Driest January-February Since 1852 for Northern California
Driest January-February Since 1852 for Northern California
After a wet November and December the past two months have been the driest start to a year since 1852 for most of central and northern California. San Francisco (downtown) has picked up only 1.34” of precipitation since January 1st, its 3rd driest such period on record (since 1849). Normal for the two months is 8.96”.
Sacramento has seen just 1.32” during January-February (normal is 7.66”). San Francisco and Sacramento have the longest precipitation POR’s (periods of record) in the state with data beginning in the fall of 1849 for both cities. San Francisco’s driest Jan-Feb was in 1852 when just .72” was measured. The same year was also Sacramento’s driest with a total of .70” for the two months. Amazingly (given the long POR’s for both sites), the 2nd driest such period was just one year earlier in 1851 when San Francisco picked up 1.26” and Sacramento 1.00”. So this year is now ranked the 3rd driest start to the year for both cities. For other sites in the region without POR’s dating back to 1852, this year ranks as the driest such period. Here are some of the two-month totals (January-February 2013) for other sites in the San Francisco Bay Area and northern California (listed from north to south):
Eureka: 4.33” (normal 12.13”)
Redding: 1.51” (normal 11.47”)
Santa Rosa: 1.19” (normal 13.45”)
Sacramento: 1.32” (normal 7.66”)
San Francisco (downtown): 1.34” (normal 8.96”)
Oakland: .81” (normal 10.15”)
Hayward: .67” (normal 6.77”)
San Jose: .81” (normal 6.18”)
Fresno: 1.47” (normal 4.22”)
Sierra Snow Survey: Driest January-February on Record
These graphs illustrate the results of the latest Sierra snow survey made on February 28th. Graphic by John Blanchard, San Francisco Chronicle, based on data provided by the California Department of Water Resources.
The latest snow survey, made on February 28th, showed that the snowpack in the Sierra had shrunk to just 29” or about 66% of normal (this the average for the entire Sierra mountain range). This is especially remarkable since the snowpack was ahead of normal at the beginning of the year just two short months ago. In the Tahoe area the snowpack shrunk from 134% of normal on January 1st to 67% by March 1st. In the northern and central Sierra it was the driest Jan-Feb since records began in 1926 with an average of just 2.2” of melted precipitation (13% of normal). The previous driest Jan-Feb for this area was 1991 when 4” of precipitation was measured (this according to the California Department of Water Resources). The Sierra snowpack provides about one-third of the water demand for the entire state of California’s on an annual basis.
San Luis Reservoir in California’s central valley is currently only at 69% of average for this date. However, this under capacity is partially related to restricted pumping due to a controversy over the Delta smelt, an endangered fish species that inhabits the Delta marshes west of Sacramento. Photo by John Chacon, California Department of Water Resources.
Still at least two months of the rainy season to go
Fortunately, there is still plenty of time to make up for the current precipitation deficits. A small storm is expected on Tuesday and Wednesday this week with .25-1.5” of rain or its melted equivalent forecast. Following this storm the next week looks dry. However, some of California’s wettest storms on record have occurred in late March and April. Furthermore, excessive rain and snowfall in late November and December have precluded any chance that this wet season will rank as among one of the driest. It has simply been an exceptional mid-season dry spell. Last year at this time the season was running much drier than this year with cumulative precipitation amounts half of where they are this year. Then in mid-March (2012) incredible rainfall struck the state bringing the totals closer to normal, see my blog last April on this historic turn around. Hopefully, we will see a similar event occur later this spring.
Christopher C. Burt
Weather Historian
Reader Comments
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4:59 AM GMT on March 05, 2013
Thanks for this correction Tom! The image was copied from the Cal. Dept. Water Resources home web site and clearly identified in their caption as being San Pedro at 11 a.m today. I see they have since corrected the information to place San Luis now (9 p.m.)!
Here is the maximum and minimum temperature from March 2 to 5 with the difference in brackets:
2nd - 38 16.2 (22)
3rd - 39.1 15.6 (23)
4th - 39 15.6 (23)
5th - 39.2 18.8 (21)
March is the transition month between winter and summer and as per the IMD website, the avg max should be 37.6 and min 21, but I doubt the avg max is correct as we do not see such high temperature even during peak summer months - Apr (avg is 33) and May (avg is 33.3)
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