Central Plains Tornado Outbreak
Posted on Friday, April 13, 2012 at 5:00 PM MST
NORMAN, OK -- Two straight days of taking a gamble and targeting areas close to home left me with the two extremes as far as results go: one day put me up close and personal with a fairly serious tornado less than a mile from my house, and the other day was uneventful, which for a high risk day is about as good a bust as you can get.
The SPC had been forecasting the big outbreak on Saturday April 14th since the previous weekend, and had already gone High Risk by the morning Day 2 Outlook on Friday, which was the earliest it had ever issued a High Risk and was just the second time in its history that it issued a Day 2 High Risk. Since all forecasts pointed to the highest risk for severe weather to be in the late evening and overnight and I wanted to avoid the chase crowds, I opted to make my main chase day Friday, especially since the elevated tornado risk was very close to home and the chaser crowds would be much less.
A cluster of supercells formed in southwest Oklahoma early in the afternoon and began tracking northeast along Interstate 44. One cell in particular caught my eye, which was located to the southwest of Chickasha, which I was tracking on radar from my house. The projected storm track showed it going up into southwest Oklahoma City, so I grabbed my things and set off to chase it.
The initial chase plan was to head to Blanchard and document it from Highway 9 as it passed to the north and west. I didn't even make it close to there. In the time it took me to drive from my house out to I-35 (less than 10 minutes), the storm had developed a vigorous mesocyclone on its southeast flank and was beginning to turn right, so I quickly adjusted my plan and set up to the north of Goldsby.
One of the interesting things about the dynamics of these big supercells is that as a mesocyclone develops, the storm's rotation pulls the whole storm to the right. In general, the stronger the rotation, the more the storm pulls to the right. You will often hear chasers and meteorologists call this type of storm a "Right-Mover." You can also have left-movers, but they usually occur when a supercell splits, like I saw on April 9th up in Woodward.
The mesocyclone on this supercell developed and strengthened so quickly, that it turned the storm pretty significantly to the east and pointed it straight at downtown Norman. I could see the storm turn to the right both from my location north of Goldsby and on radar, so it was time to reposition to the east. The only way across the Canadian River is on I-35, so I raced back north on I-35 to go east on Highway 9 and reposition on the east side of Norman. With a brand new windshield, I wanted absolutely no part of any hail core that was associated with the storm.
As I got off of I-35 and started heading east on Highway 9, you could see the beginnings of a tornado vortex signature start to form on radar. The storm was a huge HP (high-precipitation) mess, so all I could see to the west was absolutely black skies and a white wall of rain, coming straight at me.
By the time I had gotten over to the southeast side of Norman, it was becoming clearer and clearer that a tornado may be imminent. Realizing that this was an HP mess (so no good photo ops) and there were no really good options to the south as far as escape routes go (and I was only about 5 minutes from home), the best decision was to head for home to take shelter.
I pulled into the driveway and quickly began unloading my cameras and things out of the truck. As I was locking the truck up, the tornado sirens began blaring, so I went inside and turned the TV on to see what was going on. They said a tornado had been confirmed on the ground near the OU campus. It took me a couple seconds to put it all together, but this tornado was headed straight for the house. Time to gather a couple things and head for the safe room.
I had actually spent the morning prepping and stocking the safe room in anticipation of the High Risk day on Saturday, and boy was I glad I did so. It was a pretty tense several minutes sitting in the safe room listening to the wind and rain pound the house as the tornado passed. The main circulation/vortex passed between half a mile and a mile from the house, so I was probably in the outer fringes of the circulation. As soon as the main circulation was to my east, I grabbed the camera and headed back outside and did manage to get some nice shots of the back of the mesocyclone as it moved away. The storm continued to produce tornadoes as it moved northeast, and had a multi-vortex tornado on the ground as it crossed Interstate 40 near Shawnee. And this was only the beginning of the outbreak.
I once again decided to target the area close to home on Saturday (since I wanted to avoid the chaser crowds and be close to home in case anything happened. I focused mainly on the extreme southern part of the High Risk area and the part of the Moderate Risk area to the southwest of that.
As the day went on, models and forecasts showed tornadic supercells exploding in West-Central Oklahoma around dinnertime, so that became my primary target. It was amazing watching the tornado outbreak unfold over Kansas and northern Oklahoma on TV throughout the day.
As the dinnertime hours rolled around, severe weather and tornado parameters were maxed out across much of northwestern Oklahoma and were still extremely high over West-Central Oklahoma, but the area had remained under cloud cover nearly all day, significantly reducing surface heating and allowing what little bit of a cap that was there to still hold. With no boundary around either, there was simply no way to initiate the upward motion required to form thunderstorms. The focus then shifted to a dangerous and explosive squall line that was supposed to come ripping across Oklahoma overnight.
In the meantime, I tracked a very powerful, long-track tornadic supercell that came out of the Texas panhandle and began producing tornadoes near Waynoka, OK right at sunset. The shots from the news helicopters of the tornadoes forming are just breathtaking (see photos). The storm produced strong tornadoes for over two hours, prompting a Tornado Emergency in Wichita, Kansas shortly before 10 PM.
After a short lull in the action after the tornado passed just south and east of Wichita, the explosive squall line very quickly formed in the Texas panhandle around 10:30 PM as the cold front overtook the dryline and nearly instantly became severe and came plowing into western Oklahoma during the 11:00 hour.
When the squall line came ripping into western Oklahoma, the tornado parameters were absolutely maxed out (quite a bit more than they were on May 24th last year), particularly north of I-40. There was so much spin and wind shear in the atmosphere it would cause the squall line to wiggle. If a cell was able to break out in front it would instantly become supercellular and tornadic. Unfortunately one cell was able to do that at about 12:15 AM, which struck the northwest side of Woodward with a deadly tornado with less than 3 minutes of warning.
My original plan was to get a couple hours of sleep while this line tracked across western Oklahoma, but after watching the disaster unfold in Woodward, I decided that was probably not the wisest thing to do. A PDS (Particularly Dangerous Situation) Tornado Watch was still in effect for pretty much the entire northwest quadrant of Oklahoma, and tornado parameters were still extremely high right through the I-35 corridor and the Oklahoma City metro.
The squall line was at its peak strength between about 12:30 AM and 2:30 AM. At one point the squall line was over 800 miles long (no that's not a type-o), stretching from north of Topeka, Kansas all the way down to just north of the Mexican border in southwest Texas. A good portion of the line had Severe Thunderstorm Warnings on it.
Between 2:30 and 3:00 AM, the very potent squall line was beginning to encroach on the Oklahoma City metro, with the Tornado Watch extended to include the metro. There was still so much spin in the atmosphere that even the small updrafts had pretty good rotation in them. You could see the cells on radar really trying to break out ahead of the line, but this time it was south of I-40, which really peaked my interest, since strong tornadoes could still easily form in any cell that could break out ahead of the line. Fortunately, as we closed in on 3:00 AM, the line was able to hold together strong.
I don't know whether to call it luck or irony or what, but the feature that really helped Central Oklahoma was actually the same feature that caused this massive tornado outbreak: the potent low pressure system coming out of the southwest. As system came roaring out of the southwest, it accelerated the westerly winds behind the cold front, which ended up being strong enough to undercut the squall line with cold air, choking off its fuel supply and both significantly weakening the whole line and eliminating any remaining tornado threat. By 3:45 AM, as the line was beginning to come into the western Oklahoma City metro, it had been undercut so much it had come back down below severe parameters and was weakening, so there were no warnings as it came into the metro.
The line came through Norman around 4:15 AM, giving us a pretty good lightning display and some gusty winds and heavy rain, but that was about it. Cool stable air settled in behind the front, closing the book on another memorable Great Plains Tornado Outbreak. It has been one heck of a start to storm season here in Tornado Alley. Quiet weather over the southern plains the next week will be a nice little break, but I'm already looking forward to the next chase.
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