Describe the New Feature

During the latest working session with CPC, it was determined that the method for calculating HSS for multi-categorical thresholds differs from MET.

MET method: Fill in the NxN contingency table, using the user-defined cat_thresh on the forecast and observation fields for each gridpoint. Sum Hits and Misses across the bins, and use the HSS equation to calculate 1 HSS value for the table. If the user applied hss_ec_value, set C2 variable to what user assigned.

CPC method: Fill in the NxN contingency table, using the user-defined cat_thresh on the forecast fields. Observation fields are predetermined to be hits or misses (binary). For each forecast field threshold, calculate the 2x2 Hits and Misses and use the HSS equation to calculate an HSS value for each forecast threshold. Additionally, this will always utilize a user's hss_ec_value.

Another description of this would be that regardless of the number of bins, CPC will evaluate each threshold as a 2x2 contingency table with a predefined C2 value in the HSS equation.

As MET capability currently stands, the hss_ec_value variable is only applicable to MCTS line type. But as the description above indicates, CPC would need this functionality in the CTS line type (or alternatively, numerous columns in MCTS where each threshold has its own HSS value).

While not performed in the traditional manner of HSS, Barb Brown confirmed that this passes statistical soundness.

Acceptance Testing

Probability of Exceedance fields (fcst) and binary observation fields, which @j-opatz can provide.

The acceptance criteria would be to replicate CPC's HSS value for maximum temperature (85th percentile) with the provided data.

Time Estimate

Unknown, engineer will need to fill in
Issues should represent approximately 1 to 3 days of work.

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Funding Source

Split 2700041, 2793541

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