Seasonal forecasts Laura Ferranti and the Seasonal Forecast Section User meeting 15-17 June 2005

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Text of Seasonal forecasts Laura Ferranti and the Seasonal Forecast Section User meeting 15-17 June 2005

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Seasonal forecasts Laura Ferranti and the Seasonal Forecast Section User meeting 15-17 June 2005 Slide 2 Outline: -Performance 2004-2005 -Drought conditions over the Iberian peninsula -Progress with the multi-model system - Some results from the experimentation done to test the next system (S3). Slide 3 2004-2005 Performance Monsoon 2004 Tropical storm activity Anomalously cold Feb 2005 Slide 4 SST predictions for the JJA 2004 i.c. 01/05/2004 JJA 2004 SST anomaly Op. anal-era40 (1987-2001) Slide 5 Precipitation JJA 2004 GPCP anomalies (1987-2001) Prob. for the below normal categoryEnsemble mean anomaly Slide 6 Tropical storm activity: Climate 2004 Observed tropical storm frequency over the Atlantic: Over Western North Pacific: Slide 7 Slide 8 2mt anomalies JFM 2005 Slide 9 January February March 2005 Slide 10 user meeting 15-17 June 2005 10 Seasonal forecast performance Feb 2005 Forecasts starting on 1 st January Slide 11 Seasonal forecast performance JFM 2005 Z 500 Feb 2005 Slide 12 Accumulated precip 1 Sept 2004 10 June 2005 Slide 13 Accumulated precip 1 Oct 2004 31 May 2005 % of normal Instituto da gua, Portugal Slide 14 Drought index 31 May 2005 Instituto da gua, Portugal Weak drought Moderate drought Severe drought Extreme drought % of territory affected by drought 31 May 05 15 May 05 Weak drought 45 Moderate drought 2823 Severe drought 2028 Extreme drought 4844 Slide 15 Precipitation, Centre/South Portugal Instituto da gua, Portugal Monthly precipitationAccumulated Accumulated, climate Slide 16 Southern Iberian Peninsula 40-37N 9E-0W: Soil MoisturePrecipitation (GPCP) 2005 2004 2003 2002 2001 months Slide 17 Seasonal predictions of precipitations: Slide 18 summer 2005 versus summer 2003 Precipitation (GPCP) Soil Moisture 2005 2004 2003 2002 2001 40-50N 0-15E Slide 19 Probability of 2m Temp > upper tercile of the model climate JJA 2005 JJA 2003 Slide 20 Probability of 2m Temp > upper tercile of the model climate for JJA 2005 Forecasts start 1 May 2005 Met Office ECMWF Mto France Slide 21 Probability of 2m Temp > upper tercile of the model climate Forecast start 1 April 2005 Met Office ECMWF Predictions for JJA 2005 Mto France Slide 22 Conclusions -Predictions of the monsoon precipitation for JJA 2004 verified well. -Over the West Pacific basin the forecast predicted successfully higher tropical storm activity than the climatology. Over the Atlantic the forecast has not been as good. -Beyond the first month the skill of the seasonal forecast for a single month can be limited by the chaotic nature of the atmosphere. -Dry conditions over the Iberian Peninsula were consistently predicted since November 2004. -For the next summer warm anomalies are predicted over the South- western Europe. Slide 23 Multi-model : Verification of the individual multi-model component is completed this includes the original and revised Mto France system. Multi-model products as well as their verification is in progress. What issues are involved for reaching the operational status: - A suitable hind-cast ensemble size covering the same period. - Some coordination on how to display the products on the web. Slide 24 Mto France S2 Mto France S1 Slide 25 Mto France S2Mto France S1 Slide 26 Mto France S2Mto France S1 Slide 27 System 3 experimentation: Slide 28 Too weak easterlies Slide 29 System 3 experimentation: Slide 30 Slide 31 Slide 32 Experimentation for System 3: Results from coupled integrations with a more recent version of the atmospheric model (CY29R1) indicate generally a higher skill except for a specific season and location. This seems to be related with the mean state of the atmospheric model that tends to underestimate the easterlies over the central tropical Pacific. One possible solution to this problem may be a correction term during the model integration. Further experimentation is in progress including the testing of the latest atmospheric cycle.