Tropical Cyclones as a Global Prediction Problem

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Tropical Cyclones as a Global Prediction Problem

• Chris Davis
• ESSL/MMM and RAL

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Scientific Foci

• Genesis
• Landfall
• Extratropical Transition

gt All foci are linked by need for knowledge and
prediction of scale interactions

• Upscale growth of deep convection
• Scale contraction in waves and cyclones

gt Strong link with THORPEX
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Approaches

• Predictability Studies (1-2 weeks)
• Seasonal prediction (2 weeks to several
  months)
• Process studies
• Field campaigns
• Extended quasi-idealized simulations
• Global and high-resolution mesoscale models
  essential
• Prediction is fundamentally probabilistic
• Basic research and many applications

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Genesis Process Studies

• Collect and analyze observations crucial to
  understand organization of convection
• 1. Genesis Environment
• Baroclinic Systems
• Wave Accumulation
• 2. Mesoscale Organization
• Mesoscale vorticity
• Cloud Physics
• Air-sea interaction and PBL
• gt All crucial for evaluating and improving
  models across scales

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Global Tropical Cyclone Formation
From Watterson et al., 1995 J. Climate
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Tropical Cyclogenesis (N. Pacific)
Eastern Pacific
Western Pacific
Dependence on MJO Phase
From Maloney and Hartmann 1999
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Genesis over the Atlantic
Baroclinic
Easterly Waves
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Landfall Seasonal Prediction

• Predict Cyclone Numbers and Intensity
• Appropriate specification of frequency and
  intensity (e.g. ACE)
• Development regions (helps specify tracks)
• Dominant tracks of TCs

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Interannual Variability
Chan et al., 2004 J. Climate
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Initial Prediction Efforts
Shear forecasts by UKMET ensemble fixed SST from
1 June
From Thorncroft and Pytharoulis, 2002, WAF
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ET Predictability

• Interaction with mid-latitude baroclinic systems
• Latent heating vs baroclinic processes
• Identify key forecast periods where uncertainty
  largest

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Forecast Skill Bifurcation
ET Tracks
From Jones et al., 2003 Wea. And Forecasting
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Downstream Effect of Christobal (1999)
Precipitation
Courtesy of Mel Shapiro
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External Linkages/Overlaps

• NOAA CPC (seasonal prediction)
• NOAA CDC
• NCEP/Navy (hurricane modeling/ocean coupling)
• NHC (requirements)
• HRD (research and data)
• U Miami (Chen modeling)
• CSU (Bill Gray outlooks)
• FSU (Krishnamurti super-ensemble)

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Critical Needs

• Global or hemispheric coupled atmos/ocean model
  with adaptive nesting (WRF)
• Fundamental studies on scale interaction
• Observations of convection/wave interaction
• Extended cloud-resolving modeling studies
• Probabilistic prediction techniques
• Ensembles
• Statistical methods
• Improved cloud and boundary-layer
  parameterizations
• Downdrafts and cloud physics
• Air/sea interaction