Tags

, , , , , , , , , , ,

So the SPC originally had much of Virginia in an Enhanced Risk for severe weather for May 1st:VA_swody1 May 1

High shear values and abundant surface moisture (DP’s>65 in many places) coupled with upper level support and an approaching cold front all served to set the stage. But the threat in Virginia didn’t materialize and by the 20Z SPC update we were back in a Slight Risk with the Enhanced portion withdrawn mostly north of the Mason-Dixon line.

But that didn’t deter me a bit. I headed out just after lunchtime to get east of the Blue Ridge amid gusty southwesterly surface winds, low ceilings, and intermittent heavy drizzle. This was all shown on most of the short-range models and was a concern for limited instability. Given the setup with bulk shear vectors parallel to storm motion it was apparent that a squall line was in order later that afternoon. But…if a discrete cell could go up ahead of the line rotation was almost guaranteed.

That last consideration drove most of my thinking as I pushed east to the U.S. Route 29 corridor at Gretna. I sat there a while watching radar and finally decided to give chase to a small but relatively organized cell rapidly steaming northeast toward Brookneal. Pushing hard to catch up with it along VA Route 40 I could see an updraft and a rain-free base but that was about it.IMG_6822

Reversing course from Brookneal I rolled back west to Gretna and diverted off Rte 40 to watch this developing storm (#2):

It had a nice rain-free base and I was tempted to follow it but there was an even better-looking storm moving across the NC/VA state line west of Danville. Thus I abandoned storm #2 and dove south on Rte 29 to the Tightsqueeze vicinity. The radar representation of this next storm (#3) intrigued me:

I sat in place for roughly 15 minutes as this storm approached and was rewarded with a view of a nice lowering underneath as it cleared a distant tree line. I think what I witnessed during this period was the storm cycling down and then back up, because by the time I had to move in order to give chase it had accelerated and looked like this:Third storm wall cloud

I pushed east via a rural route across the crest of the White Oak Mountain ridge line to keep up. Along the way I paused briefly to observe and photo the now huge and very low wall cloud perhaps a mile north of me:Third storm crossing ridge line

I turned left to follow the storm via a northeast leading county route. However in my attempt to keep up with this rapidly moving storm – and chasing solo – I made a wrong tactical navigation decision when I reached VA Route 57. In my (incorrect) estimation the storm was going to overtake my current route before I could get in front of it. Therefore I diverted onto Rte 57 to push a few miles east and then use rural roads to get back in front of it. That was a wrong move that I may have avoided if I’d had a chase partner with me instead of doing everything myself.

When that plan backfired I wound up completely out of position on this monster cell, exacerbated by a wrong turn that cost me several minutes. Zooming along country roads never brought me close enough to see a lot of detail and I wound up on the VA Route 40 corridor near the hamlet of Cody. What to do next?

Widening out the radar view I noticed the aforementioned squall line had taken shape and was approaching the Rte 29 corridor. What was even more interesting was that a section of the line nearing the Danville VA vicinity was now tornado-warned. It took about 20 seconds to decide I needed to drop south so I swapped directions, heading down the Cody Road to U.S. Route 501 and then rolling toward Halifax.

In Halifax I turned west on VA Route 360 to maneuver into a vantage point from which to watch the oncoming convection. By this time the tornado warning had been dropped but there was still rotation indicated on that part of the line. (Most of the line itself was still severe-warned.) I continued west on 360 for a bit and then pushed a couple miles south at Vernon Hill. Finding an open vantage point I settled in to watch the line approach.

The area of rotation was still evident on radar and I’m pretty sure this lowering (under storm #4) was the associated wall cloud. However at this point that part of the line was becoming outflow dominant so the wall cloud morphed into a shelf cloud as I watched:

At this juncture I couldn’t see any way to avoid the squall line so after checking the VIL parameter for hail potential (none was evident) I decided to conduct a “static core punch”. After some sheets of rain, a gust or two that may have topped 30 mph, and no hail I was on the west side of the line.

Once the rain finished I rolled westward toward home. I noticed on radar that a few light post-frontal showers had popped up. I just had to stop and photograph this view of these rain shafts backlit by the setting sun:Backlit showers post frontal

So May Day wasn’t convectively ballistic but it was a nice chase day!

 

Advertisements