Our weather fortunes have been swinging dramatically of late. This past week was a remarkable one with the most impressive 4-day temperature tumble I’ve ever seen in the summer. Afternoon highs in Bakersfield went from 111 degrees on Wednesday (a record and the latest hottest day of the year this millennium) to only 80 on Sunday, 31 degrees cooler in only 4 days.
This type of wholesale swing in weather from one extreme to another occasionally happens in the cool season. But it is extremely rare in the summertime. Climatologists often characterize a climate by comparing “daily” temperature variation to “seasonal” variation. For example, tropical climates see very little month to month change in temperature- say from April to November. Instead places like Hawaii or Panama see greater variation from morning to afternoon of any particular day than they do seasonally. Of course, that is not the case if you live at the mid-latitudes, like in Kansas or California where the range in temperature from January to July is much greater than from any morning to afternoon. But in the summer, Kern County takes on more of a tropical character with only minimal day to day changes. It is usually either hot or very hot. In the winter, on the other hand, we can experience very mild days followed by a cold front that presents drastic shifts in temperature. But what we’ve seen recently is highly unusual for the summer in Kern County.
This taste of autumn will be short lived. While some snow actually fell in the Sierra above 9,000 feet we will once again see near triple digit heat before this work week is up. Another cool down is likely toward the end of the Labor Day weekend, but not as stunning as our August roller coaster ride. It appears that the extreme heat is probably over. Hence, I have issued my “no more 110s” forecast. That will be followed by my “no more 100s” and my “no more 90s” forecast- all at the appropriate times.
Not only has the temperature been in yo-yo mode, but so has the tropical Pacific Ocean. After a beneficial El Nino year that gave us our much needed rainfall to mitigate the drought that had been plaguing California, it is now apparent that La Nina is blossoming into full form. Previously warmer than normal sea surface temperatures west of Peru are now cooler than normal. This is the definition of a “La Nina” episode. Ramifications for California and all the western U.S. are generally the complete opposite of what happens during an El Nino. So rather than above normal precipitation, it is looking more and more likely that this coming winter will be an anemic rainy season. My forecast is for near to slightly below average rainfall in the state. Temperatures should be extremely variable, on average a bit higher than normal, featuring one or two cold snaps with widespread freezing temperatures. Sea temperatures in the eastern Pacific are near to a bit below normal. But sea temperatures in the Atlantic and Gulf of Mexico are running very high again- just like in 2005. With mid to upper 80 degree water in the Gulf and tropical Atlantic, I am expecting a very active Atlantic hurricane season with several memorable hurricanes to watch in September and October. A few tropical systems may menace the U.S. coastline.
To be sure we are in for more big swings through the autumn. Hopefully, rains will come with the changes and not just windy duststorms. Additionally, we are only now entering the heart of the wildfire season. Santa Ana winds are destined to affect southern California and Kern County. But at least the extreme heat for 2010 is mostly over. Only 22 times has Bakersfield officially hit 100 or higher. In a normal year that happens 38 times. By this week it should have occurred 34 times. That puts our cooler than normal summer of 2010 into perspective. Get ready for an active autumn and winter season just ahead.