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The figures below provide verification examples, over multiple or single cases, illustrating typical IFS model characteristics, be they strengths or weaknesses.  Key points for the forecast user are highlighted in the captions.

Fig8.1.16.3-1: Reliability diagram of tropical cyclone strike probabilities, at day 10, for TCs in existence at T+0, for year July to June (years indicated by colours) showing reasonably good reliability (plots are near the diagonal), but a tendency towards over- confidence (plots to right of diagonal).

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Fig8.1.16.3-3: IFS model forecast location error of tropical cyclones (HRESand HRES and CTRL) - blue; Ensemble Mean (EM) - Yellow)  and ENS spread (Red dots).  The diagram indicates that in 2016 the average location error and spread at:

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Although often very useful it should be remembered that these are an experimental product based upon identification of the warm-core circulation during the forecast period.  The technique can mis-identify misidentify 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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A limit is placed on the roughness length scale parameter in order to avoid the effect of too much drag from the sea surface in the lower atmosphere and enable more realistic (stronger) winds to be forecast in the vicinity of relatively intense tropical cyclones.  It should also be noted that tropical cyclone development with strengthened winds has only a limited effect upon the size and character of waves developed by the Wave model.  The model change to limit the roughness length scale at very high speeds was introduced in cycle 47r1 in June 2020.   See Section on Waves near tropical storms.

RSMC official forecasts of tropical cyclones take precedence

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