High Wind — San Francisco County, California

2002-12-15 to 2002-12-16 · San Francisco County, California

Wider weather episode

December turned out to be one of the wettest on record at many locations throughout theCWA. There were three primary episodes of precipitation in December, the first a two-day storm on the 9th and 10th. With less than an inch and a half accumulation at any one location over the period, flooding problems were not an issue. However, the rainfall totals helped to further saturate the soil. The next and by far most serious storm episode begin on the 13th of the month and lasted on and off through the 21st. A very strong and moist jet stream developed across the Pacific Ocean and brought a series of storms into California. Wave after wave of locally heavy rain pounded the north bay counties for days. Flooding became a serious issue, not just for urban and small stream flooding, but for mainstem flooding as well. Flood warnings were issued for the Russian and Napa rivers and the forecast points along these rivers reached flood stage on the 16th and 17th of the month. With a flood stage of 19 feet, the Healdsburg gauge on the Russian River crested at 19.56 feet. With a flood stage of 32 feet, the Guerneville gauge on the Russian River crested at 33.57 feet. With a flood stage of 13 feet, the St. Helena gauge on the Napa River crested at 15.47 feet. With a flood stage of 25 feet, the Napa gauge on the Napa River crested at 26.44 feet. Most of the mainstem flooding was minor in nature but there were areas of moderate flooding, mostly agricultural land. The last storm episode occurred from the 28th to the 31st. These storms appeared to have the development to create serious flooding problems and because of that flood warnings were issued for the mainstems of the Russian and Napa rivers. The jet stream that set up actually drove these storms further north than expected and the possible flooding over the north bay counties never materialized as serious as believed. A good 2 to 4 inches of rain did fall over the area during that time with the most significant amounts over the coastal mountains. Urban and small stream flooding did occur and there was great concern for possible mudslides due to the saturation of the soil. Historically, December 2002 became the 6th wettest in downtown San Francisco, our most well known location, since records began in 1849. The total of 12.03 inches was 378% of normal and accounted for 54% of the total seasonal rainfall for that location. Across the HSA at the end of December seasonal rainfall totals averaged 150 to 200 percent of normal for San Francisco and the north bay, and 125 to 175 percent of normal for the south bay and Monterey/San Benito counties.Some 24 hour rain falls are as follows:DEC 13-18/2002 Storm Total 4pm to 4pmLocation 12/13 12/14 12/15 12/16San Francicso Bay AreaRichmond 2 1.9 0.51 1.63Concord 0.9 0.5 0.45 0.85Fremont 0.39 0.97 0.22 1.14Kentfield 5.5 4.17 0.91 2.26Livermore 0.38 0.94 0.56 2.66San Rafael 4.51 2.98 1.16 2.72Moffett Field 0.34 1.01 0.73 1.36Napa 1.8 2.7 0.55 2.27Oakland Musm 2.69 2.09 0.19 2.04Oakland AP 1.17 1.88 0.2 1.27Pacifica 2.11 2.55 0.17 2.05Redwood City 1.35 2.58 0.34 1.94San Jose AP 0.15 1.08 0.58 1.08San Jose 0.15 0.72 0.63 1.05SFO 1.04 1.6 0.22 2.23San Francisco DT 1.14 1.89 0.29 1.88Santa Rosa 2.15 3.12 0.85 1.98Monterey Bay AreaBig Sur Station 0.89 2.06 1.01 2.52Carmel Valley 0.09 0.43 0.81 1.73Gilroy 0.36 0.31 0.98 1.95Hollister 0.05 0.38 0.44 1.94King City 0.11 0.09 0.26 1.14Mntry NWSFO 0.15 0.38 0.7 1.14Morgan Hill T 1.22 0.87 2.75Salinas 0.24 0.64 0.09 0.68Santa Cruz 2.88 3.59 0.46 1.24Watsonville 1.45 2.35 0.6 1.1

Source: NOAA Storm Events Database, event_id 5326658. Narrative written by the NWS forecast office that issued the report.