Some Synoptic Aspects and Dynamic Features of Vortices Associated with the Tornado Outbreak of 3 April 1974

Abstract

Abstract A study has been made of certain aspects of the “jumbo” tornado outbreak of 3 April 1974. The region characterized by a) surface dew point temperature Td⩾55°F, b) 500 mb winds ⩾60 kt, and c) veering winds ⩾15° in the 500 mb to 850 mb layer, contained 85 of the 93 tornado tracks determined in Fujita's initial aerial survey. Analyses of three storm cells with hook echoes, associated with tornado families (a total of nine tornadoes) in southeast Indiana, showed that 1) the velocity of a storm cell and accompanying hook are approximately the same, 2) tornadoes may move across and to the left of parent thunderstorm track at angles up to 21°, where 3) this angle tends to be less for longer tornado tracks, and 4) the tornado speed can differ from the speed of the hook. usually beginning close to it but ending several miles to the north of the hook (for left-moving tracks). Selected radar sequences show the prominent features of developmental, mature, and dissipative stages for each storm cell. A motion ...