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Tercile Probabilities

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Precipitation Probability Forecast

Calibrated Subseasonal Tercile categories precipitation forecasts lagged behind real time from the S2S database.

The default map shows the latest forecast for weeks 2-3 ahead (i.e. the 14-day Thursday-Wednesday target period, 8 to 21 days after the forecast is issued), as probability of the dominant tercile category. Previous forecasts can be viewed through the control bar menu. The weeks 3-4 forecast (i.e. the 14-day target period, 15 to 28 days after the forecast is issued) is also available. The smaller side map shows a verification of the forecast in current view as the observed tercile values according to the 1999-2010 training period of the calibration of the forecast. New forecasts are issued weekly on Thursdays but are released on a monthly basis. Please note that these forecasts are “lagged”, i.e. they are not available in real time.

Clicking on the map will show, for the clicked grid box, the probabilities for the 3 forecasts categories (Below-, Near- and Above- Normal).

The probabilistic forecasts shown here are obtained from the statistical calibration of three models (ECMWF, NCEP CFSv2 and CMA, each run on Thursdays) from the Subseasonal to Seasonal (S2S) Prediction Project database (Vitart et al, 2017) which are combined with equal weight to form multi-model ensemble precipitation tercile probabilities forecasts. Individual model forecasts are calibrated separately for each point, start and lead using Extended Logistic Regressions (ELR; Vigaud et al, 2017) based on the historical performance of each model, and thus provide reliable intra-seasonal climate information in regards to a wide range of climate risk of concerns to the decision making communities and for which subseasonal forecasts are particularly well suited.

As subseasonal-to-seasonal (S2S) forecasting techniques are being developped, and more and more models are made available in (near) real-time, this Maproom shows the type of forecast information that can be currently delivered at these time scales.

While the verification map gives you a sense of the performance of a specific forecast issue, you can navigate from here to the Historical Skill Maproom to explore skill scores of historical performance of the forecasting system, by climatological month of issue.


Dataset Documentation

Forecast: Global 1˚ Multi-Model Ensemble forecasts probabilities by category and dominant terciles probabilities available here obtained from the statistical calibration of three models (ECMWF, NCEP CFSv2 and CMA) from the WWRP/WCRP Sub-seasonal to Seasonal Prediction Project.

Historical precipitation: Global 1˚ NOAA UNIFIED precipitation data set, historical and real-time available here.



Contact with any technical questions or problems with this Map Room.