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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
OutlineOutline
Hindcast VerificationHindcast Verification
Real-Time Forecast VerificationReal-Time Forecast Verification
Hindcast VerificationHindcast Verification
Real-Time Forecast VerificationReal-Time Forecast Verification
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
DateDate 7 Dec.7 Dec.10 10
Apr.Apr.3 3
JuneJune2 2
Aug.Aug.
SeasonalSeasonal
ForecastForecastXX XX XX XX
2013Forecast Schedule
2013Forecast Schedule
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
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
% 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
% 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
% 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%
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
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.”