© 2005 Accurate Environmental Forecasting

Climate and Hurricane Risk Climate and Hurricane Risk Climate and Hurricane Risk Climate and Hurricane Risk

Dr. Dail RoweDr. Dail Rowe

Accurate Environmental ForecastingAccurate Environmental Forecasting

www.accufore.comwww.accufore.com

© 2005 Accurate Environmental Forecasting

The Team

• This presentation is based on the work of a team of scientists at Accurate Environmental Foresting, Inc. and Climatek, Inc: – AEF

• Dr. Michael Dickinson • Dr. Dail Rowe

– Climatek• Dr. James Elsner (Florida State University)• Dr. Thomas Jagger

© 2005 Accurate Environmental Forecasting

Today’s Discussion

• Climate changes hurricane risk.– Regional risk changes by more then 200%

• Climate factors influencing hurricane activity:– El Niño – Southern Oscillation (ENSO)– North Atlantic Oscillation (NAO) – Atlantic Sea-surface Temperature (SST)

• Scientists generally agree on overall Atlantic basin activity.

• Recent innovations:– Regions at risk– Hurricane intensity– Translation from hazard to insured loss– Forecasting

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El-Niño / Southern Oscillation (ENSO)

El Niño (warm event)La Niño (cold event)

Sea surface temperature patterns in the eastern tropical Pacific Ocean change global weather patterns.

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ENSO Modulates Vertical Wind-shear

http://hurricanes.noaa.gov Hurricanes derive their power by transporting water vapor from the ocean surface up a natural chimney to the upper atmosphere.

Their strength relies on the existence of this chimney structure.

© 2005 Accurate Environmental Forecasting

ENSO Modulates Vertical Wind-shear

http://hurricanes.noaa.gov Weak wind-shear is conducive to hurricane development.

La Niña = weak shear and more hurricanes

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ENSO Modulates Vertical Wind-shear

http://hurricanes.noaa.gov Strong wind-shear disrupts hurricane structure.

El Niño = strong shear and fewer hurricanes

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North Atlantic Oscillation (NAO)

High NAOHigh NAO Low NAOLow NAO

NAO determines the strength of the atmospheric circulation in the Atlantic basin and is calculated as the difference in sea level pressures between Reykjavik, Iceland and Gibraltar.

Hurricanes that form in these conditions are more likely to travel westward towards the southern US.

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Atlantic Sea Surface Temperature

Warmer ocean surface temperatures promote hurricane growth and development.

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SST leads to decadal variability

Detrended May-June average SST anomalies

There is a clear multi-decadal signal in Atlantic Sea Surface Temperatures.

Casual analysis of the hurricane record shows a clear link between SST and hurricane activity.

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SST impact on hurricanes

Major hurricanes tracks from 1951-1998 stratified by SST

Cool Atlantic SST Warm Atlantic SST

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Cold vs. Warm SST Regimes

                            Major Hurricanes     U.S. Landfalls    Florida Landfalls Cold: 1900 - 1925:        32                           8                           2Cold: 1970 - 1994:        38                           9                           2                                   1.4 / yr                   1 / 3 yrs             1 / 12.5 yrs

 Warm: 1926 - 1969:     115                        23                         12                                   2.6 / yrs                1 / 1.3 yrs             1 / 2.1 yrs Warm: 1995 - 2004:      38                           6                          4                                   3.8 / yrs                1 / 1.7 yrs             1 / 2.5 yrs

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Modeling of Climate Factors and Hurricane Activity

• We employ a statistical modeling approach as in Elsner and Jagger (2004) and Elsner and Bossak (2005) to relate climate factors and hurricane activity.– Based on 130 year climate and hurricane records

• The Hurricane Climate Risk Index is a regional measure of the climate-conditioned annual hurricane probability relative to the averaged probability.

Probability in Climate of InterestAverage Probability

Index =

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Consensus and Innovation

• Most agree on projections of overall Atlantic Basin hurricane activity for the upcoming season.

• Innovations are occurring– Regions at risk– Storm intensity– Forecasting– Translation from hazard to insured loss

Intensity AEF NOAA TSR CSU Average

Named Storms 13.2 12-15 13.9 15 9.9

All Hurricanes 7.5 7-9 7.8 8 6.0

Major Hurricanes 3.7 3-5 3.6 4 2.6

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Hurricane Index: 1938

Climate SST        NAO        ENSO        ENSO Trend

Factors: 0.21    0.31      -0.65        -0.23

Category 3-5 HurricanesCategory 1-5 Hurricanes

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Hurricane Index: 1989

Category 3-5 Hurricanes

Climate SST        NAO        ENSO        ENSO Trend

Factors: 0.08    0.32      -0.73        0.36

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Hurricane Index: 1994

Category 3-5 Hurricanes

Climate SST        NAO        ENSO        ENSO Trend

Factors: -0.11    0.78      0.33        0.31

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Hurricane Index: 2004

2004 was moderately risky for hurricanes in general, but…

All hurricanes

SST: 0.31

NAO: -0.51

ENSO: 0.24

ENSO Trend: 0.58

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Hurricane Index: 2004

2004 was moderately risky for hurricanes in general, but…

it was VERY risky for extreme events in the southeast US.

All hurricanes

Cat 4-5 hurricanesCat 3.5-5 hurricanes

SST: 0.31

NAO: -0.51

ENSO: 0.24

ENSO Trend: 0.58

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Climate Forecasts

• ENSO and Atlantic SST forecasts have useful skill at lead times of at least 9 months.– Good Florida to Maine risk forecasts well in advance

of the hurricane season.

• Forecasts of summer NAO conditions are less skillful.– Forecasts of Gulf of Mexico activity improve just prior

to the hurricane season.

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Insured Loss and Climate

• The climate induced changes in hurricane frequency and severity indicated by the Index can be used to modify the frequency and severity assumptions governing the creation of the synthetic events sets commonly used to probabilistically evaluate hurricane related insured risk.

• AIR and AEF have recently integrated our Index technology with AIR’s hurricane catalog to produce forecasts of how climate variability will affect the probability of insured loss during the upcoming hurricane season.

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Insured Loss and Climate

Damage Assessment

Synthetic Hurricane Event Set

Insured Loss Estimation

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Insured Loss and Climate

Damage Assessment

Synthetic Hurricane Event Set

Insured Loss Estimation

18 39

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Insured Loss and Climate

Damage Assessment

Synthetic Hurricane Event Set

Insured Loss Estimation

18 39

Climate induced changes in Loss Exceedance Curves

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Conclusions

• Climate variability modifies both the frequency and severity of hurricanes on a regional basis.– Regional changes of more then 200%– El Niño, the North Atlantic Oscillation, and Atlantic

sea-surface temperature are all important factors

• The AEF/AIR Climate Conditioned Hurricane Catalog permits users to evaluate the effect of climate variability on their hurricane related exposure.