Refactor supported input path handling.

jobs/JREGIONAL_GET_EXTRN_MDL_FILES

@@ -167,28 +167,29 @@ check_var_valid_value "ICS_OR_LBCS" "valid_vals_ICS_OR_LBCS"
 #
 #-----------------------------------------------------------------------
 #
-# Set the parameter anl_or_fcst that determines whether we want to get 
-# analysis or forecast files.  This depends on whether we want these files 
-# to generate initial condition and surface field files or lateral boundary 
-# condition files.  Also, set time_offset_hrs, which is the offset in 
-# hours between the current cycle's starting time and the starting time 
-# of the external model providing the LBCs.
+# Set parameters for grabbing either the initial conditions from analysis or
+# forecast files of external models, or the lateral boundary conditions
+# from external models. The script has been called to do the work for
+# one or the other.
 #
 #-----------------------------------------------------------------------
 #
 if [ "${ICS_OR_LBCS}" = "ICS" ]; then
-  anl_or_fcst="ANL"
-  time_offset_hrs="0"
+  if [ ${EXTRN_MDL_ICS_OFFSET_HRS} -eq 0 ] ; then
+    anl_or_fcst="ANL"
+    time_offset_hrs=0
+  else
+    anl_or_fcst="FCST"
+    time_offset_hrs=${EXTRN_MDL_ICS_OFFSET_HRS:-0}
+  fi
 elif [ "${ICS_OR_LBCS}" = "LBCS" ]; then
   anl_or_fcst="FCST"
-  time_offset_hrs="${EXTRN_MDL_LBCS_OFFSET_HRS}"
+  time_offset_hrs=${EXTRN_MDL_LBCS_OFFSET_HRS:-0}
 fi
 #
 #-----------------------------------------------------------------------
 #
-# Set the name of and then create the directory in which to stage the 
-# external model files for the current cycle (if it doesn't already exist).  
-# Then change location to that directory.
+# Create the directory where the exetrnal model files should be stored
 #
 #-----------------------------------------------------------------------
 #

ush/config_defaults.sh

@@ -599,6 +599,24 @@ NDAS_OBS_DIR="/path/to/observation-directory/ndas/proc"
 # data availble at least every 6 hours.  It is up to the user to ensure 
 # that this is the case.
 #
+# EXTRN_MDL_ICS_OFFSET_HRS:
+# Users may wish to start a forecast from a forecast of a previous cycle
+# of an external model. This variable sets the number of hours earlier
+# the external model started than when the FV3 forecast configured here
+# should start. For example, the forecast should start from a 6 hour
+# forecast of the GFS, then EXTRN_MDL_ICS_OFFSET_HRS=6.
+
+# EXTRN_MDL_LBCS_OFFSET_HRS:
+# Users may wish to use lateral boundary conditions from a forecast that
+# was started earlier than the initial time for the FV3 forecast
+# configured here. This variable sets the number of hours earlier
+# the external model started than when the FV3 forecast configured here
+# should start. For example, the forecast should use lateral boundary
+# conditions from the GFS started 6 hours earlier, then
+# EXTRN_MDL_LBCS_OFFSET_HRS=6.
+# Note: the default value is model-dependent and set in
+# set_extrn_mdl_params.sh
+#
 # FV3GFS_FILE_FMT_ICS:
 # If using the FV3GFS model as the source of the ICs (i.e. if EXTRN_MDL_NAME_ICS
 # is set to "FV3GFS"), this variable specifies the format of the model
@@ -614,6 +632,8 @@ NDAS_OBS_DIR="/path/to/observation-directory/ndas/proc"
 EXTRN_MDL_NAME_ICS="FV3GFS"
 EXTRN_MDL_NAME_LBCS="FV3GFS"
 LBC_SPEC_INTVL_HRS="6"
+EXTRN_MDL_ICS_OFFSET_HRS="0"
+EXTRN_MDL_LBCS_OFFSET_HRS=""
 FV3GFS_FILE_FMT_ICS="nemsio"
 FV3GFS_FILE_FMT_LBCS="nemsio"
 #