Rare Collision Caused a Swarm of Tornadoes "Federal storm scientists yesterday raised the count of tornadoes that struck Sunday and Monday to 88 from 69 and said the tally was likely to continue rising for several weeks as they examined local weather and damage reports. The scientists also mapped out the forces that created the twister outbreak, the worst in November in a decade, and saw in them a distinctive, but rare recipe for widespread disaster: a collision between a big pre-winter gush of frigid air and an unusually broad reservoir of residual tropical warmth and moisture flowing from the Gulf of Mexico."