It’s December. Do You Know Where Your Rain Is?

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It’s December now in the Bay Area, and if you’re fastidious about your weather expectations, you look out the window and want to see rain. Or at least a little gray. But in the wake of the little wind event of the past couple of days, what I see out there is a sparkling azure sky without a hint of a cloud.

Our climate is mostly dry from sometime in April to sometime in October, mostly wet from October to April, except when it’s not. And when it’s not, we’ve got trouble. Yes, things in the cities are beautiful, and when you turn on the spigot, water from somewhere magically appears. But you know that somewhere–up in the Sierra, out in the Valley–things aren’t so good. There won’t be enough mountain snow to help replenish the reservoirs in the spring. The farmers will want water they cannot get. The fish and wildlife that depend on an abundant flow of water through the Delta, species threatened because for decades they were last in line when people thought about how to spend the water we bank, will suffer. The edge to the anxiety comes from the knowledge that drought happens here, and drought can become a social and political as well as a natural and environmental mess.

Feeling nervous yet? I am. I follow Jan Null, a Bay Area meteorologist. Here’s his climate summary for last month:

November 2011 was a cool and mostly dry month across California. Monthly average maxima anomalies were -1.0 (San Jose) to -3.6 degrees (Los Angeles), while monthly mean anomalies were -0.8 to -2.3 degrees. North of the Tehachapis rainfall was well below normal ranging from 28% of normal (Sacramento) to 69% (Eureka) while Southern California was quite wet with Los Angeles and San Diego at 152% and 309% of normal respectively.

Sometimes, to reassure myself that all will soon be well, I might take a spin through weather and climate sites to see what the professionals are saying about the forecast. That image to the right is a graphic of the Quantitative Precipitation Forecast from the California Nevada River Forecast Center. During a wet period, the map will be a glorious swirl of color–blue and green and yellow, depicting progressively heavier precipitation, and sometimes orange and splashes of red and magenta when it’s really wet (there’s a scale at the top of the map; click on the image for a full-size version). Gray, on the other hand, means dry. No rain in the lowlands. No snow in the uplands. No reassurance.

Next, here’s how one of the meteorologists down in the Bay Area National Weather Service office in Monterey sums up the coming week in the Area Forecast Discussion (using familiar all-caps weather advisory style):

DRY WEATHER LOOKS TO BE IN STORE FOR THE DISTRICT SUNDAY THOUGH NEXT WEEK. HOWEVER…THE MODELS ARE STARTING TO SHOW SOME DIFFERENCES. THE ECMWF KEEPS A STRONG RIDGE ALONG 135W STRETCHING INTO THE GULF OF ALASKA WITH A STRONG SHORTWAVE DIVING DOWN THROUGH THE GREAT BASIN LATE THURSDAY INTO FRIDAY. THIS SCENARIO WOULD BRING ANOTHER BOUT OF GUSTY OFFSHORE WINDS. THE GFS WEAKENS AND FLATTENS THE RIDGE BY THE END OF NEXT WEEK…WITH A SHORTWAVE MOVING INTO THE NORTHERN PLAINS NOT DIVING SHARPLY SOUTHEAST. THIS WOULD NOT BE A WINDY SCENARIO FOR THE DISTRICT. REGARDLESS OF THE MODEL…DRY WEATHER IS IN STORE THROUGH THE END OF THE NEXT WORKWEEK.

Got that? The major question the weather persons are dealing with is whether or not the forecast models indicate another windstorm for the coming week. Chances of rain–none apparent.

The pluviophile now turns eyes to the coming month, even though we’re exiting the realm of forecasting and prediction and entering into one of probabilities and outlooks. But here goes: The National Weather Service Climate Prediction Center says the Bay Area should have “near median” precipitation in the period from eight to 14 days from now (median in this case meaning rainfall along the lines of the “middle 10 years” of the past three decades in terms of rainfall); the northern quarter of California is looking at below-median rainfall during that period. The center’s one-month outlook shows equal chances of above, below, or near median precipitation. That’s because “there were no strong and consistent climate signals” among the forecast models.

And one last stop: Both the most recent U.S. Drought Monitor report and the seasonal outlook, through the end of February, show California drought-free (things look scary in Texas, though).

So where’s the rain? Like that TV show used to say: Out there. Somewhere.

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