# Forecast Skill Degradation — 2026-08-01

> Auto-generated by `scripts/validate_forecast.py`. Measures how well the propagation scoring algorithm predicts contact distances as the weather profile ages. The lag-0h profile uses actual conditions at contact time (ground truth). Lag-Nh uses the weather profile from N hours earlier — representing the forecast that would have been available at that lead time.

- **Total contacts** (≥2020): 59,203
- **Contacts with all 6 profiles**: 12,929 (21%)
- **Generated**: 2026-08-01T22:03:32+00:00

Higher ρ = better distance prediction. Δρ(0h→Nh) = ρ(0h) − ρ(Nh) measures skill degradation — positive values mean the forecast skill is worse than using current conditions.

## Per-Band Per-Lag Spearman ρ

| Band | N | ρ(0h) | ρ(1h) | ρ(3h) | ρ(6h) | ρ(12h) | ρ(24h) | Δρ(0→6h) | Δρ(0→24h) |
|------|--:|-------:|------:|------:|------:|------:|------:|----------|------------|
| 10000 MHz | 11825 | -0.0033 | -0.0007 | +0.0201 | -0.0189 | -0.0128 | +0.0021 | +0.0156 | -0.0054 |
| 24000 MHz | 971 | +0.3140 | +0.3166 | +0.3227 | +0.3761 | +0.3629 | +0.2531 | -0.0622 | +0.0609 |
| 47000 MHz | 108 | +0.1438 | +0.1373 | +0.1644 | +0.2084 | +0.0689 | +0.1420 | -0.0646 | +0.0018 |

## Key Findings

- **Monotonic degradation** (ρ decreases with lead time): 0/3 bands
- **Non-monotonic bands** (ρ increases at some lead): 10000 MHz, 24000 MHz, 47000 MHz
  - This may indicate the algorithm puts disproportionate weight on noisy short-term features that vary within hours. If ρ(6h) > ρ(0h), the current-conditions score is noisier than the 6h-lagged score — weather features at lag-0 may introduce variance that degrades the correlation.
- **ρ(6h) > ρ(0h)**: 2 bands — the 6-hour lagged score outperforms current-conditions
- **Mean Δρ(0→6h)**: -0.0371
- **Mean Δρ(0→24h)**: +0.0191

## Caveats

- **Lagged profiles use analysis data**: The HRRR profiles at T−N represent actual weather conditions at that earlier time, not a true forecast run initialized at T−N. Real HRRR forecasts would contain model error growth; these measurements capture the degradation from weather *evolution* alone (the lower bound of forecast skill loss).
- **Snap to nearest grid point**: Profiles are looked up at the HRRR grid point nearest to the contact location (rounded to 0.125°). A single point approximates the full path's conditions.
- **Filter threshold**: Only bands with ≥30 contacts having ALL 6 profiles (lag-0 through lag-24) are included in the table.
- **Censored data**: Contacts are confirmed success events only. Correlation ρ measures discrimination among successful contacts.