It’s no longer a question of 100% drought coverage for the stricken state of California. That barrier was crossed months ago. Today, it’s how severe that drought coverage has become. And in a state that is sitting just east of what appears to be a years-long impenetrable barrier of blocking high pressure systems, the situation just grows worse and worse.
(California drought map as of July 15, 2014. Areas in orange indicate severe drought, red indicates extreme drought, and brick indicates exceptional drought. Image source: US Drought Monitor)
For Californians now used to watching storm systems veer far to the north, carrying their precious load of moisture away from the state, the water scarcity situation grew more dire last week as nearly 82 percent of the state slipped into extreme and exceptional drought. These two aridity ratings are the highest levels provided by the US drought monitor. The other 18% of the state not covered by these two extremes merely sweltered under severe drought conditions.
To the east and north, other states quietly slipped into total or near total drought coverage as well. Nevada shows 100 percent drought coverage with Arizona, New Mexico, Utah and Oregon not far behind at 90% + coverage.
It’s a situation that will continue to deepen so long as a climate-change induced long-term blocking pattern remains in place. And as of mid summer, there appears to be little to over-ride a freakishly persistent weather pattern that has now lasted into its second year.
Impacts for California Deepen
Throughout the state, signs of aridity abound. Hydroelectric power supplies are in jeopardy, cities are hiring water police to ensure restrictions on use are enforced, the state’s agriculture has lost more than 2.2 billion dollars so far this year, and drilling into the limited supply of ground water has reached a record pace.
Snow pack stores in the state’s Sierra Nevada Mountain range are long since melted. Exposed glaciers are now dissipating at record rates with some glaciers seeing 70 degree (F) temperatures on their lofty perches atop 12,000 foot high mountains. Overall, current rates of glacier loss, if sustained, will render the entire Sierra Nevada Range in California ice-free within just 60 years, according to recent estimates.
Recent satellite imagery from NASA vividly shows this ominous loss of snow pack over the past three years in which the powerful and persistent west coast blocking pattern increasingly dominated:
(Top frame: California’s Sierra Nevada Mountain Range as of June 24, 2014 showing zero snow pack coverage. Bottom frame: same region of California showing much more widespread snow pack during early July of 2011. Image source: NASA’s Earth Observatory)
Note that as of June 24 of 2014 the Sierra Nevada showed no snow coverage in the satellite picture. This compares to recent years during the 2000s and 2010s when snow pack, though greatly diminished from past decades, typically remained on some peaks throughout the summer. Now all regions are devoid of white, cooling, water-providing snow and even the glaciers have taken on a dirty gray and brown pallor.
Human-caused Climate Change’s Role in the California Drought
Central to the story of the years-long loss of California rainfall is a large, high amplitude ridge in the Jet Stream that has tended to dominate over the US and Canadian West Coast and a broad section of the Northeastern Pacific. This ridge has involved a powerful south to north flow of air up over the Northeastern Pacific and North American West Coast. This flood of air often invaded the Arctic before swooping down to deliver cooler air to the Eastern United States even as the US West Coast sweltered and dried out.
This high amplitude ridge in the Jet Stream is thought to have been facilitated by a general loss of snow and sea ice cover that has only intensified since 2007. For over the past seven years, not one day has seen average sea ice coverage in the Arctic with typical sea ice extent and area values ranging between 20 and 50 percent below levels seen during the late 1970s and early 1980s. Such a major loss of ice coverage is thought to be pulling the Jet Stream north even as it makes it more wavy. These large waves, called Rossby Wave patterns, tend to get stuck, as has been the case with the Pacific Ocean ridge. This sticking weather pattern has lead to hot and dry conditions persisting over California for more than two years now.
El Nino Strong Enough to Break the Block Increasingly In Doubt
Earlier this year, a major warming event in the surface and subsurface waters of the Equatorial Pacific raised the possibility of a potential strong El Nino later this year. But atmospheric conditions have continued to remain unfavorable for strong El Nino formation. Ironically, the very same powerful high pressure systems enforcing heat and drought over the US West may also be strengthening the equatorial trade winds and inhibiting El Nino formation.
(The strong Kelvin Wave that formed this winter and spring has now delivered most of its heat to the surface, aiding in the record global temperatures of May and June. Atmospheric feedback reinforcing this powerful Kelvin Wave has been sporadic at best, calling into doubt the potential for El Nino formation. A second warm, down-welling wave appears to be forming between 180 and 160 East Longitude. If this second wave appears it may only be enough to establish a weak to moderate El Nino. If it does not, the prospects for El Nino may fade. This is bad news for those hoping for drought relief in California but, perhaps, short-term good news for a globe already reeling under the impacts of human-caused climate change as record atmospheric temperatures, globally, may not be so extreme for 2014. Image source: Climate Prediction Center.)
A strong El Nino may have broken the blocking pattern and delivered an epic surge of moisture to the US West Coast (one that may well have set off extraordinarily powerful storms for the region). But now, NOAA only forecasts a weak-to-moderate event and the potential exists that no El Nino will form at all.
This is bad news for Californians suffering under one of the worst droughts ever recorded for the state. It raises the potential that the West Coast blocking pattern will remain in place for another year or more. And with highs continuing to form and deepen off the US West Coast, as the potential for a strong El Nino fades, there appears to be little hope for relief for an already hard-hit area.