Alert archive / Ohio / Mesoscale Discussions in 2004

Mesoscale Discussion 790

May 21, 200418 counties in Ohio; 10 counties in Pennsylvania; 5 counties in West Virginia

The Storm Prediction Center issued this mesoscale discussion at May 21, 2004, 4:45 AM EDT for 18 counties in Ohio; 10 counties in Pennsylvania; 5 counties in West Virginia. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: May 21, 2004, 4:45 AM EDT (08:45 UTC)
Expired: May 21, 2004, 5:45 AM EDT
In force: 60 min
Issued by: the Storm Prediction Center

All 33 counties

Belmont County, OH, Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Fairfield County, OH, Franklin County, OH, Guernsey County, OH, Harrison County, OH, Hocking County, OH, Jefferson County, OH, Licking County, OH, Monroe County, OH, Morgan County, OH, Muskingum County, OH, Noble County, OH, Perry County, OH, Tuscarawas County, OH, Washington County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Fayette County, PA, Greene County, PA, Indiana County, PA, Lawrence County, PA, Washington County, PA, Westmoreland County, PA, Brooke County, WV, Hancock County, WV, Marshall County, WV, Ohio County, WV, Wetzel County, WV

The radar

The Pittsburgh radar (KPBZ), 98 km from the middle of the area, began a volume at 08:44 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

Pittsburgh, PA (KPIT), launched 00:00Z, 8.8 hours before the alert went out and 102 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: 1205 J/kg
Mixed-layer CIN: -7 J/kg
Mixed-layer LCL: 1103 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 163 m²/s²
0-3 km storm-relative helicity: 267 m²/s²
Significant tornado parameter: 0.9
Supercell composite: 7.9

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 10:05 PM EDT	Severe Thunderstorm Watch	SPC	Defiance, Fulton, Lucas, Williams	5 hr
May 21, 2:40 AM EDT	Mesoscale Discussion	SPC	Ashland, Carroll, Columbiana, Coshocton, Crawford, Cuyahoga and 20 more	65 min
May 21, 10:40 AM EDT	Mesoscale Discussion	SPC	Allen, Crawford, Cuyahoga, Defiance, Erie, Fulton and 14 more	2 hr
May 21, 1:05 PM EDT	Severe Thunderstorm Watch	SPC	Allen, Ashland, Auglaize, Champaign, Coshocton, Crawford and 32 more	4 hr
May 21, 2:19 PM EDT	Mesoscale Discussion	SPC	Ashland, Ashtabula, Carroll, Columbiana, Crawford, Cuyahoga and 27 more	116 min
May 21, 3:15 PM EDT	Severe Thunderstorm Watch	SPC	Ashtabula, Belmont, Carroll, Columbiana, Cuyahoga, Geauga and 10 more	6 hr
May 21, 4:25 PM EDT	Severe Thunderstorm Watch	SPC	Athens, Auglaize, Champaign, Clark, Clinton, Darke and 21 more	6 hr
May 21, 6:35 PM EDT	Severe Thunderstorm Watch	SPC	Gallia, Meigs	4 hr
May 21, 6:53 PM EDT	Mesoscale Discussion	SPC	Adams, Allegheny, Armstrong, Bedford, Berks, Blair and 47 more	97 min
May 21, 8:34 AM EDT	Mesoscale Discussion	SPC	Jefferson	86 min
May 21, 5:31 PM EDT	Mesoscale Discussion	SPC	Barbour, Berkeley, Boone, Braxton, Calhoun, Clay and 30 more	89 min

Nearby

Mesoscale Discussions in Ohio, 2004 Mesoscale Discussions in Pennsylvania, 2004 Mesoscale Discussions in West Virginia, 2004 Every mesoscale discussion in 2004

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.