January 12, 2005

Cold Front Helped Create California Storm

The rain that has drenched California for the past several days is being caused by a cold front from the northern Pacific combining with moisture from the southern Pacific.

The low-pressure system slid down the West Coast from Alaska and stalled several hundred miles off the coast of San Francisco for three or four days. There, the cold front drew warm, moisture-laden air from the southern Pacific until it grew to 1,000 miles in diameter and moved onshore.

Such a confluence of pressure systems is not unusual. In this case, however, the jetstream in the upper atmosphere was slower than normal in pushing the big system east, said National Weather Service meteorologist Bruce Rockwell.

"This storm was so huge it almost created its own environment, and it takes a tremendous amount of energy to move a storm that big," he said.

Rockwell said the country has not seen the last of the storm.

"It'll be over Utah and Arizona soon, and we'll probably see problems in the Midwest in a day or two," he said.