scholarly journals Winds and Gusts during the Thomas Fire

Fire ◽  
2018 ◽  
Vol 1 (3) ◽  
pp. 47 ◽  
Author(s):  
Robert Fovell ◽  
Alex Gallagher
Keyword(s):  
California History ◽  
Model Simulations ◽  
Santa Ana ◽  
Area Burned ◽  
Wind Gusts ◽  
Wind Event ◽  
Downslope Wind ◽  
Ventura County ◽  
Fire Origin

We analyze observed and simulated winds and gusts occurring before, during, and immediately after the ignition of the Thomas fire of December 2017. This fire started in Ventura county during a record-long Santa Ana wind event from two closely located but independent ignitions and grew to become (briefly) the largest by area burned in modern California history. Observations placed wind gusts as high as 35 m/s within 40 km of the ignition sites, but stations much closer to them reported much lower speeds. Our analysis of these records indicate these low wind reports (especially from cooperative “CWOP” stations) are neither reliable nor representative of conditions at the fire origin sites. Model simulations verified against available better quality observations indicate downslope wind conditions existed that placed the fastest winds on the lee slope locations where the fires are suspected to have started. A crude gust estimate suggests winds as fast as 32 m/s occurred at the time of the first fire origin, with higher speeds attained later.

The Northern California Wildfires of 8–9 October 2017: The Role of a Major Downslope Wind Event

2019 ◽  
Vol 100 (2) ◽  
pp. 235-256 ◽  
Author(s):  
Clifford F. Mass ◽  
David Ovens
Keyword(s):  
San Francisco ◽  
Weather Prediction ◽  
Economic Loss ◽  
California History ◽  
Wind Event ◽  
Downslope Wind ◽  
Forecast Models ◽  
Strong Winds ◽  
Meteorological Modeling

AbstractA series of large wildfires began over the terrain north of San Francisco, California, during the evening of 8 October 2017 and spread across nearly 250,000 acres, including areas near the towns of Santa Rosa and Napa. These “Wine Country” wildfires were the most destructive in California history, with 44 deaths; the loss of 9,000 buildings; damage to approximately 21,000 structures; $10 billion of insured losses; and substantially greater total economic loss.This paper describes the synoptic and mesoscale conditions that were associated with the wildfires, with strong, easterly “Diablo” winds playing a central role in both initiating and supporting the fires. The climatological conditions preceding the fires are reviewed, including near-normal precipitation and above-normal temperatures during the summer, as well as much above-normal precipitation the previous winter, which led to abundant dry grass that provided fuel for the wind-driven fires.High-resolution meteorological modeling realistically simulated the strong winds associated with this event. Importantly, operational mesoscale forecast models provided excellent forecasts of the high winds several days in advance. It appears that a vulnerable power system, urbanization of fire-prone areas, flammable invasive species, and poor communication of dangerous conditions contributed to this catastrophic event. The potential for mitigating or preventing such destructive wildfires using skillful weather prediction is examined, as well as the possible role of global warming.

scholarly journals The Synoptic and Mesoscale Evolution Accompanying the 2018 Camp Fire of Northern California

2020 ◽  
pp. 1-45
Author(s):  
Clifford F. Mass ◽  
David Ovens
Keyword(s):  
Sierra Nevada ◽  
Northern California ◽  
Wind Event ◽  
Downslope Wind

CapsuleThe Camp Fire of November 2018 was associated with a strong, well-forecast, downslope wind event over the western slopes of the Sierra Nevada near Paradise, California.

scholarly journals Diurnal Variation of Downslope Winds in Owens Valley during the Sierra Rotor Experiment

2008 ◽  
Vol 136 (10) ◽  
pp. 3760-3780 ◽  
Author(s):  
Qingfang Jiang ◽  
James D. Doyle
Keyword(s):  
Diurnal Variation ◽  
Numerical Simulations ◽  
Western Slope ◽  
Owens Valley ◽  
Mountain Waves ◽  
Downslope Winds ◽  
Wind Event ◽  
Downslope Wind ◽  
Rotor Experiment ◽  
The Impact

The impact of diurnal forcing on a downslope wind event that occurred in Owens Valley in California during the Sierra Rotors Project (SRP) in the spring of 2004 has been examined based on observational analysis and diagnosis of numerical simulations. The observations indicate that while the upstream flow was characterized by persistent westerlies at and above the mountaintop level the cross-valley winds in Owens Valley exhibited strong diurnal variation. The numerical simulations using the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) capture many of the observed salient features and indicate that the in-valley flow evolved among three states during a diurnal cycle. Before sunrise, moderate downslope winds were confined to the western slope of Owens Valley (shallow penetration state). Surface heating after sunrise weakened the downslope winds and mountain waves and eventually led to the decoupling of the well-mixed valley air from the westerlies aloft around local noon (decoupled state). The westerlies plunged into the valley in the afternoon and propagated across the valley floor (in-valley westerly state). After sunset, the westerlies within the valley retreated toward the western slope, where the downslope winds persisted throughout the night.

scholarly journals Cloud-resolving-model simulations of nocturnal precipitation over the Himalayan slopes and foothills

2021 ◽  
Author(s):  
Shiori Sugimoto ◽  
Kenichi Ueno ◽  
Hatsuki Fujinami ◽  
Tomoe Nasuno ◽  
Tomonori Sato ◽  
...  
Keyword(s):  
Moisture Transport ◽  
Wrf Model ◽  
Synoptic Scale ◽  
Reanalysis Dataset ◽  
Near Surface ◽  
Model Simulations ◽  
Lower Elevation ◽  
Circulation Patterns ◽  
Downslope Wind ◽  
Cloud Resolving Model

AbstractA numerical experiment with a 2-km resolution was conducted using the Weather Research and Forecasting (WRF) model to investigate physical processes driving nocturnal precipitation over the Himalayas during the mature monsoon seasons between 2003 and 2010. The WRF model simulations of increases in precipitation twice a day, one in the afternoon and another around midnight, over the Himalayan slopes, and of the single nocturnal peak over the Himalayan foothills were reasonably accurate. To understand the synoptic-scale moisture transport and its local-scale convergence generating the nocturnal precipitation, composite analyses were conducted using the reanalysis dataset and model outputs. In the synoptic scale, moisture transport associated with the westward propagation of low pressure systems was found when nocturnal precipitation dominated over the Himalayan slopes. In contrast, moisture was directly provided from the synoptic-scale monsoon westerlies for nocturnal precipitation over the foothills. The model outputs suggested that precipitation occurred on the mountain ridges in the Himalayas during the afternoon, and expanded horizontally towards lower-elevation areas through the night. During the nighttime, the downslope wind was caused by radiative cooling at the surface and was intensified by evaporative cooling by hydrometeors in the near-surface layer. As a result, convergence between the downslope wind and the synoptic-scale flow promoted nocturnal precipitation over the Himalayas and to the south, as well as the moisture convergence by orography and/or synoptic-scale circulation patterns. The nocturnal precipitation over the Himalayas was not simulated well when we used the coarse topographic resolution and the smaller number of vertical layers.

Regions of influence and environmental effects of Santa Ana wind event

2019 ◽  
Vol 12 (9) ◽  
pp. 1019-1034 ◽  
Author(s):  
Christian Adrián Álvarez ◽  
Noel Carbajal
Keyword(s):  
Environmental Effects ◽  
Santa Ana ◽  
Wind Event

scholarly journals Ignitions explain more than temperature or precipitation in driving Santa Ana wind fires

2021 ◽  
Vol 7 (30) ◽  
pp. eabh2262
Author(s):  
Jon E. Keeley ◽  
Janin Guzman-Morales ◽  
Alexander Gershunov ◽  
Alexandra D. Syphard ◽  
Daniel Cayan ◽  
...  
Keyword(s):  
Urban Growth ◽  
Minor Role ◽  
Santa Ana ◽  
Substantial Role ◽  
Area Burned ◽  
The Past ◽  
Antecedent Precipitation ◽  
A Minor ◽  
Autumn And Winter ◽  
Wind Intensity

Autumn and winter Santa Ana wind (SAW)–driven wildfires play a substantial role in area burned and societal losses in southern California. Temperature during the event and antecedent precipitation in the week or month prior play a minor role in determining area burned. Burning is dependent on wind intensity and number of human-ignited fires. Over 75% of all SAW events generate no fires; rather, fires during a SAW event are dependent on a fire being ignited. Models explained 40 to 50% of area burned, with number of ignitions being the strongest variable. One hundred percent of SAW fires were human caused, and in the past decade, powerline failures have been the dominant cause. Future fire losses can be reduced by greater emphasis on maintenance of utility lines and attention to planning urban growth in ways that reduce the potential for powerline ignitions.

Dust pollution caused by an extreme Santa Ana wind event

2021 ◽  
Author(s):  
Christian A. Álvarez ◽  
Noel Carbajal ◽  
Luis F. Pineda-Martínez
Keyword(s):  
Dust Pollution ◽  
Santa Ana ◽  
Wind Event

scholarly journals Observational study for strong downslope wind event under fine weather condition during ICE-POP 2018

2021 ◽  
Author(s):  
Chia-Lun Tsai ◽  
Kwonil Kim ◽  
Yu-Chieng Liou ◽  
Jung-Hoon Kim ◽  
YongHee Lee ◽  
...  
Keyword(s):  
Surface Wind ◽  
Weather Condition ◽  
Gradient Force ◽  
Mountain Range ◽  
Strong Wind ◽  
Mountainous Areas ◽  
Budget Analysis ◽  
Fine Weather ◽  
Wind Event ◽  
Downslope Wind

Abstract. A strong downslope wind event under fine weather condition on 13–15 February 2018 was examined by various observational and high resolution reanalysis datasets during the 2018 Winter Olympic and Paralympic games in Pyeongchang, Korea. High spatio-temporal resolution of wind information was obtained by Doppler lidars, automatic weather stations (AWS), wind profiler, and sounding observations under the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games (ICE-POP 2018). This study aimed to understand the possible generation mechanisms of localized strong wind event across high mountainous areas and in the lee side of mountains associated with the underlying large-scale pattern of a low-pressure system (LPS). The spatial distribution of linear trends for surface wind shows different patterns, exhibiting increased trend in the lee side and a persistent one in mountainous areas with the approaching LPS. Surface wind speed was intensified dramatically from ~3 to ~12 m s−1 (gust was stronger than 20 m s−1 above ground) at a surface station in the lee side (named as GWW). However, the mountainous station at DGW site appeared to have a persistently strong wind (~10 m s−1) during the research period. Budget analysis of horizontal momentum equation and local reanalysis data suggests that the pressure gradient force (PGF) derived by adiabatic warming along the downslope and subsequent hydraulic jump in the lee side of mountains was a main factor in the acceleration of the surface wind at the GWW site. Detailed analysis of the retrieved 3D winds reveals that the PGF also dominate at the DGW site, which causes the persistent strong wind that is related to the channeling effect across the valley areas in the mountain range. The observational evidence presented here shows that the different mechanisms in local areas under the same synoptic condition with LPS are important references in determining the strength and persistence of the orographic-induced strong winds under fine weather condition.

An Unusual Summertime Downslope Wind Event in Fort Collins, Colorado, on 3 July 1993

1995 ◽  
Vol 10 (4) ◽  
pp. 786-797 ◽  
Author(s):  
William R. Cotton ◽  
John F. Weaver ◽  
Brian A. Beitler
Keyword(s):  
Wind Event ◽  
Downslope Wind ◽  
Fort Collins

scholarly journals Climatology of Near‐Surface Daily Peak Wind Gusts Across Scandinavia: Observations and Model Simulations

2021 ◽  
Vol 126 (7) ◽  
Author(s):  
Lorenzo Minola ◽  
Cesar Azorin‐Molina ◽  
Jose A. Guijarro ◽  
Gangfeng Zhang ◽  
Seok‐Woo Son ◽  
...  
Keyword(s):  
Near Surface ◽  
Model Simulations ◽  
Wind Gusts
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