Yes, we all are quite aware of the incredible rainfall that has come to Kern County this month. And I’m sure you know it has broken records. But perhaps you don’t know the sheer magnitude of this weather anomaly.
I explained in a previous blog the confluence of several important weather features that have coincided recently to bring us this jackpot of rainfall. But let me tell you of the large scale entities that had to be overcome in order for the rain to happen the way it did. First of all, a La Nina event has been brewing in the equatorial Pacific of late. Currently it is a moderate to strong episode and that usually means drier than average weather for the state of California. This mega-factor was trumped by a large blocking ridge of high pressure over northern Canada and the timely appearance of a Madden-Julian Oscillation (MJO) zone of convection northwest of Hawaii. The strong “La Nina” polar jet stream was suppressed south just in time to pick up MJO tropical moisture and sling it into central California for 6 days in a row. Secondly, Bakersfield’s rainy season is only getting started in December. It peaks in February and March with a combined average of 2.62” of rain and 14 rain-days in those two months. More than 40% of the entire year’s normal rainfall occurs from Groundhog Day through the end of March. The reasoning behind that goes back to positioning of the jet stream and when it is most likely to impact the central California coastline. In fact, the south valley’s climatologically coolest day of the year is December 27th, earlier than most every other city in America. Once the rainy season really kicks in, rainfall from the Pacific turns out to be a warming influence- mitigating the dry and cool weather from November and December. Most locales in the nation have a climatology “coolest” date in mid to late January, but Bakersfield is different in that regard.
Since the bulk of our rainy season is normally later, records might be considered easier to beat in December. For example, the all-time record daily rainfall for the month (before this year) was 1.02” in 1931 and 1936. Those totals were slashed on the 18th and 19th of December this year. The weekend before Christmas was more typical of Seattle. Those two days saw flooding rains totaling 2.90” in Bakersfield- more rain that normally falls in the two wettest months combined. Our previous wettest December gauged 2.98”. This month hit 5.37” by Christmas Day.
It was great imagery that Christmas 2010 marked two huge records that are unmatched in our time. First was the establishment of December 2010 as the wettest month of all time in Bakersfield (records go back to 1889), and secondly, enough rain was accumulated for the entire water year tally to be exceeded (the water year runs from July 1st to June 30th the next calendar year). Regarding the first record, the previous mark for wettest month was 5.36” in February 1998. That was a particularly virile El Nino year. That month recorded 18 rain-days and the 1997-98 water year is still the greatest ever at 14.73”. The calendar year 1998 was also greatest ever at 13.32”. It should be noted that through Christmas Day, Bakersfield’s 2010 calendar year total was 12.05”, currently number 2 for all-time. Records go back 122 years, making this December number one out of 1464 months- truly notable.
Secondly, this is the earliest our annual water year total has been reached- by far. The second earliest achievement of the water year total was in late January 1933. The third earliest was February 3, 1998 in the extremely wet El Nino year we’ve been talking about. So as the next cold storm approaches a few more potential statistical delicacies might be tempting meteorologists across the area. One is to somehow squeeze out 1.28” of rain before midnight Friday and set a new calendar year record. The other might be to receive 1.12” of rain bringing the monthly total to 6.49” so we can say an entire year’s worth of rain fell in one month. As far as the water year total goes- well, we’ve got until June 30th to set more records. Currently we sit at 6.80” (awaiting the upcoming storm). That means another 7.93” would tie the all-time record of 14.73” and a hundredth more would break it.
Might that happen? It’s hard to say. This has been a very tough year for short range forecasting, much less long range. All the fundamentals had pointed to a slightly drier than average year only a few weeks ago. And then- wham! The stars aligned and out popped the Pineapple Express. One could think it should be easy to see more rain and set more records. But I’ve noticed a trend toward just the opposite. If the La Nina dynamics snap back into place, as they should at some point in the near future, then my “sandwich season” theory would come to pass. The faucet would be turned off and Washington State might resume being on the receiving end of a La Nina storm track. If you were to ask me today what I thought the traditionally wettest part of the year (Feb-Mar) should look like, I would be forced to side with the percentages- that say “drier than normal”. But once again, with the panoply of strange weather events lately (bitter western cold snap in November, record hot weather in late September and again in early November, eastern blizzard, etc) I speak with a bit less confidence than in seasons past.
Someone commented on my last posting that I had failed to mention the impact of Global Warming on all of this, saying I didn’t believe in it. Indeed, I have always represented that the earth is gradually getting warmer. I have concluded, however, that humanity is unable to change what is naturally happening despite our misguided efforts to command the skies. And to that point, I expect the world will continue slowly warming in response to solar stimulation. As the oceans warm they release more carbon dioxide from a dissolved state in the waters to free gas in the atmosphere, hence, the increased CO2 levels. Warming causes CO2 elevation, not the other way around.
And finally, weather patterns may become a bit harder to predict owing to greater variation. Is this an example of that? Perhaps yes. If so, get those red pencils out ready to strike the old records and write in new ones. After all, records are made to be broken.