High Wind — San Bernardino and Riverside County Valleys - the Inland Empire, California

2007-10-21 to 2007-10-22 · San Bernardino and Riverside County Valleys - the Inland Empire, California

Event narrative

A strong Santa Ana wind event caused widespread wind damage across the Inland Empire. Wind gusts in excess of 70 mph snapped power poles, toppled trees, overturned big rigs, and damaged roofs. In one of the hardest hit areas, the wind caused an estimated $2.6 million in damage at Mt. San Jacinto College. Many of the surrounding homes sustained minor to major roof damage. Elswhere, a portion of the 215 freeway between Devore and I-10 was shut down as a result of the high wind, overturned big rigs, and blowing dust.

Wind gusts of 50 mph or greater were observed for 19 consecutive hours at Beaumont and 14 hours (5 consecutive hours) at Ontario. A peak wind gust of 79 mph was measured at Palm Avenue Elemntary School in San Bernardino.

Wider weather episode

Very strong surface high pressure over the Great Basin and extreme packing of the isobars along the crest of the Transverse and Peninsula Ranges resulted in an extended period of very strong, damaging, Santa Ana winds in the mountains and valleys of Southern California. During the morning of the 22nd, the pressure gradient averaged an impressive 0.2 to 0.3 mb/mile across the mountain crests. For example, a 10 mb pressure gradient was observed over a distance of just 45 miles between Ontario and Apple Valley, a 9 mb pressure gradient was observed over a distance of just 35 miles between Borrego Springs airport and Ramona airport, and an 8 mb offshore pressure gradient was observed over a distance of just 25 miles between Rialto airport and Big Bear City airport. Widespread wind gusts in excess of 65 mph with local gusts near 80 mph were reported in the Inland Empire, San Bernardino foothills, Santa Ana mountains and foothills, and San Diego County mountains and foothills. Several locations in and below passes and canyons experienced tropical storm force winds or greater for more than 36 hours.

A peak wind gust of 85 mph was measured at Fremont Canyon, 79 mph at Palm Elementary in San Bernardino, 75 mph at Descanso and Mira Loma, 74 mph at Fallbrook and Rancho Cucamonga, 69 mph at Potrero, 67 mph at Beaumont, 66 mph at Ontario, 63 mph at Case Springs and El Cariso, 62 mph at Campo prior to the power outage, 59 mph at Julian and Alpine, and 58 mph at Cameron and Chino.

The strong winds downed countless trees and power poles, damaged many roofs, damaged fences, damaged or destroyed outbuildings, damaged or destroyed road signs, overturned several high-profile vehicles, generated large dust storms, and fanned the flames of several large and devestating wildfires.

Source: NOAA Storm Events Database, event_id 64332. Narrative written by the NWS forecast office that issued the report.