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Weekly mean anomaly from model climate.

The weekly mean anomaly charts display charts display the anomaly between the between the forecast weekly mean and the corresponding weekly mean in the ERSUBS-M-climateClimate.

Charts available are: 2m temperature, surface temperature, total precipitation, mean sea level pressure, winds.  Click on the central small icon in the bottom right of the web frame to show the colour scale of values appropriate to each display.

Colouring on the charts is implies >90% significance for the anomaly from ER SUBS-M-Climate.  White shading on the maps only implies <90% significance of the anomaly and show where the ensemble forecast is not significantly different from the sub-seasonal range climatology (ERSUBS-M-climateClimate), according to a Wilcoxon-Mann-Whitney (WMW) test.  It does not necessarily point to a forecast of average nor to a 'don't know' forecast of climatology.

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The weekly anomaly probability charts display the probability that the weekly mean anomalies are greater than zero.  The probability is calculated from the number of ensemble members which show an anomaly within the higher half of the the ERSUBS-M-climateClimate distribution. 

Charts available are: 2m temperature, surface temperature, total precipitation, mean sea level pressure. 

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• The chart displays the probability of the forecast anomaly lying in the upper half of the ERSUBS-M-climateClimate distribution (i.e. above normal; warmer or wetter etc than the mean of the ERSUBS-M-climateClimate). 

White on the plot can currently signify a number of different things - e.g. median of the forecast is about the same as the median of the re-forecasts. This fact that there are several potential interpretations can be confusing for users and ECMWF plans to offer improved products to address this later in 2024. 

Note: On precipitation charts the range of colours available for "below average" anomalies (brown colours) is constrained by the local climatology in the ERSUBS-M-climateClimate.  For example if all ENS members showed a dry week, the mean (-ve) anomaly could be no larger in magnitude than the mean in the ERSUBS-M-climateClimate.  So in some locations the strongest dry signal one can ever see will only be in the first or the second of the brown shades.

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The weekly anomaly probability charts display the probability that the weekly mean anomalies are in the lower or uppermost third (tercile), fifth (quintile) or tenth (decile) of the ERSUBS-M-climateClimate distribution.

Charts available are: 2m temperature, surface temperature, total precipitation, mean sea level pressure.

The probability is calculated from the number of ensemble members which show an anomaly within the highest or lowest tercile, quintile or decile of the the ERSUBS-M-climateClimate.

Terciles:  Three equally probable domains can be defined: below normal, normal and above normal.

• The upper tercile chart displays the probability of the forecast anomaly lying in the upper tercile of the ERSUBS-M-climate distribution (i.e. warmer or wetter).
• The lower tercile chart displays the probability of the forecast anomaly lying in the lower tercile of the ERSUBS-M-climate distribution (i.e. cooler or drier etc).

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• The upper quintile chart displays the probability of the forecast anomaly lying in the highest quintile of the ERSUBS-M-climate distribution (i.e. warmest or wettest).
• The lower quintile chart displays the probability of the forecast anomaly lying in the lowest tercile of the ERSUBS-M-climate distribution (i.e. coolest or driest).

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• The upper decile chart displays the probability of the forecast anomaly lying in the highest decile of the ERSUBS-M-climate distribution (i.e. very warmest or very wettest).
• The lower decile chart displays the probability of the forecast anomaly lying in the lowest decile of the ERSUBS-M-climate distribution (i.e. very coolest or very driest).

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• 500hPa geopotential height.
• anomaly of 2m temperature.
• anomaly of 10m wind.
• anomaly of sunshine duration; the fraction of time there is sunshine compared with mean sunshine duration in the ERSUBS-M-climate (e.g. +0.01 means 1% more sunshine than in the ER SUBS-M-climate; -0.05 means 5% less sunshine).

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The northern mid-latitude Hovmöller diagrams show the time evolution of the ensemble mean anomaly of geopotential height at 500hPa or 1000hPa, averaged over the latitude band 35N-60N (Northern extra-tropics) or 25S-50S (Southern extra-tropics).  The anomaly has been computed by averaging all the members of the real-time forecast and subtracting the mean of the ERSUBS-M-climateClimate.   Contours are plotted every 1.5dam.  Since it is an ensemble mean, the structures shown below the horizontal line are much more detailed in the first days of the forecast (top part) than in the last days (bottom part).   Shaded areas represent the ensemble spread and are displayed only when the amplitude of the anomaly exceeds 2dam.  On average spread will naturally increase with forecast lead time, though occasionally, when moving to longer lead times, there can be a reduction.

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• mean 500hPa geopotential height and the height anomaly from the corresponding weekly mean 500hPa geopotential height of the ERSUBS-M-climateClimate.
• mean 10hPa geopotential height and the temperature anomaly from the corresponding weekly mean 10hPa temperature of the ERSUBS-M-climateClimate.

Click the mouse over any location on the ensemble charts to produce probability information in diagrammatic form.  Diagrams available:

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The ROCmap shows the ROC score computed over each grid point with a resolution of 2.5 degrees longitude by 2.5 degrees latitude.  The charts  The charts are anomalies derived from previous sub-seasonal range ensemble forecasts compared with ERwith SUBS-M-climateClimate. 

The map colours show values of the ROC score shaded according to the scale above the map:

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The Ranked Probability Skill Score charts give a measure of the sub-seasonal range ensemble forecasts and is a measure of how good forecasts are in matching observed outcomes.  Forecasts falling into the upper or lower terciles of ERSUBS-M-climateClimate, are verified against the subsequent reanalysis or operational analysis (for precipitation, 24hr forecasts).  This is equivalent to the Brier skill score where upper and lower terciles are used.

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