WeatherWhys Blog

Dry weather persists into spring

Dry weather persists into spring
A tractor drives across a dry field in Kern County. (File photo)

January has ended drier than normal, missing the mark by .72" and adding to our growing hydrological concerns. Upstream weather systems seem to keep avoiding central and southern California as February dawns, typically the wettest month of the year.

La Nina persists in the equatorial Pacific. The latest computer model predictions for sea surface temperature anomalies keep the water cooler than it should be, with a peak of this La Nina episode expected either in March or April. Thereafter, sea temperatures will rise a bit and La Nina 2010-12 should end. But it probably won't be in time for Kern County. Although there have been a handful of rainy periods this water year (beginning last July), they have been few and far between. A little over a week ago, during a 3-day period, Bakersfield picked up .44". Before that we endured a 61-day period of rainlessness. December was cold and dry. Janaury has been mild and dry. With the assurance of La Nina continuing, it appears only token amounts of rainfall and snow in the mountains can be expected.

It is understood that the effects of La Nina bring about drier than normal conditions for the southern tier of states. Meantime, the northern tier see slightly above normal precipitation. Rainfall patterns during "El Nino" are exactly opposite. Typical La Nina weather is precisely what has happened. Texas has been devastated by the exceptionally dry weather with widespread wildfires this past summer- all due to an historically dry summer. At the same time, Texas suffered through one of the hottest summers on record, much hotter than a average Bakersfield summer (plus they have humidity).

The current La Nina, which is indicated by cooler than normal water temperature, has really come in two installments. Our first bout with La Nina was late in 2010 as the diagnosis was coming in of chilly Pacific water in the equatorial regions. But a very unusual situation developed with the Arctic Oscillation, another cyclic teleconnection that affects Pacific jet stream patterns. Instead of dry conditions, we saw the wettest month ever in Bakersfield with nearly a year's worth of moisture from the sky in December 2010. Records go back to 1889. But this highly unlikely scenario has not played out 2 years in a row. We can be happy that the rains did fall 13 months ago. They have boosted our water table and reservoirs, possibly preventing a more dire situation today.

My forecast for February is more below normal precipitation, following the track of December and January. I expect and early start to Spring. According to the newest 30-year climatological averages, February is the wettest month at 1.24" normally. The previous climatology in use through last year placed March as the wettest month. In either case, I predict residents of the south valley will be hoping for rain with each weather system that comes through. And while there will be rain (it won't be like summer, without a drop), I suspect rain totals will fall short in both February and March. April may bring a surprise, but the abnormally dry conditions should persist. Therefore, a drought is likely to develop this spring in much of California.