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How Well Forecast Were the 2004 and 2005 Atlantic and U.S. Hurricane Seasons? Mark Saunders and Adam Lea Department of Space and Climate Physics Benfield.

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Presentation on theme: "How Well Forecast Were the 2004 and 2005 Atlantic and U.S. Hurricane Seasons? Mark Saunders and Adam Lea Department of Space and Climate Physics Benfield."— Presentation transcript:

1 How Well Forecast Were the 2004 and 2005 Atlantic and U.S. Hurricane Seasons? Mark Saunders and Adam Lea Department of Space and Climate Physics Benfield Hazard Research Centre University College London Royal Meteorological Society Meeting Hurricanes 15th March 2006

2 RMetSoc Hurricanes March 2006Slide /5 Hurricane Seasons Rank as the most active and damaging consecutive hurricane years on record. Rank as the most active and damaging consecutive hurricane years on record. Seven intense hurricane landfalls on the U.S. (norm is one). Seven intense hurricane landfalls on the U.S. (norm is one). Estimated total damage bill approaching US $ 200 bn (norm is US $ 10bn). Estimated total damage bill approaching US $ 200 bn (norm is US $ 10bn). 11:00 UT 29 August 2005 (Courtesy NOAA)

3 RMetSoc Hurricanes March 2006Slide 3 Structure 1. How unusual were 2004 and 2005? 2. Reasons for high Atlantic and U.S. hurricane activity in 2004 and Seasonal Forecast Comparison (a) Atlantic basin hurricane activity. (b) U.S. landfalling hurricane activity. 4.Forecast Business Application. 5.Conclusions.

4 RMetSoc Hurricanes March 2006Slide Hurricane Season Most active and damaging on record. Most tropical storms: 27 Most hurricanes: 15 Most Cat 5 hurricanes: 3 Most major hurricanes to strike the U.S.: 4 Highest US hurricane insured damage: ~ US $ 50bn. 1

5 RMetSoc Hurricanes March 2006Slide 5 Major Gulf Hurricanes in 2004/5 First time since 1915/6 that four major hurricanes have struck the Gulf Coast in two years.

6 RMetSoc Hurricanes March 2006Slide 6 Florida Damaging Storms 2004 Courtesy of NOAA and UW-CIMSS First time since 1886 that four hurricanes have struck the same state in one year.

7 RMetSoc Hurricanes March 2006Slide 7 Most Costly US Insured Losses

8 RMetSoc Hurricanes March 2006Slide 8 2. Reasons for high Atlantic and U.S. hurricane activity in 2004 and 2005

9 RMetSoc Hurricanes March 2006Slide 9 August/September 2004/5 Sea Surface Temperature Anomaly ( average) +0.67°C SST anomaly in hurricane main development region

10 RMetSoc Hurricanes March 2006Slide 10 August/September 2004/5 Anomaly in Vertical Wind Shear ( average)

11 RMetSoc Hurricanes March 2006Slide 11 August/September 2004/5 Mean Sea Level Pressure Anomaly ( average)

12 RMetSoc Hurricanes March 2006Slide 12 August/September 2004/ mb Height Averaged Wind Anomalies ( average) Steering winds on-shore

13 RMetSoc Hurricanes March 2006Slide 13 3.Seasonal Forecast Comparison

14 RMetSoc Hurricanes March 2006Slide 14 Organisations Providing Seasonal Forecasts Seasonal Atlantic hurricane forecasts for the 2004 and 2005 seasons were issued by: Tropical Storm Risk (TSR) (9 for each season) Gray/Colorado State University (6 for each season) NOAA (2 for each season) Meteorological Institute, Cuba (2 for each season)

15 RMetSoc Hurricanes March 2006Slide 15 U.S. ACE Index Combines storm numbers, intensity and duration within a single index (Saunders and Lea, 2005). Combines storm numbers, intensity and duration within a single index (Saunders and Lea, 2005). Defined as the sum of the squares of hourly maximum 1-min sustained winds for all storm systems over the U.S. mainland while they are at least tropical storm in strength. Defined as the sum of the squares of hourly maximum 1-min sustained winds for all storm systems over the U.S. mainland while they are at least tropical storm in strength. Strongly linked to U.S. hurricane insured loss (Collins and Lowe, 2001) with a rank correlation of 0.7 for the period Strongly linked to U.S. hurricane insured loss (Collins and Lowe, 2001) with a rank correlation of 0.7 for the period The U.S. ACE (Accumulated Cyclone Energy) Index:

16 RMetSoc Hurricanes March 2006Slide 16 Deterministic Forecasts for 2005

17 RMetSoc Hurricanes March 2006Slide 17 Deterministic Forecasts for

18 RMetSoc Hurricanes March 2006Slide 18 Probabilistic Forecasts for 2005 North Atlantic ACE Index

19 RMetSoc Hurricanes March 2006Slide 19 Probabilistic Forecasts for 2005 U.S. ACE Index

20 RMetSoc Hurricanes March 2006Slide 20 Probabilistic Forecasts for 2004 North Atlantic ACE Index

21 RMetSoc Hurricanes March 2006Slide 21 Probabilistic Forecasts for 2004 U.S. ACE Index

22 RMetSoc Hurricanes March 2006Slide 22 U.S. Hurricane Prediction Model Saunders, M. A. and A. S. Lea, Seasonal prediction of hurricane activity reaching the coast of the United States, Nature, 434, , First example of useful skill for predicting seasonal US landfalling hurricane activity and damage. First example of useful skill for predicting seasonal US landfalling hurricane activity and damage. The model has a sound physical basis. The model has a sound physical basis. The model will benefit risk awareness and offers good potential for application in business decision making. The model will benefit risk awareness and offers good potential for application in business decision making.

23 RMetSoc Hurricanes March 2006Slide Forecast Business Application

24 RMetSoc Hurricanes March 2006Slide 24 Background The TSR early August forecast model (Saunders and Lea, 2005) correctly anticipates whether U.S. hurricane losses are above-median or below- median in 74% of years between 1950 and The TSR early August forecast model (Saunders and Lea, 2005) correctly anticipates whether U.S. hurricane losses are above-median or below- median in 74% of years between 1950 and This skill combined with the success of the seasonal U.S. landfalling hurricane forecasts for 2004 and 2005, suggests that forecast precision may now be high enough to offer potential benefit to industries whose returns are affected by hurricane damage. This skill combined with the success of the seasonal U.S. landfalling hurricane forecasts for 2004 and 2005, suggests that forecast precision may now be high enough to offer potential benefit to industries whose returns are affected by hurricane damage.

25 RMetSoc Hurricanes March 2006Slide 25 Hurricane Loss Probability US hurricane total insured loss contingent on the TSR (Tropical Storm Risk) 1st August forecast. The chance of a large total loss is much higher in those years when the forecast is high.

26 RMetSoc Hurricanes March 2006Slide and 2005 For the damaging 2004 and 2005 hurricane seasons the TSR early August forecasts predicted U.S. landfalling hurricane activity in the upper quartile and upper decile respectively. For the damaging 2004 and 2005 hurricane seasons the TSR early August forecasts predicted U.S. landfalling hurricane activity in the upper quartile and upper decile respectively. Thus TSR would have recommended that insurance companies purchase extra protection. Thus TSR would have recommended that insurance companies purchase extra protection.

27 RMetSoc Hurricanes March 2006Slide Conclusions 2004 and 2005 Atlantic and U.S. landfalling hurricane seasons were both predicted to be active (upper tercile activity to high probability) from the previous December and 2005 Atlantic and U.S. landfalling hurricane seasons were both predicted to be active (upper tercile activity to high probability) from the previous December. Overall the TSR forecasts slightly outperformed those from the other forecast groups (certainly the case for U.S. landfalling activity). Overall the TSR forecasts slightly outperformed those from the other forecast groups (certainly the case for U.S. landfalling activity). Seasonal forecast precision now appears high enough to be practically useful. Seasonal forecast precision now appears high enough to be practically useful.


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