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

All stations (mean of daily station errors) · NCEP GFS · lead day 9

ALL · gfs · lead 9

Target day = initialization date + 9 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, 2 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
tmax00Zbilinear30d21 2 QC4.67 [4.22, 5.08]2.16-1.02 [-2.11, 0.18]6.13 [5.62, 6.61]16% [12%, 20%]32%45%-0.08-1.002026-08-10 → 2026-08-30
tmax00Zbilinear90d21 2 QC4.67 [4.18, 5.10]2.16-1.02 [-2.12, 0.49]6.13 [5.57, 6.64]16% [12%, 20%]32%45%-0.08-1.002026-08-10 → 2026-08-30
tmax00Zbilinear365d21 2 QC4.67 [4.13, 5.11]2.16-1.02 [-2.18, 0.43]6.13 [5.54, 6.62]16% [12%, 21%]32%45%-0.08-1.002026-08-10 → 2026-08-30
tmax00Zbilinearall21 2 QC4.67 [4.19, 5.11]2.16-1.02 [-2.24, 0.51]6.13 [5.60, 6.62]16% [12%, 20%]32%45%-0.08-1.002026-08-10 → 2026-08-30
tmax00Znearest30d21 2 QC4.88 [4.44, 5.31]2.26-1.02 [-2.12, 0.23]6.29 [5.76, 6.81]15% [9%, 19%]30%41%-0.13-1.102026-08-10 → 2026-08-30
tmax00Znearest90d21 2 QC4.88 [4.33, 5.34]2.26-1.02 [-2.13, 0.56]6.29 [5.60, 6.83]15% [7%, 20%]30%41%-0.13-1.102026-08-10 → 2026-08-30
tmax00Znearest365d21 2 QC4.88 [4.33, 5.32]2.26-1.02 [-2.15, 0.51]6.29 [5.58, 6.82]15% [7%, 20%]30%41%-0.13-1.102026-08-10 → 2026-08-30
tmax00Znearestall21 2 QC4.88 [4.36, 5.32]2.26-1.02 [-2.26, 0.60]6.29 [5.61, 6.83]15% [7%, 20%]30%41%-0.13-1.102026-08-10 → 2026-08-30
tmax12Zbilinear30d21 2 QC4.90 [4.28, 5.45]1.51-1.52 [-2.15, -0.89]6.41 [5.66, 7.14]14% [9%, 18%]29%39%-0.13-0.402026-08-10 → 2026-08-30
tmax12Zbilinear90d21 2 QC4.90 [4.23, 5.52]1.51-1.52 [-2.19, -0.85]6.41 [5.62, 7.20]14% [8%, 19%]29%39%-0.13-0.402026-08-10 → 2026-08-30
tmax12Zbilinear365d21 2 QC4.90 [4.20, 5.54]1.51-1.52 [-2.20, -0.82]6.41 [5.57, 7.30]14% [8%, 19%]29%39%-0.13-0.402026-08-10 → 2026-08-30
tmax12Zbilinearall21 2 QC4.90 [4.19, 5.58]1.51-1.52 [-2.17, -0.78]6.41 [5.56, 7.30]14% [8%, 19%]29%39%-0.13-0.402026-08-10 → 2026-08-30
tmax12Znearest30d21 2 QC5.06 [4.32, 5.71]1.50-1.49 [-2.10, -0.85]6.57 [5.70, 7.38]14% [9%, 20%]27%38%-0.17-0.392026-08-10 → 2026-08-30
tmax12Znearest90d21 2 QC5.06 [4.27, 5.76]1.50-1.49 [-2.16, -0.80]6.57 [5.64, 7.44]14% [7%, 20%]27%38%-0.17-0.392026-08-10 → 2026-08-30
tmax12Znearest365d21 2 QC5.06 [4.24, 5.81]1.50-1.49 [-2.17, -0.76]6.57 [5.58, 7.54]14% [7%, 21%]27%38%-0.17-0.392026-08-10 → 2026-08-30
tmax12Znearestall21 2 QC5.06 [4.23, 5.83]1.50-1.49 [-2.15, -0.73]6.57 [5.57, 7.53]14% [7%, 21%]27%38%-0.17-0.392026-08-10 → 2026-08-30
tmin00Zbilinear30d21 2 QC4.30 [3.96, 4.59]2.01+1.34 [-0.23, 2.88]5.34 [4.91, 5.72]11% [8%, 13%]27%41%-0.12-0.762026-08-10 → 2026-08-30
tmin00Zbilinear90d21 2 QC4.30 [3.92, 4.61]2.01+1.34 [-0.38, 2.99]5.34 [4.89, 5.72]11% [8%, 14%]27%41%-0.12-0.762026-08-10 → 2026-08-30
tmin00Zbilinear365d21 2 QC4.30 [3.92, 4.63]2.01+1.34 [-0.39, 3.02]5.34 [4.88, 5.74]11% [8%, 13%]27%41%-0.12-0.762026-08-10 → 2026-08-30
tmin00Zbilinearall21 2 QC4.30 [3.91, 4.67]2.01+1.34 [-0.43, 3.26]5.34 [4.89, 5.79]11% [8%, 13%]27%41%-0.12-0.762026-08-10 → 2026-08-30
tmin00Znearest30d21 2 QC4.38 [4.06, 4.66]2.05+1.52 [-0.08, 3.04]5.44 [5.06, 5.79]12% [9%, 15%]27%44%-0.14-0.792026-08-10 → 2026-08-30
tmin00Znearest90d21 2 QC4.38 [4.05, 4.67]2.05+1.52 [-0.22, 3.16]5.44 [5.01, 5.80]12% [9%, 16%]27%44%-0.14-0.792026-08-10 → 2026-08-30
tmin00Znearest365d21 2 QC4.38 [4.06, 4.69]2.05+1.52 [-0.24, 3.21]5.44 [5.05, 5.83]12% [9%, 16%]27%44%-0.14-0.792026-08-10 → 2026-08-30
tmin00Znearestall21 2 QC4.38 [4.06, 4.71]2.05+1.52 [-0.31, 3.42]5.44 [5.03, 5.85]12% [9%, 16%]27%44%-0.14-0.792026-08-10 → 2026-08-30
tmin12Zbilinear30d21 2 QC3.85 [3.61, 4.05]1.00+1.39 [0.51, 2.09]4.89 [4.58, 5.15]17% [15%, 20%]34%49%-0.00+0.132026-08-10 → 2026-08-30
tmin12Zbilinear90d21 2 QC3.85 [3.54, 4.07]1.00+1.39 [0.32, 2.13]4.89 [4.53, 5.17]17% [15%, 20%]34%49%-0.00+0.132026-08-10 → 2026-08-30
tmin12Zbilinear365d21 2 QC3.85 [3.54, 4.09]1.00+1.39 [0.24, 2.17]4.89 [4.47, 5.19]17% [15%, 20%]34%49%-0.00+0.132026-08-10 → 2026-08-30
tmin12Zbilinearall21 2 QC3.85 [3.56, 4.10]1.00+1.39 [0.29, 2.21]4.89 [4.53, 5.21]17% [15%, 20%]34%49%-0.00+0.132026-08-10 → 2026-08-30
tmin12Znearest30d21 2 QC4.02 [3.75, 4.25]0.97+1.45 [0.58, 2.13]5.01 [4.68, 5.26]15% [13%, 17%]30%45%-0.05+0.152026-08-10 → 2026-08-30
tmin12Znearest90d21 2 QC4.02 [3.68, 4.30]0.97+1.45 [0.37, 2.17]5.01 [4.57, 5.28]15% [12%, 17%]30%45%-0.05+0.152026-08-10 → 2026-08-30
tmin12Znearest365d21 2 QC4.02 [3.67, 4.31]0.97+1.45 [0.33, 2.19]5.01 [4.59, 5.29]15% [12%, 17%]30%45%-0.05+0.152026-08-10 → 2026-08-30
tmin12Znearestall21 2 QC4.02 [3.68, 4.32]0.97+1.45 [0.37, 2.27]5.01 [4.59, 5.30]15% [12%, 17%]30%45%-0.05+0.152026-08-10 → 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 ALL, lead day 9, 00Z bilinear tmax+10+50-5-102026-08-10: +0.93 °F2026-08-11: +2.26 °F2026-08-12: -1 °F2026-08-13: -5.01 °F2026-08-14: -3.71 °F2026-08-15: -1.3 °F2026-08-16: -2.53 °F2026-08-17: -4.88 °F2026-08-18: +0.13 °F2026-08-19: -3.57 °F2026-08-20: +0.93 °F2026-08-21: +0.65 °F2026-08-22: +3.25 °F2026-08-23: -0.19 °F2026-08-24: -0.82 °F2026-08-25: +2.59 °F2026-08-26: -3.43 °F2026-08-27: -3.19 °F2026-08-28: -4.24 °F2026-08-29: +2.58 °F2026-08-30: -0.93 °F2026-08-102026-08-30°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 (21 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.93
2026-08-29+2.58
2026-08-28-4.24
2026-08-27-3.19
2026-08-26-3.43
2026-08-25+2.59
2026-08-24-0.82
2026-08-23-0.19
2026-08-22+3.25
2026-08-21+0.65
2026-08-20+0.93
2026-08-19-3.57
2026-08-18+0.13
2026-08-17-4.88
2026-08-16-2.53
2026-08-15-1.30
2026-08-14-3.71
2026-08-13-5.01
2026-08-12-1.00
2026-08-11+2.26
2026-08-10+0.93

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at ALL, lead day 9-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 0 days-6 to -5 °F: 1 day-5 to -4 °F: 2 days-4 to -3 °F: 4 days-3 to -2 °F: 1 day-2 to -1 °F: 2 days-1 to 0 °F: 3 days0 to 1 °F: 4 days1 to 2 °F: 0 days2 to 3 °F: 3 days3 to 4 °F: 1 day4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 2.53 · P90 |e| 4.24 °F-100+10 °Fn = 21 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
-10.00-9.000
-9.00-8.000
-8.00-7.000
-7.00-6.000
-6.00-5.001
-5.00-4.002
-4.00-3.004
-3.00-2.001
-2.00-1.002
-1.00+0.003
+0.00+1.004
+1.00+2.000
+2.00+3.003
+3.00+4.001
+4.00+5.000
+5.00+6.000
+6.00+7.000
+7.00+8.000
+8.00+9.000
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08212.29 -1.02

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21

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 21 -0.34 [-0.97, 0.29] no
GraphCast (IFS init) 21 -1.46 [-2.41, -0.66] yes
ECMWF IFS HRES 16 +0.37 [-0.78, 1.28] no
Persistence (baseline) 21 +0.34 [-0.31, 0.94] no

Cite this page

ShortCastCheck, ALL gfs lead 9, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/ALL/model/gfs/lead/9/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: ALL (All stations (mean of daily station errors)), model gfs, lead day 9. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/ALL/model/gfs/lead/9/

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