Rain Snow on the Drought

October 16, 2015

d7dfe440-98af-11e3-a20a-4197883a2af2_calif-terra-nasa-2014Overcast cushioned with a moist-fog here this Friday afternoon on California’s north coast, and precipitation-warm, with rain still expected maybe tonight and into tomorrow.
Forecasts call for just a quick rain patch, however, so small appears gone and dry-again by Sunday, predicted by the NWS to be ‘Mostly Sunny.’

Our drought continues, even though forecasts from the NOAA yesterday indicated good winter rainfall, even up here in the north, where it’s really needed.

(Illustration: NASA satellite image of California’s drought in early 2014, found here).

Yet it’s not the rain that’s the real-crucial important point, the bottom line for drought relief is snow.
From the LA Times this morning:

The new forecast is particularly significant because it shows the increased rain reaching far into Northern California to the mountain ranges and system of reservoirs that provide the state with huge amounts of its water.
Earlier forecasts showed El Niño providing rain mainly to Southern California.
If El Niño acts as it has before, “there will be a number of significant storms that will bring heavy rains. What that brings will be floods and mudslides,” said Mike Halpert, deputy director of the National Weather Service’s Climate Prediction Center.
“We’re more confident we’re going to be seeing El Niño through this winter.”
This prompted officials, who had generally been reluctant to predict El Niño’s effect on the drought, to say they expect the rains will ease the drought conditions but won’t end them.
“If the wettest year were to occur, we still wouldn’t erase the deficit that’s built up in the last four years,” said hydrologist Alan Haynes for the National Oceanic and Atmospheric Administration.

Los Angeles and San Diego have a 60 percent likelihood of a wet winter, according to the latest forecast.
In Silicon Valley, there is more than a 50 percent likelihood of a wet winter.
In far Northern California, the forecast calls for a slightly higher chance of a wet winter over a dry winter.
The forecast for a wet winter now covers the mountains that feed California’s most important reservoirs, Shasta Lake and Lake Oroville.

Ideally, precipitation would fall in Northern California’s mountains as mostly snow, so it can be kept frozen for many months and refill reservoirs at a slow, gentle pace as it melts in the spring and summer.
But in recent years, abnormally hot winters have brought precipitation that has come down there as mostly rain — a big problem because too much rain all at once, even in a drought, will force dam officials to flush out excess water to ensure dams don’t overflow and have enough capacity to keep incoming floodwaters from destroying cities downstream.
Scientists say they don’t know if the northern mountains will see more snow or more rain.
The other big problem is the intensity of this four-year drought.
It will almost certainly take years to catch up and will require years of consistent above-average rains to get there.

Where’s the percentage for us, more than ‘a slightly higher chance‘ bullshit.

Science writer Bob Henson at WunderBlog yesterday detailed the NOAA winter forecast with this note about California:

One important element will be the temperatures that accompany any big winter storms.
If they’re on the warm side — a big problem in recent years — then the snowpack accumulating over the Sierra Nevada could end up disappointingly low.
Regardless, aquifers and ecosystems stand to benefit big time if El Niño produces as expected.

An optimistic uplift, there.

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