Developments in Seasonal Atlantic Basin Tropical Cyclone Prediction

Phil Klotzbach

Department of Atmospheric Science

Colorado State University

Ph. D. Defense

July 9, 2007

Acknowledgments

Mentor – Dr. Gray

Ph. D. Advisor – Dr. Schubert

Ph. D. Committee Members – Drs. Mielke and Pielke

CSU Student Colleagues – Eric Blake, Matt Eastin, Brian McNoldy, Stacey Seseske, Wes Terwey, Jonathan Vigh

Friends and Family – Especially my parents for providing me with an outstanding home education

National Science Foundation and Lexington Insurance Company

Outline Introduction

Data

Atlantic Basin Multi-Decadal Variability

Seasonal Forecast Developments

2007 Hurricane Forecast

United States Landfalling Hurricane Probability Webpage

Hurricanes and Global Warming

Introduction

The globe’s atmosphere and oceans function as one unit.

Current circulation features have considerable precursor information

regarding the coming month’s or coming season’s amount of

hurricane activity.

OUTGOING LONGWAVE RADIATION

ABSORBED SOLAR RADIATION

LATENT HEAT FLUX

NET ENERGY BALANCE

TEMPERATURE

OCEAN HEAT FLUX

SUBSURFACE HEAT STORAGE

SENSIBLE HEAT AND POTENTIAL ENERGY FLUX

THERMAL INERTIA

Flow diagram for climate modeling, showing feedback loops. From Robock (1985).

Arago’s Admonition:

“Never, no matter what may be the progress

of science, will honest scientific men who

have regard for their reputations venture

to predict the weather.”

So easy a caveman could do it.

Data

• NCEP/NCAR Reanalysis – globally gridded (2.5° x 2.5°) dataset for many surface and upper-level features from 1948-present

• National Hurricane Center “best track” dataset – best estimates of six-hourly location and intensity of tropical cyclones

1 2

3

H

H

Courtesy of John Marshall (MIT)

1860 1900 1940 1980 2020

THC - Strong

(Goldenberg et al. 2001)

Top 20 AMO Years – Bottom 20 AMO Years (1878-2006) - SLP

AMO Index

1.2 2.6 1.5 3.9Major Hurricanes per Year

STRONG THC WEAK THC

gyre - gyre +

+

+

+ –

–

–

SLPA – SLPA +

13

26

10

40

1900-25 1926-69 1970-94 1995-06

Annual Number of 6 Hour Periods for Cat. 3-4-5 Hurricanes in the Atlantic

Date8

Dec.3

Apr.31

May3

Aug.4

Sep. 2

Oct.

Seasonal

ForecastX X X X

Monthly Forecast

X X X

New Forecast Development Methodology

• Use predictors using surface data from the two months prior to the forecast issue date

• Hindcast Net Tropical Cyclone activity metric only

• Develop forecast on data from 1950-1989

• Test forecast on “independent” data from 1990-2004

• New forecast schemes must show comparable skill in both time periods

EQ.

Oct-Nov SLP3

`

2

1

New December Forecast Predictors

Oct-Nov SST

Oct-Nov SLP

Early December Observed versus Hindcast NTC (1950-1989)

0

50

100

150

200

250

1950 1955 1960 1965 1970 1975 1980 1985

NT

C

Observed NTC

Predicted NTC

r2 = 0.51

Developmental

Early December Observed versus "Forecast" NTC (1990-2004)

0

50

100

150

200

250

1990 1992 1994 1996 1998 2000 2002 2004

NT

C

Observed NTC

Predicted NTCr2 = 0.49

Applied

EQ.

Feb-Mar SST

3`

2

1

New April Forecast Predictors

Feb-Mar SLP

Feb-Mar SST

Early April Observed versus Hindcast NTC (1950-1989)

0

50

100

150

200

250

1950 1955 1960 1965 1970 1975 1980 1985

NT

C

Observed NTC

Predicted NTCr2 = 0.53

Developmental

Early April Observed versus "Forecast" NTC (1990-2004)

0

50

100

150

200

250

1990 1992 1994 1996 1998 2000 2002 2004

NT

C

Observed NTC

Predicted NTCr2 = 0.66

Applied

EQ.

Predicted July-Nov AMM

Index2

1

New June Forecast Predictors

April-May SST

3`

April-May SST

Early June Observed versus Hindcast NTC (1950-1989)

0

50

100

150

200

250

1950 1955 1960 1965 1970 1975 1980 1985

NT

C

Hindcast NTC

Observed NTCr2 = 0.42

Early June Observed versus Hindcast NTC (1950-1989)

0

50

100

150

200

250

1950 1955 1960 1965 1970 1975 1980 1985

NT

C

Predicted NTC

Observed NTCr2 = 0.42

Developmental

Early June Observed versus "Forecast" NTC (1990-2004)

0

50

100

150

200

250

1990 1992 1994 1996 1998 2000 2002 2004

NT

C

Forecast NTC

Observed NTCr2 = 0.54

Early June Observed versus "Forecast" NTC (1990-2004)

0

50

100

150

200

250

1990 1992 1994 1996 1998 2000 2002 2004

NT

C

Predicted NTC

Observed NTCr2 = 0.54

Applied

EQ.

12

New August Seasonal Forecast Predictors

June – July SST

3

June – July SST

June – July SLP

Pre 1-August NSD S of 23.5°N,

E of 75°W

4

August Statistical Scheme – Hindcast Skill for NTC (1900-1948)

Observations Hindcasts

Observations Hindcasts

August Statistical Scheme – Hindcast Skill for NTC (1949-2005)

NS NSD H HD MH MHD NTC

Top 10 9.2 57.9 5.2 26.5 2.7 7.5 113.0

Bottom 10 4.3 24.5 2.4 8.2 0.7 1.8 39.2

Ratio (1900-1948)

Ratio (1949-2005)

2.1

2.1

2.4

2.6

2.2

2.5

3.2

3.7

3.9

4.9

4.2

7.3

2.9

3.4

Top 10 – Bottom 10 Atlantic Basin TC Ratios for 1900-1948 Period Using Forecast Equations Developed on 1949-1989

16 Landfalls

3 Landfalls

December April June August

Top 10 7 6 7 6

Bottom 10 2 2 2 2

Ratio 3.50 3.00 3.50 3.00

Top 10 versus Bottom 10 Florida Peninsula and East Coast Major Hurricane Landfalls based on NTC Hindcasts (1949-2005)

Skill of Seasonal Forecasts

Skill of Seasonal Forecasts

Correlation of CSU Forecasts of NTC with Observations

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

December April June August

Skill of Cane and Zebiak Forecast Model for Nino 3 SST

Predicted versus Observed Named Storms (1984-2006) - Issued on 1 August

0

5

10

15

20

25

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006

Po

st-1

Au

gu

st N

amed

Sto

rms

Predicted NS

Observed NS

r2 = 0.53

2007 Hurricane Predictions2007 Hurricane Predictions

Forecast ParameterStatistical Forecast

Analog Forecast

31 May 2007 Forecast

1950-2000 Climatology

Named Storms (NS) 15.7 12.7 17 9.6

Named Storm Days (NSD) 80.5 71.2 85 49.1

Hurricanes (H) 9.7 7.5 9 5.9

Hurricane Days (HD) 40.2 38.9 40 24.5

Major Hurricanes (MH) 3.7 3.7 5 2.3

Major Hurricane Days (MHD) 8.2 11.4 11 5.0

Accumulated Cyclone Energy (ACE)

158 150 170 96

Net Tropical Cyclone Activity (NTC)

164 158 185 100

2007 FORECAST AS OF 31 MAY 2007

PROBABILITIES FOR AT LEAST ONE MAJOR (CATEGORY 3-4-5) HURRICANE

LANDFALL ON EACH OF THE FOLLOWING COASTAL AREAS FOR 2007

1) Entire U.S. coastline – 74% (average for last century is 52%)

2) U.S. East Coast including Peninsula Florida - 50% (average for last century is 31%)

3) Gulf Coast from the Florida Panhandle westward to Brownsville - 49% (average for last century is 30%)

4) Expected above-average major hurricane landfall risk in the Caribbean

New Landfalling Hurricane Web Application

Currently Available at the following URL:

In partnership with the GeoGraphics Laboratory – Bridgewater State College,

Bridgewater MA

http://www.e-transit.org/hurricane

Areas for which Landfall Probabilities are Issued

U.S. 1

Sub – U.S. 2

Regions 11

Sub – Regions 55

Counties 205

REGION 2 - TEXAS & LOUISIANA

V

AJ

C

C

C

LH

J

O

(a)(c)(b)

Future Work

Monthly Probabilities

User-Selected Probabilities (Daily, Weekly Periods)

Potential Damage

Open AtlanticOcean Differences

1933 Hurricane Season

2005 Hurricane Season

Courtesy of

Chris Landsea (2006)

Figure 4 – From Webster et al. (2005)

Basin 1986-1995 1996-2005 Ratio (1996-2005 / 1986-1995)

North Atlantic 10 25 250%

Northeast Pacific 37 23 62%

N. Atl. + NE Pac. 47 48 102%

Northwest Pacific 75 76 101%

North Indian 3 4 133%

South Indian 26 36 138%

South Pacific 13 16 123%

Northern Hemisphere 125 128 102%

Southern Hemisphere 39 52 133%

Global 164 180 110%

Category 4-5 Hurricanes by Ten-Year Periods

Basin Correlation with ACE Correlation with Cat. 4-5 Hurricanes

North Atlantic 0.57 0.39

Northeast Pacific 0.58 0.59

Northwest Pacific -0.28 -0.11

North Indian -0.07 -0.29

South Indian -0.32 -0.18

South Pacific -0.38 -0.20

Correlation between Boreal Summer Basin-wide Sea Surface Temperatures and Tropical Cyclone Activity

(1986-2005)

y = -9.85x + 928.93

0

200

400

600

800

1000

1200

1400

1990 1993 1996 1999 2002 2005

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Tro

pic

al S

ST

An

om

aly

(°C

)Global ACE

SST

Klotzbach (2006)

Kossin et al. (2007)

ATLANTIC

THC

STRONG

ATLANTIC

THC

WEAK

GLOBE COOLING

GLOBE WARMING

CAT 3-4-5 TRACKS

CAT 3-4-5 TRACKS

PENINSULA FLORIDA LANDFALLING MAJOR HURRICANES

1925-1965 41 Years

1966-2006 41 Years

2050

Background 280 ppm

310 ppm

365 ppm

39

La

nd

falls

22

La

nd

falls

0.95 year

0.54 year

CO 2

zero

Conclusions

• An active hurricane season is predicted in 2007

• The recent increase in Atlantic basin hurricane activity is largely driven by natural multi-decadal variability

Questions???