FLASH FLOODS...
the most DANGEROUS weather
During the summer monsoon period, the warm
temperatures combine with the increasing moisture
to enhance the risk of thunderstorms with torrential
rainfalls. Thus people across southern New Mexico
and western Texas must stay alert for life-
threatening flash floods. Remember floods are the NUMBER ONE weather- related killer in the United States and over the past 40 years almost twice as many people have died from floods as they have from tornadoes.
Flash floods usually develop within an environment
with warm moist air in the lower levels and relatively
cool temperatures aloft. In addition, a slow-moving
lifting mechanism such as cold front or an upper-level
trough will increase the risk of heavy rainfall. Most
flash floods are also caused by slow-moving
thunderstorms or by thunderstorm clusters which
move repeatedly over the same area. When this happens as much as 6 inches of rain can fall over a given location in less than 6 hours. On August 19, 1978, 10 inches of rain fell on the east slopes of the Organ Mountains at White Sands Missile Range, causing flash flooding which drowned 5 people.
During the late summer and autumn, flooding may also be induced by weakening or dying hurricanes
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moving inland from the Pacific Ocean or even the
Gulf of Mexico.
Floods are also possible during the winter and early
spring months as well. A slow moving low pressure
system can sometimes pull abundant moisture into
the borderland during the cool-season with widespread rainfalls. If significant amounts of snow cover the mountains, the rainfall, combined with the melting
snow, may cause rivers to overflow, especially near the Gilas in southwestern New Mexico. Unlike flash
floods, these type of flood events can evolve over
many hours or even several days. Nevertheless they
can be just as dangerous and destructive.
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