Wildfire — San Bernardino, California

2003-10-21 to 2003-10-31 · near Fontana, San Bernardino, California

Wider weather episode

Named the Grand Prix Fire, this fire was started by arsonist on October 21, 2003. It burned 59,448 acres before being fully contained on November 5, 2003. During the first seven days, the fire increased rapidly in size and burned across freeways, railways, and into the communities of Glen Helen, Cajon Canyon, Mt. Baldy Village, Lytle Creek, Rancho Cucamonga, and Fontana. It destroyed 135 houses, 60 outbuildings, 1 commercial property, 1 helicopter, 11 cars, 1 boat, 1 trailer, and several miles of utility and highway infrastructure. It also damaged another 71 houses and 10 outbuildings. Atmospheric conditions preceding the fire were: maximum temperatures near 105 degrees, minimum relative humidity around 5%, and winds from the northeast 10 to 20 mph during the night and morning hours, switching to southwest 5-10 mph during the afternoon hours. After the fire started, the afternoon southwest winds became more dominate, and the fire generally was wind driven. On October 24, the predominate wind direction returned to northeast and gusted 40 to 70 mph with relative humidities ranging from a minimum of 3% to a maximum of 28%. On October 25, when the northeast winds temporarily relaxed, the fire became plume dominated as the heat column rose into the dry and unstable mid and upper layers. During this time and for about 30 minutes following the collapse of the plume, fire whirls were observed. On October 26, the west flank of the Old Fire and the east flank of the Grand Prix Fire merged in the Cajon Pass, forming a 30 mile long flaming front. The west flank of the Grand Prix Fire that had now burned into Los Angeles County and the Angeles National Forest, was renamed the Padua Fire for administrative purposes. Smoke from these fires forced the closure of air traffic for four hours at Ontario, Los Angeles, Burbank, and Orange County airports. On the 8th day of the fires, the northeast winds finally relaxed. The following day, October 29, the wind flow switched to the southwest, and the air mass moistened rapidly. Through the remaining days of October and into early November, precipitation fell over the fire area, with rainfall averaging from 0.25 to over 1.00 inch, while 3 to 12 inches of snow fell at elevations above 6500 feet. However, the fire though not as active, was not fully contained when the month of October ended.

Source: NOAA Storm Events Database, event_id 5335896. Narrative written by the NWS forecast office that issued the report.