
Chance of a watch
80%
All 42 counties

Cherokee County, AL, Cleburne County, AL, DeKalb County, AL, Etowah County, AL, Jackson County, AL, Madison County, AL, Marshall County, AL, Catoosa County, GA, Chattooga County, GA, Dade County, GA, Floyd County, GA, Haralson County, GA, Polk County, GA, Walker County, GA, Simpson County, KY, Bedford County, TN, Cannon County, TN, Cheatham County, TN, Coffee County, TN, Davidson County, TN, DeKalb County, TN, Dickson County, TN, Franklin County, TN, Grundy County, TN, Hamilton County, TN, Lincoln County, TN, Marion County, TN, Marshall County, TN, Maury County, TN, Montgomery County, TN, Moore County, TN, Robertson County, TN, Rutherford County, TN, Sequatchie County, TN, Smith County, TN, Sumner County, TN, Trousdale County, TN, Van Buren County, TN, Warren County, TN, White County, TN, Williamson County, TN, Wilson County, TN

The radar

The Northeast Alabama radar (KHTX), 35 km from the middle of the area, began a volume at 18:24 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Nashville Metro, TN (KBNA), launched 12:00Z, 6.4 hours before the alert went out and 107 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, Nashville Metro, TN at 12:00Z on 2017-04-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 329 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, Nashville Metro, TN at 12:00Z on 2017-04-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 231 square meters per square second.19395878Sfc1 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
329 J/kg
Mixed-layer CIN
-20 J/kg
Mixed-layer LCL
815 m above ground
0-6 km bulk shear
41 kt
0-1 km storm-relative helicity
231 m²/s²
0-3 km storm-relative helicity
284 m²/s²
Significant tornado parameter
0.3
Supercell composite
2.0

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.

IssuedProductOfficeCountiesLasted
Apr 30, 10:06 AM CDTMesoscale DiscussionSPCAutauga, Bibb, Chilton, Colbert, Coosa, Cullman and 16 more84 min
Apr 30, 10:36 AM CDTTornado WatchSPCAutauga, Baldwin, Bibb, Blount, Chilton, Choctaw and 27 more8 hr
Apr 30, 1:36 PM CDTTornado WatchSPCCalhoun, Chambers, Cherokee, Clay, Cleburne, Coosa and 10 more5 hr
Apr 30, 3:42 PM CDTMesoscale DiscussionSPCAutauga, Calhoun, Chambers, Cherokee, Clay, Cleburne and 8 more2 hr
Apr 30, 12:54 AM CDTMesoscale DiscussionSPCBallard, Carlisle, Fulton, Graves, Hickman96 min
Apr 30, 1:10 AM CDTSevere Thunderstorm WatchSPCCalloway, Carlisle, Fulton, Graves, Hickman6 hr
Apr 30, 2:58 AM CDTMesoscale DiscussionSPCBallard, Calloway, Carlisle, Fulton, Graves, Hickman and 3 more92 min
Apr 30, 1:58 PM CDTMesoscale DiscussionSPCGreenup2 hr
Apr 30, 3:58 PM CDTMesoscale DiscussionSPCAdair, Barren, Boyle, Casey, Clinton, Cumberland and 14 more92 min
Apr 30, 5:41 AM CDTMesoscale DiscussionSPCBenton, Carroll, Chester, Crockett, Decatur, Dyer and 11 more64 min

Nearby

Mesoscale Discussions in Tennessee, 2017Mesoscale Discussions in Alabama, 2017Mesoscale Discussions in Georgia, 2017Every mesoscale discussion in 2017

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.