On 7 November 2011, several supercells moved across portions of western and central OK. The most notable of these was one supercell that produced at least six tornadoes from Tillman to Caddo county. A page with more detailed information has been published by the Norman, OK NWS at this link.
One of the most notable events that took place during this localized tornado outbreak was the passage of an EF-4 tornado very close to an Oklahoma Mesonet site. This was the first EF-4 to have occurred in OK during the month of November since records started being kept in 1950. Stations from the mesonet are no stranger to extreme or unusual conditions. A mesonet site near Nowata, OK recorded a low temperature of -31F early in 2011. On 24 May 2011, a mesonet site in Canadian Co. recorded a wind gust of 150.8mph with the passage of a tornado. With this event, the mesonet station not only had a close call, but was rendered inoperative by the Tipton, OK tornado. Thefrom the site that was collected before the tower was blown down was remarkable. As you can see, a substantial pressure drop occurred as the tornado approached and winds increased rapidly. A very nice perspective on the tornado passage can be found on the AGU Blogosphere from meteorologist Dan Satterfield.
From photographs taken from several angles by the Oklahoma Mesonet, it appears the tower didn’t take a direct hit from the tornado, but not before recording a pressure drop to 913.47mb…which is quite substantial. Winds peaked just under 90mph but were likely higher since other mesonet sites have recorded substantially higher wind gusts.
Severe weather in the southern plains is not uncommon in the autumn. In fact, the first tornado I ever witnessed in person took place in Tulsa, OK on 5 December 1975. Rated on the old Fujita scale as an F-4, it probably would still be rated as an EF-4 by today’s standards. With the various atmospheric elements in place, autumn frequently has it’s share of substantial severe convective events. This most recent outbreak was no exception and, on the brighter side, brought some much needed rains to a drought stricken areas.