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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 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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Fig8.1.16.2-3: 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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