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 Agencies required to forecast TC genesis Of varying priority (NHC/CPHC=7, JTWC=3) Of varying priority (NHC/CPHC=7, JTWC=3) Numerical global models Numerical global models Getting better as resolution improves Getting better as resolution improves Tendency towards overprediction Tendency towards overprediction Unknown biases Unknown biases Statistical guidance Statistical guidance Lack of real-time, objective statistical guidance Lack of real-time, objective statistical guidance May be due to rarity of formation (needle in a haystack) May be due to rarity of formation (needle in a haystack) 2 64th Interdepartmental Hurricane Conference3 March 2010

Overview of TC Formation Probability (TCFP) Product Available for N Atlantic (2006), NE Pacific (2006) and NW Pacific (2008) basins. Available for N Atlantic (2006), NE Pacific (2006) and NW Pacific (2008) basins. Uses large-scale environmental and convective predictors Uses large-scale environmental and convective predictors 3-step statistical scheme (Screening, LDA, Probability) 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 24-hour probability of TC formation over each 5 x 5 degree lat/lon grid box in domain 3 64th Interdepartmental Hurricane Conference3 March 2010

Input Parameters ABBREVParameter DescriptionSource LATLatitude ( ° )ATCF PLAND% land coverageLand covrge DSTRMDistance to nearest TC (km)ATCF SSTSea surface temp ( ° C)Reynolds VSHEAR hPa vertical shear (kt)NCEP GFS CIRC850 hPa circulation (kt)NCEP GFS THDEVVertical instability ( ° C)NCEP GFS HDIV850 hPa horizontal divergence (m/s)NCEP GFS SLPSea-level Pressure (hPa)NCEP GFS PCCOLD% coverage by pixels colder than -40 ° CSat WV BTWARMAvg. cloud-cleared brightness temp ( ° C)Sat WV CPROBClimatological formation probabilityBest Track 4 64th Interdepartmental Hurricane Conference3 March 2010

Recent Product Improvements Extended to Indian Ocean and S. Hemisphere Extended to Indian Ocean and S. Hemisphere Added to development dataset Added to development dataset Experimental version running since Aug 2009 Experimental version running since Aug th Interdepartmental Hurricane Conference3 March 2010

Most Important Predictors Same predictors most important in all basins Same predictors most important in all basins However, rank of importance varies However, rank of importance varies NORMALIZED COEFFICIENTSNATLNEPNWPNIOSIOSPAC Clim Formation Prob Circulation (850-mb) Cold Cloud Coverage Distance to Existing TC N. Indian Ocean S. Indian Ocean N.W. Pacific S. Pacific N.E. Pacific N. Atlantic S. Atlantic 6 64th Interdepartmental Hurricane Conference3 March 2010

Verification Summary Brier skill scores and ROC skill scores Brier skill scores and ROC skill scores All positive  forecasts more skillful than climatology All positive  forecasts more skillful than climatology Small  skill could be better Small  skill could be better Reliability Reliability Overpredicts at high prob in N. Atl Overpredicts at high prob in N. Atl Underpredicts at high probs in all other basins Underpredicts at high probs in all other basins Gridbox-to-gridbox comparisons may be too strict Gridbox-to-gridbox comparisons may be too strict Consider fuzzy verification methods Consider fuzzy verification methods 7 64th Interdepartmental Hurricane Conference3 March 2010

2009 – Tropical Atlantic 8 64th Interdepartmental Hurricane Conference3 March 2010

2009 – NE Pacific 9 64th Interdepartmental Hurricane Conference3 March 2010

2009 – NW Pacific 10 64th Interdepartmental Hurricane Conference3 March 2010

N. Indian Ocean (2009) 11 64th Interdepartmental Hurricane Conference3 March 2010

S. Hemisphere (2009) 12 64th Interdepartmental Hurricane Conference3 March 2010

Current Status Objective TC formation guidance product Objective TC formation guidance product Global domain Global domain Automated, real-time Automated, real-time Displays real-time, climatology, and anomaly plots of formation probability and input parameters Displays real-time, climatology, and anomaly plots of formation probability and input parameters Limitations Limitations Essentially a nowcast Essentially a nowcast Low probability values (10-25% max) Low probability values (10-25% max) Skill relative to climatology is moderate Skill relative to climatology is moderate 13 64th Interdepartmental Hurricane Conference3 March 2010

Next Goal: Extend Forecast Be consistent with NHC Genesis Probabilities (48 hrs) Be consistent with NHC Genesis Probabilities (48 hrs) GFS forecast fields (extend to 5 days) GFS forecast fields (extend to 5 days) Use larger-scale averages of convective parameters Use larger-scale averages of convective parameters Explore new predictors Explore new predictors 14 64th Interdepartmental Hurricane Conference3 March 2010

Thank You! References 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. 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. DeMaria, M., J.A. Knaff, and B.H. Connell, 2001: A Tropical Cyclone Genesis Parameter for the Tropical Atlantic. Wea. Forecasting, 16, 219– th Interdepartmental Hurricane Conference3 March 2010