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The charts show the strike probability based on the number of members that predict a tropical cyclone, each member having equal weight.  To be counted, the tropical cyclone centre must track within a 300km radius of the location within a time window of 48 hours. The charts are also useful during and after extratropical extra-tropical transition of these features as they move into mid-latitudes.  However, the technique can sometimes mis-identify incorrectly identify as a tropical cyclone a high-latitude circulation containing something of a warm core (e.g. a well occluded frontal depression with cooler air encircling some warm, moist air remnants near the centre). The result will be spurious probabilities of tropical storm strikes.  Future improvements to the technique will will aim to remove this problem.

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Fig8.1.16.2-1: To view tropical cyclone activity:

1. On the charts page, click on latest tropical activity.  Click on the tropical cyclones activity (Including genesis) frame (top left frame).  
2. Colours give strike probability of tropical cyclone etc.  Select point of interest ENSgrams etc..
3. Select time of forecast as desired.
   
4. Display of ENSgrams (including wavegrams),

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1. extreme forecast indices extreme forecast indices (EFI) and cumulative distribution functions (CDF), and vertical profiles for selected point.

These products provide a quick assessment of high-risk areas, allowing for some uncertainty in the exact timing or position.  The strike probabilities can be generated for three storm categories:

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Fig8.1.16.2-3: Spurious indication of tropical storm strike probability near Iceland.  The technique has mis-identified has incorrectly identified a high-latitude well-occluded frontal depression as being a tropical cyclone (because it has a warm core).

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Tropical cyclone, tropical storm, and hurricane strike probability charts are also available on ecCharts.  These are an experimental product based upon identification of the warm-core circulation during the forecast period.  They are useful during and after extratropical extra-tropical transition of these features as they move into mid-latitudes.  ecCharts have the advantage that boundary layer (or any other) winds can be superimposed.

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