Published: September 24,2014
The crippling multi-year drought in California and other parts of the West is drying up wells, parching fields, and even allowing mountains to rise like an uncoiled spring.
(MORE: California Wells Running Dry | Before/After Lake Photos)
Almost 60 percent of California is categorized in exceptional drought, the worst category of drought in the weekly drought monitor analysis (see map below). Reservoir levels in the Golden State are well below average levels for late September.
However, an impressive Pacific storm by late September standards, shown in the satellite image at right, will wring out significant rainfall in parts of the thirsty West.
Real Rain, At Last!
A sharp dip in the jet stream will lumber slowly into the West over the next few days.Ahead of the attendant cold front, an atmospheric river, a long, narrow plume of deep moisture from the tropics, will be pulled into parts of the West.
Moisture in the atmosphere associated with this storm, known as precipitable water to meteorologists, could be over five standard deviations above late September averages. In English, that means this is a highly-unusually moist storm for this time of year.
Heavier rain began to surge into western Washington, western Oregon and northwest California late Tuesday night, and it will persist through much of Wednesday in southwest Oregon and northwest California before diminishing Thursday.
How much total rain are we expecting?
- Coastal ranges of northwest California, southwest Oregon: 2-5 inches possible
- Northwest California to western Washington lower elevations: Generally 1-2 inches
- Rest of Northern California, Sierra: Generally less than 0.5 inch
- San Joaquin Valley, Southern California: Little or no rain
This rain is mainly good news for existing large fires in far northwest California and western Oregon, but much lighter amounts in the Sierra won't provide much relief for the King Fire near Lake Tahoe.
(INTERACTIVE: Current West Large Fire Locations, Radar)
We say "mainly" good news, because rain falling on burn scars, those areas charred by recent wildfire, may trigger flash flooding and mudslides.
(ALERTS: Calif. Flood Watches/Warnings)
Furthermore, brisk winds ahead of the front may initially lead to rapid fire spread.
Drought Denter?
Yes, runoff triggered by soaking rain from this September storm in far northwest California will raise reservoir levels a tad.However, the key to drought relief in California is not rain, but snow.
Critical to water supply in this part of the country is the buildup of winter snowpack in the mountains, whose meltwater in the spring replenishes reservoirs.
Snowmelt provides up to 75 percent of the West's freshwater supply. The Sierra and, to a lesser degree, Colorado River snowmelt, is crucial for California.
In short, California and the West needs a persistently wet winter, with a combination of significant rain and mountain snow to replenish groundwater and reservoir levels.
Instead of last winter's dominant high pressure ridge blocking storms from sweeping in from the Pacific Ocean, water resource managers are hoping for a parade of Pacific storms guided by a more frequent west-to-east flow from the Pacific Ocean.
(INFOGRAPHIC: The Drought In Numbers)
The heart of California's wet season runs from November through March. In that five-month period, Tahoe City, California, picks up 97 percent of its average seasonal snow and San Francisco measures 85 percent of its average annual rain.
Defined by sunshine, suffering an historic drought, Californians will be rooting hard for rain and snow this winter.
No comments:
Post a Comment