Download or read book Numerical Simulation of Thunderstorm Gust Fronts written by Keith L. Seitter and published by . This book was released on 1983 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thunderstorm gust front is an important feature for both the maintenance and initiation of storms. Previous studies have shown that the thunderstorm outflow producing the gust front can be treated as an atmospheric density current to a good approximation. In this study, a new version of the density current speed equation, based on the surface pressure rise, is derived. This equation is shown to give much better results than other commonly used forms when applied to twenty previously reported gust front observations. A two-dimensional numerical model is used to investigate the dynamics of atmospheric density currents. Simulations with this model show the effects of the environmental wind relative to the storm and the wind shear on the propagation of the gust front and the depth of the thunderstorm outflow. The results of these simulations are discussed in terms of the conditions necessary for the gust front to remain in a position that is beneficial for the maintenance of the storm. Moist processes are included in the model and simulations are made to investigate atmospheric density current propagation through a moist atmosphere. The lifting that occurs during gust front passage is calculated and it is found that even when this lifting is sufficient to bring moist parcels above their level of free convection; deep convection is prohibited by other aspects of the circulation. The generation of an arc cloud by the gust front is found to result in a less intense and slower gust front compared to an outflow that did not produce an arc cloud. This result is interpreted in terms of the gust front speed equation based on the surface pressure rise. (Author).
Download or read book A Numerical Investigation of Severe Thunderstorm Gust Fronts written by Kenneth E. Mitchell and published by . This book was released on 1975 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigations of Thunderstorm Gust Fronts from Project NIMROD Data written by Roger M. Wakimoto and published by . This book was released on 1981 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates the thunderstorm gust front with the aid of Project NIMROD data. The main goal is to present the time dependent solution of the gust front. RHI and VAD cross sections of reflectivity and Doppler velocity were constructed for different three minute radar scans to determine the vertical structure. These analyses revealed that the life cycle of the gust front could be divided into four stages: 1) the formative stage; 2) the early mature stage; 3) the late mature stage; and 4) the dissipation stage. A new finding was a horizontal roll detected in the reflectivity patterns during stages II and III. This phenomenon was called a "precipitation roll." Rawinsonde launchings revealed the thermodynamic structure of the gust front. The cold air layer was found to correspond closely to the observed surface pressure rise. Calculations confirmed that the collision of two fluids produced nonhydrostatic pressure forces at the leading edge of the outflow. A dry, cool layer at the top of the gust front was a result of the low level outflow that was lifted vertically at the frontal boundary and advected back by the circulation within the bead of the gust front. The equation for the propagation speed of a density current was confirmed to accurately predict the movement of the gust front, thus disproving the theory that the gust front is an advecting phenomenon. Comparisons are made between the gust front and the "downburst" to emphasize their different nature.
Download or read book Thunderstorm Gust Fronts written by United States. Federal Aviation Administration. Systems Research and Development Service and published by . This book was released on 1978 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thunderstorm gust fronts written by and published by . This book was released on 1978 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Variation of the Low Level Winds During the Passage of a Thunderstorm Gust Front written by R. W. Sinclair and published by . This book was released on 1973 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Thunderstorm Gust Front Detection System Part I System Operation and Significant Case Studies Part II Statistical Results written by and published by . This book was released on 1979 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Dulles International Airport wind and wind shear detection system recorded more than 160 events from November 1976 through March 1978. Eighty-two percent of 113 significant events occurred in conjunction with thunderstorms, squall-lines and frontal passages. The chief source of false alarms for anemometers was boundary layer disturbances representing 10% of the total; while gravity shear waves related to the 500mb winds caused the most false alarms for pressure sensors (4% of the total). Using complementary arrays of wind and pressure sensors, total system false alarms can be greatly reduced. These data demonstrate the importance of stable surface layers in determining how well surface temperature and wind measurements represent flow at higher levels and explain underestimates of system severity. Moreover, because we demonstrate the value of wind vector information and since temperature is a scaler quantity, there seems little operational value in using temperature sensors as part of a detection system. Conversely, pressure sensors will not reliably detect relatively thin outflows (100-200 M thick) occurring at a distance from downflows having small dimensions. Again, the wind and pressure sensors combine to provide a total system offering good reliability for detection of thunderstorm outflows. The results suggest an array configuration (composed of wind and pressure jump sensors) for use in airport warning systems. This configuration extending about 10km from the airport provides a warning for Thunderstorm gust-fronts.
Download or read book Detection of Gust Fronts Using Surface Sensors written by A. J. Bedard and published by . This book was released on 1977 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thunderstorm Gust Fronts written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thunderstorm Downdraft and Gust Front Structure as Revealed by a Numerical Simulation written by Eric Dale Skyllingstad and published by . This book was released on 1983 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gust Front Vs Non gust Front Thunderstorms written by Theresa A. Aguilar and published by . This book was released on 2012 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: For environmental conditions the following parameters (ranked by importance) contributed to GF and NGF separation: lifted condensation level, Bulk Richardson number, 700 mb mixing ration, modified lifted index, and surface virtual potential temperature. Compared to NGF storms, the majority of GF storms had higher cloud base (2.5 km versus 2.0 km-above ground level:, drier air aloft (3.9 g/kg versus 5.0 g/kg), and higher convective available potential energy (1022.7 J/kg versus 554.8 J/kg. These conditions are conductive to stronger, more organized thunderstorms with evaporation, due to entrainment, likely assisting in cooling the storm air appreciably and influencing the downdraft and associated gust front. However, more thunderstorm events need to be investigated to substantiate these preliminary findings.
Download or read book Aircraft Observations of Wind Shear Accompanying a Severe Thunderstorm Gust Front written by Robert T. Glancy and published by . This book was released on 1979 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A thunderstorm gust front detection system written by and published by . This book was released on 1979 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thunderstorms Thunderstorm morphology and dynamics written by Edwin Kessler and published by . This book was released on 1981 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Life Cycle of Thunderstorm Gust Fronts as Viewed with Doppler Radar and Rawinsonde Data written by Roger M. Wakimoto and published by . This book was released on 1982 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Practical Meteorology written by Roland Stull and published by Sundog Publishing, LLC. This book was released on 2018 with total page 942 pages. Available in PDF, EPUB and Kindle. Book excerpt: A quantitative introduction to atmospheric science for students and professionals who want to understand and apply basic meteorological concepts but who are not ready for calculus.
Download or read book Turbulent Transport Model of Wind Shear in Thunderstorm Gust Fronts and Warm Fronts written by W. S. Lewellen and published by . This book was released on 1978 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
