Add rotated latitude longitude projection to mapping.py (#3123)

* initial attempt to add rotated_latitude_longitude

#3099

* added test for rotated lat/lon mapping

* changed to single quotes because of flake

* fixed rotated latlon test assertion

src/metpy/plots/mapping.py

@@ -206,3 +206,14 @@ def make_polar_stereo(attrs_dict, globe):
     kwargs = CFProjection.build_projection_kwargs(attrs_dict, attr_mapping)
 
     return ccrs.Stereographic(globe=globe, **kwargs)
+
+
+@CFProjection.register('rotated_latitude_longitude')
+def make_rotated_latlon(attrs_dict, globe):
+    """Handle rotated latitude/longitude projection."""
+    attr_mapping = [('pole_longitude', 'grid_north_pole_longitude'),
+                    ('pole_latitude', 'grid_north_pole_latitude'),
+                    ('central_rotated_longitude', 'north_pole_grid_longitude')]
+    kwargs = CFProjection.build_projection_kwargs(attrs_dict, attr_mapping)
+
+    return ccrs.RotatedPole(globe=globe, **kwargs)

tests/plots/test_mapping.py

@@ -241,6 +241,22 @@ def test_polar_stereographic_std_parallel():
     assert crs.proj4_params['lat_ts'] == 60
 
 
+def test_rotated_latitude_longitude():
+    """Test handling a rotated latitude longitude projection."""
+    attrs = {
+        'grid_mapping_name': 'rotated_latitude_longitude',
+        'grid_north_pole_latitude': 36,
+        'grid_north_pole_longitude': 65,
+        'north_pole_grid_longitude': 0.0,
+    }
+    crs = CFProjection(attrs).to_cartopy()
+
+    assert isinstance(crs, ccrs.RotatedPole)
+    assert crs.proj4_params['o_lon_p'] == 0
+    assert crs.proj4_params['o_lat_p'] == 36
+    assert crs.proj4_params['lon_0'] == 180 + 65
+
+
 def test_lat_lon():
     """Test handling basic lat/lon projection."""
     attrs = {'grid_mapping_name': 'latitude_longitude'}