Numerical Simulation of Thunderstorm Gust Fronts

Item

Title
Numerical Simulation of Thunderstorm Gust Fronts
Date
1983
Index Abstract
Coming Soon
Photo Quality
Not Needed
Report Number
AFGL TR 83-0329
Creator
Seitter, K. L.
Corporate Author
Air Force Geophysics Laboratory
Date Issued
1983-12-13
Extent
34
Identifier
ADA141214
Distribution Classification
1
DTIC Record Exists
No
Distribution Change Authority Correspondence
None
Abstract
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.
Report Availability
Full text available by request
Provenance
IIT
Type
report
Format
34 pages ; 28 cm.