Chase Log: March 21st, 2005


Click on any of the SPC products below (Convective Outlooks, Watches, or MCDs) to see the SPC's "Severe Thunderstorm Events" page pertaining to this event.


MAP

Total Distance: ~515 miles
Target Area: Ardmore, OK, to Dallas, TX, to Paris, TX
Chase Area: South of Sherman to Paris, TX
Maximum SPC Risk category: Moderate
Watches: Tornado Watch 56, 57
Mesoscale Discussions (MCDs):

A pretty typical early-season severe weather event was forecast for the southeastern OK, northeastern TX, southwestern AR, and western LA area, as a deep cyclone moved (and slowly weakened) from southwestern KS to northeastern OK. Meanwhile, the chase area would be in the left-exit region of a model-forecast 110+kt upper-level jet. Overall, shear looked very impressive, with 0-3km SR-helicity forecast to be in the 350-550 m2/s2 range and 50-70kt 0-6km deep-layer shear. As is typical for the time of year, however, surface moisture was going to be a problem, with many chasers hoping to see low 60 Tds up to the Red River by early afternoon. Nonetheless, the SPC had highlighted the risk with a moderate risk starting with the Day 2 outlook.

By morning, there were two lines of convection stretching from central Texas towards the Arklatex area. The dryline had surged to near I35 in southcentral OK while we were on our way towards Gainesville on I35. We had to make a decision whether to go east out of Ardmore (and thus stay north of the Red RiveR) or continue south to Gainesville before heading east. Since Tds were better to the south, our decision wasn't too difficult. So, we made it to Gainesville, went east on 82, and ended up in Sherman, where we waited for initiation. Dewpoints in the immediate vicinity were right near 60 degrees, though there was a relatively narrow patch of cirrus that was stretching across the area. The towering cumuli we had seen earlier were dissipating, though there was renewed development just northeast of Dallas. In addition, I had just gotten off the phone with Aaron, Ben, and Chris, who were on their way down from Durant towards Sherman. Noting that the only significant signs of growth were to the south of our position, we opted to head for the struggling convection on the northeast side of Dallas.

With Aaron et al. caught up with us, we made it near Trenton, TX, before stopping to watch the LPish storm trying to get its act together. It was quite apparent at that time that instability was the limiting factor, as the storm showed obvious signs of rotation, though was heavily tilted downwind. There were a few more towering cumuli south-southwest of our "storm", though they looked a little more linear in nature. After watching this "storm" move VERY slowly to the east-northeast (NWS was saying 15-25 mph), we opted to head southeast a bit to get a better view of a storm to the southwest of Greenville. By the time we got to Greenville, the northern storm (which we started out with) was looking the best it had looked, while the southern storm was looking a little weaker (despite radar showing the opposite). At any rate, we headed northeast out of Greenville towards Paris. We stopped several times along the way to watch the storm and take some pics/video. The structure continued to show signs of being in an environment of a little too much shear for the low instability.

By the time we neared Paris, the storm finally started to look like a more classic supercell. We pulled over on 19 / 1184 in Lamar county as the RFD surged around the mesocyclone, quickly causing full occlusion. That said, there was an awesome beaver tail feature stretching well east-southeast of the updraft. There was also awesome downward motion evident in the RFD. After this full occlusion, the storm started to look like it was actually going to do something soon. So, we continued toward Paris since there were not any substantial roads that would get us east. While finally heading east on 286 south of Paris, we noticed a funnel cloud rapidly developing underneath the new low-level mesocyclone. A few moments after pulling off the road, we saw out first tornado of 2005! The condensation funnel touched down once or twice, and we were a little far north to see much intense rotation. After about 45-60 seconds, this tornado lifted. Not long afterwards, however, a second funnel cloud developed and dropped down. Tornado #2 of 2005! This tornado had some very interesting features and motions, with a few moments of helical-type shapes and motions. This tornado was probably on the ground for less than a minute, and visual occlusion became evident. We darted east then southeast on 271, hoping to get south and east of the updraft. We did see another wall cloud as the storm was passing southeast of Paris, though this feature didn't last too long before we had a new mesocyclone well east of our position.

We followed the storm towards Blossom, but eventually gave up as light became an issue. We headed back to Paris, where we ate at Chili's... Overall, the chase wasn't quite as good I had hoped it would be, but still not a bad way to start off 2005! No strong tornadoes, no large hail, but I can't really complain about any chase in which I see a tornado.

For what it's worth, I must say that the chase territory between I35 and Paris was EXCELLENT! The area was very flat and relatively tree-less, despite how it seemed like everyone else was warning to avoid that area like a plague! So, don't let people fool you with hear-say about how bad the chase territory is down near Sherman and Paris, because it's as good as most of western Oklahoma! Well, that is until you get to Paris, east of which the land becomes more hilly and much more tree-dense.

Clickable chase map with picture location!

3-21-05 Chase Pictures

Click on any photo to see a larger version

We sat at this location for quite some time watching the updraft struggle to maintain itself. There were occassional "puffs" of enhanced vertical accelerations/velocities, and the updraft did look crisp for most of the time. The shear, however, was pretty obvious, causing the updraft to take on a highly tilted appearance. Pileus was a common sight atop the occassional enhanced updraft pulses. There was an intense RFD surge in the moments prior to this photo. The clear slot really began to take shape about a half an hour before this time, but this was the first very apparent occlussion we noted. There was some cyclonic rotation at this time, but there was also some obvious anticyclonic rotation south of the surge (which it to be expected). My first tornado of 2005! The storm produced a funnel cloud that lowered rather rapidly as we were driving east on the south side of Paris (on Hwy 286). We were a couple miles from the tornado, so this was the best we could muster. A zoomed-in view of the first tornado from our location on the south side of Paris. Another view of the first tornado. Not surprisingly enough, this was the only time that the updrat was very vertically-oriented (as opposed to highly leaning over). The second tornado as viewed from the some location as the previous tornado. This funnel did come all the way down to the ground immediately after this photo was taken. It's interesting that the tornado appeared to be moving significantly faster than storm motion, likely being pushed by the surging RFD. This wall cloud developed after we drove southeast of Paris, hoping to get south of the storm's path. A nice clear slot is seen on the left -- south -- side of the wall cloud. Unfortunately, this rotation dissipated rather quickly, as a new mesocyclone developed quite a bit east of this one.