126:. This effect is especially dangerous with respect to wildfires as it can enhance the updraft generated by the heat in such fires. While the Diablo wind pattern occurs in both the spring and fall, it is most dangerous in the fall, when vegetation is at its driest. California's predominantly Mediterranean climate has an extended dry period from May through October.
20:
97:, gravity-driven winds, draining air off the high deserts, while the Diablo-type wind originates mainly from strongly sinking air from aloft, pushed toward the coast by higher pressure aloft. Thus, Santa Anas are strongest in canyons, whereas a Diablo wind is first noted and blows strongest atop the various mountain peaks and ridges around the Bay Area.
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The Diablo wind is created by the combination of strong inland high pressure at the surface, strongly sinking air aloft, and lower pressure off the
California coast. The air descending from aloft as well as from the Coast Ranges compresses as it sinks to sea level where it warms as much as 20 °F
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Because of the elevation of the coastal ranges in north-central
California, the thermodynamic structure that occurs with the Diablo wind pattern favors the development of strong ridge-top and lee-side downslope winds associated with a phenomenon called the
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and the Diablo Valley. This is the reverse of the normal summertime weather pattern in which an area of low pressure (called the
California Thermal Low) rather than high pressure lies east of the Bay Area, drawing in cooler, more humid air from the ocean.
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The dry offshore wind, already strong because of the offshore pressure gradient, can become quite strong with gusts reaching speeds of 40 miles per hour (64 km/h) or higher, particularly along and in the lee of the ridges of the
61:. In fact, in decades previous to the 1991 fire, the term "Santa Ana" was occasionally used as well for the Bay Area dry northeasterly wind, such as the one that was associated with the
93:". While hydraulic jumps can occur with Santa Ana winds, the same thermodynamic structure that occurs with them typically favors "gap" flow more frequently. Santa Ana winds are
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45:, with many media and government groups using the term Diablo winds for strong, dry downslope wind over northern and central California.
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drops. This warming is in addition to, and usually greater than, any contact heating that occurs as the air stream crosses the
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278:’ Committee on Fire Prevention and Engineering Standards, reprinted in the Virtual Museum of the City of San Francisco
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57:, perhaps to distinguish it from the comparable, and more familiar, hot dry wind in Southern California known as the
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is a name that has been occasionally used for the hot, dry wind from the northeast that typically occurs in the
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Monteverdi, John (1973). "The Santa Ana weather type and extreme fire hazard in the
Oakland-Berkeley Hills".
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The name "Diablo wind" refers to the fact that the wind blows into the inner Bay Area from the direction of
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359:
Doyle Rice (October 29, 2019). "What are Diablo winds fanning
California's fires". USA Today. p. A3.
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The same wind pattern also affects other parts of
California's coastal ranges and the western slopes of
328:"The dynamics of gap flow over idealized topography. Part II: Effects of rotation and surface friction"
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extract from the Report on the
Berkeley, California Conflagration of September 17, 1923
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and evoking the fiery, sensationalist connotation inherent in "devil wind".
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Effects tend to be halved at farther southern coasts, and even can spawn
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290:, San Jose Mercury News, Jan Null, October 26, 1999
137:may recur, Diablo events in autumn tend to precede
149:south are generally unaffected by Diablo events.
141:events by a few weeks with a lull in between as
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145:declines. Southern Californian coasts from
85:(11 °C), and loses relative humidity.
53:The term first appeared shortly after the
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302:"Mountain Waves and Downslope Winds"
100:In both cases, as the air sinks, it
387:Weather events in the United States
332:Journal of the Atmospheric Sciences
276:National Board of Fire Underwriters
16:Northern California weather pattern
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326:Gabersek, S.; Durran, D. (2006).
226:from the original on 2019-10-25.
23:Explanation for the Diablo wind.
38:during the spring and fall.
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259:10.1080/00431672.1973.9931644
133:in Santa Barbara. Although
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309:Meteorological Monographs
102:heats up by compression
55:1991 Oakland firestorm
32:San Francisco Bay Area
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382:Climate of California
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300:Durran, D. (1990).
251:1973Weawi..26c.118M
222:. 24 October 2019.
184:Dine's compensation
74:Contra Costa County
36:Northern California
63:1923 Berkeley Fire
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345:10.1175/JAS3786.1
219:Los Angeles Times
194:Relative humidity
106:relative humidity
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143:solar incidence
135:Santa Ana winds
131:Sundowner winds
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59:Santa Ana winds
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288:WEATHER CORNER
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179:Hydraulic jump
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174:Sundowner wind
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159:Santa Ana wind
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147:Ventura County
139:Santa Ana wind
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110:Central Valley
91:hydraulic jump
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169:Norte (wind)
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72:in adjacent
70:Mount Diablo
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239:Weatherwise
189:Thermal low
124:Coast Range
28:Diablo wind
371:Categories
214:"LA Times"
200:References
164:Foehn wind
95:katabatic
80:Formation
315:: 59–83.
224:Archived
153:See also
104:and its
247:Bibcode
117:Impacts
377:Winds
305:(PDF)
49:Name
340:doi
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