Forecasting severe weather events, more than 24 h ahead, at METEO FRANCE: An operational trial 11th...
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Forecasting severe weather events, more than 24 h ahead, at METEO FRANCE: An operational trial 11th EMS/10th ECAM, B. Gillet-Chaulet, DPREVI/PG January 23 2009, 15 H, Meteosat.
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Transcript of Forecasting severe weather events, more than 24 h ahead, at METEO FRANCE: An operational trial 11th...
Forecasting severe weather events, more than 24 h ahead,
at METEO FRANCE:An operational trial
11th EMS/10th ECAM,
B. Gillet-Chaulet,
DPREVI/PG
January 23 2009, 15 H, Meteosat.
Context and motivations :
Beyond the short range (24 H) at METEO FRANCE No equivalent oper. warning procedures available (not yet…) NWP improvements during recent years
« Predictability » => Express uncertainty
Xynthia windstorm : 3 days in advance !
Approach and Product :
occurrence of “severe weather events”– Definition :
orange or red level, “Vigilance” procedure, 24 h ahead.
- Violent winds,
- Heavy rains *, (not floods).
- Violent thunderstorms,
- Snow/Ice.
• (not temperatures).
For one entire Day (00 to 24H), D+2, D+3… Zoning (fixed), administrative regions (significant) Risk Index (usual thunderstorms/fogs…)
=> Quantify the risk
Risk Scale:
0, no risk,
1, low,
2, medium,
3, high.
In the past, (CNP -National Service- : December. 2004, ¼ de France). Reference/”truth” data : “Vigilance” level . Example : How much is a “low” risk (1),
– Over the north-eastern regions, – Parameter – D+2 ?
Approach and Product :
In the past, (CNP -National Service- : December. 2004, ¼ de France). Reference/”truth” data : “Vigilance” level . Example : How much is a “low” risk (1),
– Over the north-eastern regions, – Parameter – D+2 ?
Approach and Product :
In the past, (CNP -National Service- : December. 2004, ¼ de France). Reference/”truth” data : “Vigilance” level . Example : How much is a “low” risk (1),
– Over the north-eastern regions, – Parameter – D+2 ?
Approach and Product :
nothing nothing nothing nothing
20 % 1/5 in this example
D+2, Regions (in total):
3
36
68
87
8
0
10
20
30
40
50
60
70
80
90
100
quasi nul faible moyen élevé
Risque prévu
Fré
qu
en
ce
ob
se
rv
é
Prévision 2005/2010
Fréq. Phén. 2005/2010
Fréq. Obs/Prév
295 103 103 76 13
3504 3092 286 111 15
N Cases
Period:
1st Nov – 1st April
2004/2005
to
2009/2010
(Winter before last)
Approach and Product :
Forecast
No Risk Low Medium High
Climatic
frequency
3
36
68
87
8
0
10
20
30
40
50
60
70
80
90
100
quasi nul faible moyen élevé
Risque prévu
Fré
qu
en
ce
ob
se
rv
é
Prévision 2005/2010
95%
95%
Fréq. Phén. 2005/2010
95%
95%
Fréq. Obs/Prév
295 103 103 76 13
3504 3092 286 111 15
Rare phenomena:
Significant ?
Period:
1st Nov – 1st April
2004/2005
to
2009/2010
(Winter before last)
Approach and Product :
D+2, Regions (in total):
N Cases
No Risk Low Medium High
Forecast
Climatic
frequency And Feed-back(Low risk ?)
1
28
70
100
8
0
10
20
30
40
50
60
70
80
90
100
quasi nul faible moyen élevé
Risque prévu
Fré
qu
en
ce
ob
se
rvé
Prévision 2005/2010
95%
95%
Fréq. Phén. 2005/2010
95%
95%
Prév. 2010/2011
Fréq. 2010/2011
Fréq. Obs/Prév
48 5 18 19 6
608 510 65 27 6
Latest Winter :
1st Nov – 1st April
2010/2011
Reliable !
Approach and Product :
D+2, Regions (in total):
N Cases
HighMediumLowNo Risk
Climatic
frequency
Forecast
Sample size, season, region, range, discrimination between indexes…
“Calibration” (« Dressing ») :
Approach and Product :
No Risk,
Low,
Medium,
High.
No Risk,
Low,
Medium,
High.
Examples : XynthiaValid for : Sunday 28/02/2010
3 days ahead 2 days ahead
D+3 D+2
No Risk
Low
Medium
High
Calibrated Scale:
South-East, 7/09/2010Valid for : Tuesday 7/09/2010
3 days ahead 2 days ahead
D+3 D+2
Lyon, daily rainfall
104,1 mm
Absolute Record
(previous 1935)
No Risk
Low
Medium
High
Calibrated Scale:
Paris under the snow, 8/12/2010Valid for : Wednesday 8/12/2010
3 days ahead 2 days ahead
D+3 D+2
FRANCE - A la mi-journée, la neige continuait de tomber sur la place de la
Concorde à Paris. L'Île-de-France, comme dix-neuf autres départements, ont été placés par Météo France en vigilance
orange neige et verglas ce mercredi. AFP/ Médina DE MIGUEL
No Risk
Low
Medium
High
Calibrated Scale:
235
108
0
50
100
150
200
250
300
350
400
450
pod
détectés non détectés
275
3494
0
500
1000
1500
2000
2500
3000
3500
4000
far
prévus à tort non prévus
Events point of view (ROC) :
D+2, Regions (in total), Period 2004-2011 (01/11 – 01/04) :
Probability of detection (POD)( Hit Rate) :
Probability of false detection (POFD)(False alarm rate) :
Scale /10 !
69% 7%
No Risk,
Low,
Medium,
High.
Scale
Observed Not Observed
badgood
235
108
0
50
100
150
200
250
300
350
400
450
pod
détectés non détectés
275
3494
0
500
1000
1500
2000
2500
3000
3500
4000
far
prévus à tort non prévus
19
324
0
50
100
150
200
250
300
350
400
450
pod
détectés non détectés
2
3767
0
500
1000
1500
2000
2500
3000
3500
4000
far
prévus à tort non prévus
69% 7%
6% 0, %
AROC = 0.81 ( 0.84 , 0.79 )
Events point of view (ROC) :
D+2, Regions (in total), Period 2004-2011 (01/11 – 01/04) :
Probability of detection (POD)( Hit Rate) :
Probability of false detection (POFD)(False alarm rate) :
Observed Not ObservedScale /10 !
Scale
No Risk,
Low,
Medium,
High.
Scale
No Risk,
Low,
Medium,
High.
goodbad
Conclusion :
Thanks to recent improvements (research, operational…)
Signal at D+2, D+3, and beyond ! (7 Day test…)(Non deterministic)
Proposal of synthesis… -> Since 1st of March 2010, daily issue (14 H 30 local time) :
– COGIC, SCHAPI, CNIR, CRIR, INVS (feed back ?)
CNP production (regions collaboration), Available on the internal Website
http://previ-gene/ Similar products already available on
several Websites…(MET OFFICE)
Thank you for your attention
One
Context
back
Title : Forecasting severe weather events, more than 24 hours ahead, at METEO FRANCE:
An operational trial.
For the short range, typically 24 hours ahead, severe weather forecast procedures have been in effect for a long time. The French “vigilance” watch map celebrates its tenth anniversary in 2011. It puts in concrete form the first mission of METEO FRANCE in the domain of protection of people and goods, and has proved generally successful. Improvements in numerical weather prediction during recent years, now enable a focus on forecasting dangerous weather phenomena at longer ranges (e.g. within the Medium Range) and beyond the requirements for triggering a “vigilance” warning. However, this can not be just a simple extension of the validity of the vigilance watch map, because uncertainty generally quickly increases with the forecast range and makes a deterministic approach difficult.
A systematic production, experienced on a daily basis since December 2004 at the national forecasting service of METEO FRANCE has tried to forecast the risk of occurrence of dangerous phenomena (violent winds, heavy rain, violent thunderstorms, snow/ice) that might reach orange or red warning levels of “vigilance”, several days ahead.
Every morning, a risk index has been assessed by the forecasters, based on their study of deterministic models, numerous EPS products, for a given day from D+2 until D+7, and over given geographical areas of France. The index has been selected from no risk, unlikely, likely, certain. After choosing a reference or “truth” data (the colour of “vigilance” actually issued at the considered scale), accuracy and skill of the forecast has been shown. Then the idea has been to provide, in real time, the probabilities corresponding to the reliability of the chosen index taking into account the phenomenon, the samples representativeness and the discrimination between indexes.
Since March 2010, encouraging results have allowed us to propose institutional partners of METEO FRANCE a forecast of the risk of occurrence of these phenomena in terms of probabilities at the scale of the administrative French regions for D+2 and D+3.
First feed-back from the users is interesting, but shows that probabilities must be correctly interpreted. In fact, one still thinks that a probability of 50% corresponds to the toss of a coin, whereas it is significantly high when the climatological frequency of the phenomenon is low. Furthermore, decision makers have to learn how to make best use of this new type of information.
Abstract:
Résumé :
Ce travail concerne la prévision des phénomènes météorologiques présentant un risque pour la sécurité des personnes et des biens. A vingt-quatre heures d’échéances, des procédures d’avertissement existent depuis longtemps : la « Vigilance » de Météo France fête ses dix ans d’existence en 2011. Les progrès notables réalisés en prévision ces dernières années permettent d’anticiper ces phénomènes à des échéances plus lointaines. Cependant, leur faible prévisibilité empêche une approche déterministe. Une production systématique, quotidienne, expérimentée depuis décembre 2004 à DPREVI/PG, s’attache à prévoir le risque d’occurrence des phénomènes « Vent violent, Pluie-innondation, Orages, Neige-verglas » susceptibles de relever des niveaux de vigilance orange ou rouge, à plusieurs jours d’échéance. En mars 2010, les résultats encourageants ont permis de proposer aux partenaires institutionnels de Météo France une prévision du risque d’occurrence de ces phénomènes, assortie d’une probabilité calibrée, à l’échelle des régions économiques françaises, pour les journées J+2 et J+3.
