California Hopes for a Wet Winter
The hype is on for a big El Nino-fueled rainy season this coming winter and spring in California. The latest data indicates that the developing (already in progress) El Nino event should become just as strong (perhaps even stronger) than the record setters of 1982-1983 and 1997-1998. Here’s a look at how those seasons panned out for the state precipitation-wise and where precipitation totals for this year and season now stand.Precipitation in California as of mid-October 2015
This calendar year and precipitation season (which began on July 1st) has consisted of two different regional narratives. The first has been a much wetter than normal start to the season for southern California. In fact, for San Diego precipitation has been at near record levels since the beginning of the rainy season on July 1st.Accumulated precipitation curves for San Diego since the beginning of the rainy season July 1st. Two record-breaking rain events (in part due to moisture entrained from dissipated tropical storms) has propelled San Diego’s July 1st to date (Oct. 12th) precipitation up to 3.37”, just shy of the record amount of 3.76” set during the same time period in 1939 (another year that saw tropical storm-related precipitation soak the city). Rainfall is now normal for the calendar year in the city thanks to this summer’s storms.
Graph from NOW data.
Los Angels has also seen much above normal rainfall since July 1st with a 3.22” total compared to a normal of just .46” for the period. Meanwhile, precipitation has been running much below normal for central and northern California, both for the calendar year and the season to date. In fact, for San Francisco, it has so far been the driest calendar year on record as of October 12th with a paltry 3.25” of rainfall since January 1st, drier than Las Vegas or Phoenix and falling short of the previous driest year-to-date experienced just two years ago when 3.94” had accumulated as of October 12, 2013. 2013 went on to become the city’s driest calendar year on record with an annual total of just 5.59”.Accumulated precipitation curves for San Francisco since January 1st. The label at the bottom of this NOW graphic is wrong. 2015 has seen just 3.25” of precipitation since January 1st whereas 2013 saw 3.94” accumulate by this same time that year. Since the current rainy season began on July 1st, San Francisco has picked up .20” of drizzle and rainfall compared to a normal of .50” by this date (Oct. 12th).
Below are two tables of how the current precipitation season stands (July 1st to date top table) and how the calendar year has fared (January 1st to date bottom table). I’ll be the first to admit that these figures are not too meaningful since the rainy season normally doesn’t get underway until November, so just a FYI.California Precipitation During the Big El Nino Seasons of 1982-83 and 1997-98
Should the current El Nino season result in precipitation amounts similar to those of the seasons of 1982-83 and 1997-98 California may expect some record amounts of rain to fall. Some of the sites that saw all-time record seasonal precipitation occur in 1982-83 and 1997-98 are listed below with their respective precipitation POR’s:Season of 1982-83 all-time seasonal records set
FRESNO: 23.57” (POR 1881-)
SACRAMENTO: 37.49” (POR 1850-)Season of 1997-98 all-time seasonal records set
BAKERSFIELD: 14.66” (POR 1889-)
FORT BRAGG: 79.13” (POR 1901-)
MONTEREY: 47.12” (POR 1847-)
MT. SHASTA CITY: 75.89” (POR 1889-formerly known as Sisson)
SANTA BARBARA: 46.99” (POR 1864-)
SANTA MARIA: 32.56” (POR 1885-)
Neither season resulted in seasonal precipitation records for the state’s major cities of Los Angeles, San Diego, or San Francisco, but nevertheless were very wet. Los Angeles
(downtown site) picked up 31.25” in 1982-83 and 31.01” in 1997-98. Normal is 14.93” and the record was 38.18” set in 1883-84. San Diego
received 18.26” in 1982-83 and 17.78” in 1997-98. Normal is 10.33” and the record was 25.97” in 1883-84. San Francisco
(downtown site) picked up 38.17” in 1982-83 and 47.22” in 1997-98. Normal is 23.65” and the record was 49.27” in 1861-62. The 1997-98 season was the city’s 2nd wettest on record.
In both of the earlier cases cited above, the heaviest of the precipitation that fell occurred in January and February. February 1998 was particularly anomalous ranking as the wettest February on record for the state as a whole (average state-wide precipitation being 11.50”). All-time monthly precipitation records (for any month) were set at Los Angles (20.51”) and Monterey (14.26”) and it was the wettest February on record for many other sites (including San Francisco with 14.89”). Below is a chart of the distribution of the rainfall month-by-month for San Francisco in both 1982-83 and 1997-98:Monthly precipitation in San Francisco during the El Nino events of 1982-83 and 1997-98 compared to average for such.
Graphic courtesy of the San Francisco Chronicle based on data supplied by Jan Null at Golden Gate Weather Services.
Of course, there is no guarantee that this coming winter will turn out as wet as those of 1982-83 and 1997-98 and other factors aside from El Nino will play an important role. It should be noted, of course, that even if record or near-record precipitation such as that in the previous two cases does occur it is unlikely to end the current drought affecting the state. Of critical importance is how much of the precipitation falls as snow in the Sierra Nevada. If the storms are warm and the rain falls in just a series of intense storms much of the benefit will be lost to run-off into the Pacific Ocean.
The best source for keeping track of how this year’s El Nino will impact California is Daniel Swain’s California Weather Blog.
Christopher C. Burt