El Nino? Are you there?
Happy (almost) Winter Solstice :) We are now (almost) officially in astronomical winter - and we've been in meteorological winter for 21 days so far. And the question on everyone's mind is:
Where is the rain for California??
El Nino - an anomalous warming of the Eastern equatorial Pacific - is still going strong, with weekly SST anomalies in the NINO3.4 region running about 3 degrees Celsius above average, still on pace to be the strongest* El Nino on record. So, after months of hype and dire warnings, many Californians (especially southern Californians) are left wondering: Where the f*ck is the rain? Well, the short answer is: so far, it's all to the North.
Raining in the Northwest, dry"ish" in California.
Here's a map of total precipitation anomalies (percent % of "normal") for the month of December:
As you can see by all those blues and purples in Oregon - it's been raining, and it's been raining a LOT. Unfortunately for California, all of this copious water falling from the sky hasn't made it south (as evidenced by all the oranges and reds). Yet.
A cumulative time series of total rainfall in California so far this rainy season (taken from @ZLabe on twitter) shows California running well behind the other 5 "strong" El Ninos for which we have reliable data:
The climate reasons for a lot of rainfall up North vs. no rainfall here in California so far this El Nino-year are, as yet, undetermined. During a strong El Nino the jet stream 'usually' shifts southward, bringing with it an active storm track. This year, the storm track has certainly been active, but the jet has not shifted southward. It is always dangerous to use such few data points (only 2-5 strong El Nino's) to try and forecast large-scale climate phenomena, as this year has shown. Whether it will rain like all indications have said it would, remains to be seen. I won't lie - I am getting a little worried.
However, all hope is not lost.
First up: some rain this week for CA
First and foremost, it looks like the rain (for this week at least) may finally be shifting southward. Los Angeles seems to be largely spared from the action, but a 1/4" on Saturday followed by another 1/4" tomorrow is certainly welcome. Further north, however, zonal WNW flow and a relatively strong jet is driving some significant rain and snow into NorCal and the Sierra Nevada mountain range (where it is needed the most). Here is a hi-resolution model estimate of the total rainfall the state can expect to receive between 10am this Monday (Dec 21, today) morning through 10pm Tuesday (Dec 22) evening:
Today and tomorrow: We may be looking at 3-6" rain equivalent in the high Sierras, with 1-2" near the Bay and 0.1-0.5" here in the Southland.
For Los Angeles: expect light showers to begin sometime late Monday evening/Tuesday morning and persist through Tuesday. Additionally: Gusty winds, especially in the deserts may begin later Tuesday as the flow turns less westerly and more northerly.
However, next week (December 28-January 4), things are going to dry out again, as this simulation from the longer-range CFS model suggests (yellows indicate below-normal rainfall):
A pattern change in mid-January?
With December coming to a close on a relatively ho-hum dryish note, the longer-range climate models are starting to suggest that the big "PATTERN CHANGE" moment is going to come in mid-January, and persist through March.
Here, again, is the CFS weekly rain anomaly forecast for the week of January 11, showing a shift to slightly above-normal precipitation:
But it doesn't end there. The CFS forecasts this pattern to ramp up through February and March, with both months likely to have well-above normal rainfall:
It's a long way to go before we close the books on this "El Nino Winter". If the models are any indication - we may yet see the deluge we were promised.
As usual, stay tuned!