Dissipation Stage

[John Hudson]

Could someone explain why tornadoes often
"hook" to the left (ie: Greensburg) as they begin to rope out?

This is yet one more tidbit of info I need for a section of the book I'm working on. I'll be putting an acknowledgement (and thanks) to Stormtrack's members at FOB when it's all finished, as you all have been so much help!


John

 

[Gerard Jebaily]

Ill do the best i can to answer although Jeff Snyder could prolly be much better at the details.

Basically the tornado looses its energy and starts to dissipate when its cut off from its warm moist inflow. In the same way the cold air from a cold front overtakes the warm front and therefore creates an "occluded" front. The entire mesocyclone occludes itself outside of the warm moist inflow on the bottom right side of the storm. In a way it gets “pinched” off by the cold air and pulled away with no warm moist air to root itself too. And usually as it occludes it moves off to the north and west. If I am inaccurate on anything, please someone correct me.

Edit: (*"I think"*) The reason the greensburg tornado did the all out hook to the left is that as it occluded, it lost its center of gravity in the circulation of the meso and did a spin around the occluding meso before it completly lifted.

 

[Gerard Jebaily]

For some reason ST isnt letting me edit my post so im going to reply with another edit.


"And usually as it occludes it moves off to the north and west (similar to the way the low pressure center does in an occlusion with mid-latitude cyclogenesis.)

 

[Dan Nichols]

For those who need to edit, often like myself, there is a brief window: maybe 24 hours? Though I'm not completely sure. So do your editing as soon as possible. Once the EDIT button disappears, it's too late.

 

[Bobby Prentice]

Could someone explain why tornadoes often "hook" to the left (ie: Greensburg) as they begin to rope out?

A likely reason why a tornado would take a sharp left hook at the end of its path could be due to the tornado rotating cyclonically around its parent mesocyclone during the mesocyclone occlusion process. These two processes occurring simultaneously would lead a sharp hook at the end of the tornado's path (ala Greensburg, KS on May 4, 2008). The image below shows the mesovortex core evolution process, but not the effects of a sharp left hook at the the end of a tornado's path due to the tornado rotating cyclonically around its parent mesocyclone.

[SIZE=-1]Conceptual model of mesocyclone core evolution. The "L" shows the mesocyclone location with convective-scale cold and warm/stationary fronts extending from the meso. The cold front is the leading edge of the rear flank downdraft, while the warm/stationary front represents the southern edge of the forward flank downdraft from rain-cooled air north of the boundary. The bold lines are tornado tracks. The insert shows tornado family tracks and the small square in the insert is the region expanded in the schematic. (original source...Burgess and Lemon, 1990)
[/SIZE]