Nearly 50 years ago there was a deadly outbreak of tornadoes across the upper Midwest (states with tornadoes were IN, OH, MI, WI, IL, and IA) on Palm Sunday 1965. Palm Sunday that year was on April 11th. This was the largest outbreak of tornadoes on a single day up to that point in our recorded weather history. There were at least 47 tornadoes and fatalities exceeded 261 people.
The image above has become an icon of severe storm photography and was taken by Paul Huffman near Elkhart, Indiana. It captures a double vortex tornado crossing a highway and railroad tracks - the tornado is so close that debris can be seen in the air near left side of photo. Fujita et al. published a detailed study of the event in Monthly Weather Review (January 1970 issue) and the abstract is below. Fujita's aerial survey documented numerous tracks of looping, "suction spots", which are now known to be damage tracks of sub-vortices embedded within multi-vortex tornadoes. The paper demonstrates how crude the radar and satellite data were 50 years ago.
I remember that day vividly. I was a junior in college and was home, in southern Illinois, for the Spring/Easter break. I was playing golf that afternoon with my Dad and several others at a course on the Mississippi River bluffs east of St. Louis. The dryline came through and we finished our round in winds gusting to at least 50 mph from the southwest. Even though the area was within a tornado watch, all of the thunderstorms and tornadoes occurred far to the north of where we were.
This year the severe thunderstorm season has been very calm so far. The two maps here are from SPC and show the areas affected by tornado watches above and severe thunderstorm watches below - only 4 of each flavor have been issued so far during 2015.
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