if fcst/obs field lists cannot be built by using the opposite (fcst v…

…s. obs) list of files and template, then try to get the list of times from its own file

metplus/wrappers/series_analysis_wrapper.py

@@ -1043,6 +1043,13 @@ def get_formatted_fields(self, var_info, fcst_path, obs_path):
         fcst_field_list = self._get_field_list('fcst', var_info, obs_path)
         obs_field_list = self._get_field_list('obs', var_info, fcst_path)
 
+        # if the field lists could not be built by using the opposite (fcst/obs) file list,
+        # then try to build them using its own file list
+        if not fcst_field_list:
+            fcst_field_list = self._get_field_list('fcst', var_info, fcst_path, other='FCST')
+        if not obs_field_list:
+            obs_field_list = self._get_field_list('obs', var_info, obs_path, other='OBS')
+
         if not fcst_field_list or not obs_field_list:
             return None, None
 
@@ -1051,8 +1058,10 @@ def get_formatted_fields(self, var_info, fcst_path, obs_path):
 
         return fcst_fields, obs_fields
 
-    def _get_field_list(self, data_type, var_info, file_list_path):
-        other = 'OBS' if data_type == 'fcst' else 'FCST'
+    def _get_field_list(self, data_type, var_info, file_list_path, other=None):
+        if other is None:
+            other = 'OBS' if data_type == 'fcst' else 'FCST'
+
         # check if time filename template tags are used in field level
         if not self._has_time_tag(var_info[f'{data_type}_level']):
             # get field info for a single field to pass to the MET config file