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Predicted tropical storm frequency

These parameters are calculated over the same weekly periods as the other monthly forecast products and are averaged over an ocean basin.  The tropical cyclone identifying algorithms are the same as are used for the medium range tropical cyclone activity products.  

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1. On Charts page, enter Tropical Storm Frequency
2. Click on Tropical Storm Frequency diagram - Extended Range
   
3. As desired select other base times, or Accumulated Cyclone Energy or Tropical Storm Frequency from drop down menu.

Predicted accumulated cyclone energy (ACE)

Accumulated cyclone energy is the sum of the squares of the estimated maximum sustained velocity of every active tropical storm at six-hour intervals.

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Fig8.2.3.2: The Accumulated Cyclone Energy (ACE) product takes into account number, strength, and duration of all the tropical storms forecast by the extended ensemble during the weekly period within each arbitrarily defined ocean basin, and totals their energy.  This value is compared with a similarly derived ACE from the extended range for the same week to determine the significance level for the given basin.  If this is greater than 90% the basin is shaded.  Green bars represent the forecast and orange bars the real climatology - these can be directly compared.

Tropical storm strike probabilities

This product shows a grid point chart of tropical storm strike probability (probability of a tropical storm passing within 300km), calculated over weekly periods.  It is similar to the tropical cyclone activity charts produced for the medium-range forecasts. 

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