P19: Probabilistic Hurricane Forecasts for Risk Management

1. P19: Probabilistic Hurricane Forecasts for Risk Management Thomas Nehrkorn and Ross N. Hoffman tnehrkor@aer.comrhoffman@aer.com  Atmospheric and Environmental Research, Inc., 131 Hartwell Ave, Lexington Massachusetts 02421-3126 www.aer.com BACKGROUND ILLUSTRATION • Large economic effects of US land-falling hurricanes require risk management through a variety of approaches: • Defensive strategies • Insurance • Weather Derivatives • Optimizing risk management requires timely, quantitative forecast information that • Includes uncertainty information • Is tailored to the specific exposure • For demonstration of the technical approach, consider: • coarse-resolution (1.5 deg) gridded fields from 51-member ECMWF ensemble • Known deficiencies: • underpredicted strength • unresolved scale Katrina 12Z 29 Aug Analysis APPROACH • Define metrics tailored to the client • As an example, we compute two indices proposed by Kantha (2006): • Hurricane Intensity Index (HII): • Hurricane Hazard Index (HHI): • Combine deterministic and probabilistic forecasts from all available sources • Need to correct for known biases • Need to account for different error magnitudes of different forecasts • Need to calibrate resulting ensemble

2. P19: Probabilistic Hurricane Forecasts for Risk Management Thomas Nehrkorn and Ross N. Hoffman tnehrkor@aer.comrhoffman@aer.com  Atmospheric and Environmental Research, Inc., 131 Hartwell Ave, Lexington Massachusetts 02421-3126 www.aer.com Control 2-day Forecast Histograms of Derived Indices Ensemble 980 hPa Spaghetti Hurricane Intensity Index (HII) Hurricane Hazard Index (HHI) Raw and Scaled Ensemble Histograms of Vmax References: L. Kantha, 2006: Time to Replace the Saffir-Simpson Hurricane Scale? EOS, 87, No. 1, doi 10.1029/2006EO010003. Richard D. Knabb, Jamie R. Rhome, and Daniel P. Brown, 2006: Tropical Cyclone Report Hurricane Katrina 23-30 August 2005, http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf