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Abstract
A ground-based Doppler radar technique is developed for detecting a tropical cyclone center position. Accurate determination of the cyclone center position, based on Doppler velocity measurements, will become essential for the issuance of hurricane advisories, forecasts, and warnings once a network of WSR-88D Doppler radars is deployed on the United States coastlines, islands, and military bases during the 1990s. This will allow high-resolution detection and tracking of hurricanes nearing land for the first time.
Simulated Doppler velocity data, which were reconstructed from wind field data collected by reconnaissance aircraft during Hurricanes Alicia (1983) and Gloria (1985), were used to test the concept of using ground-based Doppler radar data to estimate cyclone center location. The center range and azimuth estimates of a hurricane signature were calculated from the simulated coastal Doppler radar velocity data. Preliminary results indicate that the technique performed well for estimating center locations from the radar measurements compared with storm center positions determined from in situ aircraft measurements.
Abstract
A ground-based Doppler radar technique is developed for detecting a tropical cyclone center position. Accurate determination of the cyclone center position, based on Doppler velocity measurements, will become essential for the issuance of hurricane advisories, forecasts, and warnings once a network of WSR-88D Doppler radars is deployed on the United States coastlines, islands, and military bases during the 1990s. This will allow high-resolution detection and tracking of hurricanes nearing land for the first time.
Simulated Doppler velocity data, which were reconstructed from wind field data collected by reconnaissance aircraft during Hurricanes Alicia (1983) and Gloria (1985), were used to test the concept of using ground-based Doppler radar data to estimate cyclone center location. The center range and azimuth estimates of a hurricane signature were calculated from the simulated coastal Doppler radar velocity data. Preliminary results indicate that the technique performed well for estimating center locations from the radar measurements compared with storm center positions determined from in situ aircraft measurements.
Abstract
No abstract available.
Abstract
No abstract available.
Abstract
Simulated WSR-88D (Weather Surveillance Radar-1988 Doppler) radar data were used to investigate the effects of discrete azimuthal sampling on Doppler velocity signatures of modeled mesocyclones and tornadoes at various ranges from the radar and for various random positions of the radar beam with respect to the vortices. Results show that the random position of the beam can change the magnitudes and locations of peak Doppler velocity values. The important implication presented in this study is that short-term variations in tornado and far-range mesocyclone intensity observed by a WSR-88D radar may be due to evolution or due to the chance positions of the radar beam relative to the vortex’s maximum rotational velocities or due to some combination of both.
Abstract
Simulated WSR-88D (Weather Surveillance Radar-1988 Doppler) radar data were used to investigate the effects of discrete azimuthal sampling on Doppler velocity signatures of modeled mesocyclones and tornadoes at various ranges from the radar and for various random positions of the radar beam with respect to the vortices. Results show that the random position of the beam can change the magnitudes and locations of peak Doppler velocity values. The important implication presented in this study is that short-term variations in tornado and far-range mesocyclone intensity observed by a WSR-88D radar may be due to evolution or due to the chance positions of the radar beam relative to the vortex’s maximum rotational velocities or due to some combination of both.
Abstract
Simulations were conducted to investigate the detection of the Doppler velocity tornado signature (TS) and tornadic vortex signature (TVS) when a tornado is located at the center of the parent mesocyclone. Whether the signature is a TS or TVS depends on whether the tornado’s core diameter is greater than or less than the radar’s effective beamwidth, respectively. The investigation included three radar effective beamwidths, two mesocyclones, and six different-sized tornadoes, each of which had 10 different maximum tangential velocities assigned to it to represent a variety of strengths. The concentric tornadoes and mesocyclones were positioned 10–150 km from the radar. The results indicate that 1) azimuthal shear at the center of the mesocyclone increases as the associated tornado gains strength before a TS or TVS appears, 2) smaller tornadoes need to be much stronger than larger tornadoes at a given range for a signature to appear within the mesocyclone, and 3) when the tornado diameter is wider than about one-quarter of the mesocyclone diameter, the TS or TVS associated with a given mesocyclone appears when the tornado has attained about the same strength regardless of range.
Abstract
Simulations were conducted to investigate the detection of the Doppler velocity tornado signature (TS) and tornadic vortex signature (TVS) when a tornado is located at the center of the parent mesocyclone. Whether the signature is a TS or TVS depends on whether the tornado’s core diameter is greater than or less than the radar’s effective beamwidth, respectively. The investigation included three radar effective beamwidths, two mesocyclones, and six different-sized tornadoes, each of which had 10 different maximum tangential velocities assigned to it to represent a variety of strengths. The concentric tornadoes and mesocyclones were positioned 10–150 km from the radar. The results indicate that 1) azimuthal shear at the center of the mesocyclone increases as the associated tornado gains strength before a TS or TVS appears, 2) smaller tornadoes need to be much stronger than larger tornadoes at a given range for a signature to appear within the mesocyclone, and 3) when the tornado diameter is wider than about one-quarter of the mesocyclone diameter, the TS or TVS associated with a given mesocyclone appears when the tornado has attained about the same strength regardless of range.
Abstract
A tornadic vortex signature (TVS) is a degraded Doppler velocity signature that occurs when the tangential velocity core region of a tornado is smaller than the effective beamwidth of a sampling Doppler radar. Early Doppler radar simulations, which used a uniform reflectivity distribution across an idealized Rankine vortex, showed that the extreme Doppler velocity peaks of a TVS profile are separated by approximately one beamwidth. The simulations also indicated that neither the size nor the strength of the tornado is recoverable from a TVS. The current study was undertaken to investigate how the TVS might change if vortices having more realistic tangential velocity profiles were considered. The one-celled (axial updraft only) Burgers–Rott vortex model and the two-celled (annular updraft with axial downdraft) Sullivan vortex model were selected. Results of the simulations show that the TVS peaks still are separated by approximately one beamwidth—signifying that the TVS not only is unaffected by the size or strength of a tornado but also is unaffected by whether the tornado structure consists of one or two cells.
Abstract
A tornadic vortex signature (TVS) is a degraded Doppler velocity signature that occurs when the tangential velocity core region of a tornado is smaller than the effective beamwidth of a sampling Doppler radar. Early Doppler radar simulations, which used a uniform reflectivity distribution across an idealized Rankine vortex, showed that the extreme Doppler velocity peaks of a TVS profile are separated by approximately one beamwidth. The simulations also indicated that neither the size nor the strength of the tornado is recoverable from a TVS. The current study was undertaken to investigate how the TVS might change if vortices having more realistic tangential velocity profiles were considered. The one-celled (axial updraft only) Burgers–Rott vortex model and the two-celled (annular updraft with axial downdraft) Sullivan vortex model were selected. Results of the simulations show that the TVS peaks still are separated by approximately one beamwidth—signifying that the TVS not only is unaffected by the size or strength of a tornado but also is unaffected by whether the tornado structure consists of one or two cells.
Abstract
A new parametric model of vortex tangential-wind profiles is presented that is primarily designed to depict realistic-looking tangential wind profiles such as those in intense atmospheric vortices arising in dust devils, waterspouts, tornadoes, mesocyclones, and tropical cyclones. The profile employs five key parameters: maximum tangential wind, radius of maximum tangential wind, and three power-law exponents that shape different portions of the velocity profile. In particular, a new parameter is included controlling the broadly or sharply peaked profile in the annular zone of tangential velocity maximum. Different combinations of varying the model parameters are considered to investigate and understand their effects on the physical behaviors of tangential wind and corresponding vertical vorticity profiles. Additionally, the parametric tangential velocity and vorticity profiles are favorably compared to those of an idealized Rankine model and also those of a theoretical stagnant core vortex model in which no tangential velocity exists within a core boundary and a potential flow occurs outside the core. Furthermore, the parametric profiles are evaluated against and compared to those of two other idealized vortex models (Burgers–Rott and Sullivan). The comparative profiles indicate very good agreements with low root-mean-square errors of a few tenths of a meter per second and high correlation coefficients of nearly one. Thus, the veracity of the parametric model is demonstrated.
Abstract
A new parametric model of vortex tangential-wind profiles is presented that is primarily designed to depict realistic-looking tangential wind profiles such as those in intense atmospheric vortices arising in dust devils, waterspouts, tornadoes, mesocyclones, and tropical cyclones. The profile employs five key parameters: maximum tangential wind, radius of maximum tangential wind, and three power-law exponents that shape different portions of the velocity profile. In particular, a new parameter is included controlling the broadly or sharply peaked profile in the annular zone of tangential velocity maximum. Different combinations of varying the model parameters are considered to investigate and understand their effects on the physical behaviors of tangential wind and corresponding vertical vorticity profiles. Additionally, the parametric tangential velocity and vorticity profiles are favorably compared to those of an idealized Rankine model and also those of a theoretical stagnant core vortex model in which no tangential velocity exists within a core boundary and a potential flow occurs outside the core. Furthermore, the parametric profiles are evaluated against and compared to those of two other idealized vortex models (Burgers–Rott and Sullivan). The comparative profiles indicate very good agreements with low root-mean-square errors of a few tenths of a meter per second and high correlation coefficients of nearly one. Thus, the veracity of the parametric model is demonstrated.
Abstract
When a thunderstorm mesocyclone changes range relative to a Doppler radar, the deduced core diameter and mean rotational velocity of the Doppler velocity mesocyclone signature oscillate back and forth, even though the radar beam’s physical width changes uniformly with range. The authors investigated the oscillations using a model mesocyclone and a simulated Doppler radar that collected data with an azimuthal sampling interval of 1°. They found that the oscillations are a consequence of changing data point separation with range relative to the Doppler velocity peaks of the mesocyclone signature.
Abstract
When a thunderstorm mesocyclone changes range relative to a Doppler radar, the deduced core diameter and mean rotational velocity of the Doppler velocity mesocyclone signature oscillate back and forth, even though the radar beam’s physical width changes uniformly with range. The authors investigated the oscillations using a model mesocyclone and a simulated Doppler radar that collected data with an azimuthal sampling interval of 1°. They found that the oscillations are a consequence of changing data point separation with range relative to the Doppler velocity peaks of the mesocyclone signature.
Abstract
A variety of single Doppler velocity patterns that simulate those observed in a nondivergent environment is presented. Measurements in optically clear air and/or widespread precipitation are simulated, using horizontally uniform wind fields that vary with height. Vertical profiles of wind speed and direction indicated by the simulated Doppler velocity fields agree well with Doppler radar measurements. Horizontally uniform winds veering with height produce a striking S-shaped pattern, indicative of warm air advection; winds backing with height produce a backward S, indicative of cold air advection. A maximum in the vertical profile of wind speed is indicated by a pair of concentric contours, one upwind and one downwind of the radar. The presence of a frontal discontinuity is indicated by rapid variation of wind direction within the frontal zone. The wind speed profile controls the overall pattern including the spacing between contours, whereas the vertical profile of wind direction controls contour curvature.
Abstract
A variety of single Doppler velocity patterns that simulate those observed in a nondivergent environment is presented. Measurements in optically clear air and/or widespread precipitation are simulated, using horizontally uniform wind fields that vary with height. Vertical profiles of wind speed and direction indicated by the simulated Doppler velocity fields agree well with Doppler radar measurements. Horizontally uniform winds veering with height produce a striking S-shaped pattern, indicative of warm air advection; winds backing with height produce a backward S, indicative of cold air advection. A maximum in the vertical profile of wind speed is indicated by a pair of concentric contours, one upwind and one downwind of the radar. The presence of a frontal discontinuity is indicated by rapid variation of wind direction within the frontal zone. The wind speed profile controls the overall pattern including the spacing between contours, whereas the vertical profile of wind direction controls contour curvature.
Abstract
A parametric tangential wind profile model is presented for depicting representative pressure deficit profiles corresponding to varying tangential wind profiles of a cyclostrophic, axisymmetric vortex. The model employs five key parameters per wind profile: tangential velocity maximum, radius of the maximum, and three shape parameters that control different portions of the profile. The model coupled with the cyclostrophic balance assumption offers a diagnostic tool for estimating and examining a radial profile of pressure deficit deduced from a theoretical superimposing tangential wind profile in the vortex. Analytical results show that the shape parameters for a given tangential wind maximum of a non-Rankine vortex have an important modulating influence on the behavior of realistic tangential wind and corresponding pressure deficit profiles. The first parameter designed for changing the wind profile from sharply to broadly peaked produces the corresponding central pressure fall. An increase in the second (third) parameter yields the pressure rise by lowering the inner (outer) wind profile inside (outside) the radius of the maximum. Compared to the Rankine vortex, the parametrically constructed non-Rankine vortices have a larger central pressure deficit. It is suggested that the parametric model of non-Rankine vortex tangential winds has good potential for diagnosing the pressure features arising in dust devils, waterspouts, tornadoes, tornado cyclones, and mesocyclones. Finally, presented are two examples in which the parametric model is fitted to a tangential velocity profile, one derived from an idealized numerical simulation and the other derived from high-resolution Doppler radar data collected in a real tornado.
Abstract
A parametric tangential wind profile model is presented for depicting representative pressure deficit profiles corresponding to varying tangential wind profiles of a cyclostrophic, axisymmetric vortex. The model employs five key parameters per wind profile: tangential velocity maximum, radius of the maximum, and three shape parameters that control different portions of the profile. The model coupled with the cyclostrophic balance assumption offers a diagnostic tool for estimating and examining a radial profile of pressure deficit deduced from a theoretical superimposing tangential wind profile in the vortex. Analytical results show that the shape parameters for a given tangential wind maximum of a non-Rankine vortex have an important modulating influence on the behavior of realistic tangential wind and corresponding pressure deficit profiles. The first parameter designed for changing the wind profile from sharply to broadly peaked produces the corresponding central pressure fall. An increase in the second (third) parameter yields the pressure rise by lowering the inner (outer) wind profile inside (outside) the radius of the maximum. Compared to the Rankine vortex, the parametrically constructed non-Rankine vortices have a larger central pressure deficit. It is suggested that the parametric model of non-Rankine vortex tangential winds has good potential for diagnosing the pressure features arising in dust devils, waterspouts, tornadoes, tornado cyclones, and mesocyclones. Finally, presented are two examples in which the parametric model is fitted to a tangential velocity profile, one derived from an idealized numerical simulation and the other derived from high-resolution Doppler radar data collected in a real tornado.
A Hole in the Weather Warning System
Improving Access to Hazardous Weather Information for Deaf and Hard of Hearing People
In this article, the problems deaf and hard of hearing people experience when attempting to access the weather warning systems in Oklahoma and Minnesota are documented. Deaf and hard of hearing people cannot hear Civil Defense sirens, cannot listen to local radio stations that are broadcasting emergency information through the Emergency Alert System, cannot access weather warnings through conventional National Oceanic and Atmospheric Administration (NOAA) Weather Radio, and often have problems obtaining weather information from local television stations due to the lack of text information. These problems had forced deaf and hard of hearing people to rely on looking at the sky or having hearing people alert them as their primary methods of receiving emergency information. These problems are documented through the use of a survey of277 deaf and hard of hearing people in Minnesota and Oklahoma as well as specific examples.
During the last two years, some progress has been made to “close this hole” in the weather warning system. The Federal Communications Commission has approved new rules, requiring that all audio emergency information provided by television stations, satellite, and cable operators must also be provided visually. In addition, the use of new technology such as pager systems, weather radios adapted for use by those with special needs, the Internet, and satellite warning systems have allowed deaf and hard of hearing people to have more access to emergency information.
In this article, these improvements are documented but continuing problems and possible solutions are also listed.
In this article, the problems deaf and hard of hearing people experience when attempting to access the weather warning systems in Oklahoma and Minnesota are documented. Deaf and hard of hearing people cannot hear Civil Defense sirens, cannot listen to local radio stations that are broadcasting emergency information through the Emergency Alert System, cannot access weather warnings through conventional National Oceanic and Atmospheric Administration (NOAA) Weather Radio, and often have problems obtaining weather information from local television stations due to the lack of text information. These problems had forced deaf and hard of hearing people to rely on looking at the sky or having hearing people alert them as their primary methods of receiving emergency information. These problems are documented through the use of a survey of277 deaf and hard of hearing people in Minnesota and Oklahoma as well as specific examples.
During the last two years, some progress has been made to “close this hole” in the weather warning system. The Federal Communications Commission has approved new rules, requiring that all audio emergency information provided by television stations, satellite, and cable operators must also be provided visually. In addition, the use of new technology such as pager systems, weather radios adapted for use by those with special needs, the Internet, and satellite warning systems have allowed deaf and hard of hearing people to have more access to emergency information.
In this article, these improvements are documented but continuing problems and possible solutions are also listed.
