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 The Thunderstorm written by United States. Thunderstorm Project and published by . This book was released on 1949 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Monthly Weather Review written by and published by . This book was released on 1987 with total page 932 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 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 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 Conference on Severe Local Storms written by and published by . This book was released on 1981 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 40 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.

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 Field Program Operations written by Jean Theodore Lee and published by . This book was released on 1981 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 1980 Spring Observation Program extended from April 15 to June 19 at the National Severe Storms Laboratory, Norman, Oklahoma. Aircraft, rawinsonde network, mesoscale surface network, low-level wind shear alert system at Will Rogers World Airport, 444 m instrumented tower and satellite observations augmented a conventional weather radar and a new, dual Doppler weather radar system to obtain concurrent data on weather hazards to aircraft. Storm days and data acquired are detailed. An objective for the spring program was to determine the characteristics and detectability of turbulence, wind shear and other aircraft operational weather hazards using indirect (radar) probes. The South Dakota School of Mines T-28 aircraft and the National Aeronautics and Space Administration's F-106 aircraft made thunderstorm penetrations during Doppler radar and lightning operations. Data obtained are discussed, and the analysis of a turbulence case and two gust front cases are presented. These indicate the Doppler radar's potential use to detect and dimensionalize aviation weather hazards both in-cloud and in optically clear air. These studies and additional ones now in progress will provide material for guideline development as to siting and uses of the Next Generation Radar (NEXRAD) in aviation-related situations. (Author).

Download or read book The Thunderstorm written by United States. Weather Bureau and published by . This book was released on 1949 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Analysis of the Relation Between Horizontal Temperature Variations and Maximum Effective Gust Velocities in Thunderstorms written by Harry Press and published by . This book was released on 1949 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analysis is presented of the relations between the horizontal temperature variations and the maximum observed effective gust velocities for the data obtained during operations of the United States Weather Bureau thunderstorm project in Florida and Ohio. The results indicate that the relation when extended to include frontal conditions appears useful for forecasting the intensity of turbulence for thunderstorms in temperate regionsl. The relation does not appear useful, however, for forecasting the intensity of turbulence in subtropical regions.

Download or read book Investigation of the Detectability and Lifetime of Gust Fronts and Other Weather Hazards to Aircraft written by Dušan S. Zrnić and published by . This book was released on 1983 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thunderstorms a Social Scientific Technological Documentary Thunderstorm morphology and dynamics written by and published by . This book was released on 1982 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Curricula in the Atmospheric and Oceanographic Sciences written by and published by . This book was released on 1982 with total page 404 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 Atmospheric Boundary Layers written by Alexander Baklanov and published by Springer Science & Business Media. This book was released on 2007-10-30 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents peer-reviewed papers from the NATO Advanced Research Workshop on Atmospheric Boundary Layers held in April 2006. The papers are divided into thematic sessions: nature and theory of turbulent boundary layers; boundary-layer flows: modeling and applications to environmental security; nature, theory and modeling of boundary-layer flows; air flows within and above urban and other complex canopies: air-sea-ice interaction.