(all charts correspond to weekly means)
(all charts correspond to weekly means)
The weekly mean anomaly charts display the anomaly between the forecast weekly mean and the corresponding weekly mean in the ER-M-climate.
Charts available are: 2m temperature, surface temperature, total precipitation, mean sea level pressure, winds.
Colouring on the charts is implies >90% significance for the anomaly. This does not mean the white shading on the maps necessarily points to:
Click the mouse over any location on the ensemble charts to produce probability information in diagrammatic form. Diagrams available:
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.
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 ER-M-climate distribution.
Charts available are: 2m temperature, surface temperature, total precipitation, mean sea level pressure.
Two equally probable domains can be defined: below normal and above normal.
White on the plot means that either:
This plot structure circumvents the fact that some ER-M-Climate distributions will be skewed (i.e. the climatological probability of seeing more than the mean is far from 50%).
Note: On precipitation charts the range of colours available for "below average" anomalies (brown colours) is constrained by the local climatology in the ER-M-climate. 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 ER-M-climate. 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.
Click the mouse over any location on the ensemble charts to produce probability information in diagrammatic form. Diagrams available:
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.
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 ER-M-climate 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 ER-M-climate.
Terciles: Three equally probable domains can be defined: below normal, normal and above normal.
Quintiles: Five equally probable domains can be defined:
Deciles: Five equally probable domains can be defined.
Click the mouse over any location on the ensemble charts to produce probability information in diagrammatic form. Diagrams available:
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.
These multi-parameter charts charts display the ensemble weekly mean:
Click the mouse over any location on the ensemble charts to produce probability information in diagrammatic form. Diagrams available:
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.
Hovmöller or Time-Longitudes diagrams show the time evolution of the ensemble mean anomaly of a parameter. The x-axis represents the longitude, the y-axis represents the time evolution (time increasing downwards). Past results lie above the horizontal line and forecast results lie below.
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 ER-M-climate. 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.
The Madden-Julian Oscillation (MJO) Hovmöller diagrams show the ensemble mean anomalies of outgoing long wave radiation, zonal wind at 850hPa, and velocity potential at 200hPa averaged over a tropical band (15N-15S).
The mean flow and anomaly charts show, at global or regional scales, the weekly:
Click the mouse over any location on the ensemble charts to produce probability information in diagrammatic form. Diagrams available:
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.
The extended range products should always be used with historical skill metrics in mind.
Broad indications of ensemble performance and predictability in the extended range should be taken into account when considering the extended range output. Users should consult verification information:
The Relative Operating Characteristics give a measure of the effectiveness of a forecast system to predict an event that actually happens balanced against forecast of an event that fails to occur. ROC is derived from measuring the area beneath the results plotted on a ROC diagram. ROC area values indicate:
The Reliability diagrams give a measure of the tendency of the forecast system to over- or under-forecast and event. The diagram plots the frequency of a forecast probability of an event against the frequency that the event occurs. Ideally these should match and is shown by the diagonal line. Where the plot lies:
An explanation of reliability diagrams and ROC diagrams is given in the annex to this guide.
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 are anomalies derived from previous extended range ensemble forecasts compared with ER-M-climate.
The map colours show values of the ROC score shaded according to the scale above the map:
The RPSS map shows the RPSS score computed over each grid point with a resolution of 2.5 degrees longitude by 2.5 degrees latitude.
The Ranked Probability Skill Score (RPSS) compares the Ranked Probability Score of a probabilistic forecast system with a reference of some sort, usually climatology.
The Ranked Probability Skill Score charts give a measure of the extended 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 ER-M-climate, 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.
The map colours show values of the RPSS score (equivalent to the Brier skill score) shaded according to the scale above the map: