Wednesday, July 30, 2014

Video from July 24th chase

Upon reviewing and speeding up my dashcam video from July 24th I realized that we may have missed a funnel underneath the original wallcloud. I sent the sped up video clip to NWS Blacksburg for them to review. After looking at the video and checking radar data their overall conclusion was that it could have been a brief funnel as a weak mid-level mesocyclone was present at the time but it's too far away to tell for sure. At any rate here's the sped up video clip (the feature of interest appears just to the left of the power pole guide wire in the frame around :30):

video

It's not a big deal - funnel or not - but I was a bit embarrassed at having missed the feature in real time. My "excuse" was that we had been frantically seeking a vantage point from which to view this storm and by the time we stopped and turned on our recording and streaming gear we weren't looking closely enough to notice this. We were also pretty far from the wallcloud (~10-15 miles) so neither surface inflow nor rotational motion was easy to discern. Additionally the storm became outflow dominant shortly thereafter and the wallcloud morphed into a shelf cloud.

That's my story and I'm sticking to it...

Monday, July 28, 2014

BUSTed in late July

Given a steamy airmass over Virginia, a strong cold front approaching from the west, and significant upper level support providing plenty of shear I was very hopeful for a fruitful chase yesterday (Sunday 7/27). The only flies in the ointment I could see ahead of time were (a) an SPC Moderate Risk outlook for the region just west of my chase area and (b) the potential for morning rainfall (possibly as an MCS). The former "fly" seems to always be a downer on my chase chances as Moderate Risks and I don't get along very well. Unfortunately the latter "fly" has the same effect on chasing here in the Old Dominion as the atmosphere rarely has time and space to destabilize again before sunset.

Given the juicy airmass in place I headed east before noon to get in place in the Piedmont ahead of the mid-morning showers. I was hopeful that a decent storm or two would pop along any outflow boundary that might form but I saw nothing but stratiform rain and overcast. The rain departed to the east but the overcast remained behind...for most of the rest of the day. That was the nail in the coffin for afternoon or evening convection even though the shear was robust and surface-based instability was acceptable for storms. The cap just never broke.

I hung around the Rte 29 corridor all afternoon into the evening, even cheering on a weak line of cumulus that built just west of my location. I wasn't alone as Bill Hark - a well known chaser from Richmond - parked 25 minutes south of me in Danville awaiting storms as well. My son joined me for a bit in a futile wait for something to chase. By this time I knew better than to expect a widespread outbreak but I was hopeful that one or two cells might go up, tap into the abundant shear, and begin rotating. I was also wary of giving up too soon and missing the storm of the day, having done that during previous chases!

When it became glaringly obvious that all the severe action was focused on far southwestern VA, eastern TN, and northwestern NC (places I choose not to chase) with NOTHING likely to occur in my chase region I finally gave up and returned home just before sunset. The best thing about the entire day was that I was able to eat dinner with my son and his family. Time with kids and grandkids is always well-spent!!


Saturday, July 26, 2014

Looks like a springtime setup

The strong cold front and upper level support that is at the leading edge of some very cool air for late July will first bring severe weather to the Mid-Atlantic. A possible (probable?) Mesoscale Convective System will cross West Virginia early tomorrow morning. That plus the conditions behind the MCS has prompted the Storm Prediction Center to issue a rare Day 2 Moderate Risk for our western neighbors. Meanwhile it seems that after this morning mayhem - which hopefully will expend most of its energy on crossing the Appalachians - the atmosphere will sufficiently recover to again fire up strong to severe storms over much of Virginia. In fact here's this morning's (12Z) NAM depiction of the significant tornado parameter for 8 pm Sunday:
This jives with the forecast for instability and deep layer shear over much of the Old Dominion and is more representative of a springlike setup than late July.

Timing and MCS strength is key here. If the complex comes thru earlier Sunday morning and/or weaker than current thinking the setup east of the mountains will spawn storms (and likely discrete supercells) by late afternoon. If said complex is later/stronger than thought the atmospheric recovery will be delayed and the second phase of storms will occur near nightfall. Either way I will be out chasing even after dark tomorrow if the storms warrant. (In other words if there are discrete supercells over chaseable territory I'm not letting a little thing like darkness stop me!)

Thursday, July 24, 2014

Severe weather ahead of strong July cold front

Although I don't think we chased under any severe watches today there was plenty of action that could (should?) have warranted a watch. After picking my son up in Gretna we wandered around Pittsylvania county for a while awaiting convection. We finally made a move north on U.S 29 to intercept a cell with radar-indicated rotation that was heading east across Bedford county toward the southern suburbs of Lynchburg.

After we rolled north of Altavista I pulled off the road to enable us to peruse the radar more closely. It turned out another cell - again with indicated rotation - was moving northeast from the Rocky Mount vicinity. A quick vector analysis led us to conclude that these two storms were headed for a collision somewhere in southeastern Bedford county. (Insert "Twister" quote here...) Thus we quickly rerouted onto VA Rte 43 west. Even tho' I was pretty certain we would get pinned west of the Smith Mountain ridgeline with little hope of keeping up with the storm I wanted to take a good look at this activity before everything merged into a big rainy messy complex.

After finally passing what appeared to be a sewage transport tanker truck with a very inexperienced driver (it stopped 3 times on the road while the driver repeatedly ground the gears) we reached our target area. Desperately searching for an open area with a vantage point facing the right direction we wound up a couple miles south of Huddleston in a field pointed west. We watched and live streamed for quite a while as a wallcloud on the southern edge of the complex took direct aim at us:
As the feature came closer it morphed into a shelf cloud, indicating the storm had become outflow dominant. We kept snapping photos, albeit staying very close to the chasemobile as the lightning threat grew:

In fact the lightning became such a threat I was unwilling to get far enough away from the vehicle to keep the annoying power pole out of the frame as the shelf cloud got even closer:

Finally as the feature overtook us and when the rain began we beat feet southward to find a route by which to get back to the Rte 29 corridor and keep up with this storm. Unfortunately we weren't able to do so as another strong storm popped up to our south, making me nervous about driving along narrow winding roads in heavy rain with rotation overhead. Thus the storm we were chasing escaped to the east even though we tried hard to keep up:
We did eventually make our way back to Rte 29 at Altavista and, amid very heavy rain, motored toward Gretna to drop off my son at home. 

The rain increased in intensity as the storm I had noticed to our south developed a distinct rotational couplet on radar right over town. Thus after dropping off my son I continued east of Gretna in an attempt to catch up with this storm. The interest in doing so increased exponentially when a tornado warning was - finally - issued on this cell and I tried desperately to get into a viewing position. However the blinding rain, poor visibility, and winding roads eventually convinced me I was never going to get into position to see anything. So I pulled off the storm and called it a chase near Chatham, overall satisfied with what we had seen.

Thursday, July 17, 2014

Last storm during July 15th chase

This is a photo of the ground-scraping wall cloud we witnessed from our position a few miles northeast of Yanceyville NC:
Now, this is a velocity radar image at about the same time:

See why we diverted from dinner to chase this last storm? Unfortunately we were never able to get a clearer view underneath the wall cloud so something could have dropped from it without us witnessing it. Still, this was a very cool sight for the East Coast!!