Importance to the Off-Shore Energy Industry

James Done

Chad Teer, Wikipedia

NCAR Earth System LaboratoryNational Center for Atmospheric Research

NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network and the Research Program to Secure Energy for

America

Outline

• Historical Gulf Storms

• Large-Scale Drivers of Gulf Storms

• Storms, Climate Variability and Change over the Gulf

- NRCM

- Emanuel Model

• Assessing the Impact of Climate Variability and Change on Storm Damage

Historical Gulf Storms1966-2008: Average 4.0 storms/yr in blue box, 1.7 storms/yr in red box

Genesis locations of storms

that entered the red box.

¼ formed in black box.

Timeseries of basin-wide storm counts (blue),

storms that entered red box (red)

and ratio (black)

1966 2007

Large-Scale Drivers of Gulf StormsThe favorable summer climate is modulated by variability on a range of temporal

and spatial scales.

• Atmospheric Drivers:

- low latitude wave activity,

- wave amplification zones.

• Oceanic Drivers:

- loop current

• Coupled Drivers: El-Nino, Atlantic Meridional Mode and the Atlantic Multi-Decadal Oscillation . . .

Example: Madden-Julian Oscillation

TC genesis is 3.5 times more likely during westerly phase of the MJO.

Maloney and Hartmann (2000)

The MJO is an eastward moving equatorial disturbance.

Tracks of storms separated by phase of the MJO

Ocean TrendsGlobal model is fully coupled to the sea.

• Global model shows a dramatic increase in Tropical Cyclone Heat Potential and an increase in the 70m temperature.

• Global model has a negative bias but recent increase has also been observed.

1995 – 2005 2020 – 2030 2045 - 2055

Downscaling with NRCM: TC Numbers

• Multi-Decadal variability in Northern Gulf storm counts

15 10 20

Downscaling with NRCM: Normalized Track Density

Downscaling with NRCM:Location of Max Intensity

Downscaling with NRCM: TC Intensity

Distributions of max wind for all cyclones moving over the area occupied by offshore energy facilities in the Gulf of Mexico:

NRCM vs Obs NRCM: Time-Slices

• No mechanisms for low-latitude formation• No change in storm counts in Gulf

Downscaling with Emanuel Model: Normalized Track Density

Downscaling with Emanuel Model: Intensity

Distributions of max wind for all cyclones moving over the area occupied by offshore energy facilities in the Gulf of Mexico:

Emanuel (green) vs Obs (blue) Emanuel: Time-Slices

Assessing Damage: The Willis Hurricane Index

Goal: To develop a comprehensive hurricane damage index. Initial development for the Off-Shore facilities in the Gulf.

Adaptable to:

• Real-time Damage Forecasts

- uses only information readily available in advisory reports from the relevant hurricane warning center.

• Seasonal and Climate Variability and Change

- all parameters can be extracted directly from dynamical seasonal prediction and climate models.

Thunderhorse after Hurricane Dennis 2005

www.willisresearchnetwork.com

26°N

87°W100°W

Lat/Lon Box used for WHI

Data and Methods

Data:

• Willis Energy Loss Data (WELD) for the Gulf of Mexico (7 hurricanes) inflated by CEPCI (Arnold and Chiltern 1963) to 1998 values;

Critical Hurricane Parameters:

• The amount of energy dissipated at the surface by maximum winds

• The radial extent and character of the surface wind field (n mile)

• The translational speed of the hurricane (kt).

Combined these are a proxy for waves, currents and storm surge.

Data and Method ctd.Method:

• Base development largely on physical principles with care not to over specify the use of the small available data base;

• Independent testing to come from application during 2010 hurricane season;

• Combine the three critical factors in an additive formula:

0 0 0

( ) ( ) ( ) ,aa bb ccm h t

m h t

v R vWHI a b c

v R v

Parameter Contributions

Intensity=0.23

Translation Speed=0.71

Size=0.48

Parameter Determination

Intensity Term:

Set aa=3 following Emanuel (2005) Power Dissipation Index

Normalise by setting vm0=65 kt

Constrained to hurricanes vm>65 kt

Set a=1 through experimentation and sensitivity analysis

0 0 0

( ) ( ) ( ) ,aa bb ccm h t

m h t

v R vWHI a b c

v R v

Size Term:

Set bb=1 for consistency with areal coverage of storm winds, given translation

Normalise by setting Rh0=50 n mile

Set b=5 through experimentation and sensitivity analysis

0 0 0

( ) ( ) ( ) ,aa bb ccm h t

m h t

v R vWHI a b c

v R v

Parameter Determination

Parameter Determination

Translation Term:

Set cc=2 from regression on available data

Normalise by setting vt0=15 kt

Set c=5 through experimentation and sensitivity analysis

Also set vt <25kt on physical grounds and >7kt based on a posteriori checking.

0 0 0

( ) ( ) ( ) ,aa bb ccm h t

m h t

v R vWHI a b c

v R v

The WHI for the Gulf of Mexico

3 2( ) 5( ) 5( )65 50 1525 65,

7, 7,

m h t

t m

t t

v R vWHI

For v and v

If v v

Application to Gulf Losses

Maximum WHI vs Losses

Average WHI vs LossesR2 =0.91

R2 =0.96

3 2( ) 5( ) 5( )34 50 1525 34,

7, 7,

m h t

t m

t t

v R vWHI

For v and v

If v v

• Changed Vm threshold from 65 to 34 kts. i.e. from Cat 1 to tropical storm strength.

• All parameters extracted directly from NRCM and Emanuel Model Storms

Application to Climate Variability and Change: NRCM and Emanuel Storms

26°N

87°W100°W

Lat/Lon Box used for WHI Calculations

15 10 20

Number of StormsAverage Storm WHI

1524.4

1019.3

2022.1

Average Storm DamageMax Storm Damage

$5.7b$22.5b

$2.5b$20.4b

$4.3b$24.1b

NRCM 1995-2005 2020-2030 2045-2055

Number* of StormsAverage Storm WHI

4127.2

4027.0

4227.1

Average Storm DamageMax Storm Damage

$7.3b$12.2b

$7.2b$11.1b

$7.2b$10.1b

Emanuel Model

WHI Results

• NRCM storms show multi-decadal variability whereas Emanuel storms show almost no change. • Emanuel storms are slower → higher average damage.• NRCM storms can be very large → higher maximum damage

15 10 20

Number of StormsAverage Storm WHI

1524.4

1019.3

2022.1

Average Storm DamageMax Storm Damage

$5.7b$22.5b

$2.5b$20.4b

$4.3b$24.1b

NRCM 1995-2005 2020-2030 2045-2055

Average Storm WHI 27.2 27.0 27.1

Average Storm DamageMax Storm Damage

$7.3b$12.2b

$7.2b$11.1b

$7.2b$10.1b

Emanuel Model

WHI Results

• NRCM storms show multi-decadal variability whereas Emanuel storms show almost no change. • Emanuel storms are slower → higher average damage.• NRCM storms can be very large → higher maximum damage

For Gulf Offshore Facilities• Real-time Forecasts• Seasonal and Climate Variability and Change

Potential Extension to Universal Application (Landfall)

• Similar physical principles apply (intensity, size, translation speed), but:

• Heterogeneity of landfall infrastructure and topography;

• Variability in building codes and designs;

• Lack of impact data.

WHI Summary

Summary

• Gulf storms have both local and remote influences.-important for investigations into future Gulf Storms.

• Global model shows dramatic increase in TC heat potential over the Gulf. – need a fully coupled high resolution model to realize this energy source.

• Application of WHI provides a first order assessment of likely changes in net damage to off-shore facilities.

• Results based on NRCM and Emanuel storms are limited by small sample size.- NRCM 12 km currently underway.- apply Emanuel model to ensemble of global model future climates.

Extra Slides

Downscaling with Emanuel Model: Intensity

Average max Max max Count*factor

1995-2005 31.25 74.32 116

Obs 31.08 67.85 31

2020-2030 34.57 69.40 81

2045-2055 32.44 65.01 101