Modeling and Forecasting Lee Side Spillover Precipitation Resulting

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Modeling and Forecasting Lee Side Spillover Precipitation Resulting in Major Flooding in an Urban

Modeling and Forecasting Lee Side Spillover Precipitation Resulting in Major Flooding in an Urban Valley Location Michael L. Kaplan, Phillip J. Marzette, Christopher S. Adaniya and K. C. King Division of Atmospheric Sciences Desert Research Institute Reno, Nevada S. Jeffrey Underwood Department of Geography University of Nevada Reno, Nevada

Presentation Overview 1. Formation of meso-Γ scale vortices in blocked flow 2. Meso-Β/Γ scale

Presentation Overview 1. Formation of meso-Γ scale vortices in blocked flow 2. Meso-Β/Γ scale observations (Reno) during the 2005 flood 3. Simulated counter-rotating vortices during the flood 4. Sensitivity to model initial conditions during the flood 5. Summary and key conclusions

Counter-Rotating Meso-γ Scale Lee Side Vortices (~10 -20 km/3 -6 hours or less) Ø

Counter-Rotating Meso-γ Scale Lee Side Vortices (~10 -20 km/3 -6 hours or less) Ø Lee side blocking of upstream unsaturated flow function of dry Froude Number (linear theory) l l l u=2000 m MSL average (valley-crest) cross-mountain top wind velocity N=2000 m MSL average (valley-crest) Brunt-Vaisalla frequency H = Average upstream mountain height (~1000 m for Carson Range between valley (1500 m) and crest (2500 m) MSL)

Counter-Rotating Vortices

Counter-Rotating Vortices

Key Observations Near Reno For The 2005 Flood Event Ø Multi-sensor analysis of the

Key Observations Near Reno For The 2005 Flood Event Ø Multi-sensor analysis of the precipitation field (inches) for 30– 31 December 2005.

NARR: 250 -h. Pa Height/Isotachs/Wind Barbs 0600 UTC 1500 UTC

NARR: 250 -h. Pa Height/Isotachs/Wind Barbs 0600 UTC 1500 UTC

NARR MSLP and Surface Wind Barbs 0600 UTC 1500 UTC

NARR MSLP and Surface Wind Barbs 0600 UTC 1500 UTC

Reno Meteogram – 12/31/05

Reno Meteogram – 12/31/05

Upper Air Data: Observed and Simulation NCAR/NCEP Simulation Fr = 0. 406 AVN Simulation

Upper Air Data: Observed and Simulation NCAR/NCEP Simulation Fr = 0. 406 AVN Simulation Observed Reno radiosonde Fr = 0. 482 Fr = 0. 521

Simulated PMSL/Surface Winds/Terrain at 1500 UTC 12/31/05 NCEP Simulation AVN Simulation

Simulated PMSL/Surface Winds/Terrain at 1500 UTC 12/31/05 NCEP Simulation AVN Simulation

Simulated 800 mb Vertical Velocity (w) at 1500 UTC 12/31/2005 NCEP Simulation AVN Simulation

Simulated 800 mb Vertical Velocity (w) at 1500 UTC 12/31/2005 NCEP Simulation AVN Simulation

Summary and Conclusions Urban scale prediction in complex terrain is difficult reflecting larger scale

Summary and Conclusions Urban scale prediction in complex terrain is difficult reflecting larger scale Froude number and simulated blocking errors Blocking may be key to organizing lee side vortices and convergence zones on the urban scale, which control precipitation Better initial data, resolution and microphysics are likely key to improving flooding prediction for spillover precipitation in a lee side urban valley region

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