This guide explains how to collect gridded Quantitative Precipitation Forecast (QPF) data from the National Oceanic and Atmospheric Administration’s (NOAA) Weather Prediction Center (WPC). It can also be used as a general framework for accessing other NOAA datasets or for reading GRIB (GRB) files into an HEC-RTS forecast. The NOAA File Transfer Protocol (FTP) site hosts a variety of data products, including QPF grids, Excessive Rainfall Outlooks, and GIS shapefiles.

This guide is intended as a template that demonstrates the process for retrieving QPF grids from NOAA. The included script is provided as-is and is not guaranteed to be maintained or updated.

Prerequisites

This guide includes several predefined elements that may vary from model to model. You should review and adjust these elements as needed to best fit your specific modeling requirements.

Step 1: Edit the HEC-MetVue Command-Line Utility 

This workflow uses the HEC-MetVue command-line utility ProjectTinToGrid.cmd, with minor modifications.

  1. Navigate to your HEC-RTS installation and locate the HEC-MetVue directory.
  2. Open the utilities/windows folder.
  3. Copy ProjectTinToGrid.cmd and rename the copy to something appropriate for your use case.
    1. In this example, the file is renamed to Qpf2SHG.cmd.
  4. Right-click the new .cmd file and select Edit.
  5. Change set usage_help=-? to set usage_help=%* near the bottom of the file. 
  6. Remove the pause command at the end of the file.
    1. This prevents the command window from remaining open after execution and helps streamline scripted workflows.

Step 2: Modify the Script 

The getQPF.py script retrieves QPF data from NOAA and then uses the modified command-line utility to convert the data into a format compatible with HEC-RTS.

Most of the script updates dynamically, but some values are hard-coded and may need to be adjusted.

  1. Open the script in the HEC-RTS Script Editor or an IDE of your choice.
  2. Navigate to line 220.
    1. Line 220 directs output to the forecast.dss file for an HEC-RTS forecast run.
  3. Review line 221.
    1. This defines the F-Part of the DSS pathname for the grids being written.
    2. The value must match the F-Part specified on line 224.

  4. Lines 222 and 223 typically do not need to be changed for HEC-RTS modeling.

    1. These lines write the grids to a DSS file in SHG format for use in an HEC-HMS model.

  5. Review line 224.
    1. This line defines the full DSS pathname for the output grids.
    2. Ensure the F-Part matches the value specified on line 221.
  6. At line 257, update the path to the HEC-MetVue command-line utility created in Step 1.
    1. If the command file is located in HEC-MetVue/utilities/windows, only the filename at the end of the path needs to be changed.
    2. Replace Qpf2SHG.cmd with the name of your modified command file.

Step 3: Run the Script in HEC-RTS

To run the script in HEC-RTS:

  1. Place the script inside the scripts folder within your watershed directory.
  2. Launch HEC-RTS and load the watershed.
  3. Navigate to the Modeling tab and open a forecast of interest.

    1. This script retrieves time-window information from the active forecast, so it must be run from within an active HEC-RTS forecast.

  4. From the Scripts menu, select Run.

  5. Select the getQPF script from the list and click Run.

  6. You may monitor progress in the HEC-RTS console. A popup window will appear when the script finishes executing.

Final Review

If the script completes without errors, the QPF data should be available in the forecast.dss file associated with the forecast. The data location should match the output path defined in the script.

Additional Resources

  • Documentation for the ProjectTinToGrid utility can be found here. 
  • Information on using masks with the HEC-MetVue command-line utility can be found here. 
  • NOAA WPC GRIB data source information can be found here.