A Surge of Maritime Tropical Air—Gulf of California to the Southwestern United States

Abstract

This synoptic study, for the period 13?16 July 1972, involved the use of surface, radiosonde, and radar observations, as well as satellite pictures. Isentropic analysis indicated that the depth of the moisture with this surge of tropical air was of the order of 8000 to 12,000 ft. A unique feature of this type of surge is its resemblance to a giant sea-breeze effect, where the main advective forces result from the low-level pressure gradient between the desert thermal low and the relatively higher pressures over the cooler Gulf of California. This effect is emphasized by the lack of upper-air support, as shown in the mean vector winds from 10,000 to 20,000 ft for the period of concern. Satellite photographs and film loops give a dramatic picture of the movement of the cloud mass initially associated with the surge. They also suggest that one of the mechanisms that may be a factor in the development of the cloudy, showery area at the mouth of the Gulf of California is an easterly wave. These extensive and active cloud areas apparently establish the low-level conditions favorable for the northward push of the surge.