FIG 3 - uploaded by Roger Edwards
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Outline map showing location of Rockwell Pass, the Rattlesnake RAWS site, the Kern River Gorge, and Kings Canyon/Sequoia National Parks (inset) in relation to sounding and radar sites utilized in sounding and hodograph reconstructions and radar analyses, as explained in text. (Background outline map: Terry Dorschied, Arizona Geographic Alliance.)
Source publication
This manuscript documents the tornado in the Rockwell Pass area of Sequoia National Park, California, that occurred on 7 July 2004. Since the elevation of the tornado’s ground circulation was approximately 3705m (~12 156 ft) MSL, this is the highest-elevation tornado documented in the United States. The investigation of the storm’s convective mode...
Contexts in source publication
Context 1
... location of this event (Figs. 3 and 4) presented a challenge in documenting the Rockwell Pass storm me- teorologically. Although there were several surface ob- servation sites nearby, they were located in the Owens Valley to the east, at a much lower elevation, and in a desert ...
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... there were data available for the Remote Automated Weather Station (RAWS) at Rattlesnake, a surface observational platform located in the Kern River Canyon about 15 km south of Rockwell Pass (Figs. 3 and 4). The temperature, dewpoint, and wind for the afternoon hours between 1900 and 2300 UTC 7 July 2004 (see Table 2) from Rattlesnake (at 2621 m MSL) indicated an abruptly strengthening upvalley (southerly) flow with gradually increasing temperatures and dewpoints. This is important because the tornadic thunderstorm devel- oped west of ...
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... the Weather Surveillance Radar-1988 Doppler (WSR-88D) at Hanford, California (KHNX) (see Fig. 3), was located fairly close to the event, the eastern portion of Sequoia National Park is topographi- cally blocked from the radar's field of view. The De- partment of Defense's Doppler radar at Edwards Air There is an intervening storm between the photographer and the cumulonimbus that would shortly produce the Rockwell Pass tornado. ...
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... view. The De- partment of Defense's Doppler radar at Edwards Air There is an intervening storm between the photographer and the cumulonimbus that would shortly produce the Rockwell Pass tornado. Note the sharply defined backsheared anvil and overshooting top at left on the Rockwell Pass storm's west end. (Photo by Bill Hensley.) Force Base (KEYX; Fig. 3) observed the Rockwell Pass thunderstorm, though from a great distance (Table 3). Since the level-II data for KEYX were not archived, the lower-resolution level III data had to be used instead. Unfortunately, since the KEYX radar was in clear-air mode on the day of the Rockwell Pass tornado, the highest reflectivity archived in this ...
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... tornado location was between National Weather Service (NWS) radiosonde sites (see Fig. 3) at Reno, Nevada (KRNO); Desert Rock, Nevada (KDRA); Elko, Nevada (KEKO); and Vandenberg Air Force Base, California (KVBG). All of these were distant enough from the tornadic storm or at distinctly different elevations to preclude the direct use of their data for establishing its proximity thermodynamic and shear environment. An ...
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... the convective mode of the parent thunderstorm and the evidence that the convection was surface based were issues needing some clarification, the authors first attempted to construct an inferred sounding (not shown) based upon sounding information from KVBG at 0000 UTC 8 July 2004 (Fig. 3), located southwest of the Rockwell Pass area. The sounding had essentially no CAPE, unless a surface-based parcel was ...
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... the WSR-88D site at KEYX (Fig. 3) was so distant from the storm (about 190 km), the storm's radar echo was only observable on the lowest three elevation angles (0.58, 1.58, and 2.58). This presents some challenges in the radar diagnosis of the event. The approximate height of the centerline of the radar beam at those three elevation angles is provided in Table 3. ...
Citations
... In this sense, the relationship between complex terrain and tornadogenesis is not clear. Even though tornadoes (supercell or non-supercell) can occur at high elevations, over the 3500 meters above sea level (MASL) (Monteverdi et al. 2014); the lack of instrumentation at these regions makes their analysis difficult. Evidence from atmospheric models suggests that some instability parameters, including the significant tornado parameter (Thompson et al. 2003), are aligned with terrain features like coastlines, valleys, and ridges (Katona et al. 2016). ...
Tornadoes are extreme manifestations of severe storms that occur around the world. In Mexico, the most affected region by the tornado phenomenon is the Trans-Mexican Volcanic Belt (TMVB), a complex topographic region in the central part of the country with a large population density. This research work aims to investigate the role of the complex topography in the generation of instability conditions that favored the formation of two tornadoes almost in the same place (western TMVB) on August 7, 2012, and September 16, 2014. Numerical experiments with the WRF-ARW model were performed in order to obtain knowledge about several important weather conditions preceding each tornado event and to identify the role of the complex terrain in the generation of instability necessary for their formation. Notwithstanding this real complexity, similar patterns in instability parameters and meteorological variables were found for the two tornadoes. The complex terrain seems to be essential in the generation and increase in instability preceding each tornado event. This work is the first approach to understand the meteorological phenomena, in the complex topography of Mexico, which leads to the formation of tornadoes. Understanding natural hazards such as tornadoes represents a first phase in the process of disaster risk reduction.
... Further, the study used aggregate data and so the interpretations do not necessarily apply at the level of individual tornadoes. Last, the effect cannot be extrapolated to infer that tornadoes will never occur where elevation roughness is extreme (see, e.g., Monteverdi et al. 2014). That is, no amount of elevation variation will guarantee safety from a tornado. ...
The statistical relationship between elevation roughness and tornado activity is quantified using a spatial model that controls for the effect of population on the availability of reports. Across a large portion of the central Great Plains the model shows that areas with uniform elevation tend to have more tornadoes on average than areas with variable elevation. The effect amounts to a 2.3% [(1.6%, 3.0%) = 95% credible interval] increase in the rate of a tornado occurrence per meter of decrease in elevation roughness, defined as the highest minus the lowest elevation locally. The effect remains unchanged if the model is fit to the data starting with the year 1995. The effect strengthens for the set of intense tornadoes and is stronger using an alternative definition of roughness. The elevation-roughness effect appears to be strongest over Kansas, but it is statistically significant over a broad domain that extends from Texas to South Dakota. The research is important for developing a local climatological description of tornado occurrence rates across the tornado-prone region of the Great Plains.
