Direction from which wind is blowing.<br /></p><p><br /></p><p>In FM-92 GRIB, encoded as GRIB Code-table 4.2 discipline 0 (meteorology), category 2 (momentum), #0 wind direction.<br /></p><p><font color="#ff0000"><br /></p><p></font><font color="#ff0000">Note that BUFR Table B provides additional descriptors with further refined semantics:</font><br /></p><p><font color="#ff0000">- 0 11 016 : Extreme counter clockwise direction of a variable wind; and</font><br /></p><p><font color="#ff0000">- 0 11 017 : Extreme clockwise direction of a variable wind.</font><br /></p><p><font color="#ff0000"><br /></p><p></font><font color="#ff0000">There seems little or no value in defining UML classes that match this detailed level of semantic specification. In usage, the class WindDirection will be qualified by the semantics of an attribute or association role. The model documentation should express the associated refined semantics. Other scenarios where a Measure class may be qualified include _MINIMUM_ visibility, _MINIMUM ONE MINUTE MEAN_ RVR etc. Again, in these situations the semantics of the base class can be cleanly expressed using model documentation.</font><br /></p><p><font color="#ff0000"><br /></p><p></font><font color="#ff0000">In contrast, prevailing visibility has complex semantics when compared to the base visibility definition. Here, there is value in ensuring consistent semantics are expressed by defining a specialised class for PrevailingVisibility.</font><br /></p>