March 18, 2012 Storm Chase:
Models consistently progged a full latitude trof to move into the western U.S. and quickly traverse eastward. As it moved into the Great Plains, the southern part of the system would close and cutoff from the main jet. The primary issue was, at what point this would occur. It appeared either way that Sunday would be a favorable day to chase as the upper system was developing in the western U.S. and stronger flow aloft was progged across the Texas panhandle and Oklahoma. Several days of moisture return and in-general good moisture in the Gulf this winter meant that upper 50s/low 60s dewpoints were already in-place east of the dryline. In fact this gave some of the models difficulty, especially the NAM which wanted to forecast the dryline on the NM/TX border. There weren’t any glaring issues in the prior days of this event but a few became obvious within 36-48 hours. The initial issue was the lowering of CAPE values in the threat area as opposed to the prior few days which had 3000 J/Kg across this area. It was then noted that an ill-timed shortwave trof was moving through the area around mid-morning, moving slowly northeast and this would delay surface heating in the threat area. The only good news from this was that the cap would keep much of the activity light and hence not much more than drizzle was expected. The other item was cirrus, which some call “cirrus screw-us.” The latter being the impact on surface heating, especially this time of year. The forecast changed very little by Sunday morning with instability remaining the primary issue, all other features seemed to be well handled by the models. SPC had a slight risk posted across the Texas panhandle/western OK, extending north/south from there.
By mid-morning the previously forecast shortwave trof became apparent with some drizzle across northwest Texas and lots of cloud enhancement. This limited surface heating across western Oklahoma. By early afternoon, the clouds started to thin and the cirrus decreased some that decent surface heating occurred in the areas adjacent to the Texas panhandle. The latter had warmed quite nicely with CAPE values near 2000 J/Kg. The cap was expected to erode by mid-afternoon as stronger flow aloft moved across the panhandle. A tornado watch was issued by 3pm and storm development occurred near Childress and farther south. These storms quickly became severe as they moved northeast. Other updrafts developed farther north but did not become mature supercells. Their lack of development appeared strongly tied to the cirrus streaming above them. A few cirrus holes had developed earlier in the day, which likely allowed these updrafts to grow. Eventually they ceased development and there was no development in the Texas panhandle until evening. The three supercells, lined up from Childress south-southwest where the main storms in this area. All three eventually had tornado warnings on them with four confirmed tornadoes from the Childress storm (all in Oklahoma). The storms dissipated by early evening as predicted by SPC, with lower-end severe thunderstorms developing farther west on the dryline.
SPC Event Page: http://www.spc.noaa.gov/exper/archive/event.php?date=20120318
Team: Greg Whitworth and Putnam Reiter
Miles Driven: 450
Time: 10.5 hours
We left Oklahoma City around 1pm and headed west on I-40 to Shamrock. That had been our spot for a few days and while we toyed with other areas, it did remain the best idea. The setup as noted above didn’t change much, so we really didn’t talk too much about the weather. We did drive through some drizzle and lots of enhanced cumulus due to the previously mentioned shortwave trof. As we neared the Texas panhandle, the lower level clouds thinned and so did a little of the cirrus above that deck. The temperature quickly responded, rising into the mid 70s, previously it had been in the upper 60s/near 70F. There had to be something telling about a chase in Shamrock, Texas, a day after St. Patty’s Day.
Once in the panhandle the cirrus came and went, we noticed a rather dramatic change in temperature when this would occur. I guess it was foreshadowing relative to the impending storm chase. We reached Shamrock about 3:15pm and already had received word of a tornado watch. Getting some gas in the car and a chance for Greg to eat, we kicked on RADAR to see two storms south of us. Both were well developed and quickly heading to being mature supercells. We also noted some convection to our southwest, which seemed to promising. Greg got done eating and we decided to head south and see what the storms near us were doing. RADAR did not show a good display for them and Greg noted the cirrus seemed to be interfering with their development. As we got due east of them, they had not done much more than what we saw over the previous 30-45 minutes Seeing that the storm near Childress was now a supercell, we thought it best to head on south and engage that storm. Also, the Childress storm was heading towards Hollis and our best chance to get ahead of it was to take HWY 62 into Hollis. With that being said, we had to “shoot the gap” ahead of the storm and get east before it got there. We didn’t have much trouble getting this done and got into Hollis with just a little rain. After a quick break and looking at RADAR, we shifted east to just outside of Hollis and setup shop.
Hollis proved a great spot to watch the storm, we long had the rain-free base in view and as we sat east of Hollis, we were able to continue watching the storm. It was moving northeast at about 30mph, a little faster than we thought. As the storm got into Oklahoma, a few other storms had developed near it and a storm merger looked imminent. As this was occurring, we thought it best to shift east a little bit to Gould and then drift north. Once back in position we noted wall cloud development but a rather strong rear-flank downdraft each time the wall cloud would tighten up. The storm merger was complete but there was not a tornado that we could see. As we sat north of Gould, the storm did get a whole lot more interesting, but I will say several times Greg and I thought it was done. In fact, at one point we toyed with turning around and heading south for the tornadic storm in northwest Texas. However, one of our chase rules is to not leave a rotating wall cloud, which we periodically had seen.
The biggest problem we ran into at this point was the lack of road options. So, we had to disengage the storm long enough to reposition east and a bit north. Unfortunately we had to deviate about 10 miles east of the storm south of Mangum and then drive north to get another view. As we got north of Mangum a tornado warning was issued on our storm, much to our surprise. We still had the rain free base in view but didn’t see a tornado. We got to a decent dirt road, hard to come by in this part of Oklahoma, and drove west about half a mile. We didn’t see a tornado but we did see rain curtains wrapping around the updraft area. We went back to the main road (HWY 283) and drove north some, watching the storm. Several items were apparent, 1) road options and storm movement were about to be a problem and 2) the storm was reorganizing again. At this point, we decided to disengage again and get east. The very long line of chasers/locals made it difficult to get safely turned around on 283 but we managed to do so and went a mile south to HWY 9 and then east. Getting to Granite, we went north and got just past the “hills” and saw what looked to be a cone funnel. This was reported via amateur radio via us but little other activity was heard. The feature disappeared and we went a few miles farther north.
The storm still looked to be in a good shape and sure enough another funnel developed shortly after the cone disappeared. This funnel quickly extended towards the surface and stayed that way for about 2 minutes. We were pretty sure it was a tornado, but could not see debris or certain ground contact. The funnel, being 9/10th to the ground was reported. No other reports were made that we heard. Looking at the video we took, the funnel was indeed a tornado. This was confirmed by people closer to the activity and the prior cone funnel was also a tornado. Greg got a picture of it and several chasers also noted it.
After this tornado, the storm quickly lost features and we decided to head home. We gave the storm a little more time, but it was obvious the last tornado was the end. We also knew that the storm was moving beyond the first row of counties in Oklahoma and in an area recently impacted by the shortwave trof (drizzle etc), the temperature showed 68F in the inflow. The storm became elevated and raced north at 50mph, which truly was the end. We headed back east on HWY 152 and then north on HWY 54 to I-40 and east to Oklahoma. The chase ended at 10:50pm.
– AT&T sucks in the Texas panhandle and iMessage doesn’t work well once 3G is gone. Learned how to turn it off though.
– Get reflective vests. I’m not sure who/whom came up with this idea, but it is a good one. We’re going to nab a few. I saw several chasers wearing them and thought it was a great idea.
– This isn’t for us, but the chaser community in general. We noted numerous chasers parking in the road, not obeying traffic rules, and even putting their tripods in the middle of dirt roads. This stuff is routinely noted by those of us that try to follow the “rules.” I’ll admit, I do speed from time to time, but you won’t catch us in the road or passing unsafely. I’m not quite sure what turning on your flashers does when traveling at 60mph and passing other cars, but it happened to us a few times. It also doesn’t help that the locals come out after about an hour or so of watching it on TV. Also, gone are the days when this group could hide on the back roads since we had GPS. Everyone else has it now, so we’ll find another way to adjust. One way that worked for us was to intentionally pull ourselves off the storm and reposition ahead of the group. We may have missed a few features/events but it sure kept us alone.
Engaged Storm: Hollis, OK
Hail: No, but 2.50 was reported.
Tornado: Got three of them both near Retrop.