Forecast Windows

Overview

Subsequent to receiving ratings, the Clearinghouse Provider must process and disseminate the Limits Forecast. To ensure the Forecast is available to the appropriate downstream internal processes and external entities on-time, a delivery deadline must be established for the Ratings Providers. Moreover, per Order 881, it is incumbent upon the Ratings Provider to produce a new Ratings Forecast every hour using an updated forecast of ambient conditions. Consequently, there is also a limit to how early a Ratings Forecast should be generated and proposed to the Clearinghouse Provider.

The following timeline illustrates Forecast Windows that are open for full hour (duration) then close an hour in advance of the first hour of the provided forecast (deadline).

sequential forecast windows illustrated

Defining Forecast Windows

Establishing the duration and deadline of Forecast Windows is the purview of the Clearinghouse Provider; a TROLIE implementation should therefore have options to support configuring them. Configuration mechanisms are not prescribed by the TROLIE API Specification nor does it explicitly nominate “Forecast Window” anywhere in the API. Rather, the Specification prescribes two normative responses for on-time versus late Ratings Forecast Proposals.

On-Time 202 Accepted

A TROLIE implementation will return 202 Accepted when it receives an on-time (and valid) Ratings Forecast Proposal. As discussed in Submitting Forecast Ratings, the client must PATCH the overall Ratings Forecast of the Clearinghouse Provider with their own proposal. Since the overall proposal requires additional processing after the Forecast Window deadline, the TROLIE server returns 202 Accepted to confirm that the PATCH contained a valid proposal and will be processed by the Clearinghouse.

NOTE: The Ratings Provider populates the proposal-header.begins to indicate the intended Forecast Window. Accordingly, the TROLIE server checks proposal-header.begins to determine if the proposal is late or not.

Late 409 Conflict

Again, submitting a Ratings Forecast Proposal to TROLIE is done by PATCHing the Ratings Forecast of the Clearinghouse Provider’s footprint. If that overall Ratings Forecast is no longer accepting submissions, i.e., the Forecast Window is closed for the forecast being proposed, attempting to PATCH it conflicts with the server’s state, so a 409 Conflict client error with an appropriate application/problem+json response, like the following:

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{
  "type": "//trolie.example.com/spec/client-errors/409/forecast-Window-closed",
  "title": "Conflict: Forecast Window Closed",
  "status": 409,
  "detail": "The proposed forecast was late. The first hour of the forecast was 2025-05-07T12:00:00-0500, and it was received at 2025-05-07T11:23:45-0500, but the Forecast Window closed at 2025-05-07T11:00:00-0500."
}

Forecast Processing State Machine

When one window closes, another one opens.

Below is a simplified state machine that describes the three concurrent states of when TROLIE is processing forecasts. It illustrates how accepting Forecast Proposals and serving Limits Snapshot is decoupled from compiling all of the received forecasts and submitting them in the overall Forecast Proposal to the Clearinghouse.

Forecast State