Hunting for the Keys to Tornadogenesis

The National Storm Chaser Convention is happening this weekend in Denver. It is a great collection of speakers organized by storm chaser Roger Hill and researcher Tim Samaras, both who have appeared on WeatherBrains in the past couple of month.

Erik Rasmussen is one of the most respected tornado researchers in the world. He appeared at the ChaserCon when I attended in 2003. He spoke there again yesterday, talking about his specialty: tornado formation. The presentations are being streamed live on SevereStudios.com for a fee. They will be archived for seven days. The cost is $29.95.

Most supercell thunderstorms contain mesocyclones capable of producing tornadoes. Rasmussen calls them tornado cyclones. A tornado is the inner portion of that cyclone that has gathered enough angular momentum or spin to produce intense windspeeds. Rasmussen’s theory is that the failure of a supercell to produce a tornado is a failure of this tornado cyclone to contract. The strength of the inner portion depends on the amount of spin in the outer portion and the removal of mass upward trough the vortex. Rasmussen believes the key will be found in understanding why most supercells don’t transport sufficient air upward through the cyclone.

The WSR-88D radar network is so widely spaced that the radars cannot see the lowest levels of the atmosphere. Rasmussen says that as long as we can’t see the lower levels, it will be impossible to determine the difference between tornadic and non-tornadic cyclones in real time. Research projects like VORTEX 2, as well as radar networks like CASA will help to resolve some of the lower level features that are critical in tornado formation and perhaps unlock the keys to why some storms produce tornadoes, while others don’t.

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