Tuesday, October 29, 2019

Long-range forecast provides glimmer of hope in wildfire-ravaged California

Updated Oct. 29, 2019 3:38 PM




As wildfires ransack much of California, high wind events have been coming fast and furious. Firefighters are not only battling against the wind-fanned blazes, but dry conditions are also providing plenty of fuel due to dry vegetation.
Break from high winds on the near horizon
The pattern responsible for frequent and strong wind events in California is forecast to end soon.
"Relief from wind is coming for much of the state before the end of this week," AccuWeather Senior Meteorologist Brett Anderson said.
Multiple strong high pressure areas have moved in from the northern Pacific Ocean and settled across the Northwest and Great Basin of the United States in recent weeks, triggering high wind events.
The middle of the autumn is prime time for wild winds and wildfires in California. While this pattern is fairly common, the frequency of these wind events has been higher than average and associated, in part, with the frequency of snowstorms that have hit the Rockies during October.
Since air flows from high pressure to low pressure, in this case from the interior western U.S. to the Pacific Ocean off of California, it gains speed blowing downhill from the Sierra Nevada first and then the Coastal Ranges. However, the air is also squeezed and rushed as it flows through the canyons and passes in the form of Sundowner, Diablo and Santa Ana winds.
It is the high winds along with the dry air, dry brush and urban sprawl that are contributing to the fire conditions being experienced in California.
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"While the dry pattern will continue during the first seven to 10 days of November, the storm track and subsequent track of high-pressure area will shift farther inland," Anderson said.
That shift should translate to fewer strong wind episodes and less frequent wind episodes in general starting on Thursday in Northern California and Friday in Southern California.
When might beneficial rain arrive?
During the second week of November, another pattern change may take place.
"We are fairly confident that a more west to east pattern in the jet stream will develop from the Pacific Ocean and extend into the U.S. before the middle of November," Tyler Roys, AccuWeather long-range meteorologist, said.
What such a pattern would do is allow moisture and storms with rain and high-country snow from the northern Pacific to ride into not only Washington and Oregon, but also at least part of Northern California.
It is possible the first soaking rainstorm will arrive in Northern California between Nov. 10 and 12.
While the amount of rain in Northern California this far out is not set in stone and is subject to the exact track and strength of the storm train, it is possible that northern parts of the state could receive enough rain to inhibit new and possibly extinguish existing wildfires.
The longevity of the wet pattern may be brief, but it may only take one soaking storm to bring significant improvement to the situation.
Rainfall farther south is much less likely and may be non-existent in the pattern.
"Southern California may have to wait for many weeks before rain arrives," Anderson said.
It may not be until late November or December before Southern California manages to capture significant rain.
On average, rainfall begins to slowly increase during the latter part of October and November with the wettest months typically during the winter from December to March in California.
Where dry weather remains and winds occasionally kick up, the wildfire danger will persist, albeit not at the same critical levels that the state has been experiencing in late October.
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