WPC Verification
Forecast Products
 
QPF's:    24-Hourly    6-Hourly    Days 4-5/6-7    5-Day Total
Medium Range:    Min Temps    Max Temps    Prob of Pcpn (PoP)    WPC Grids
Sea-level Pressure
 
Verification for specific events:    Hurricane Isaac QPF    Hurricane Sandy QPF
 

Quantitative Precipitation Forecasts

How Threat Scores and Bias are Computed

24-Hourly QPF's
Monthly Record Threat Scores

Annual WPC Day-1 / Day-2 / Day-3 Threat Scores
and Observed Areal Coverage;
Annual WPC Day-1 / Day-2 / Day-3 Bias
.50 inch (1961-2024) 1.00 inch (1961-2024) 2.00 inches (1970-2024)
Threat Bias Threat Bias Threat Bias

Annual WPC vs. NWP Guidance Threat Scores
1993-2024
1.00 inch
Day 1 Threat Percent Improvement Over NWP

Monthly WPC vs. NWP Guidance Threat Scores and Bias
March 2024 to March 2025
.50 inch 1.00 inch 2.00 inches
Day 1 Threat Bias Threat Bias Threat Bias
Day 2 Threat Bias Threat Bias Threat Bias
Day 3 Threat Bias Threat Bias Threat Bias

Monthly WPC Threat Score and Bias Comparisons (.50", 1.00", 2.00")
March 2024 to March 2025
Day 1 Day 2 Day 3
Threat Bias Threat Bias Threat Bias

Monthly WPC Threat Score and Bias Comparisons (Day 1 / Day 2 / Day 3)
March 2024 to March 2025
.50 inch 1.00 inch 2.00 inches
Threat Bias Threat Bias Threat Bias

NAM and GFS QPF Verification by Region
 
Object-oriented Verification


6-Hourly QPF's
Monthly Record Threat Scores

Monthly WPC vs. NWP Guidance Threat Scores
Update
March 2024 to March 2025
00-06 Hours .25 inch .50 inch

Monthly WPC vs. NWP Guidance Threat Scores
Day 1
March 2024 to March 2025
06-12 Hours .25 inch .50 inch
12-18 Hours .25 inch .50 inch
18-24 Hours .25 inch .50 inch
24-30 Hours .25 inch .50 inch

Monthly WPC vs. NWP Guidance Threat Scores
Day 2
March 2024 to March 2025
30-36 Hours .25 inch .50 inch
36-42 Hours .25 inch .50 inch
42-48 Hours .25 inch .50 inch
48-54 Hours .25 inch .50 inch

Monthly WPC vs. NWP Guidance Threat Scores
Day 3
March 2024 to March 2025
54-60 Hours .25 inch .50 inch
60-66 Hours .25 inch .50 inch
66-72 Hours .25 inch .50 inch
72-78 Hours .25 inch .50 inch

WPC vs. NWP Guidance - Threat Scores
October 2024 - March 2025
All 6-Hour Periods .25 inch .50 inch


Days 4-5/6-7 QPF's

Annual WPC Days 4-5/6-7 Threat Scores
and Observed Areal Coverage (2001-2024)
.50 inch 1.00 inch 2.00 inches
Threat Threat Threat

Monthly WPC vs. NWP Guidance Threat Scores and Bias
March 2024 to March 2025
.50 inch 1.00 inch 2.00 inches
Days 4-5 Threat Bias Threat Bias Threat Bias
Days 6-7 Threat Bias Threat Bias Threat Bias

Monthly WPC Threat Score and Bias Comparisons
.50", 1.00", 2.00"
March 2024 to March 2025
Days 4-5 Threat Bias
Days 6-7 Threat Bias


5-Day Total QPF's
Monthly WPC vs. NWP Guidance Threat Scores and Bias
March 2024 to March 2025
.50 inch 1.00 inch 2.00 inches 3.00 inches 4.00 inches
Threat Bias Threat Bias Threat Bias Threat Bias Threat Bias

Monthly WPC Threat Score and Bias Comparisons
.50", 1.00", 2.00", 3.00", 4.00"
March 2024 to March 2025
Threat Bias


Medium-Range Forecasts

Overview of data plotted on annual charts

Minimum Temperatures

Annual Mean Absolute Error (MAE) Charts (1972 - 2024)
WPC MAE for days 3-7 min temp fcsts
WPC -vs- Guidance MAE for day 3 min temp fcsts
WPC -vs- Guidance MAE for day 4 min temp fcsts
WPC -vs- Guidance MAE for day 5 min temp fcsts
WPC -vs- Guidance MAE for day 6 min temp fcsts
WPC -vs- Guidance MAE for day 7 min temp fcsts


Monthly Performance Charts (March 2024 - March 2025)
WPC RMS errors for Days 3-7 min temp fcsts
WPC percent improvement over MOS MAE (adjusted stations only) for Days 3-7 min temp fcsts
WPC winning percent vs MOS for Days 3-7 min temp fcsts


Year-to-Date Performance Chart (January - March 2025)
WPC improvement over MOS MAE, including percentage of stations adjusted, for Days 3-7 min temp fcsts


Maximum Temperatures

Annual Mean Absolute Error (MAE) Charts (1972 - 2024)
WPC MAE for days 3-7 max temp fcsts
WPC -vs- Guidance MAE for day 3 max temp fcsts
WPC -vs- Guidance MAE for day 4 max temp fcsts
WPC -vs- Guidance MAE for day 5 max temp fcsts
WPC -vs- Guidance MAE for day 6 max temp fcsts
WPC -vs- Guidance MAE for day 7 max temp fcsts


Monthly Performance Charts (March 2024 - March 2025)
WPC RMS errors for Days 3-7 max temp fcsts
WPC percent improvement over MOS MAE (adjusted stations only) for Days 3-7 max temp fcsts
WPC winning percent vs MOS for Days 3-7 max temp fcsts


Year-to-Date Performance Chart (January - March 2025)
WPC improvement over MOS MAE, including percentage of stations adjusted, for Days 3-7 max temp fcsts


Probability of Precipitation (PoP)

Monthly Performance Charts - 24-Hour PoP (March 2024 - March 2025)
WPC Brier scores for days 3-7 PoP fcsts
WPC percent improvement over MOS Brier score (adjusted stations only) for days 3-7 PoP fcsts
WPC winning percent vs MOS for Days 3-7 PoP fcsts


Year-to-Date Performance Chart - 24-Hour PoP (January - March 2025)
WPC improvement over MOS Brier score, including percentage of stations adjusted, for Days 3-7 PoP fcsts


Monthly Performance Charts - 12-Hour PoP (December 2018 - December 2019)
WPC Brier scores for days 3-7 12-Hour PoP forecasts
WPC percent improvement over MOS Brier score for days 3-7 12-Hour PoP forecasts

WPC Gridded Medium-Range Forecasts


How grids are verified
 
Monthly Performance Charts (December 2019)
Note:  MAE = Mean Absolute Error
 
Forecasts prepared by WPC meteorologists
NBM/WPC/NDFD Minimum Temperature 
(Days 4-7) 		MAE Bias
NBM/WPC/NDFD Maximum Temperature 
(Days 4-7) 		MAE Bias
NBM/WPC/NDFD 12-Hour PoP 
(Days 4-7) 		Brier Score

Products derived from forecasts prepared by WPC meteorologists
NBM/WPC/NDFD Dew Point Temperature 
(valid every 6 hours from F90-F180) 		MAE Bias
NBM/WPC/NDFD Wind Speed 
(valid every 6 hours from F90-F180) 		MAE Bias
NBM/WPC/NDFD Wind Direction 
(valid every 6 hours from F90-F180) 		MAE Bias
WPC/NDFD Cloud Cover 
(valid every 6 hours from F90-F180) 		MAE Bias

Mean Sea Level Pressure (PMSL)


WPC -vs- Guidance Anomaly Correlations