High Wind — San Diego County Mountains, California

2007-10-21 to 2007-10-22 · San Diego County Mountains, California

Event narrative

Wind gusts in excess of 70 mph toppled trees, damaged countless roofs, snapped power poles, and overturned high profile vehciles. Numerous large oaks and pines, some greater than 2 feet in diameter, were snapped at their bases. One large pine was seen hanging upside down from the top of some power lines near Wynola. Road signs that were not consumed by fire were toppled or snapped in half by the high winds. A few outbuildings were destroyed and several more were severely damaged. Downed power lines resulted in several large and devestating wildfires.

At Julian, wind gusts of 50 mph or greater were observed for 18 consecutive hours while wind gusts of 40 mph or greater were observed for 39 hours (29 consecutive hours).

At Descanso, wind gusts of 50 mph or greater were observed for 14 hours (4 consecutive hours) while wind gusts of 45 mph or greater were observed for 26 hours (15 consecutive hours).

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 64333. Narrative written by the NWS forecast office that issued the report.