"A flash flood is a flood in which the rapid rise in stream level and the resulting inundation follows the observable causative event by about four hours or less. For rain-caused flash floods meteorology is complex, and limited amounts of real-time data make timely forecasts of exact location very difficult. Lack of reports of flash-flood occurrences adds to the difficulty. Many occur that are never reported to the National Weather Service (NWS)"--Introduction.

This synoptic study for the period 13 to 16 July 1972, involved the use of surface, radiosonde, and radar observations, as welI as satellite pictures. Isentropic analyses indicated that the depth of the moisture with this surge of tropical air was of the order of 8,000 to 12,000 feet. 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 feet for the period of concern. SateIIite photographs and film loops give a dramatic picture of the movement of the cloud mass 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

Two commonly used methods of hydrologic analyses are parametric reconstruction and development of frequency distributions. Both techniques can be used to develop estimates of potential of damaging flash floods. However, under conditions of limited data, many areas may not have experienced enough flash floods to be recognized as prone to flash flooding. This paper gives a method to infer expected severity for flooding based on frequency analysis, which does not require a complete spectrum of data over a given basin. This method was used to estimate potential peak flows on Sabino Canyon, Arizona, and probability of occurrence of specified magnitudes was analyzed. These estimates indicate a strong possibility of damaging flash floods occurring in areas where none have occurred in several decades.