Showing papers on "Air-mass thunderstorm published in 1973"
TL;DR: In this paper, the structure and mechanism for maintenance of the Great Plains squall line thunderstorm were studied through formulation of a two-dimensional, time-dependent numerical model, and the appropriate physical equations were integrated forward in time to study changes in the motion, thermal and moisture fields in and around the squallline thunderstorm.
Abstract: The structure and mechanism for maintenance of the Great Plains squall line thunderstorm are studied through formulation of a two-dimensional, time-dependent numerical model. The environmental conditions known to be favorable for squall line development and maintenance include a convectively unstable air mass whose motion is characterized by strong vertical shear of the horizontal wind. These conditions are used to specify an environment in an x-z plane upon which a disturbance is superimposed. The appropriate physical equations are integrated forward in time to study changes in the motion, thermal and moisture fields in and around the squall line thunderstorm. The vertical shear of the horizontal environmental wind is varied from one experiment to another with the result that broader and longer lasting cloud circulations occur in the stronger shear cases. Specific areas where three-dimensional effects must be important are discussed from an examination of variable fields during periods when the ...
63 citations
TL;DR: In this paper, an analysis is made of 11 nocturnal thunderstorm occurrences that have no obvious synoptic scale support, and the pressure patterns and local terrain configurations are input to a numerical boundary-layer model that computes the vertically integrated boundary layer convergence.
Abstract: An analysis is made of 11 Great Plains nocturnal thunderstorm occurrences that have no obvious synoptic scale support. The pressure patterns and local terrain configurations are input to a numerical boundary-layer model that computes the vertically integrated boundary-layer convergence. The time and space phasing of the vertical velocities thus obtained are in good agreement with the time and space phasing of all 11 thunderstorm occurrences for the beginning of the activity, but they are acceptable in only 6 cases for the termination of the activity. There is a tendency for the model to forecast boundary-layer convergence where no thunderstorms occur; but in many such cases, stability and humidity data are unfavorable for thunderstorm activity.
11 citations
01 Jul 1973
TL;DR: In this article, three time histories of wind profiles in thunderstorm gust fronts at Cape Kennedy and three at Oklahoma City are analyzed, and the coherence between microscale wind speed variations at different levels has the same proportions as in non-thunderstorm cases.
Abstract: Three time histories of wind profiles in thunderstorm gust fronts at Cape Kennedy and three at Oklahoma City are analyzed. Wind profiles at maximum wind strength below 100 m follow logarithmic laws, so that winds above the surface layer can be estimated from surface winds once the roughness length is known. A statistical analysis of 81 cases of surface winds during thunderstorms at Tampa revealed no predictor with skill to predict the time of maximum gust. Some 34% of the variance of the strength of the gust is accounted for by a stability index and surface wind prior to the gust; the regression equations for these variables are given. The coherence between microscale wind speed variations at the different levels has the same proportions as in non-thunderstorm cases.
7 citations