diff --git a/src/wrf/projection.py b/src/wrf/projection.py
index 0aa930b..5a75064 100644
--- a/src/wrf/projection.py
+++ b/src/wrf/projection.py
@@ -85,22 +85,36 @@ if cartopy_enabled():
             self._threshold = np.diff(self.x_limits)[0] / 720
 
 
-def _ismissing(val):
-    """Return True if a value is None, greater than 90.0, or less than -90.
+def _ismissing(val, islat=True):
+    """Return True if a value is None or out of bounds.
     
-    This function is used to check for invalid latitude values.
+    This function is used to check for invalid latitude/longitude values.
     
     Args:
     
         val (numeric): A numeric value.
         
+        islat (:obj:`bool`): Set to False if checking for longitude values.
+        
     Returns:
     
-        :obj:`bool`: True if the value is None, greater than 90.0, or less
-        than -90.0.  Otherwise, False is returned.
+        :obj:`bool`: True if the value is None, or an out of bounds value.
     
     """
-    return val is None or val > 90. or val < -90.
+    if islat:
+        if val is None:
+            return True 
+        
+        if math.fabs(val) > 90.:
+            return True
+    else:
+        if val is None:
+            return True 
+        
+        if math.fabs(val) > 360.:
+            return True
+    
+    return False
 
 
 class WrfProj(object):
@@ -639,6 +653,9 @@ class Mercator(WrfProj):
             if self.truelat1 == 0. or _ismissing(self.truelat1) 
             else self.truelat1) 
         
+        self._stand_lon = (0. if _ismissing(self.stand_lon, islat=False) 
+                           else self.stand_lon)
+        
     
     def _cf_params(self):
         
@@ -658,7 +675,7 @@ class Mercator(WrfProj):
         _pyngl.mpProjection = "Mercator"
         _pyngl.mpDataBaseVersion = "MediumRes"
         _pyngl.mpCenterLatF = 0.0
-        _pyngl.mpCenterLonF = self.stand_lon
+        _pyngl.mpCenterLonF = self._stand_lon
         
         _pyngl.mpLimitMode = "Corners"
         _pyngl.mpLeftCornerLonF = geobounds.bottom_left.lon
@@ -677,7 +694,7 @@ class Mercator(WrfProj):
             return None
         
         local_kwargs = dict(projection = "merc",
-                            lon_0 = self.stand_lon,
+                            lon_0 = self._stand_lon,
                             lat_0 = self.moad_cen_lat,
                             lat_ts = self._lat_ts,
                             llcrnrlat = geobounds.bottom_left.lat,
@@ -699,12 +716,12 @@ class Mercator(WrfProj):
         
         if self._lat_ts == 0.0:
             _cartopy = crs.Mercator(
-                                central_longitude = self.stand_lon,
+                                central_longitude = self._stand_lon,
                                 globe = self._globe())
         
         else:
             _cartopy = MercatorWithLatTS(
-                central_longitude = self.stand_lon,
+                central_longitude = self._stand_lon,
                 latitude_true_scale = self._lat_ts,
                 globe = self._globe())
             
@@ -717,7 +734,7 @@ class Mercator(WrfProj):
                        "+lon_0={} +lat_ts={}".format(
                                             Constants.WRF_EARTH_RADIUS,
                                             Constants.WRF_EARTH_RADIUS,
-                                            self.stand_lon,
+                                            self._stand_lon,
                                             self._lat_ts))
         
         return _proj4
diff --git a/src/wrf/util.py b/src/wrf/util.py
index 67d30eb..6a297d0 100644
--- a/src/wrf/util.py
+++ b/src/wrf/util.py
@@ -3392,7 +3392,7 @@ def latlon_coords(var, as_np=False):
     
         var (:class:`xarray.DataArray`):  A variable.
         
-        to_np (:obj:`bool`): Set to True to return the coordinates as 
+        as_np (:obj:`bool`): Set to True to return the coordinates as 
             :class:`numpy.ndarray` objects instead of 
             :class:`xarray.DataArray` objects.