Add Difficulty Index use-case for NRL transitioned capability

[TaraJensen]

Describe the New Feature

The Difficulty Index is now transitioned to METcalcpy and METplotpy. Now, the DTC needs to add a METplus use case that produces the Difficulty Index using these capabilities.

Here is a description of the Difficulty Index from NRL: "The overall aim of this work is to graphically represent the expected difficulty of a decision based on a set of forecasts (ensemble) of, e.g., significant wave height as a function of space and time. There are two basic factors that can make a decision difficult. The first factor is the proximity of the ensemble mean forecast to a decision threshold, e.g. 12ft seas. If the ensemble mean is either much lower or much higher than the threshold, the decision is easier; if it is closer to the threshold, the decision is harder. The second factor is the forecast precision, or ensemble spread. The greater the spread around the ensemble mean, the more likely it is that there will be ensemble members both above and below the decision threshold, making the decision harder. The challenge is combing these factors into a continuous function that allows the user to assess relative risk."

Acceptance Testing

Model data: NCEP WaveWatch III data

Tests Required for new functionality: Outputs needs to match the output provided by NRL original code.

Time Estimate

Estimate the amount of work required here. Issues should represent approximately 1 to 3 days of work. 3 working days

Sub-Issues

Consider breaking the new feature down into sub-issues.

• [x] Identify tools: None
• [x] Request new sample data from NRL
• [x] Figure out what category this use case falls under: medium range
• [x] Meet with George, Hank, and Minna about how to approach this
• [x] Reproduce wind output
• [x] Add pytest?

Relevant Deadlines

January 18, 2021

Funding Source

NRL - 2700021

Define the Metadata

Assignee

• [X] Select engineer(s) or no engineer required: George McCabe
• [X] Select scientist(s) or no scientist required: Lindsay Blank

Labels

• [X] Select component(s)
• [X] Select priority
• [X] Select requestor(s)

Projects and Milestone

• [X] Review projects and select relevant Repository and Organization ones or add "alert:NEED PROJECT ASSIGNMENT" label
• [X] Select milestone to next major version milestone or "Future Versions"

Define Related Issue(s)

Consider the impact to the other METplus components.

• [X] METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy

https://github.com/dtcenter/METcalcpy/issues/27 https://github.com/dtcenter/METcalcpy/issues/37 https://github.com/dtcenter/METplotpy/issues/47

New Feature Checklist

See the METplus Workflow for details.

• [x] Complete the issue definition above, including the Time Estimate and Funding source.
• [x] Fork this repository or create a branch of develop. Branch name: feature_<Issue Number>_<Description>
• [x] Complete the development and test your changes.
• [x] Add/update log messages for easier debugging.
• [ ] Add/update unit tests.
• [x] Add/update documentation.
• [x] Push local changes to GitHub.
• [x] Submit a pull request to merge into develop. Pull request: feature <Issue Number> <Description>
• [x] Define the pull request metadata, as permissions allow. Select: Reviewer(s), Project(s), Milestone, and Linked issues
• [x] Iterate until the reviewer(s) accept and merge your changes.
• [x] Delete your fork or branch.
• [x] Close this issue.

[georgemccabe]

On feature_628_diff_index, the new use case is running in the use case tests via GitHub Actions with error. METcalcpy and METplotpy are obtained via manage_externals.

I believe the only step remaining is to write the use case documentation.

Side note: A PR was created for changes to METplotpy (https://github.com/dtcenter/METplotpy/pull/77) to fix part of the difficulty index code so it can use the latest version of matplotlib (3.3.3) instead of relying on an old version. This change replaces the use of deprecated functionality that will no longer be supported in 2 minor versions of matplotlib. Once merged into develop, this change will automatically apply to this use case and improve the output.