Extended Abstract (288K)13.4
A High Resolution Numerical Simulation of the Landfall of Hurricane Opal (1995)
Glen Romine, University of Illinois, Urbana, IL; and R. Wilhelmson
Landfalling hurricanes are frequently accompanied by severe weather, which may extend well outward from the cyclone center. High winds, destructive storm surge and torrential rainfall often occur near the hurricane core. The public generally recognizes these threats near the center of the cyclone, but is less aware of the fact that severe weather can occur well away. In fact, the actual threat of localized severe weather is often maximized at a distance of 200-400 km from the eye in outer hurricane rainbands, where shear and buoyancy are favorable for the generation of tornado producing storms (McCaul 1991). Recent high-resolution simulations within the modeling community are providing novel insight into the role of convective scale processes in hurricane organization and evolution. Using models at cloud-scale horizontal resolution, it is now possible to resolve individual convective elements within their parent cyclone environment. This study examines a high-resolution (1.1 km) simulation of Hurricane Opal (1995) carried out using the MM5 with an emphasis on the convective scale processes associated with outer rainband convection in addition to the larger scale circulation and organization.
The simulated hurricane achieves an intensity and track close to observations. The asymmetry of Hurricane Opal is well captured in the simulation, as is the explosive deepening rate. The mesoscale convective environment in the simulation favors the development of supercells, using the criteria of Strensrud et al. (1997), within an arc in the eastern semi-circle. Convective elements exhibiting behavior analogous to tropical cyclone mini-supercells develop within this favorable environment in our simulation. These elements organize into linear bands with close cell spacing such that storm interaction occurs at times. Convective cells favorably modify storm-relative environmental parameters from those of the mesoscale environment, as was also found in cloud-scale simulations by Brooks et al. (1994). This environment modifying behavior allowed cells to progress into regions that on the mesoscale appeared unfavorable to support supercells yet on the storm scale remained robust.
Supplementary URL: http://pampa.ncsa.uiuc.edu/~romine/opal.html
Session 13, High Resolution Prediction
Thursday, 15 August 2002, 3:30 PM-5:45 PM
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