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Coupled Hurricane-Ocean Models Transitioned to Operations

This study discusses the transition of hurricane-ocean models to operations, comparing 3D and 1D ocean coupling, impact of warm ocean eddies, and testing a new framework. Results show promising improvements in hurricane forecasts.

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Coupled Hurricane-Ocean Models Transitioned to Operations

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  1. Developing Coupled Tropical Cyclone-Wave-Ocean Models for Transition to OperationsIsaac GinisYalin Fan, Richard Yablonsky, Biju ThomasGraduate School of OceanographyUniversity of Rhode IslandMorris BenderGeophysical Fluid Dynamics Laboratory, NOAA63th Interdepartmental Hurricane Conference

  2. Coupled Hurricane-Ocean Models Transitioned to Operations • 2001 – GFDL/POM at NCEP in the Atlantic basin (3D coupling) and Eastern and Central Pacific (1D coupling). • 2007 – HWRF/POM at NCEP in the Atlantic basin (3D coupling). • 2008 – GFDN/POM at FNMOC in the Atlantic basin (3D coupling) and all other ocean basins (1D coupling) • 2009 – GFDN/POM at FNMOC 3D coupling in the Northern Pacific.

  3. Today’s Discussion • What are the differences between 3D and 1D ocean coupling for hurricane forecasts? • Impact of warm ocean eddy’s circulation on hurricane-induced cooling and its implication for hurricane intensity. • Test experiments with a new coupled hurricane-wave-ocean framework.

  4. Ocean response to hurricane forcing: 1. Vertical mixing/entrainment A T M O S P H E R E Wind stress → surface layer currents Current shear → turbulence Turbulent mixing → entrainment of cooler water O C E A N Warm sea surface temperature Sea surface temperature decreases Cool subsurface temperature Subsurface temperature increases This is a 1-D (vertical) process

  5. Ocean response to hurricane forcing: 2. Upwelling A T M O S P H E R E Cyclonic wind stress → divergent surface currents Divergent currents → upwelling Cyclonic hurricane vortex Upwelling → cooler water brought to surface O C E A N Warm sea surface temperature Cool subsurface temperature This is a 3-D process

  6. SST cooling within hurricane inner-core in 3D and 1D ocean models Hurricanes have historically translated in the Gulf of Mexico: < 5 m s-1 73% and < 2 m s-1 16% of the time in the western tropical North Atlantic at < 5 m s-1 62% and < 2 m s-1 12% of the time

  7. Temperature vertical cross-section in 3D and 1D ocean models 3-D 1-D Speed = 2.5 m s-1

  8. Warm-core ring is not just high ocean heat content Since warm water is deep in the ring, WCRs generally restrict hurricane-induced SST cooling But can a WCR’s circulation modify hurricane-core SST cooling via advection?

  9. A T M O S P H E R E Prescribed translation speed Cyclonic hurricane vortex < < < < < < < < O C E A N Homogeneous initial SST Vary position of ring relative to storm track < < < < Horizontally-homogeneous subsurface temperature Warm core ring evident in subsurface temperature field WCRC WCRR WCRL CTRL

  10. SST and Surface Currents in 4 idealized experiments WCRC CTRL WCR Storm Storm WCRL WCRR WCR Storm Storm WCR

  11. Differences in SST cooling within hurricane inner-core with and without WCR > > 3-D 1-D WCR WCR < < Storm Storm The presence of a warm core eddy in advance of a hurricane may in some cases create a less favorablecondition for hurricane intensification WCRR SST – CTRL SST WCRR SST – CTRL SST

  12. Conventional Coupling Between Hurricane and Ocean Models Hurricane Model Momentum flux (τ) Sensible heat flux (QH) Latent heat flux (QE) Momentum flux (τ) Wind speed (Ua) Temperature (Ta) Humidity (qa) Surface current (Us) SST (Ts) Air-Sea Interface Ocean Model

  13. Atmospheric Boundary Layer Momentum & KE Flux Heat & Humidity Flux Turbulence Sea Spray Wave induced stress Reynolds stress  Airflow separation Intermittency Air-Sea Interface Nonbreaking Waves Breaking Waves Stokes drift Momentum & KE Flux Bubbles Intermittency of Momentum & KE injection (Langmuir) Turbulence Ocean Boundary Layer

  14. Coupled Hurricane-Wave-Ocean Framework • Implemented in GFDL model in research mode. • To be implemented in HWRF later this year

  15. Sea State Dependence of Surface Parameters Surface Roughness Drag Coefficient Based on the coupled GFDL hurricane-wave-ocean coupled model simulations

  16. Hurricane Rita simulation: Initial time Sept. 20, 2005 12Z

  17. Hurricane Rita simulation: Initial time Sept. 20, 2005 12Z

  18. Improved track forecasts of Hurricane Rita with inclusion of wave coupling Sept. 19 00Z Sept. 20 12Z

  19. Little improvement in intensity forecasts of Hurricane Rita with inclusion of wave coupling

  20. Summary • 1D ocean models have significant limitations for coupled hurricane-ocean forecasting, particularly for slower moving storms and over mesoscale ocean features. • Initial test experiments with the newly developed coupled hurricane-wave-ocean framework show promises for improving hurricane forecast skill. • Sea spray effects are being included in collaboration with C. Fairall and J.-W. Bao (ESRL). • Future plans include implementation of the new air-sea interaction framework into GFDN and HWRF models.

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