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The guidelines in Section 1.1.6 hold for most cyclones, but very small cyclones pose extra difficulties. They may be beyond the capabilities of the IFS horizontal resolution.  And even very small cyclones can have a sting jet associated.  Accordingly forecasters need to treat ensemble output with particular care when there is potential for very small cyclones to develop - say with lateral dimensions of order 200km or less.

1.1.7 Local winds  due to orography

Detail of winds to the lee of and around isolated mountains inland or mountainous islands are not likely to be captured.  This is because:

  • horizontal resolution (~9km) may not capture the geographic features sufficiently.
  • smoothing of the orography is likely to underestimate the mountain heights (possibly by factor of 4 in isolated mountainous island). 

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