How can I use my latitude and longitude variables inside of my Jquery?

Question

So I'm attempting to make a little app right now that displays weather information based on a user's location. I can easily pass in values to my latitude and longitude to make it work properly, but I can't seem to get coordinates and assign them to my variables. What am I missing?

Note: I am newer to javascript and I'm willing to bet it's something stupid.

var latitude = 0;
var longitude = 0;

function getLocation() {
  if (navigator.geolocation) {
    navigator.geolocation.getCurrentPosition(displayLocation);
  } else {
    alert("Geolocation is not supported by this browser.");
  }
}

function displayLocation(position) {
  latitude = position.coords.latitude;
  longitude = position.coords.longitude;
  return;
}


jQuery(document).ready(function($) {
  $.ajax({
  url : "http://api.wunderground.com/api/7c5cbc3e4db2885a/geolookup/conditions/q/" + latitude + "," + longitude + ".json",
  dataType : "jsonp",
  success : function(parsed_json) {
    var location = parsed_json['location']['city'];
    var temp_f = parsed_json['current_observation']['temp_f'];
    var desc = parsed_json['current_observation']['weather'];
    var wind_dir = parsed_json['current_observation']['wind_dir'];
    ("Current temperature in " + location + " is: " + temp_f);

    $('#location').html(location);
    $('#temp_f').html(temp_f);
    $('#desc').html(desc);
    $('#wind_dir').html(wind_dir);
    $('#icon_url').attr('http://icons.wxug.com/i/c/i/clear.gif', img);
  }

 });

});