Worryingly dry winter to be interrupted by strong weekend storm

With 4 days left in January (our rainiest month here in Los Angeles), an anxious city is still waiting for the "flooding" rains that the "Godzilla" El Niño was supposed to bring. We had a brief taste of some of the aforementioned weather during the first week of January. However, since then, it's been dry, dry dry. In fact, here is a plot of the total accumulated precipitation to date, matched against the accumulated precipitation from the 1997-98 El Niño (grey-blue) and the seasonal "average" (black)

To put a few numbers to the data: To date, downtown Los Angeles has received 3.77" since October 1. In 1997-98, we had received over double that by this point: 7.71". The seasonal average to-date is 6.75". As is obvious to any observer, this El Niño winter has not materialized..... yet.

If you're worried (I'm worried), you can take solace in the fact that, in 1997-98, most of the torrential rains came in February. Indeed, downtown Los Angeles picked up almost 14 inches of rain in February 1998! 

Some help *is* on the way...

This crazy dry weather we're having this week will be (briefly) interrupted by a fairly powerful weekend storm. The models have been pretty consistently in agreement that a wave of energy sneaking in underneath the dome of high-pressure and combining forces with a potent Atmospheric River and screaming upper-level jet stream, to bring a period of moderate to heavy rain on Sunday afternoon. Here is a gif animation of the Atmospheric River I'm talking about:

That river of green is what we call an "Atmospheric River" - anomalously high water vapor content streaming north and west from the tropical Pacific. As you seen in the animation, this river starts impacting Northern California tomorrow and persists through Friday and Saturday - soaking the Sierra in a hearty episode of rain and snow. A bubble of energy sneaks up along the river from the south which drags it southward into SoCal sometime Sunday morning. The combination of a moist atmosphere and a powerful upper-level stream should wring out between 0.75 and 1.5" of rain over most of the Southland Sunday afternoon. Strong southerly flow will favor the South-facing mountain slopes, and some of the more likely foothill areas could see 2"+

And then, just as quickly as it comes, it will go.

As I always do, I'll provide much less hazy details as the event approach.

But, then what? Rain in February, Right???

Well, I guess we'll have to wait and see. Right now, the weather models are suggesting a very dry first week of February. Fingers crossed.

In the meantime, enjoy your taste of rain this weekend.

Mika ToscaComment