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Climate and Hurricane Risk
Dr. Dail Rowe
Accurate Environmental Forecasting
www.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
© 2005 Accurate Environmental Forecasting
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
© 2005 Accurate Environmental Forecasting
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 NAO
Low NAO
Hurricanes that
form in these
conditions are
more likely to
travel westward
towards the
southern US.
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.
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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
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.
Detrended May-June average SST anomalies
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SST impact on hurricanes
Cool Atlantic SST
Warm Atlantic SST
Major hurricanes tracks from
1951-1998 stratified by SST
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Cold vs. Warm SST Regimes
Major Hurricanes
U.S. Landfalls
Florida Landfalls
Cold: 1900 - 1925:
Cold: 1970 - 1994:
32
38
1.4 / yr
8
9
1 / 3 yrs
2
2
1 / 12.5 yrs
Warm: 1926 - 1969:
115
2.6 / yrs
23
1 / 1.3 yrs
12
1 / 2.1 yrs
Warm: 1995 - 2004:
38
3.8 / yrs
6
1 / 1.7 yrs
4
1 / 2.5 yrs
© 2005 Accurate Environmental Forecasting
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.
Index =
© 2005 Accurate Environmental Forecasting
Probability in Climate of Interest
Average Probability
Consensus and Innovation
• Most agree on projections of overall Atlantic Basin
hurricane activity for the upcoming season.
Intensity
AEF
NOAA
TSR
CSU
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
• Innovations are occurring
–
–
–
–
Regions at risk
Storm intensity
Forecasting
Translation from hazard to insured loss
© 2005 Accurate Environmental Forecasting
Average
Hurricane Index: 1938
Climate
Factors:
SST
0.21
NAO
0.31
Category 1-5 Hurricanes
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ENSO
-0.65
ENSO Trend
-0.23
Category 3-5 Hurricanes
Hurricane Index: 1989
Climate
Factors:
SST
0.08
NAO
0.32
ENSO
-0.73
Category 3-5 Hurricanes
© 2005 Accurate Environmental Forecasting
ENSO Trend
0.36
Hurricane Index: 1994
Climate
Factors:
SST
-0.11
NAO
0.78
ENSO
0.33
Category 3-5 Hurricanes
© 2005 Accurate Environmental Forecasting
ENSO Trend
0.31
Hurricane Index: 2004
All hurricanes
2004 was moderately risky
for hurricanes in general,
but…
SST: 0.31
NAO: -0.51
ENSO: 0.24
ENSO Trend: 0.58
© 2005 Accurate Environmental Forecasting
Hurricane Index: 2004
All hurricanes
2004 was moderately risky
for hurricanes in general,
but…
SST: 0.31
NAO: -0.51
ENSO: 0.24
ENSO Trend: 0.58
Cat 3.5-5 hurricanes
Cat 4-5 hurricanes
it was VERY
risky for
extreme
events in the
southeast US.
© 2005 Accurate Environmental Forecasting
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.
© 2005 Accurate Environmental Forecasting
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.
© 2005 Accurate Environmental Forecasting
Insured Loss and Climate
Synthetic Hurricane Event Set
Damage Assessment
Insured Loss Estimation
© 2005 Accurate Environmental Forecasting
Insured Loss and Climate
Synthetic Hurricane Event Set
Damage Assessment
Insured Loss Estimation
18
39
© 2005 Accurate Environmental Forecasting
Insured Loss and Climate
Synthetic Hurricane Event Set
Damage Assessment
Insured Loss Estimation
Climate induced changes in
Loss Exceedance Curves
18
39
© 2005 Accurate Environmental Forecasting
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.
© 2005 Accurate Environmental Forecasting