WeatherWhys Blog

Final phase of 'sandwich season' underway

Final phase of 'sandwich season' underway

You win some, you lose some. This past weekend’s weather had been expected to be rather wet on Saturday with thunderstorms and low snow levels. In fact, we only received .09” total in Bakersfield and Saturday morning was beautiful. Passes were never shut down. Major impact from the strong storm system hit generally north and south of Kern County. But rain and snow that did affect the state was indication of the third and final phase of what I have called our “sandwich season”.

Saturday was the 29th rain day of the 2010-11 water year, but only the 6th rain day since January 1st. Normal by this point would be 25 rain days. A “rain day” is a calendar day in which at least .01” of rain (measurable) is observed and recorded. Saturday and Sunday turned out to be very cool with sharply below normal daytime temperatures. On Sunday the high was only 54, 2 degrees above the record low maximum for that date. It has been particularly cool of late statewide. San Francisco set a low temperature record this morning at 37 degrees. But what I’ve noticed is a very cool bias setting up for the remainder of February into early March. Rain and snow are forecast to follow suit with the presence of low pressure troughs along the west coast. Computer models have been insistent for about 4 days now that this coming weekend will set records for cold weather. Deep polar low pressure is predicted to sweep down and cut off over California Friday and Saturday. There has even been talk among some meteorologists that snow could fall all the way to sea level. Indeed, if the computer models verify and reality plays out accordingly, then that might happen. Measurable snow has fallen in the Bakersfield area as late as March 8th (1974- 1.5”), with trace amounts as late as March 29th (1998). However reality does not always follow the computer playbook, as was witnessed this past Friday and Saturday.

Coming on the heels of a 6 week dry period in the middle of our rainy season, we are now set for about a 3 week period of above normal precipitation. As mentioned in previous blogs, Kern County had already received its annual allotment of rain (water year) by the end of December, which was the earliest on record. And as this chilly and wet scenario takes shape, I have seen some initial changes in the eastern Pacific sea surface temperature. The La Nina episode we’ve experienced since last summer is showing the first signs of reversing. Temperature anomalies are switching from cooler than normal to warmer in just the past 2 weeks off the coast of Ecuador and Peru. Computer projections concur that La Nina is going to end by May and June, but hold to a neutral state rather than pushing back to warmer than normal El Nino conditions. How will this affect our weather on the west coast? Probably with a tendency to a return to climatological norms by mid to late spring. Of course, this has been anything but a typical “La Nina winter”. It should have been warm and dry throughout the period from November to March, if past La Nina’s were any guide. It wasn’t- and the final phase should be atypical as well. Long range climate models are painting spring and summer 2011 as dry and warm to hot. Bulls eyes of strong odds it will be hotter than usual are centered over Arizona and not central California for this summer. But Pacific sea surface temperatures are trending to argue for warmer weather to sprout by the end of March into April ending the rainy season perhaps a bit earlier than usual.

I will add that this has been a very uncommon winter, and even past 18 months. Weather seems to be getting harder to forecast with more extremes. For what it’s worth, the new solar cycle number 24 is coming into maturity with impressive flares and geomagnetic storms we haven’t seen for many years. Solar cycles have been recorded and numbered since 1755.  Perhaps terrestrial weather will be affected in some measure by the new awakening of our parent star. A connection between solar activity and weather has been made by many scientists and climatologists ranging from heat budget issues to favorability of long wave jet stream positions dictated by shifts in geomagnetism. A lot of research remains to be done on that connection, but we can only wait to see what develops in the summer ahead as the sun expresses itself more boldly