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Dual-Doppler analysis of shear features within a convective rainband of Hurricane Frances (2004)

Dual-Doppler analysis of shear features within a convective rainband of Hurricane Frances (2004) Scott Gunter and John Schroeder Texas Tech University Lubbock Severe Weather Conference February 17, 2010 . Research Objectives.

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Dual-Doppler analysis of shear features within a convective rainband of Hurricane Frances (2004)

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  1. Dual-Doppler analysis of shear features within a convective rainband of Hurricane Frances (2004) Scott Gunter and John Schroeder Texas Tech University Lubbock Severe Weather Conference February 17, 2010

  2. Research Objectives • A robust dataset was collected as Hurricane Frances made landfall on the eastern coast of Florida on 5 September 2004. This dataset included dual-Doppler coverage of a convective cell in an outer rainband. Using this dataset, the objectives of this research are: • To characterize the kinematic structure of the convective cell and compare it to current conceptual models. • Examine changes in the kinematic structure of the convective cell as it crosses the coastline.

  3. Conceptual Models/Previous Research  Powell (1990) Hence and Houze (2008) 

  4. Hurricane Frances (2004)

  5. Hurricane Frances SMART-R Deployment • SR-1 deployed at Merritt Island Regional Airport • SR-2 deployed at the Space Coast Regional Airport in Titusville. • Both radars sampled the northern portions of Frances, including the convective outer rainband. • Several shear features are evident

  6. Shear Features 1 and 2

  7. Shear Feature 3 from the Melbourne, FL, WSR-88D

  8. Shear Feature 3

  9. Data Processing • Radar data were processed through REORDER and CEDRIC resulting in 35 x 20 x 2.2 km grids of reflectivity, velocity, and horizontal convergence with 100 m spatial resolution. • Two radar volumes were processed: • When the convective cell was immediately off shore • When the convective cell was immediately on shore • Roughly 5 minutes elapsed between radar volumes

  10. Preliminary Analysis Summary • Preliminary analysis shows: • The convective cell compares nicely with conceptual models: convergence on inside of convection and speed max on outside • The convective cell seems to straddle the shear feature • The shear feature most pronounced at the lowest levels (especially the speed minimum) • Horizontal convergence decreases substantially with height • Horizontal convergence also decreases as the cell makes landfall

  11. Next Steps… • Compute vertical velocity and vorticity for both volumes. • Construct vertical slices to evaluate dBz structure and kinematic properties • Compare with WSR-88D

  12. References • Hence, D.A. and R.A> Houze Jr., 2008: Kinematic structure of convective-scale elements in the rainbands of Hurricanes Katrina and Rita (2005). Journal of Geophysical Research, 113, D15108, doi:10.1029/2007JD009429. • Powell, M.D., 1990a: Boundary layer structure and dynamics in outer hurricane rainbands. Part I: Mesoscale rainfall and kinematic structure. Monthly Weather Review , 118, 891-917.

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