Cumulus is the CWMS national gridded data service, maintained by the U.S. Army Corps of Engineers. It provides centralized, on-demand access to historic, real-time, and forecast meteorological data (precipitation, temperature, and snow) sourced from the National Weather Service and other providers. For additional information, visit the Cumulus website.

This guide will teach you how to set up a Cumulus Extract Group within your HEC-RTS watershed.  

Cumulus is a USACE only resource. Access requires a CorpsNet or VPN connection and CAC authentication.

Prerequisites

You must be connected to the CorpsNet or VPN before beginning. Additionally, ensure you have CAC authentication available.

Step 1: Create a New Cumulus Extract Group

Refer to this guide for step-by-step instructions on creating a new Extract Group.

  1. Within the New Extract Group dialog, enter a Name for the new group. 
  2. Set Type to Gridded Data.
  3. Set Source to Cumulus.
  4. Click the Refresh Icon next to the URL to populate the Office and Watershed dropdowns. 
  5. Select the appropriate Office and Watershed.
  6. Click the ellipsis (...) next to the Products field.
  7. From the Available column:
    1. Select one or more products (use ctrl for multi-select).
    2. Click Add to move them to the Selected column.
  8. Click OK. A list of selected products will now appear in the New Extract Group Dialog.
  9. If you want the extract to run automatically when a forecast is created, check Run by Default.
  10. Configure the time window:
    1. Start Time: select Extract Start
    2. End Time: select Forecast Time

      You may apply an offset to Extract Start, but do not apply an offset for Forecast Time. Cumulus uses this to identify the correct forecast issuance.

  11. Click OK to create the group. 

For additional guidance on Time Window settings, see the Supplemental Information below.

Step 2: Add Inputs to the Cumulus Extract Group

It's now time to select the input data to map to the selected source data.

Option 1: Required Inputs Method

  1. From the Required Inputs table, select the needed HEC-MetVue inputs and click Add to Group.
    1. This generates the required To forecast.dss pathnames. 
  2. In the Extract Linking table, double-click the row in the From Cumulus column and click the ellipsis (...) to open the dialog.
  3. In the Cumulus DSS Selection dialog, choose the correct product and click Select.
  4. Repeat this process for each required input. 
  5. Click Apply to save your changes and then OK to close the Extract Editor.

Option 2: Ad-hoc Method

  1. Click Add Extract Data Set.
  2. From the Cumulus DSS Selection dialog, select the desired dataset and click Select.
  3. Review the To forecast.dss pathname.
    1. Ensure it matches what HEC-MetVue expects.
    2. Double-click to edit if needed.
  4. Repeat this process for each required input. 
  5. Click Apply to save your changes and then OK to close the Extract Editor.

Final Review

Create a new forecast and run the extract process using your new Cumulus Extract Group. Verify that data is correctly written to the forecast.dss file.

Supplemental Information

Forecast Dataset Behavior & Time Window Guidance

  • Cumulus can extract both observed and forecast datasets within the same group.
  • Always set the Time Window from Extract Start to Forecast Time for forecast products.
  • Forecast data is pulled in entirely, even beyond the end time. For example, a 7-day forecast product will extract all 7 days.
    • Use the HEC-MetVue Alternative Editor to trim the number of forecast days used (e.g., limit to 3 days).
  • Avoid setting the End of the Time Window to End of Simulation, as this can result in missing forecast data due to how issuance times are resolved.