March 10, 2010

Day 1 Tornado Probs - 1630z

Chase Log: Two days after our successful chase on the Hammon, Oklahoma Tornadoes another potential cold-core setup was setting up in Northeast Oklahoma. Our target area, as shown in graphic 2, was along Highway 169 east to Highway 2. We spent several hours in Welch, Oklahoma where we were surprised to find that we lost all data as soon as we entered the town.

Target Area for March 10, 2010

With our location near the town of Nowata and storm motions over 55 MPH any cells that developed ahead were impossible to catch. The one cell you see is actually beginning to enter the warm sector, which we had dismissed in favor of the cold core setup. However, one element we had not accounted for was the strong squall line over North Texas. Because of this unforeseen circumstance blowoff convection, or strataform moved over our target area inhibiting heating substantially, which in a cold-core setup is needed in order to develop a temperature gradient between the surface and the mid levels of the atmosphere. This difference in temperature causes instability, which then promotes thunderstorm growth. In cold core setups the mid levels of the atmosphere are very cold, usually below 25C and are accompanied by a very strong storm system which creates wind shear. Because of the extremely cold temperatures at 500 MB (18,000 Feet) surface temperatures only need to rise into the low 70′s before enough instability develops to create mini-supercells, a smaller and usually less intense version of a normal supercell. These storms however are still capable of producing tornadoes, usually weak. Although there have been exceptions, such as the tornado two days before this chase. Overall because of the cloud cover and limited moisture, the storms were unable to really develop. There was a notable short-term exception on the Oklahoma-Kansas line where a funnel cloud did briefly appear.