Monsoon Anvils in Arizona

November 17, 2010

Photographer: Stan Celestian
Summary Author: Stan Celestian; Jim Foster

The photo above showing mature cumulonimbus clouds looming over the Bradshaw Mountains of central Arizona was taken on August 3, 2010. These towering storm clouds began to form during the morning.  Around noon, when the picture was taken, the clouds had developed a classic anvil shape. This flattening occurs when a building storm "bumps up" against the tropopause, effectively ceasing its vertical growth. Such cloud development is a common occurrence during the monsoon season over the southwest United States. From about mid July until early September, maritime tropical air from the Gulf of California and the Pacific Ocean is forced inland where its heated by the intense summer Sun. The resulting unstable atmosphere often leads to thunderstorm activity, especially if the vapor-laden air is lifted by upslope winds. Monsoon rains account for approximately one third of the annual rainfall in Phoenix, Arizona. The desert southwest is a wonderful place to watch monsoon storms develop through their various stages. Note the saguaro cacti in the lower forground.

Photo details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D200; Focal Length: 70mm (35mm equivalent: 105mm); Aperture: f/5.0; Exposure Time: 0.010 s (1/100); ISO equiv: 100; Exposure Bias: +1.33 EV; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Manual; Light Source: Fine Weather; Flash Fired: No.