Mesoscale Association of a Low-level Jet Stream with a Squall-Line—Cold-Front Situation

Abstract

Wind and temperatures data taken at twelve levels on a television tower near Dallas, Tex., are examined during a squall-line—cold-front situation occurring during the morning hours of 8 May 1961. The observations, supplemented by Fort Worth pibal and radiosonde data, illustrate the presence of a large scale low-level jet stream in the southwesterly flow in advance of the squall line, a wind maximum and marked cooling associated with a thunderstorm outdraft and a separate, smaller scale jet stream which existed within a mesoscale high pressure area between the squall line and the cold front. This mesoscale high, of the type studied by Fujita, is produced by sub-cloud precipitation evaporation. Detailed vertical soundings show the extent of the corresponding subsidence inversion and the resulting effect on the wind speed profile.