Tornado Proximity Traces *

Pressure, temperature, and relative humidity traces obtained from regular reporting and special network surface stations in operation in Midwestern United States during the years 1951 through 1954 and located within 15 miles of a tornado are presented. It is noted from plots of the location of the stations with respect to the tornado that certain characteristics are suggested by the barograms, dependent primarily on the distance of the instrument from the tornado. Some relationships are also inferred between microcyclones and tornadoes, and between pressure jump lines and tornadoes. The available hygrothermograph traces show many instances of the drop in temperature and rise in relative humidity usually associated with the passage of a squall or pressure jump line. Plot of the pressure fall vs. distance from the tornado suggests a (Δp)2r = constant law for a “tornado-bearing microcyclone.” Finally, a suggestion is made that some tornadoes may form as a result of some interaction between a pressure jump line and a microcyclone.