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 6

ALL · gfs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 2 QC3.70 [3.49, 3.86]1.11-1.08 [-1.56, -0.51]4.80 [4.51, 5.03]18% [16%, 21%]35%51%+0.06+0.232026-08-07 → 2026-08-30
tmax00Zbilinear90d24 2 QC3.70 [3.46, 3.89]1.11-1.08 [-1.59, -0.35]4.80 [4.49, 5.05]18% [16%, 21%]35%51%+0.06+0.232026-08-07 → 2026-08-30
tmax00Zbilinear365d24 2 QC3.70 [3.42, 3.88]1.11-1.08 [-1.61, -0.29]4.80 [4.45, 5.05]18% [16%, 22%]35%51%+0.06+0.232026-08-07 → 2026-08-30
tmax00Zbilinearall24 2 QC3.70 [3.39, 3.89]1.11-1.08 [-1.58, -0.32]4.80 [4.45, 5.05]18% [16%, 22%]35%51%+0.06+0.232026-08-07 → 2026-08-30
tmax00Znearest30d24 2 QC3.82 [3.66, 3.95]1.12-1.04 [-1.51, -0.45]4.91 [4.65, 5.10]19% [17%, 22%]34%48%+0.03+0.222026-08-07 → 2026-08-30
tmax00Znearest90d24 2 QC3.82 [3.63, 3.96]1.12-1.04 [-1.53, -0.28]4.91 [4.61, 5.10]19% [16%, 22%]34%48%+0.03+0.222026-08-07 → 2026-08-30
tmax00Znearest365d24 2 QC3.82 [3.61, 3.95]1.12-1.04 [-1.56, -0.22]4.91 [4.61, 5.11]19% [16%, 22%]34%48%+0.03+0.222026-08-07 → 2026-08-30
tmax00Znearestall24 2 QC3.82 [3.60, 3.96]1.12-1.04 [-1.53, -0.24]4.91 [4.59, 5.10]19% [16%, 22%]34%48%+0.03+0.222026-08-07 → 2026-08-30
tmax12Zbilinear30d24 2 QC3.77 [3.34, 4.16]1.11-1.47 [-2.13, -0.72]5.02 [4.39, 5.55]20% [17%, 22%]36%52%+0.04+0.232026-08-07 → 2026-08-30
tmax12Zbilinear90d24 2 QC3.77 [3.21, 4.21]1.11-1.47 [-2.16, -0.40]5.02 [4.14, 5.62]20% [16%, 23%]36%52%+0.04+0.232026-08-07 → 2026-08-30
tmax12Zbilinear365d24 2 QC3.77 [3.20, 4.22]1.11-1.47 [-2.22, -0.46]5.02 [4.13, 5.61]20% [16%, 23%]36%52%+0.04+0.232026-08-07 → 2026-08-30
tmax12Zbilinearall24 2 QC3.77 [3.20, 4.28]1.11-1.47 [-2.31, -0.40]5.02 [4.10, 5.70]20% [16%, 23%]36%52%+0.04+0.232026-08-07 → 2026-08-30
tmax12Znearest30d24 2 QC3.96 [3.59, 4.34]1.10-1.44 [-2.09, -0.70]5.23 [4.67, 5.71]20% [16%, 23%]34%48%-0.00+0.232026-08-07 → 2026-08-30
tmax12Znearest90d24 2 QC3.96 [3.53, 4.37]1.10-1.44 [-2.14, -0.37]5.23 [4.48, 5.75]20% [15%, 23%]34%48%-0.00+0.232026-08-07 → 2026-08-30
tmax12Znearest365d24 2 QC3.96 [3.52, 4.41]1.10-1.44 [-2.17, -0.46]5.23 [4.46, 5.79]20% [15%, 24%]34%48%-0.00+0.232026-08-07 → 2026-08-30
tmax12Znearestall24 2 QC3.96 [3.52, 4.45]1.10-1.44 [-2.28, -0.37]5.23 [4.44, 5.84]20% [14%, 24%]34%48%-0.00+0.232026-08-07 → 2026-08-30
tmin00Zbilinear30d24 2 QC3.54 [3.34, 3.73]0.82+1.77 [1.30, 2.17]4.42 [4.15, 4.64]17% [16%, 19%]33%51%-0.03+0.232026-08-07 → 2026-08-30
tmin00Zbilinear90d24 2 QC3.54 [3.32, 3.74]0.82+1.77 [1.31, 2.19]4.42 [4.14, 4.66]17% [16%, 19%]33%51%-0.03+0.232026-08-07 → 2026-08-30
tmin00Zbilinear365d24 2 QC3.54 [3.32, 3.76]0.82+1.77 [1.28, 2.20]4.42 [4.13, 4.68]17% [16%, 19%]33%51%-0.03+0.232026-08-07 → 2026-08-30
tmin00Zbilinearall24 2 QC3.54 [3.32, 3.76]0.82+1.77 [1.23, 2.23]4.42 [4.14, 4.67]17% [16%, 19%]33%51%-0.03+0.232026-08-07 → 2026-08-30
tmin00Znearest30d24 2 QC3.69 [3.47, 3.89]0.85+1.88 [1.39, 2.30]4.57 [4.30, 4.83]15% [13%, 17%]33%48%-0.07+0.202026-08-07 → 2026-08-30
tmin00Znearest90d24 2 QC3.69 [3.45, 3.91]0.85+1.88 [1.39, 2.33]4.57 [4.28, 4.85]15% [13%, 17%]33%48%-0.07+0.202026-08-07 → 2026-08-30
tmin00Znearest365d24 2 QC3.69 [3.45, 3.93]0.85+1.88 [1.36, 2.34]4.57 [4.28, 4.86]15% [13%, 17%]33%48%-0.07+0.202026-08-07 → 2026-08-30
tmin00Znearestall24 2 QC3.69 [3.45, 3.91]0.85+1.88 [1.30, 2.39]4.57 [4.28, 4.85]15% [13%, 17%]33%48%-0.07+0.202026-08-07 → 2026-08-30
tmin12Zbilinear30d24 2 QC3.49 [3.33, 3.72]0.84+1.68 [1.21, 2.19]4.42 [4.17, 4.70]19% [16%, 22%]36%51%-0.01+0.212026-08-07 → 2026-08-30
tmin12Zbilinear90d24 2 QC3.49 [3.31, 3.78]0.84+1.68 [1.18, 2.32]4.42 [4.15, 4.77]19% [16%, 22%]36%51%-0.01+0.212026-08-07 → 2026-08-30
tmin12Zbilinear365d24 2 QC3.49 [3.31, 3.80]0.84+1.68 [1.18, 2.29]4.42 [4.15, 4.81]19% [16%, 23%]36%51%-0.01+0.212026-08-07 → 2026-08-30
tmin12Zbilinearall24 2 QC3.49 [3.32, 3.80]0.84+1.68 [1.16, 2.32]4.42 [4.16, 4.81]19% [16%, 23%]36%51%-0.01+0.212026-08-07 → 2026-08-30
tmin12Znearest30d24 2 QC3.59 [3.41, 3.83]0.86+1.73 [1.27, 2.23]4.56 [4.29, 4.84]18% [16%, 21%]34%50%-0.04+0.192026-08-07 → 2026-08-30
tmin12Znearest90d24 2 QC3.59 [3.39, 3.87]0.86+1.73 [1.25, 2.34]4.56 [4.27, 4.90]18% [15%, 21%]34%50%-0.04+0.192026-08-07 → 2026-08-30
tmin12Znearest365d24 2 QC3.59 [3.40, 3.89]0.86+1.73 [1.24, 2.33]4.56 [4.28, 4.94]18% [15%, 21%]34%50%-0.04+0.192026-08-07 → 2026-08-30
tmin12Znearestall24 2 QC3.59 [3.40, 3.92]0.86+1.73 [1.22, 2.35]4.56 [4.28, 4.96]18% [15%, 20%]34%50%-0.04+0.192026-08-07 → 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 6, 00Z bilinear tmax+5+2.50-2.5-52026-08-07: -0.39 °F2026-08-08: -0.04 °F2026-08-09: -0.12 °F2026-08-10: +0.52 °F2026-08-11: -0.13 °F2026-08-12: -1.17 °F2026-08-13: -1.79 °F2026-08-14: -0.35 °F2026-08-15: -2.82 °F2026-08-16: -0.56 °F2026-08-17: -2.03 °F2026-08-18: +0.09 °F2026-08-19: -1.47 °F2026-08-20: -0.61 °F2026-08-21: +0.14 °F2026-08-22: -3.61 °F2026-08-23: -0.2 °F2026-08-24: -1.82 °F2026-08-25: -0.01 °F2026-08-26: -2.43 °F2026-08-27: -3.34 °F2026-08-28: -2.36 °F2026-08-29: -2.28 °F2026-08-30: +0.95 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+0.95
2026-08-29-2.28
2026-08-28-2.36
2026-08-27-3.34
2026-08-26-2.43
2026-08-25-0.01
2026-08-24-1.82
2026-08-23-0.20
2026-08-22-3.61
2026-08-21+0.14
2026-08-20-0.61
2026-08-19-1.47
2026-08-18+0.09
2026-08-17-2.03
2026-08-16-0.56
2026-08-15-2.82
2026-08-14-0.35
2026-08-13-1.79
2026-08-12-1.17
2026-08-11-0.13
2026-08-10+0.52
2026-08-09-0.12
2026-08-08-0.04
2026-08-07-0.39

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at ALL, lead day 6-5 to -4.5 °F: 0 days-4.5 to -4 °F: 0 days-4 to -3.5 °F: 1 day-3.5 to -3 °F: 1 day-3 to -2.5 °F: 1 day-2.5 to -2 °F: 4 days-2 to -1.5 °F: 2 days-1.5 to -1 °F: 2 days-1 to -0.5 °F: 2 days-0.5 to 0 °F: 7 days0 to 0.5 °F: 2 days0.5 to 1 °F: 2 days1 to 1.5 °F: 0 days1.5 to 2 °F: 0 days2 to 2.5 °F: 0 days2.5 to 3 °F: 0 days3 to 3.5 °F: 0 days3.5 to 4 °F: 0 days4 to 4.5 °F: 0 days4.5 to 5 °F: 0 daysdashed: P50 |e| 0.78 · P90 |e| 2.7 °F-50+5 °Fn = 24 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
-5.00-4.500
-4.50-4.000
-4.00-3.501
-3.50-3.001
-3.00-2.501
-2.50-2.004
-2.00-1.502
-1.50-1.002
-1.00-0.502
-0.50+0.007
+0.00+0.502
+0.50+1.002
+1.00+1.500
+1.50+2.000
+2.00+2.500
+2.50+3.000
+3.00+3.500
+3.50+4.000
+4.00+4.500
+4.50+5.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08241.22 -1.08

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24

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 24 -0.47 [-0.88, -0.07] yes
GraphCast (IFS init) 24 -1.96 [-2.45, -1.42] yes
ECMWF IFS HRES 19 -0.32 [-0.83, 0.13] no
Persistence (baseline) 24 -0.25 [-0.60, 0.04] no

Cite this page

ShortCastCheck, ALL gfs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/ALL/model/gfs/lead/6/

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 6. 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/6/

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