Alert archive / Texas / Mesoscale Discussions in 2018

Mesoscale Discussion 137

March 18, 201813 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Mar 18, 2018, 7:55 PM CDT for 13 counties in Texas. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued: Mar 18, 2018, 7:55 PM CDT (00:55 UTC)
Expired: Mar 18, 2018, 9:30 PM CDT
In force: 95 min
Issued by: the Storm Prediction Center

Counties Angelina County, TX, Grimes County, TX, Hardin County, TX, Jasper County, TX, Montgomery County, TX, Nacogdoches County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX

The radar

The Houston radar (KHGX), 158 km from the middle of the area, began a volume at 00:55 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.

Severe Thunderstorm Watch 12Mar 18, 9:10 PM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 0.9 hours before the alert went out and 187 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: 1159 J/kg
Mixed-layer CIN: -77 J/kg
Mixed-layer LCL: 1060 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: -31 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: -0.1
Supercell composite: -1.1

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
Mar 18, 9:11 PM CDT	Severe Thunderstorm Watch	SPC	Hardin, Jasper, Newton, Sabine, San Augustine, Shelby and 1 more	3 hr
Mar 19, 1:08 AM CDT	Mesoscale Discussion	SPC	Collin, Cooke, Delta, Denton, Fannin, Grayson and 2 more	2 hr

Nearby

Mesoscale Discussions in Texas, 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.