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A Global Tropical Cyclone Formation Probability Product

A Global Tropical Cyclone Formation Probability Product. Andrea Schumacher, CIRA/CSU Mark DeMaria and John Knaff , NOAA/NESDIS/ StAR Daniel Brown, NHC. 64 th Interdepartmental Hurricane Conference 1-4 March, 2010 Savannah, GA. Motivation. Agencies required to forecast TC genesis

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A Global Tropical Cyclone Formation Probability Product

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  1. A Global Tropical Cyclone Formation Probability Product Andrea Schumacher, CIRA/CSU Mark DeMaria and John Knaff, NOAA/NESDIS/StAR Daniel Brown, NHC 64th Interdepartmental Hurricane Conference 1-4 March, 2010 Savannah, GA

  2. Motivation • Agencies required to forecast TC genesis • Of varying priority (NHC/CPHC=7, JTWC=3) • Numerical global models • Getting better as resolution improves • Tendency towards overprediction • Unknown biases • Statistical guidance • Lack of real-time, objective statistical guidance • May be due to rarity of formation (needle in a haystack) 64th Interdepartmental Hurricane Conference

  3. Overview of TC Formation Probability (TCFP) Product • Available for N Atlantic (2006), NE Pacific (2006) and NW Pacific (2008) basins. • Uses large-scale environmental and convective predictors • 3-step statistical scheme (Screening, LDA, Probability) • 24-hour probability of TC formation over each 5 x 5 degree lat/lon grid box in domain 64th Interdepartmental Hurricane Conference

  4. Input Parameters 64th Interdepartmental Hurricane Conference

  5. Recent Product Improvements • Extended to Indian Ocean and S. Hemisphere • Added 2006-2008 to development dataset • Experimental version running since Aug 2009 64th Interdepartmental Hurricane Conference

  6. Most Important Predictors N. Indian Ocean N.W. Pacific N.E. Pacific N. Atlantic • Same predictors most important in all basins • However, rank of importance varies S. Atlantic S. Indian Ocean S. Pacific 64th Interdepartmental Hurricane Conference

  7. Verification Summary1995-2008 • Brier skill scores and ROC skill scores • All positive  forecasts more skillful than climatology • Small  skill could be better • Reliability • Overpredicts at high prob in N. Atl • Underpredicts at high probs in all other basins • Gridbox-to-gridbox comparisons may be too strict • Consider fuzzy verification methods 64th Interdepartmental Hurricane Conference

  8. 2009 – Tropical Atlantic 64th Interdepartmental Hurricane Conference

  9. 2009 – NE Pacific 64th Interdepartmental Hurricane Conference

  10. 2009 – NW Pacific 64th Interdepartmental Hurricane Conference

  11. N. Indian Ocean (2009) 64th Interdepartmental Hurricane Conference

  12. S. Hemisphere (2009) 64th Interdepartmental Hurricane Conference

  13. Current Status • Objective TC formation guidance product • Global domain • Automated, real-time • Displays real-time, climatology, and anomaly plots of formation probability and input parameters • Limitations • Essentially a nowcast • Low probability values (10-25% max) • Skill relative to climatology is moderate 64th Interdepartmental Hurricane Conference

  14. Next Goal: Extend Forecast • Be consistent with NHC Genesis Probabilities (48 hrs) • GFS forecast fields (extend to 5 days) • Use larger-scale averages of convective parameters • Explore new predictors 64th Interdepartmental Hurricane Conference

  15. Thank You! • References • Schumacher, A.B., M. DeMaria, and J.A. Knaff, 2009: Objective Estimation of the 24-h Probability of Tropical Cyclone Formation. Wea. Forecasting, 24, 456–471. • DeMaria, M., J.A. Knaff, and B.H. Connell, 2001: A Tropical Cyclone Genesis Parameter for the Tropical Atlantic. Wea. Forecasting, 16, 219–233. 64th Interdepartmental Hurricane Conference

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