30 April 2004

Cool front slides under warm air

Forrest M. Mims III

Cold fronts often arrive with a bang, especially when they collide with warm moist air. While an observer on the ground experiences the arrival of a cold front almost immediately as the wind shifts, the air just above may still be moving in another direction. The animated GIF above shows this phenomena shortly after a cool front arrived at Geronimo Creek Observatory in Central Texas on 24 April 2004. The animation shows small cumulus racing south as the cool, heavy air of the front slides under midlevel clouds moving north. Thunderstorms often result when warm, moist air is pushed upward into cooler air by the arrival of a cold front. This animated GIF is from a sequence of full resolution images captured by a water-resistant Pentax Optio 33WR 3.2 megapixel digital camera operated in time lapse mode.