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Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts Phil Klotzbach and William Gray Department of Atmospheric Science Colorado State University

Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

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Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts. Phil Klotzbach and William Gray Department of Atmospheric Science Colorado State University. Outline. Hindcast Verification Real-Time Forecast Verification. - PowerPoint PPT Presentation

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Page 1: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

Verification of Colorado State University’s Atlantic Basin Seasonal

Hurricane Forecasts

Verification of Colorado State University’s Atlantic Basin Seasonal

Hurricane Forecasts

Phil Klotzbach and William Gray

Department of Atmospheric Science

Colorado State University

Phil Klotzbach and William Gray

Department of Atmospheric Science

Colorado State University

Page 2: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

OutlineOutline

Hindcast VerificationHindcast Verification

Real-Time Forecast VerificationReal-Time Forecast Verification

Hindcast VerificationHindcast Verification

Real-Time Forecast VerificationReal-Time Forecast Verification

Page 3: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

How do you calculate Net Tropical Cyclone (NTC) Activity?

NTC activity in any year consists of the seasonal totals of named storms, named storm days, hurricanes, hurricane days, major hurricanes and major hurricane days in terms of their long-term period averages and multiplied by 100.

So, as an example, let’s look at 2005:

2005 NTC Calculation (1950-2000 Climatological Values in Parentheses)

Named Storms (9.6) 28Named Storm Days (49.1) 131.50Hurricanes (5.9) 15Hurricane Days (24.5) 49.75Major Hurricanes (2.3) 7Major Hurricane Days (5.0) 17.50Note: Seasonal values are in parentheses

Now to calculate NTC, sum the following six ratios: 28/9.6 = 291, 131.50/49.1 = 268, 15/5.9=254, 49.75/24.5 = 203, 7.0/2.3 = 304, 17.5/5.0 = 350

2005 NTC = (291+268+254+203+304+350)/6 = 279

Page 4: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

DateDate 7 Dec.7 Dec.10 10

Apr.Apr.3 3

JuneJune2 2

Aug.Aug.

SeasonalSeasonal

ForecastForecastXX XX XX XX

2013Forecast Schedule

2013Forecast Schedule

Page 5: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts
Page 6: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

Post-1 August NTC (Observed vs. Cross-Validated Hindcast)

0

50

100

150

200

250

1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012

Observed

Jackknifed Hindcastr = 0.91

Page 7: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts
Page 8: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

Post-31 July Real-Time Net Tropical Cyclone Activity Forecast vs. Observations (1990-2012)

0

50

100

150

200

250

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

Predicted

Observedr = 0.65

Page 9: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

% Improvement in CSU's Forecasts from Previous 10-Year Mean

-10%

-5%

0%

5%

10%

15%

20%

25%

30%

35%

April June August

Forecast Month

% Im

pro

ve

me

nt

Me

an

Ab

so

lute

Err

or

Named Storms Named Storm Days Hurricanes

Hurricane Days Major Hurricanes Major Hurricane Days

Net Tropical Cyclone Activity

NO SKILL

SKILL

Page 10: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

% Improvement in CSU's Forecasts from Previous 10-Year Mean for Net Tropical Cyclone Activity

0%

5%

10%

15%

20%

25%

30%

April June August

Forecast Month

% I

mp

rov

em

en

t M

ea

n A

bs

olu

te E

rro

r

ALL FORECASTS SKILLFUL

Page 11: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

% Improvement in Mean Absolute Error (2008-2012) vs. (Beginning of Forecast - 2007)

April June August

Named Storms 10% 12% 12%

Named Storm Days 24% 12% 11%

Hurricanes 3% -4% -14%

Hurricane Days 41% 35% 20%

Major Hurricanes 70% 75% 83%

Major Hurricane Days 61% 46% 24%

Net Tropical Cyclone Activity 54% 63% 47%

Page 12: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

Future Work

• Redevelop April and June statistical forecast models using ERA-Interim data

• Initiate July seasonal forecast model (Klotzbach 2013, manuscript accepted for publication)

• Investigate skill of forecast models using longer-period hindcast data, including ESRL’s 20th Century Reanalysis as well as the ERA-CLIM Reanalysis which should be available by early 2014

Page 13: Verification of Colorado State University’s Atlantic Basin Seasonal Hurricane Forecasts

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.”

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.”