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Cossatot River — Daily Analysis: 2026-04-24

Classification: partial Confidence: Continued overprediction pattern suggests coefficients still too high despite recent reductions - confidence remains medium pending further calibration

Event Summary

Model overpredicted peak by 0.75 ft (29%) during a multi-band rainfall event with heavy intensity burst around 20:12 UTC.

Prediction vs Actual

Metric Predicted Actual Error
Peak height 3.34 ft 2.59 ft +0.75 ft
Total rise 0.16 ft

Band Contributions

Band Precip Predicted Rise Intensity Moisture
2 0.84" 2.35 ft HEAVY WET
3 0.91" 1.35 ft HEAVY WET
4 0.84" 0.64 ft HEAVY WET
5 1.02" 0.52 ft HEAVY WET

Analysis

The model predicted a 3.34 ft peak but observed only 2.59 ft, representing a significant 29% overprediction. The rainfall pattern showed a concentrated burst around 20:12 UTC with 0.59-0.72 inches across all bands, followed by lighter amounts. The sharp hydrograph shape and 1.8-hour rise duration suggest this was primarily a near-gauge event despite QPE showing similar amounts across bands. The gauge precipitation of 0.69 inches closely matches Band 1 QPE of 0.84 inches total, confirming the rainfall distribution.

The overprediction appears driven by the model treating this as a multi-band event when the sharp, quick response suggests Band 1 dominance. All band coefficients contributed to the overprediction, but Bands 2-3 particularly overestimated their contributions given the sharp hydrograph shape. The timing was also off by 1.7 hours, with the model predicting arrival at 05:39 but actual peak occurring at 23:00, suggesting the lag assumptions for the dominant band may be incorrect.

Coefficient Adjustments

Band Change Reason
1 -10% Sharp hydrograph suggests Band 1 dominance but still overpredicted - moderate reduction needed
2 -15% Significant overprediction for what appears to be secondary contribution based on sharp response
3 -15% Significant overprediction for what appears to be secondary contribution based on sharp response
4 -10% Moderate overprediction, but headwater bands should have minimal impact on sharp events
5 -10% Moderate overprediction, but headwater bands should have minimal impact on sharp events

Notes

Continued overprediction pattern suggests coefficients still too high despite recent reductions - confidence remains medium pending further calibration

← 2026-04-18  |  2026-04-25 →