Up Close & Sat Views of the EF2 Hammon OK Twister
Posted by JAC on 3/10/2010, 6:26 am
http://www.cnn.com/video/#/video/us/2010/03/08/ac.vo.ok.tornado.touchdown.mxf.cnn?hpt=C2

http://www.youtube.com/watch?v=l_kzKP0IYSY

http://www.youtube.com/watch?v=Y_LVXd3_p_w











After an unusually quiet February tornado-wise in the United States
(only one tornado was reported, an EF-0 in California that lasted for 3 minutes late in the day on February 27th),
two tornadoes touched down near sunset in western Oklahoma, near the town of Hammon.

The above image from NAWIPS shows 1-km GOES-12 visible imagery with superimposed contours of cloud-top cooling from about 90 minutes prior to tornado touchdown.

The growing cell that will ultimately spawn the tornado has been correctly identified.

Such cloud-top cooling is computed routinely as part of a University of Wisconsin Cooperative Institute for Meteorological Satellite Studies (CIMSS) project on convective initiation.

If the detected cloud-top cooling is co-located with changes in cloud phase (for example, from supercooled water droplets to ice crystals,
or from all water droplets to supercooled water droplets) as inferred from GOES-12 radiances for different infrared channels,
then convective initiation is deemed to be ongoing.

In this animation of 11-micron cloud temperatures overlain with Convective Initiation, note the CI Likely at 2132 UTC along the Texas/Oklahoma border.






That region of cloud top cooling and phase change then moves north-northeastward and the convective cell that spawned the tornado develops.

Convective Initiation is no longer indicated, however, because the initiation stage of convection is over by 2200 UTC.

This visible image loop from NAWIPS also shows the strong cooling at 2130 UTC, then convective development and intermittent lightning strikes associated with the Hammon cell.




Note that the algorithm locks on to the convective cell that spawns the tornado, and not adjacent cells.

The strongest cooling was associated with the storm that produced the tornado.

Similarly, only that cell had the cloud phase changes to trigger the signaling of convective initiation.

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Up Close & Sat Views of the EF2 Hammon OK Twister - JAC, 3/10/2010, 6:26 am
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