I think you would have to edit ajaxWDws.js
// optional settings for the Wind Rose graphic in ajaxwindiconwr as wrName + winddir + wrType
var wrName = 'wr-'; // first part of the graphic filename (followed by winddir to complete it)
var wrType = '.gif'; // extension of the graphic filename
var wrHeight = '58'; // windrose graphic height=
var wrWidth = '58'; // windrose graphic width=
var wrCalm = 'wr-calm.gif'; // set to full name of graphic for calm display ('wr-calm.gif')
// -- end of settings -------------------------------------------------------------------------