MONTHLY WEATHER SUMMARY
By Bill Mork
California State Climatologist, California Department of Water Resources
January 2005

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January 2005 had near normal temperatures in much of the State except for below normal temperatures in the Northeast Interior and above normal temperatures in portions of the Central Coast and Southeast Desert. The deep snow cover in the Sierra and east slope produced unusually effective radiational cooling with the average temperature at Bridgeport of 15.3 degrees about 9 degrees below normal for the month; this was the coldest January since records began in 1958. Other chilly locations in the north include Susanville 2 SW with an average temperature of 24.5 degrees, 6.3 degrees below normal, and Portola with an average temperature of 24.7degrees, 4.4 degrees below normal. Persistent snow cover also produced a cold January in the mountains of Southern California at Mount Wilson with an average temperature of 38.5 degrees, 5.9 degrees below normal, and at Big Bear Lake with an average temperature of 29.8 degrees, 4.1 degrees below normal. On the plus side, average January temperatures were about 3 degrees above normal at Lancaster, Morro Bay, and Needles.

Like the previous month, January 2005 precipitation was especially heavy in the South Coast and Southeast Desert regions where most locations were over twice normal for the month. The largest multiples were at Big Bear Lake with 18.38 inches, 448 percent of normal, Bishop with 2.90 inches, 430 percent of normal, and Blythe with 1.40 inches, 404 percent of normal. The first 11 days of the month were very stormy up and down the state with very heavy rain in the Southland and very heavy snow in the Sierra. Sierra snowfall totals were commonly 7 to 10 feet, and locally 15 feet, during this period. Some of the larger Sierra precipitation totals for January include 18.64 inches at Grant Grove, 226 percent of normal, 16.05 inches at Grass Valley, 163 percent of normal, 12.74 inches at Lodgepole, 148 percent of normal, and 10.99 inches at Yosemite, 163 percent of normal.

All of the North Coast and portions of the Sacramento drainage had below normal precipitation in January as a strong ridge of high pressure helped shield the Pacific Northwest and adjacent areas of Northern California from the very wet storms impacting much of Southern and Central California. Some of the drier locations in January include Yreka with 0.98 inches, 31 percent of normal, and Adin Ranger Station with 0.78 inches, 40 percent of normal. The Northern Sierra 8-Station Precipitation Index added 8.3 inches in January, 92 percent of average for the month. The Central Sierra Snow Laboratory at Donner Summit measured 93.3 inches on snow in the big Sierra snowstorm of December 27 - January 3.

One of the deepest surface low pressure areas in recent years passed across Northern California on January 7 with sea level surface pressure as low as 29.22 inches at Redding and at Sacramento International Airport. The Delta was on alert for high tides from the combination of peak seasonal tides, low surface pressure, and gusty west winds to over 40 miles per hour. Fortunately, there were very few problems arising from this potential lethal combination of events. Some impressive 12-hour precipitation totals on January 7 include 5.70 inches at Mining Ridge (Santa Lucia Range), 4.32 inches at Three Peaks (Santa Lucia Range), and 3.16 inches at Chilkoot Meadow (San Joaquin basin).

Interaction between a polar jet stream and strong flow of subtropical air set the stage for a prolonged period of heavy precipitation in the Southland January 7 - 11. There were millions of dollars of flood and storm-related damage throughout Southern California. The storms caused a tragic loss of life, including 10 deaths from a landslide into homes in the small coastal town of La Conchita in Ventura County. Some of the problems here concerned the previous very wet period with as much as 24.05 inches at Old Man Mountain in Ventura County December 26 - January 5. Some of the largest storm totals for January 7 - 11 include 31.94 inches at Opids Camp (Los Angeles County), 27.99 inches at Nordhoff Ridge (Ventura County), 24.64 inches at San Marcos Pass (Santa Barbara County), 22.68 inches at San Sevaine (San Bernardino County), and 12.67 inches at Palomar Mountain (San Diego County). The total rainfall of 16.63 inches in downtown Los Angeles December 27 - January 10 not only exceeded the annual average of 15.14 inches but is the largest 15-day total at that location since records began in 1873; it also represents a 100-year return for that period. At the end of January there was an estimated 5 to 7 feet of snow on the ground at Mount Pinos in Ventura County. For an outstanding summary of the Southern California heavy rain event, see the following link from the National Weather Service/California-Nevada River Forecast Center. Thanks to Mike Ekern and Dan Kozlowski who did the bulk of this valuable piece of work: http://www.wrh.noaa.gov/cnrfc/jan2005storms.php Page last updated 2/14/05.