1 APRIL 2006: ERICK, OKLAHOMA SUPERCELL


Southwest of Burns Flat, Oklahoma, observed from SR 152 looking north as we paralleled the storm.
W
e do not believe this was a tornado.
 

Eric Nguyen, Robert Hall and I intercepted a supercell south of Erick, Oklahoma south of Interstate 40 near the Texas Panhandle and Oklahoma border. We observed it for nearly two hours as it slowly morphed from a small, well-structured supercell into a larger HP with a forward flank meso. Given the easy storm motions, our entire chase distance is surprising when I look at a map. We initially engaged the storm while southbound on 283 just south of the interstate, then returned north on 34 through Carter, and continued the chase using 152 eastbound. At the intersection of 153 and 283, the storm was outflow-dominated, and we turned south to enjoy a great meal at Bianco's in Lawton with Bob Fritchie and Rachael Sigler.

We started the day hoping the dryline would sharpen more than the last few NAMs depicted. Those diffuse gradients are often unfavorable for the sort of circulations necessary for inititation. Nor did we enjoy watching the warm front glide into Kansas and come apart--that was the boundary we would have liked and which would have made a real difference for our eventual target storm. In Pampa around 21z, we noticed the wind shift ahead of the dryline. That's never a good sign as a gradual turn to southwesterly flow serves to dry the boundary layer. In addition, we believed that veered 850s were mixing out our moisture from above. A line of cu rose and fell several times to the west when finally a small storm fired in Carson County and moved north. We didn't care for the environment ahead of the cell, however, with >20F T-Tds and no boundaries.

We noticed some enhanced cu in Collingsworth County, on the Texas/Oklahoma border, and deciced to head east on 152 toward Wheeler. Our rationale was pretty thin: we guessed that the wind shift convergence zone had shifted east, or that an elevated dryline was at work. Whatever the source of lift, we knew that a storm firing on the border would quickly move into a more supportive environment since the moisture axis was still entrenched in western Oklahoma. At that point we met up with Tony Laubach, Verne Carlson, and Jon Van de Grift.

Minutes after we started east, the first reflectivities appeared for what would become our storm. Since the cell was backbuilding substantially and therefore reducing its forward speed, we changed our interception vector several times and reached a view of the updraft base from just south of Interstate 40 taking 283 southbound. For the next thirty minutes the storm was high-based with elevated circulations.

 


~2314z near Willow, OK
As the cell moved into higher theta-e air, the base came down and the persistent wall clouds lowered as well, but at the same time the character of the storm was growing more HP and outflow dominant as the core grew in aerial coverage and influence. Our storm was consistently seeded by convection to the southwest also and this wasn't helpful. We observed several clear slots around our wall clouds as RFD (which we noted as quite warm but perhaps on the dry side?) wrapped around the circulations.

~2339z 2 miles south of Carter, Oklahoma
We stayed as close as safely possible because we believed that if the storm would tornado, it would do so post-occlusion. No such luck. The rotation never sufficiently tightened. I'm quite convinced that with the presence of a boundary, this cell would have produced a fair tornado.






We never observed hail with this storm despite maneuvering in and around the meso from the north and northeast. In fact, we saw not a single stone all day until we had quit chasing and were heading south toward Snyder on SR 283 after 0200z. We experienced more pea hail after departing Bianco's in Lawton around 0400z. All these stones appeared on the edge of the bow echo formation moving through southwest Oklahoma.


Midlevel funnel observed as storm winds down