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 Fig8.2.6: Weekly mean anomaly of tropical storm strike probability for the same week as Fig8.2.3.4.  Colours give indication of more likely (positive probabilities, red to brown/black), or less likely (negative probabilities, cyan to blue/black) than shown in the extended range re-forecasts.Updated/Amended 24/10/20 - amended chart links to open access

OpenChart  diagrams

Tropical Storm Probabilities - Extended range forecast

These charts show the evolution of existing and potential tropical cyclone activity.

• Strike probability is the probability (in %) that a tropical cyclone will pass within a 300 km radius from a given location and within the 7-day time window.   The charts are based on the number of extended range ensemble members that predict a tropical cyclone, each member having equal weight. 
• Probability anomaly charts show whether the strike probabilities are higher (red shading) or lower (blue shading) than probabilities within a 20-year model climatology within the same 7-day time window.  They are computed by subtracting the model climatological probabilities from the real-time forecast probabilities.  Mean anomalies of probability are shown by the scale.
• Model extended range climate charts (ER-M-climate) show weekly mean strike probabilities (in %) within the same 7-day time window.

Tropical Storm Frequency - Extended range forecast

These charts show: 

• Tropical storm weekly mean frequency.  The frequency is derived by comparing the ensemble members probability with that of the 20-year model climatology probabilities within the same 7-day time window.
• Tropical storm weekly mean accumulated cyclone energy (ACE).  This is calculated by summing the square of the estimated maximum sustained velocity of every active tropical storm at six-hour intervals.  The ACE of a time period is the sum of the ACEs for each storm and takes into account the number, strength, and duration of all the tropical storms within the 7-day time window.