how to convert wind direction to degrees?

You could store the names and values in arrays and look up the angle corresponding to the matching name.

directionValues = 0:22.5:337.5
directionNames = {'N','NNE','NE','ENE','E','ESE','SE','SSE','S','SSW','SW','WSW','W','WNW','NW','NNW'};

directionValues(strcmp(directionNames,'NNW'))

Better yet, put that in an anonymous function

compass2degree = @(dirName) directionValues(strcmp(directionNames,dirName));

compass2degree('ESE')