Alert archive / Virginia / Tornado Watches in 2013

Tornado Watch 104

April 12, 201325 counties in Virginia

The Storm Prediction Center issued this tornado watch at Apr 12, 2013, 5:21 AM EDT for 25 counties in Virginia. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued
Apr 12, 2013, 5:21 AM EDT (09:21 UTC)
Expired
Apr 12, 2013, 8:17 AM EDT
In force
3 hr
Issued by
the Storm Prediction Center
Largest hail expected
0.5 in
Strongest gust expected
60 kt
All 25 counties

Amelia County, VA, Brunswick County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Franklin, VA, City of Hopewell, VA, City of Petersburg, VA, City of Richmond, VA, Cumberland County, VA, Dinwiddie County, VA, Fluvanna County, VA, Goochland County, VA, Greensville County, VA, Hanover County, VA, Henrico County, VA, Louisa County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nottoway County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Southampton County, VA, Sussex County, VA

The radar

The Norfolk radar (KAKQ), 105 km from the middle of the area, began a volume at 09:23 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
40%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
50%
One or more gusts of 65 knots or more
30%
Ten or more severe hail reports
10%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
70%

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Roanoke, VA (KRNK), launched 00:00Z, 9.4 hours before the alert went out and 121 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, Roanoke, VA at 00:00Z on 2013-04-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Roanoke, VA at 00:00Z on 2013-04-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 81 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1699 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
81 m²/s²
0-3 km storm-relative helicity
85 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 12, 1:58 AM EDTMesoscale DiscussionSPCAmelia, Appomattox, Brunswick, Buckingham, Campbell, Charlotte and 24 more92 min
Apr 12, 5:05 AM EDTMesoscale DiscussionSPCAlbemarle, Amelia, Amherst, Appomattox, Brunswick, Buckingham and 34 more85 min
Apr 12, 7:25 AM EDTMesoscale DiscussionSPCBrunswick, Charles City, Chesterfield, Dinwiddie, Greensville, Henrico and 10 more65 min
Apr 12, 2:34 PM EDTMesoscale DiscussionSPCGloucester, Isle of Wight, Lancaster, Mathews, Middlesex, Northampton and 11 more116 min

Nearby

Tornado Watches in Virginia, 2013Every tornado watch in 2013

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.