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Composite Analyses of Tropical Convective Systems Prior to Tropical Cyclogenesis

Composite Analyses of Tropical Convective Systems Prior to Tropical Cyclogenesis. Chip Helms Jason Dunion Lance Bosart University at Albany Cyclone Research Group 4 November 2013. Funding through NSF AGS-0849491 and NASA HSRP #NNX12AK63G. Motivatio n.

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Composite Analyses of Tropical Convective Systems Prior to Tropical Cyclogenesis

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  1. Composite Analyses of Tropical Convective Systems Prior to Tropical Cyclogenesis Chip Helms Jason Dunion Lance Bosart University at Albany Cyclone Research Group 4 November 2013 Funding through NSF AGS-0849491 and NASA HSRP #NNX12AK63G

  2. Motivation Motivating Questions and Working Hypotheses • Why do some marginal systems develop despite the presence of inhibiting factors? • Why do viable systems fail to develop?

  3. Relating Vorticity and Buoyancy Goal: Include thermodynamics in vorticity tendency without invoking thermal wind balance.

  4. Motivation Genesis Process Hypothesis Shear Tropopause Radiative Cooling/Heating Latent Heat Release Convergence and ascent along wave Concentration of background vorticity produces low-level vortex 500 hPa +PV, + Cooling (Melting, Evaporation, Radiation?) Deep convection fuels formation of stratiformsheilddownshear Deep convection forms along convergence line Surface Wave Axis

  5. Motivation Genesis Process Hypothesis Shear Tropopause Night: -B / Day: +B +/- +/- +/- +/- +B +B -/? Mid-Level Vortex 500 hPa -B Low-Level Vortex Surface +y +x

  6. Methodology Creating Subset Composites • Metrics represent system evolution • System structure • Near-system environment • Metrics define a phase space

  7. Methodology Vortex Tracker • Based on NCEP vortex tracker (Marchok2002) • Multiple fields to generate center fix • Link fixes using steering flow and previous motion • Currently using Climate Forecast System Reanalysis (CFSR)

  8. Methodology Vortex Tracker - Variables 100% = non-divergent cyclonic 0% = irrotational -100% = non-divergent anticyclonic

  9. Methodology Idealized Example

  10. Methodology Track Examples Cape Verde TCs Merging Circulations Non-developing System ???? 850 hPa Vortex Idealization

  11. Results Phase Space2010 Atlantic Hurricane SeasonPre-genesis and Non-developing

  12. Future Work Future Data Sources • Reanalyses • ERA-Interim, NCEP/NCAR, MERRA • Operational • GFS, ECMWF, CMC • Observational • CIMSS satellite winds, dropsondes, satellites

  13. Future Work Analysis Goals • Examine differences between dev/non-dev in variety of composites • Kinematic, dynamic, and thermodynamic fields • Examine how parameters vary with phase space location • SST, OHC, MPI (Emanuel 1988), ventilation index (Tang and Emanuel 2012), genesis pathway (McTaggart-Cowan et al. 2008) • Will allow us to explore why viable systems sometimes fail to develop and marginal systems sometimes succeed

  14. END

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