Raw model output on the native 0.25° grid — no MOS, no bias correction, no post-processing. Scores understate operational forecast quality. Read the fairness statement →

CastCheck methodology v0.2 · data through 2026-08-30

Washington Reagan · NCEP GFS · lead day 8

KDCA · gfs · lead 8

Target day = initialization date + 8 days. This page is a permanent link: the numbers change as history accumulates, the address and the methodology version do not.

Scores use the latest model version segment, gfs-0p25, starting 2026-08-01 — days before that ran a different version of the model and are excluded rather than silently pooled. Of the scored days, 1 carry a QC flag on the observation.

JSON for this page CSV of the daily errors Cite this page

Every number for this combination

All four windows × both initializations × both interpolations × both variables. Errors are computed in °C and shown in °F; CI is a 95 % moving-block bootstrap interval. MAE debiased and skill, debiased remove the constant offset of the window first, so a station that the model always reads a degree too warm is not scored as if it had no skill — compare the two skill columns to see how much of the error is a fixed offset. n QC next to n counts days whose observation carries a QC flag.

VariableInitMethod Windown MAE °F MAE debiased Bias °F RMSE °F ±1 °F±2 °F±3 °F Skill Skill, debiased Period
tmax00Zbilinear30d22 1 QC5.61 [4.30, 7.05]5.42-2.04 [-4.63, 0.51]7.36 [5.21, 9.36]9% [0%, 20%]18%41%-0.34-0.322026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC5.61 [4.00, 7.04]5.42-2.04 [-4.84, 0.54]7.36 [4.49, 9.30]9% [0%, 22%]18%41%-0.34-0.322026-08-09 → 2026-08-30
tmax00Zbilinear365d22 1 QC5.61 [3.97, 7.21]5.42-2.04 [-5.17, 0.91]7.36 [4.55, 9.39]9% [0%, 22%]18%41%-0.34-0.322026-08-09 → 2026-08-30
tmax00Zbilinearall22 1 QC5.61 [4.14, 7.19]5.42-2.04 [-5.45, 1.16]7.36 [4.57, 9.36]9% [0%, 20%]18%41%-0.34-0.322026-08-09 → 2026-08-30
tmax00Znearest30d22 1 QC5.67 [4.29, 7.24]5.50-1.91 [-4.61, 0.72]7.53 [5.00, 9.59]0% [0%, 0%]18%27%-0.36-0.342026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC5.67 [3.95, 7.25]5.50-1.91 [-4.87, 0.79]7.53 [4.20, 9.58]0% [0%, 0%]18%27%-0.36-0.342026-08-09 → 2026-08-30
tmax00Znearest365d22 1 QC5.67 [3.91, 7.40]5.50-1.91 [-5.11, 1.00]7.53 [4.12, 9.63]0% [0%, 0%]18%27%-0.36-0.342026-08-09 → 2026-08-30
tmax00Znearestall22 1 QC5.67 [3.92, 7.38]5.50-1.91 [-5.39, 1.27]7.53 [4.16, 9.63]0% [0%, 0%]18%27%-0.36-0.342026-08-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC4.85 [3.58, 5.70]4.57-2.19 [-4.47, 0.57]5.92 [4.54, 6.72]18% [8%, 28%]27%41%-0.16-0.112026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC4.85 [3.13, 5.75]4.57-2.19 [-4.50, 0.94]5.92 [3.56, 6.81]18% [8%, 29%]27%41%-0.16-0.112026-08-09 → 2026-08-30
tmax12Zbilinear365d22 1 QC4.85 [2.98, 5.73]4.57-2.19 [-4.59, 0.94]5.92 [3.44, 6.78]18% [4%, 29%]27%41%-0.16-0.112026-08-09 → 2026-08-30
tmax12Zbilinearall22 1 QC4.85 [3.02, 5.74]4.57-2.19 [-4.66, 0.98]5.92 [3.41, 6.78]18% [0%, 29%]27%41%-0.16-0.112026-08-09 → 2026-08-30
tmax12Znearest30d22 1 QC4.73 [3.68, 5.63]4.47-1.92 [-4.26, 0.88]5.70 [4.51, 6.58]14% [0%, 24%]27%45%-0.13-0.092026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC4.73 [3.32, 5.69]4.47-1.92 [-4.29, 1.20]5.70 [3.56, 6.65]14% [0%, 25%]27%45%-0.13-0.092026-08-09 → 2026-08-30
tmax12Znearest365d22 1 QC4.73 [3.22, 5.68]4.47-1.92 [-4.46, 1.19]5.70 [3.46, 6.61]14% [0%, 25%]27%45%-0.13-0.092026-08-09 → 2026-08-30
tmax12Znearestall22 1 QC4.73 [3.28, 5.67]4.47-1.92 [-4.45, 1.29]5.70 [3.55, 6.59]14% [0%, 24%]27%45%-0.13-0.092026-08-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC4.44 [3.49, 5.19]4.32-1.54 [-4.22, 1.50]5.14 [4.16, 5.93]9% [0%, 18%]18%32%+0.08+0.092026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC4.44 [3.38, 5.15]4.32-1.54 [-4.26, 1.48]5.14 [3.91, 5.90]9% [0%, 20%]18%32%+0.08+0.092026-08-09 → 2026-08-30
tmin00Zbilinear365d22 1 QC4.44 [3.33, 5.21]4.32-1.54 [-4.35, 1.80]5.14 [3.91, 5.94]9% [0%, 19%]18%32%+0.08+0.092026-08-09 → 2026-08-30
tmin00Zbilinearall22 1 QC4.44 [3.38, 5.19]4.32-1.54 [-4.63, 2.43]5.14 [3.96, 5.91]9% [0%, 19%]18%32%+0.08+0.092026-08-09 → 2026-08-30
tmin00Znearest30d22 1 QC4.60 [3.65, 5.42]4.25-2.19 [-4.95, 0.92]5.33 [4.26, 6.11]14% [0%, 31%]18%27%+0.05+0.102026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC4.60 [3.47, 5.46]4.25-2.19 [-5.05, 0.84]5.33 [4.02, 6.11]14% [0%, 37%]18%27%+0.05+0.102026-08-09 → 2026-08-30
tmin00Znearest365d22 1 QC4.60 [3.45, 5.61]4.25-2.19 [-5.14, 1.32]5.33 [4.05, 6.16]14% [0%, 33%]18%27%+0.05+0.102026-08-09 → 2026-08-30
tmin00Znearestall22 1 QC4.60 [3.34, 5.61]4.25-2.19 [-5.22, 1.69]5.33 [3.95, 6.17]14% [0%, 33%]18%27%+0.05+0.102026-08-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC4.01 [2.31, 4.93]3.97-0.77 [-4.03, 2.53]5.32 [3.31, 6.41]18% [4%, 40%]41%55%+0.17+0.162026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC4.01 [1.87, 5.01]3.97-0.77 [-4.14, 2.60]5.32 [2.79, 6.44]18% [0%, 47%]41%55%+0.17+0.162026-08-09 → 2026-08-30
tmin12Zbilinear365d22 1 QC4.01 [1.70, 5.07]3.97-0.77 [-4.22, 3.06]5.32 [2.41, 6.49]18% [0%, 46%]41%55%+0.17+0.162026-08-09 → 2026-08-30
tmin12Zbilinearall22 1 QC4.01 [1.28, 5.03]3.97-0.77 [-4.46, 3.35]5.32 [1.47, 6.51]18% [0%, 48%]41%55%+0.17+0.162026-08-09 → 2026-08-30
tmin12Znearest30d22 1 QC4.32 [2.67, 5.43]4.08-1.31 [-4.69, 2.11]5.49 [3.45, 6.83]14% [0%, 38%]27%36%+0.10+0.142026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC4.32 [2.31, 5.44]4.08-1.31 [-4.82, 2.20]5.49 [3.04, 6.80]14% [0%, 43%]27%36%+0.10+0.142026-08-09 → 2026-08-30
tmin12Znearest365d22 1 QC4.32 [2.29, 5.45]4.08-1.31 [-5.02, 2.55]5.49 [3.01, 6.92]14% [0%, 40%]27%36%+0.10+0.142026-08-09 → 2026-08-30
tmin12Znearestall22 1 QC4.32 [1.83, 5.54]4.08-1.31 [-5.19, 2.89]5.49 [2.11, 6.92]14% [0%, 40%]27%36%+0.10+0.142026-08-09 → 2026-08-30

+ model too warm · − model too cold · bias interval includes zero · ★ lowest MAE · = not distinguishable from the leader · ▼ significantly worse · n < 30 greyed and unranked · CI is a 95 % moving-block bootstrap interval.

Daily error, last 90 days

Daily forecast minus observed error in °F for NCEP GFS at KDCA, lead day 8, 00Z bilinear tmax+25+12.50-12.5-252026-08-09: +2.93 °F2026-08-10: -2.83 °F2026-08-11: +4.41 °F2026-08-12: -7.75 °F2026-08-13: -2.86 °F2026-08-14: +5.94 °F2026-08-15: -2.33 °F2026-08-16: +0.89 °F2026-08-17: -14.9 °F2026-08-18: -5.3 °F2026-08-19: -4.88 °F2026-08-20: +1.24 °F2026-08-21: +5.14 °F2026-08-22: +13.26 °F2026-08-23: -5.84 °F2026-08-24: +3.48 °F2026-08-25: -2.86 °F2026-08-26: +1.35 °F2026-08-27: -20.21 °F2026-08-28: -7.49 °F2026-08-29: +0.63 °F2026-08-30: -6.9 °F2026-08-092026-08-30°F, forecast − observed
Forecast − observed, °F, 00Z bilinear daily maximum. The dashed line is zero; the thick line is a centred 7-day mean, drawn only where the whole window is present. Gaps are days with no score, never interpolation. Hover a point for its date and value.
The same series as a table (22 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.90
2026-08-29+0.63
2026-08-28-7.49
2026-08-27-20.21
2026-08-26+1.35
2026-08-25-2.86
2026-08-24+3.48
2026-08-23-5.84
2026-08-22+13.26
2026-08-21+5.14
2026-08-20+1.24
2026-08-19-4.88
2026-08-18-5.30
2026-08-17-14.90
2026-08-16+0.89
2026-08-15-2.33
2026-08-14+5.94
2026-08-13-2.86
2026-08-12-7.75
2026-08-11+4.41
2026-08-10-2.83
2026-08-09+2.93

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KDCA, lead day 8-25 to -22.5 °F: 0 days-22.5 to -20 °F: 1 day-20 to -17.5 °F: 0 days-17.5 to -15 °F: 0 days-15 to -12.5 °F: 1 day-12.5 to -10 °F: 0 days-10 to -7.5 °F: 1 day-7.5 to -5 °F: 4 days-5 to -2.5 °F: 4 days-2.5 to 0 °F: 1 day0 to 2.5 °F: 4 days2.5 to 5 °F: 3 days5 to 7.5 °F: 2 days7.5 to 10 °F: 0 days10 to 12.5 °F: 0 days12.5 to 15 °F: 1 day15 to 17.5 °F: 0 days17.5 to 20 °F: 0 days20 to 22.5 °F: 0 days22.5 to 25 °F: 0 daysdashed: P50 |e| 4.64 · P90 |e| 12.71 °F-250+25 °Fn = 22 days
All scored days for 00Z bilinear daily maximum, 20 equal bins. The dashed marks are the 50th and 90th percentiles of the absolute error, mirrored on both sides. Hover a bar for its bin and count.
Bin counts as a table
From °FTo °FDays
-25.00-22.500
-22.50-20.001
-20.00-17.500
-17.50-15.000
-15.00-12.501
-12.50-10.000
-10.00-7.501
-7.50-5.004
-5.00-2.504
-2.50+0.001
+0.00+2.504
+2.50+5.003
+5.00+7.502
+7.50+10.000
+10.00+12.500
+12.50+15.001
+15.00+17.500
+17.50+20.000
+20.00+22.500
+22.50+25.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08225.61 -2.04

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means NCEP GFS has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 22 +1.08 [-0.47, 2.25] no
GraphCast (IFS init) 22 -0.81 [-3.55, 0.36] no
ECMWF IFS HRES 17 +2.69 [0.68, 4.11] yes
Persistence (baseline) 22 +1.43 [-0.81, 2.90] no

Cite this page

ShortCastCheck, KDCA gfs lead 8, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDCA/model/gfs/lead/8/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDCA (Washington Reagan), model gfs, lead day 8. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KDCA/model/gfs/lead/8/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

JSON CSV all scores methodology v0.2 licence