FLASH FLOODS...DEADLY and DESTRUCTIVE

FLASH FLOOD DETECTION Flash floods in the southwest develop when the air mass is  moist and unstable and are most likely during the summer and early autumn. However, in a few instances, winter cyclones have produced destructive heavy rainfall across the region. Thus flooding is possible anytime of the year. One process favorable for flash flooding is when a thunderstorm with heavy rains becomes stationary, dropping several inches or more of rainfall over a given area. A second  mechanism for flash flooding occurs when a line or cluster of thunderstorms moves or "trains" over the same area dropping huge amounts of rainfall in a short time. Finally, serious flooding has occurred over the borderland during the late summer and autumn when the remnants of hurricanes move into the southern Rockies. During  potential flood situation, meteorologists monitor the radar closely for slow moving thunderstorms or for thunderstorm clusters which drop rain repeatedly over the same area. Doppler radar can also estimate rainfall amounts, allowing meteorologists to quantitatively determine the flood threat. However, spotters remain critical for the Flash Flood Warning mission of the National Weather Service by providing valuable information concerning where rivers, creeks and arroyos are running high or overflowing their banks. Spotters are also essential in informing   the Weather Service and public safety officials where streets and highways are under water. Finally, spotters and cooperative observers who possess rain gages can offer valuable real-time data on how much rain is actually falling.     go to page 1                                            page 6                           go to page 7