Custom ligatures on web

I'm using SimpleWeather.js and I would like to display wind direction as an arrow instead of 1 to 3 letters. To achieve that I created a custom font with a set of custom ligatures: N, NNE, NE, ENE, etc. but instead of one arrow with specific direction, new font displays an arrow for each character. Is there a way to force rendering ligatures in a crossbrowser safe way?