Extrem Forecast Index

Pierre Eckert

Daniel Cattani

MétéoSuisse

EFI: definition Scores and verification Precipitations Wind gust Conclusion

1

0

)()1( dppFpnEFI nfn

p

Ff(p)

An Extreme Forecast Index

Takes values from –1 (all members break climate minimum records) and +1 (all beyond climate maximum records)

For a single value (e.g. deterministic) forecast with climate rank Q: EFI3=(Q-50%) [1+4(Q-50%)2]

Q=95%, EFI3=0.81

Q=98%, EFI3=0.92

Q=99%, EFI3=0.96

Verification parameters (1) Precipitations (nov.2001-apr.2003)

Predictands: 2nd max prec. / 24h of climatological regions (W, E, S)

Predictors: EFI max over regions

Thresholds 10 mm/24h 20 mm/24h 50 mm/24h

Verification parameters (2) Gusts (nov.2001-apr.2003)

Predictands: 2nd max gust / 24h of climatological regions (W, E ) Predictors:

• EFI max over regions

• EFI max over all the domain (45-48.5°N; 5-11.5°E)

Thresholds 50 km/h 75 km/h 100 km/h

Verification: scores

Event Observed Not Observed

Forecasted A B

Not Forecasted C D

• Forecasted : EFI gt given value

• Hit Rate = A / (A+C)• FAR = B / (A+B)

Precipitations : Switzerland West

Prec ge 10mm/24h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

False Alarm Rate

Hit

Ra

te T+66

T+90

T+114

T+138

Hit = 0,5EFI = 0,3 T+66hEFI = 0,2 T+90hEFI = 0,2 T+114

Precipitations : Switzerland West

Prec ge 20mm/24h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

False Alarm Rate

Hit

Rat

e T+66

T+90

T+114

T+138

Precipitations : Switzerland West

Prec ge 50mm/24h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

False Alarm Rate

Hit

Rat

e T+66

T+90

T+114

T+138

Precipitations : Switzerland South

Prec ge 10mm/24h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

False Alarm Rate

Hit

Ra

te

T+66

T+90

T+114

T+138

Precipitations : Switzerland South

Prec ge 20mm/24h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

False Alarm Rate

Hit

Rat

e T+66

T+90

T+114

T+138

Precipitations : Switzerland SouthPrec ge 50mm/24h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

False Alarm Rate

Hit

Rat

e T+66

T+90

T+114

T+138

Gusts : Switzerland West

0

50

100

150

200

250

300

350

400

450

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

EFI - region W

T+48

T+72

T+96

T+120

50km/h

75km/h

Gusts : Switzerland West

0

50

100

150

200

250

300

350

400

450

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

EFI values - large dom ain

T+48

T+72

T+96

T+120

50km/h

75km/h

Gusts: Switzerland West

Gusts ge 50 km/h

0

0.2

0.4

0.6

0.8

1

1.2

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

False Alarm Rate

Hit

Rat

e T+48

T+96

T+48 domain

T+96 domain

Gusts: Switzerland West (ref region)

Gusts ge 75 km/h

0

0.2

0.4

0.6

0.8

1

1.2

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1

False Alarm Rate

Hit

Rat

e T+48

T+96

T+48 domain

T+96 domain

Conclusion: precipitations

T+42-66h

Hit=0.6

Prec ge 10mm Prec ge 20mm Prec ge 50mm

EFI FAR EFI FAR EFI FAR

West 0.2 0.2 0.2 0.6

East 0.2 0.3 0.2 0.7

South 0.3 0.3 0.3 0.5 0.5 0.5

Conclusion: Gusts

Gust ge 75 km/h

Hit=0.5

T+36-60h T+60-84h T+84-108h T+108-132h

EFI FAR EFI FAR EFI FAR EFI FAR

West (ref region) 0.3 0.7 0.3 0.5 0.2 0.7 0.2 0.8

West (ref domain) 0.8 0.7 0.7 0.7 0.5 0.8 0.3 0.9