A cold front developed in Arizona in a region of initially small temperatur
e gradient, developing to great intensity, accompanied by damaging winds ov
er New Mexico, and then losing strength over the high plains of Oklahoma an
d Texas. The entire development of frontogenesis and frontolysis occurred i
n no more than 24 h.
The initial growth of temperature contrast was attributable mainly to horiz
ontal variation of surface heat flux during the morning, with little heatin
g in a region of dense cloud cover and scattered showers in the west and wi
th intense heating in a region of only thin high clouds to the east. The ac
companying ageostrophic circulation then resulted in a collapse toward disc
ontinuity. The frontal zone maintained an approximately steady state for a
few hours in early afternoon. At this time the westerly component of surfac
e wind just ahead of the zone was not as strong as the eastward motion of t
he zone. The passage of the zone was accompanied by a veering and strengthe
ning of the surface wind so that westerly components were briefly larger th
an the frontal motion. The tendency of the convergent wind field to produce
a frontogenesis was evidently balanced by small-scale mixing.
Subsequently the pressure trough and surface wind shift propagated eastward
more rapidly than the frontal temperature contrast. The contrast quickly w
eakened as the mixing then was unopposed. Severe convection developed durin
g the evening as the convergent surface wind shift came into contact with h
umid unstably stratified air.