(King Fire Complex fanned by strong, hot southwesterly flow on September 23, 2014 — a rising fire danger through Thursday in advance of an approaching Pacific storm system. Image source: LANCE-MODIS.)
A powerful storm system off the US and Canadian Northwest Coasts may deliver much-needed rains to central and northern California by Thursday — but not before pulling warm, dry winds up from the south in advance of the storm’s approach. The heat and winds, expected to reach 15-25 mph later today, will heighten danger for the over 7,400 firefighters already battling the 90,000 acre King Fire.
As of earlier today, the fire was 35% contained after the army of firefighters, aided by a spate of mountain drizzle, tirelessly worked through the weekend to staunch the blaze. But the new in-rush of hot, dry winds today and tomorrow will fan the still energetic wildfire, increasing the threat to more than 21,000 structures ringing the fire’s edge.
Already, ten people have suffered injuries and 32 structures were destroyed even as 2,700 people are currently evacuated from areas most vulnerable to the still-raging fire. Given the influx of more dangerous conditions, fire fighting personnel will be hard pressed to prevent further damage from an already costly and harmful blaze.
(Strong storm approaches the Western US as the ridge and associated blocking high shift eastward. Change in year and half long blocking pattern? Image source: NOAA-GOES.)
Fire Amidst Record Drought
The King Fire erupted in Central and Eastern California during mid September as century scale drought conditions continued to scorch the state. As of today, more than 50% of the state remains under the most extreme drought level with 100 percent of California suffering from some degree of drought.
This past weekend’s light rains did little to help. However, a strengthening storm track in the Pacific is likely to deliver at least some moisture to Northern and Central California by Thursday. A blocking high pressure ridge that has persisted off the US West Coast for more than a year and a half has also shifted — moving inland toward the Central and Western US. This shift appears to be slowly opening the door to some moisture for California.
(University of Maine Jet Stream modeling shows an eastward shift in the year and a half long blocking pattern and associated ridge over Western North America and the Northeastern Pacific. In today’s graphic, the ridge has shifted into the Central US with associated Rossby-Wave type troughs over both the Eastern US and Eastern Pacific. Notably both troughs now host powerful storm systems in the range of 975 mb and lower. Image source: University of Maine.)
An atmospheric pattern more favorable for El Nino development may also be favoring increased precipitation for California. However, it is still too early to determine whether a pattern favoring drought reduction is firmly in place.
Conditions in Context
Under the current rapid and powerfully enhancing regime of human-caused heating of the Earth’s oceans, ice, and atmosphere, we can expect the US West and Southwest to continue to dry as the storm track shifts northward and as rising temperatures bake more and more of the moisture out of the soil. A significant increase in the occurrence of drought in the US Southwest since the 1970s is likely a part of this larger trend, one that will almost certainly worsen as human-caused climate change intensifies.
In addition, an increasing eccentricity in the Jet Stream associated with Northern Hemisphere polar heat amplification has resulted in far more persistent weather patterns. Dome scientific studies have found that these patterns, associated with powerful Rossby-type wave patterns in the Jet Stream, have appeared with increasing frequency since the mid 2000s. As a result, cooler stormier patterns tend to persist in one region while dry, hot conditions have tended to persist in other regions. This new climate regime appears to be enhancing an already amplified drought pattern for the US West even as it has pumped up storm patterns for regions east and north. It is also worth noting that a number of studies have also found a link between major sea ice losses in the Arctic since 2007 and the intensity of the current California drought.