Extended Abstract (784K)P6.3
Numerical Simulations of Gust Front/ Microburst Collision Dynamics
Leigh Orf, University of North Carolina, Asheville, NC
A microburst is a local, intense downdraft which induces an outburst of damaging winds near the ground which extends 4 km or less. Microbursts are of interest to researchers because of the strong, occasionally damaging surface winds they produce, and the hazardous wind patterns they create for aircraft in the landing or takeoff phases of flight. The dynamics and aircraft hazards posed by an isolated microburst are well understood. Previous work investigating the interaction between colliding microbursts revealed complex dynamical regimes for certain collision geometries. In some configurations, regions of elevated wind shear were found which would be significantly hazardous to jetliners in the takeoff or landing phases of flight. These hazardous winds were found in regions well outside of the regions typically associated with an isolated microburst.
In this study, the interaction between a microburst and a thunderstorm gust front are investigated using a three-dimensional nonhydrostatic subcloud model. The model contains no microphysics, and microburst and gust fronts are initiated using a cooling forcing function. A quasi-two dimensional gust front is allowed to evolve at one end of the model domain and microbursts are initiated at varying times, leading to collisions ahead of, at, and behind the gust front head. Preliminary results indicate that when the downdraft of the microburst impinges the leading edge of the gust front, a broad region of enhanced downward and divergent winds develops. This region would pose a threat to aircraft encountering such winds. Regions of intense short-lived vertical vorticity also were found during this simulation, suggesting that so-called ``gustnado'' circulations are possible from such collisions.
Poster Session 6, Numerical Modeling of Severe Local Storms
Wednesday, 14 August 2002, 3:00 PM-4:30 PM
Previous paper Next paper