#vawx A Monday severe storm three-fer

With a cold front pressing into an uncomfortably hot and steamy airmass there was little doubt storms would fire on Monday July 26th. The SPC had much of the Virginia Piedmont under a Marginal Risk:

The short range convective allowing models (CAMs) varied a bit with regard to timing but overall it looked to be an early beginning to the chase day. Moreover, two or more rounds of storms looked likely given convective initiation on the eastern slopes of the Blue Ridge followed by lifting impulses associated with the approach of the cold front from the north. Based on those predictions I planned both to leave home during the noon hour and to not get sucked too far south during the early parts of the chase.

Picking up my chase partner before 1:00 pm we rolled south on U.S. Route 220 with an eye toward turning east on VA Route 40 at Rocky Mount. However, about the time I picked him up a storm complex crossing the Roanoke valley went severe-warned. Given the trajectory of that activity we diverted northeast through Burnt Chimney and then up VA Route 122 toward the Smith Mountain Lake vicinity. Thanks to slow traffic coupled with a construction zone (the bane of storm chasers everywhere) we barely kept ahead of the precipitation.

We finally got north of the lake and turned east to find a spot from which to observe. This was the radar reflectivity as we settled – briefly – into our vantage point:

This was our view of the storm off to the northwest:

As the precipitation expanded and moved closer we had few route options from which to choose. We finally decided to ride out most of the storm from a location a bit further east, where we had this view from our boxed-in vantage point:

The rain-free base here did exhibit a little bit of rotation which was only evident via time-lapse. This was the one hour mid-level rotation track ending at 19Z with our first position at the black star and our “trapped” spot at the magenta star:

Finally extricating ourselves from that remote corner of Bedford county I decided it was time to head north and east. Storms were firing near Charlottesville and moving south, corresponding to some stronger activity which I’d noticed on several CAMs earlier in the day. So we popped up to U.S. Route 460 and then zoomed east to Appomattox. There we motored north via Virginia Route 26 and finally settled into a hilltop vantage point which I’d found on a chase earlier this year. This was the radar reflectivity and velocity view as we began our observation of severe storm #2 from here:

The storms were moving southeast at a glacial pace (< 15 mph) so we sat here for a while, keeping an eye on the western edge where rotation seemed to be present via radar. Unfortunately the hazy air made it tough to see details until the entire complex came nearer:

The low level scud in the above photo represented a robust outflow boundary, which cooled us with sustained ~35 mph winds. We kept an eye on this activity for quite a while before concluding it was indeed weakening as shown on this one hour rotation track ending at 21Z (our location was at the black star):

However, by that time the outflow had fired convection literally just to our south. As we pulled up stakes and departed our magnificent hilltop vista a well-defined convective line was evident a couple miles to our south. Dropping south via VA Rte 26 and then turning east on a rural road we had this view of the line crossing right-to-left in front of us as it spit out numerous close-at-hand CG’s.

The convective core to our east hinted at hail just as did one not far to the west. Thus we chose to thread the needle and zoomed south via Rte 26 through the rain back to Appomattox. This is the two hour hail swath ending at 2130Z with our punch-through shown by the black arrow:

As we pushed through Appomattox this complex also went severe-warned, making for the third warned storm of our chase day.

Scooting along more rural roads south of town we finally found an open vantage point ahead of the rain. This wound up being our final stop of the day just after 5:00 p.m. as this complex visibly weakened:

Turning for home we called it a day, arriving at my partner’s house just as another severe storm began to drench the area. (I didn’t count this one as #4 since I avoided it on my way home.) I did make one last stop to photo the sunset:

Overall it was a good chase even though we didn’t see any noteworthy structure. The close CG display near Appomattox, the cooling outflow gusts, and avoiding two hail cores made for a successful chase in my book.

#vawx A case of northwest flow magic in Virginia

Yesterday – July 24th – I ventured into Franklin county on a self-limited local chase. The limitation was based on my expectation that showers/storms which formed along the eastern slopes of the Blue Ridge wouldn’t move very far before falling apart. As mentioned in yesterday’s blog entry that was pretty much the case for the area I was in.

However a wider view of activity across the southern half of Virginia held surprises. Here’s a two hour rotation track ending at 5:30 pm EDT:

The storm east of Farmville qualified as a discrete supercell, exhibiting rotation and lightning as it slowly sagged southward at about 12 mph. When I first noticed that severe-warned storm on radar I realized it would take me over 2 hours to intercept it and I expected it to have fallen apart by that time (and it pretty much did). There must have been a localized shear boundary for it to have intensified and lasted as long as it did.

Meanwhile the cell to its west – south of Lynchburg – looked to be rotating like a top on radar, but not moving. The above graphic does indicate a little rotation and it likely had a wall cloud underneath it at some point. I seriously debated going after that cell but (a) it was an hour east of me, (b) it never exhibited any lightning, and (c) I fully expected it to fall apart quickly, leaving me in a “whack-a-mole” situation. It did dump several inches of rain in that area (radar-indicated) so I suspect the rural roads were a mess.

Then after I’d headed for home base more severe-warned storms erupted south of Charlottesville, with one of them featuring a nice wall cloud captured by chaser Peter Forister. That slow-moving cell created serious flooding issues in Buckingham county.

The upshot was that my expectations of localized cells not doing much or lasting long yesterday was countered by these examples. Northwest flow can complicate even mediocre setups!

On to Monday.

#vawx A dry run for Monday?

I wasn’t sanguine about today’s chances for severe weather, but it had been long enough between chases that I went out anyway. Waiting and watching radar until after 3:00 pm I finally decided to give it a whirl despite not even seeing lightning exhibited on the returns. Motoring down U.S. Route 220 I stopped for a while near Wirtz to monitor the situation. This updraft was just to my south:

That didn’t amount to anything, so I turned around to the west to watch this shower (can’t call it a storm) approaching, even showing a small lowering/scud under the rain-free portion:

After live-streaming for a while I pulled up stakes, pushing toward Burnt Chimney before dropping south through Rocky Mount on the way to Glade Hill. There I sat for a while longer, looking at forlorn updrafts and not-very-impressive radar returns in my local area. Meanwhile a long-lived supercell slowly edged southward near the I-85 corridor, too far east for me to consider.

And as I write this a couple of nice-looking storms south of Charlottesville are sliding southeast as the evening wears on. No luck today, so now the attention shifts to Monday.

Severe weather data diving

During a quiet week here in the southern half of Virginia I decided to dive into past severe weather setups. Phil Hysell of NWS Blacksburg was very helpful in providing data on the number of severe thunderstorm warnings issued by his office going back to 2005. The data plot is shown here as of July 19th of each year:

As I’d suspected this year (2021) has had the least amount of severe setups since the drought year of 2005. Another point of note is that the past decade seems to show a steady reduction in warnings issued, especially after the incredibly active 2011 season. That could be due to a number of factors but anecdotally the overall downward trend matches my memory of less severe setups during past chasing years.

And as for 2021 itself here’s the SPC shapefile map of all severe thunderstorm watches issued to date:

The thing that jumps out at me from this graphic is the relative lack of watches issued for southern Virginia and the Carolinas vs. the DC area northward. That, of course, tracks with the lower number of warnings issued by NWS Blacksburg this year. I’m thinking this has to do with the jet stream parking itself across the Ohio valley into New England more often this year than in the past.

I’m also working on an analysis of SPC convective outlooks since 2005 but it’s proving more complex than I’d originally thought it would be. The October 2014 switch to 5 risk levels has made it difficult to gather and correlate data from before and after that date. But, it’s something to do while things are quiet!

Oh, and I haven’t done anything with tornado warnings or watches yet. Given the tropical season influence on Virginia’s tornado count it’s too early to compare 2021 with prior years.

#vawx A short-range save

My 2021 lack of chasing success continued the past several days, but not because there weren’t any storms. It seems this year when storms are scarce I have plenty of time on my hands. But when I have things scheduled the storms annoyingly decide to bubble up. Thus my lack of serious chasing this past week corresponded to having time with family and – today – enjoying a nice day with friends.

Thus I was at Smith Mountain Lake when storms blew up early this afternoon, interrupting our cookout and outdoor plans. This was the view as convection approached:

Heavy rain and frequent lightning punctuated the storm’s passage through that area. By the time we departed for home the action had moved northeast so our path was dry and clearing.

Several cells east of the Blue Ridge had gone severe-warned by the time we pulled into our driveway, but I wasn’t tempted (much) to head back out. We passed the rest of the afternoon quietly. However when I rolled out to pick up some dinner at a local restaurant another line of storms was moving in from the west. After grabbing the food I stopped briefly at a local vantage point to check out the action before rushing home, dropping off the food, and heading back out.

This was the view of a shelf cloud to the north, likely crossing through Daleville as I snapped this:

Turning around to the southwest I could see a lowering to the west of Salem as the northern end went severe-warned:

Here’s the radar reflectivity and velocity at that time:

Here’s a view of the lowering from a closer vantage point:

As the northern shelf continued on its way it became underlit by sunlight to the west, providing some nice coloration:

And here’s a view as the rain curtain drew across the Roanoke valley:

And that was it. I left the storms to themselves as they continued eastward, having already had a full day of “fun”. I am keeping an eye on tomorrow (Sunday), trying to keep my schedule clear to facilitate an honest-to-goodness chase.

#vawx A quick local chase

I hadn’t planned to chase Tuesday July 13th as we had family in the house. But when the weather radio blared a severe thunderstorm warning for our locale my oldest grandson and I piled into the chasemobile and headed to a local vantage point. This is a time-lapse of the view we had from there:

It seems to show a fading wall cloud north of the ridgeline, with another mesocyclone base forming to its south. The rotation map shows this process continuing until abruptly ending just west of Salem:

When the rain neared we pushed north to the Daleville Town Center on U.S. Route 220. We parked there and watched the now-fading convection approach. The southern edge bowed out from the outflow as the lightning also diminished:

We sat here a few minutes before calling off the chase and heading home. On the way we noticed another robust rain shaft further northeast which had fired on the outflow. That storm also received a severe warning before quickly fading into nothing.

Overall it wasn’t a bad local chase.

#vawx A non-severe but more “normal” chase

Having chosen to not chase the eastern side of TS Elsa the day before – and thus missing rain-soaked tornadoes 4 1/2 hours east of me – I had my eye on Friday July 9th as a chase day. A weak cold front was crawling across the Appalachian mountains in Elsa’s wake. Winds at the surface and up to the 700 mb level were westerly, perfect for a lee trough to set up east of the Blue Ridge. Instability in the juicy air was plentiful but shear was typically anemic so I didn’t expect much. The SPC did issue a Day 1 morning convective outlook which upgraded most of Virginia east of the lee trough to a Marginal Risk.

Short range convective allowing models (CAMs) were indicating convection firing along the U.S. Route 29 corridor during the early afternoon so I rolled down the driveway at noon. Picking up my chase partner we drove east to the Rte 29 corridor at Gretna and paused in that area for a situational awareness check. Large anvils were already evident well to our east before 2:00 pm, too far ahead of us to even consider pursuing. However, we could see updrafts steadily building in our vicinity.

We dove south on Rte 29 to get into better position on those updrafts and wound up stopping at a favored vantage point just east of Danville. This was our view of one building storm just to the north as we baked in the 90+ degree heat:

We had a visual of more updrafts to the west, with this radar representation also indicating them:

The western activity began to look a bit more interesting so to (a) get a better view and (b) cool off a bit via the chasemobile’s a/c we pushed west on the U.S. Route 58 bypass and headed to the NC Visitor’s Center just south on Rte 29. Here we had this view of the growing convection:

When this grew into a linear complex we pushed back east to stay ahead of it. Unfortunately our eastern routes were limited by a lack of available river crossings. So we wound up splashing through torrential rain on Rte 58 until we could dive south onto back roads east of Danville. Navigating those narrow rural lanes we maneuvered to Milton NC. Along the way we had this view of a substantial lowering (taken through the windshield of the chasemobile):

At Milton we continued south via NC Route 62 and wound up near Semora, where we pulled off outside the rain shaft and observed for a bit. Noticing via radar more storms growing north of this complex we decided to let “our” storm go on without us and motored back north to Rte 58. Hopping back on that highway eastbound we witnessed more lowerings as we approached the Turbeville area of Halifax county. This was the radar reflectivity view at that time:

We paused for a few minutes near Turbeville to watch and video this feature just north of the highway:

It was obviously rising into the storm’s base but no rotation was evident either visually or on radar. Thus I dubbed it a “wallcloud wannabe”.

When the nearby rain shaft quickly caught up we rolled further along Rte 58, which was aimed northeast toward more heavy rain at this point. Accordingly we dropped south via more rural roads in an attempt to stay ahead of the precipitation while keeping an eye on this storm. We were eventually unsuccessful and wound up in South Boston where we called off the chase. None of the Virginia storms (even the earlier eastern monster towers we’d seen from Gretna) had become severe-warned and didn’t look likely to do so. Thus I wasn’t tempted to keep drifting further away from home base.

And that was the story of the day’s convection in Virginia with no severe warnings and no damage reports, although that’s a good thing from “normal” people’s perspective:

So although severe weather somehow again avoided Virginia the July 9th storm chase was still more pleasing than most 2021 pursuits to date. The conditions afforded clear views of the storms vs. the messy environment of many earlier chases.