Storm Chase April 27, 2011: Oilville, Virginia Tornado and Supercell, A Tale of Two Storms


 

chase images and log by William T. Hark, M.D. Video (HD) and pictures available for licensing

 

 

The potential for a severe weather outbreak on April 27, 2011 across Alabama, Mississippi and other areas of the southeast was known for several days and additional severe weather was expected in the Mid-Atlantic by the 28th. There was a strong trough approaching from the west through the Ozarks and an associated strong jet max while a surface low was forecast to move northeastward from western Arkansas to the Great Lakes. A high risk was issued for areas in Alabama. Although everyone was focused on the high risk area, I could see the potential for tornadic storms across the Mid-Atlantic on the 27th rather than the 28th. The strong southwesterly upper level winds (500 mb level) would be approaching Virginia by afternoon of the 27th and there would be southeasterly surface and 850 mb winds. Surface moisture would be sufficient for tornadic storms. The 12Z WRF showed areas of precip along the western Virginia mountains that were expected to shift eastward. My forecast target the previous evening was near Roanoke, Virginia.

The First Storm

I had initially targeted areas in southwestern Virginia but couldn't leave work until after 2PM. There were storms already forming near Lynchburg and more to the south. The better upper level winds were moving into the area from the west, and I was concerned the storms would move away from those winds. I headed west from Richmond on Midlothian Turnpike (60). The sky already had that "severe weather appearance" by 2:43 PM with evidence of shear and low-level moisture. There was one storm to my southwest that was dominant and heading in my direction. Because of a slow school bus, I turned north on 522 and then west on 6 through Fork Union. As the storm became visible, I could see a lowering by 3:43 PM. Despite the appearance, there was no evidence of shear on ThreatNet. I watched the non-rotating wall cloud briefly, then followed the storm north on 640. I stopped again at 3:55 on State Road 619 near Cunningham and watched the developing storm. It had a wall cloud and was putting out some CG's but no definite rotation. I went east then north on 15 tracking the storm. It became less organized as I stopped briefly near the 15 – I-64 intersection. Just north of I-64, I stopped again on 15 by a large columned white house at 4:36PM. The storm had another wall cloud but was looking weaker on radar. It was moving away, and I briefly considered calling off the chase. After watching the storm for a while, I decided to continue north. With increasing upper level winds, I hoped the storm would strengthen. The storm was moving away to the northeast at about 40 miles per hour. I drove north through Orange, Virginia, then east on 20. The storm was to my east and rapidly moving northeast. I could see a nice crisp updraft. My progress east was slowed by trucks and pokey people. The storm was now tornado-warned by approximately 5:11 PM. A nice rainbow appeared to my east as I approached the storm along 20 through Locust Grove and then east on 3. Between Wilderness and Chancellorsville on 3, I stopped. The storm was to the north and had an intermittent wall cloud. I also saw a brief funnel south of the wall cloud at 5:41 PM. I watched the storm but no tornado. I headed east toward Fredericksburg. The traffic on 3 near I-95 was a nightmare, and I was watching the storm move away to the north. I turned onto I-95 and blasted north to catch up with the storm. It was still tornado-warned. At 6:07 PM, I could see a nice wall cloud to the north as I passed exit 136. I got off at exit 148 near Quantico and drove north on Route 1. The wall cloud was now to the northeast. I stopped in Dumfries to get gas. At 6:30, I could see more definition on the wall cloud, rising motion and maybe a funnel but it was getting far away. I couldn't continue the chase due to traffic, road network and the storm crossing the Potomac River into Maryland. The chase of the first storm was over. Per the NWS, there was a confirmed EF0 tornado southeast of Triangle, VA with estimated time of 6:16 PM to 6:22 PM. I was looking at the wall cloud but couldn't see the ground circulation due to trees.


2:43 PM

Radar 3:20 PM

3:43 PM

Radar 3:50 PM

3:55 PM

5:16 PM

5:41 PM

5:37 PM

6:10 PM

6:13 PM

6:14 PM

6:20 PM

The Second Storm

I headed south on I-95 toward Richmond. There were more storms southwest of Richmond heading northeast. Another intercept was possible, but I was worried about daylight. With better moisture to the south and the improved upper level winds moving in from the west, these storms had a better chance of producing a tornado. By 7:43, I was nearing Richmond. A tornado warning was issued for the storm just to my west, I was almost suckered into targeting that storm but there was a larger storm to the southwest. This would cross I-65 west of the city. Usually, it is best to target the southernmost storm in a group due to unobstructed inflow. I turned west on 295 at 7:46PM just north of Richmond, then picked up I-64 west at 7:50PM. Daylight was rapidly decreasing. I could see glimpses of the massive updraft to the southwest through the trees. The storm was rapidly moving northeast toward the interstate. Could I safely reach the point where the storm crosses I-64? I was approaching the storm from the east. There was a long stretch of poor visibility due to trees, and I was worried I'd have to stop on I-64 or risk getting munched. The storm was showing intermittent rotation on ThreatNet. I reached the Oilville exit about 8 PM and turned north on State Road 620. There was an Exxon station on a low hill just to the north. When I reached the hill and looked back south, I could see a massive striated “mothership” supercell to the south. The entire storm was visibly rotating. The sky was clear around the storm except for a few smaller clouds getting drawn into it. I filmed the storm and briefly talked with a television crew from Channel 6. This was the clearest storm structure that I have ever seen in Virginia. The storm resembled supercells that I have tracked across the Great Plains. Based on the storm movement, I decided it would be safe to carefully approach it from the east on 250 that paralleled I-64. I slowly drove west on 250 and could see a massive rotating wall cloud to the southwest at 8:09 PM approaching the road. I pulled into a driveway on the southside of 250 and filmed the developing tornado that began about 8:10 PM. The tornado crossed 250 causing bright flashes as it destroyed power lines. The tornado morphed into an elephant trunk shape by 8:12PM and continued to the north. I headed back east on 250 and north on 620 that becomes 619. I could still see the tornado to the northeast but visibility was decreasing due to darkness and trees. I lost sight of the tornado about 8:20 PM. I didn't want to continue the chase due to darkness and potential for debris on the road. If the tornado had been even 15 minutes later, I would not have had enough daylight for videography. Although I was very worried about major damage while watching the storm, I later found out that the tornado only did some minor tree and roof damage. It was later rated an F1 by the National Weather Service.


7:40 PM

8:02 PM

8:04 PM

8:06 PM

8:09 PM

8:10 PM

8:10 PM

8:10 PM

8:11 PM
All images copyright 2011 William T. Hark and cannot be reproduced without permission. On radar images, my GPS location is the white dot in the center ring.



Map of Oilville tornado intercept


Archived Storm Reports

Wakefield, VA NWS Report Sterling, VA NWS Report SPC Storm Reports . .

Archived forecast model, surface and upper air data for April 27, 2011

SPC Day 1 4PM,tornado % 4PM SPC Day 1 12:30PM MCD 622,631,633,641 Tornado Watch 233,240
250 mb 12Z , 00Z 500 mb 12Z , 00Z 850 mb 12Z , 00Z SPC Mesoscale Anaysis 1PM 500mb , 850mb , TDp, EHI, LCL , SbCAPE, SRH, SigTor
HRRR 21Z init for 00Z 1hr precip WRF 12Z init for 18Z Max Reflec WRF 12Z init for 21Z Max Reflec WRF 12Z init for 00Z Max Reflec
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All images Copyright 2011 William T. Hark