or
Northern Virginia’s Brush with Isidore
Sept 27 2002
(All times Universal except as noted)
Knowing that Hurricane/Tropical Storm/Tropical Depression Isidore was tracing a path that would likely bring a favorable severe weather potential to Northern Virginia, my son and I eagerly counted down the Storm Prediction Center (SPC) forecasts: Day 3, then Day 2, and finally Day 1 (the morning of). When the severe weather probability rose to 15% with a 5% likelihood for tornadoes for all of Virginia, we knew what our Friday afternoon would entail. After a quick phone conversation at 1530 (1130 local), we agreed to meet at 1830 at Port Royal, where U.S. Route 301 crosses the Rappahannock River. Given the forecast data and the apparent clearing that could lead to more instability and strong convection, it had looked like our best bet might be east of 301. However, when we met, the rapidly moving low level cloudiness was hanging tough even though satellite images were showing clearing to the east. After reviewing the data, we made a command decision to head home to Fredericksburg and jump on the Web to determine the best place to set up shop.
We should have known it was going to be a busy afternoon when, as we were heading west on Route 3 toward Fredericksburg, we approached a developing line of showers and saw a suspicious looking bulge underneath a rain-free base. As I watched through the windshield, what appeared to be a small funnel briefly formed (at 1900) and then dissipated. We pulled off the road to observe the cloud base rapidly transiting to the north and decided that, yes indeed, we had seen our first wall cloud/funnel combination. However, since we hadn’t been near enough to observe rotation and it had dissipated quickly, we judged it not important enough to call in a spotter report to the National Weather Service (NWS) Sterling office.
After reviewing more data and now-casting from satellite imagery, we decided to head southwest to Orange County for our initial staging point. Leaving Fredericksburg at 1955, we arrived at 2038 at Locust Grove on State Rte 20. As we approached the stop location, a small line of low-topped convection was forming and transiting SE-NW, with no rain or thunder evident. This was to set the stage for the rest of the chase, as all afternoon and evening we saw no lightning or hail and heard no thunder (the cloud depths were too shallow for electrification) and saw relatively little rain. As we scanned the skies in all directions from our hilltop location (able to see over most of the treelines), the cloudiness gradually lessened until we had a bright blue sky with sunshine at our location…perfect for destabilizing the soupy air (dewpoints were in the mid-70’s)!! At 2115, realizing that we didn’t have a lot of daylight left (this was the end of September), we left to intercept a relatively benign-looking line of clouds that was to our southwest. Heading back north on Rte 20 to the Rte 3 intersection at Wilderness, we turned west on Rte 3. At 2133 we pulled off Rte 3 onto Culpeper county Rte 669 and stopped to observe the onrushing cloud lines. The rotational dynamics of the atmosphere were evident in the clouds as they passed over and around us, many looking like wall clouds were trying to form and just hadn’t yet. At 2155, we spotted a very typical wall cloud about 10 miles to our south, underneath a rain-free base and just behind a rainshaft. After watching it for 2-3 minutes, we called in our first storm report to the NWS Sterling office and listened as the meteorologist on the other end found the storm on radar and asked us to keep an eye on it. As we observed it, the wall cloud grew in size but didn’t change much in azimuth, meaning it was headed directly for our position. Having been there and done that (both in Oklahoma and Virginia chases!), we decided to move and get to a better vantage point. Leaving our position at 2212, we headed west on Rte 3 and then north on the Stevensburg road, where we pulled off (at 2217) onto the edge of a muddy field where we had an excellent 360 degree view. There were several storm bases in view, and most of them had some form of wall cloud and small funnels underneath! We were so absorbed with the sight that the little bit of rain that did fall didn’t even faze us. After watching for several minutes with our mouths agape at the sight (remember, this is Virginia, not Oklahoma or Kansas) and ensuring that none of the rotating features were passing directly overhead, we turned to look north at the rear of one rapidly transiting storm and realized that we were looking at a massive rotating wall cloud about 3 miles north of us, with visible inflow moisture band. We called in this second storm report to the Sterling office at 2230, where the same meteorologist answered and recognized my voice. His response was something like
“Thanks for the call…we’re pretty busy right now, and we’re releasing a warning for Orange County and….holy cow, 64 knots inbound Doppler velocity! Yeah, we’ll keep an eye on that one!!”
Realizing that most of the storms were now north of us, we decided to give chase to the storm we had called in. I knew we would have a tough time keeping up with it since it was traveling at 30+ kts in a straight line and we had to follow the curvy Virginia roads. Nevertheless, we chased it up the Stevensburg road to Brandy Station, where we jumped onto US Rte 29 North. The highway speeds allowed us to reapproach the storm, which had maintained its rapidly rotating wall cloud. We saw no funnels from this cloud but were convinced that one could drop at any time (and did later on, as the Manassas tornado warning was issued for this same storm. Not wanting to drive underneath it, we turned off at Remington at 2245 and turned north on Fauquier county route 655. This curve-laden and tree-lined road prevented us from observing much of this storm while slowing us down and widening the distance between us and “our” wall cloud. Nonetheless, we reached Bealeton at 2254, with the storm now 8-10 miles ahead of us. However, there is a silver lining in every cloud!! As we approached U.S. Rte 17 in Bealeton, we heard the initial tornado warning for Fauquier county which stated that a Doppler-indicated tornado was 8 miles south of……Bealeton!!!! Sooooooo….we jumped onto Rte 17 south and sped down toward the vicinity. At 2258, we pulled onto an access road between the south-and north-bound lanes to observe what looked like a wall cloud with tendrils halfway to the ground. This must have been a decaying feature, as the entire thing was dissipating before our eyes. (I did leave the car running!!) We then went about a half-mile further south where at 2302 we pulled into the parking lot of a popular dance-hall and jumped out, scanning the storms in view for anything that looked like a funnel in order to give NWS Sterling a ground-truth confirmation of the radar-indicated tornado. While looking around, we both noticed a number of cars pulled close to the building and about 15 people huddled just inside the door, peering nervously out at the weather. Frustrated at not being able to see the base of the two wall clouds in sight, we jumped back in the car at 2306 and headed back north on Rte 17, both of us laughing uncontrollably at the looks on the peoples’ faces as they watched the two fools standing out in the middle of what they were trying to avoid. (Ah well, we storm spotters are a misunderstood lot…) Remember, no lightning, no hail, and very little rain: What danger were we in as long as we knew what to look for and what to steer clear of?
Chasing north on Rte 17 and then east on State Rte 28, we once again attempted to catch up to the storm and find a good viewing point. Paralleling the storm on Rte 28, the best we could do was to maintain our relative position. However, we were facing another challenge…we were losing the daylight. So, out of frustration, we headed south from Catlett on Fauquier county Rte 806 and found a vantage point at the top of a hill to use the dwindling twilight to observe the storms. By this time, the tornadic storm had moved far enough north that we could barely see the base, but we could see the top. To our astonishment, there was no anvil, and top itself couldn’t have been more than 15,000 feet!! As we commented on this, we watched a flanking cloud that reminded both of us of a fat cotton ball and noticed it was rotating! As the light failed, we saw what both of us swore were two separate funnels snake out of this little cloud before dissipating. This storm couldn’t have been more than 10,000 feet high!! (We didn’t call this one in since we figured the Sterling office would have thought we were crazy.) These supercells were the “bonsai” version of the ones we had observed in other chases, but they were proof of the “spin” applied to the atmosphere by the remnants of Isidore.
Since it was now dark, we left our vantage point and headed home via the back roads of Fauquier and Stafford counties. However, we weren’t done with wall clouds yet!! As I was driving down one country lane, my son said “Dad, I think you’d better pull off the road here.” That is not what you want to hear when it’s totally dark, there’s no lightning to reveal storm structure in your vicinity, and you’ve been chasing very active storms all afternoon. As I did what he suggested, he pointed out to me the wall cloud about 1 mile away that was being illuminated from below by a rural airport beacon. Between this beacon and the faint backlighting still evident from the sunset, we watched as this wall cloud grew to match the flying saucer “mother ship” configuration that I had heard of but hadn’t seen yet. When we had assured ourselves that this feature was passing us at a safe distance, we got back on the road and headed home, finally sated with enough wall clouds to last ‘til next spring if necessary.