Saturday, April 30, 2011

A Look Back At 1974 Radar

There has been much comparison being made between Wednesday's tornado outbreak and that of April 1974. It's a shame that we don't have Ted Fujita around anymore to do a painstaking areal survey of the entire region affected on April 27th. I think that it's interesting to take a quick look at radar data available then and now.
Above is a photo of the April 3rd, 1974, tornado that struck Xenia, Ohio. Below the photo is a screen shot of the nearest WSR-57 radar image at the time of the tornado. The radar data had not yet even been digitized, so the operator had to modulate image brightness to help interpret what the radar was detecting. Very crude radar technology back then, but the hook echo appendage on the Xenia storm is quite obvious.

Top image here shows Wednesday's tornado approachng Tuscaloosa - view is from further away but the tornadoes are somewhat similar in visual appearance. Bottom image is from the NWS Birmingham Doppler radar. Right panel is reflectivity capturing the hook echo and also a large blob of very intense reflectivity that indicates a debris cloud associated with the intense tornado. The right panel shows the velocity display (radar is located off to the east and a bit south of the tornado). The velocity field is extremely intense and captures both a large mesoscyclone and also the tornado vortex signature. Clearly a tremendous improvement in weather radar technology and displays have occurred since the outbreak of 1974.

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