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 4

ALL · gfs · lead 4

Target day = initialization date + 4 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
tmax00Zbilinear30d26 2 QC3.26 [3.04, 3.44]0.80-1.03 [-1.37, -0.52]4.26 [3.94, 4.49]22% [19%, 25%]40%56%+0.16+0.452026-08-05 → 2026-08-30
tmax00Zbilinear90d26 2 QC3.26 [2.98, 3.45]0.80-1.03 [-1.38, -0.42]4.26 [3.83, 4.50]22% [18%, 25%]40%56%+0.16+0.452026-08-05 → 2026-08-30
tmax00Zbilinear365d26 2 QC3.26 [2.98, 3.45]0.80-1.03 [-1.39, -0.38]4.26 [3.86, 4.49]22% [18%, 25%]40%56%+0.16+0.452026-08-05 → 2026-08-30
tmax00Zbilinearall26 2 QC3.26 [2.98, 3.45]0.80-1.03 [-1.40, -0.35]4.26 [3.85, 4.50]22% [18%, 25%]40%56%+0.16+0.452026-08-05 → 2026-08-30
tmax00Znearest30d26 2 QC3.45 [3.28, 3.60]0.83-0.93 [-1.32, -0.34]4.45 [4.24, 4.63]21% [19%, 22%]38%51%+0.11+0.422026-08-05 → 2026-08-30
tmax00Znearest90d26 2 QC3.45 [3.24, 3.63]0.83-0.93 [-1.34, -0.20]4.45 [4.20, 4.64]21% [19%, 22%]38%51%+0.11+0.422026-08-05 → 2026-08-30
tmax00Znearest365d26 2 QC3.45 [3.24, 3.64]0.83-0.93 [-1.36, -0.19]4.45 [4.20, 4.65]21% [19%, 22%]38%51%+0.11+0.422026-08-05 → 2026-08-30
tmax00Znearestall26 2 QC3.45 [3.24, 3.64]0.83-0.93 [-1.37, -0.16]4.45 [4.20, 4.65]21% [19%, 22%]38%51%+0.11+0.422026-08-05 → 2026-08-30
tmax12Zbilinear30d26 2 QC3.25 [2.85, 3.60]1.00-1.04 [-1.72, -0.25]4.20 [3.71, 4.61]22% [19%, 27%]40%56%+0.16+0.312026-08-05 → 2026-08-30
tmax12Zbilinear90d26 2 QC3.25 [2.75, 3.65]1.00-1.04 [-1.77, -0.07]4.20 [3.56, 4.64]22% [18%, 28%]40%56%+0.16+0.312026-08-05 → 2026-08-30
tmax12Zbilinear365d26 2 QC3.25 [2.75, 3.67]1.00-1.04 [-1.83, -0.09]4.20 [3.56, 4.67]22% [18%, 28%]40%56%+0.16+0.312026-08-05 → 2026-08-30
tmax12Zbilinearall26 2 QC3.25 [2.78, 3.70]1.00-1.04 [-1.84, -0.08]4.20 [3.58, 4.70]22% [18%, 28%]40%56%+0.16+0.312026-08-05 → 2026-08-30
tmax12Znearest30d26 2 QC3.49 [3.10, 3.87]1.00-0.97 [-1.67, -0.13]4.47 [4.00, 4.90]22% [19%, 25%]38%52%+0.10+0.312026-08-05 → 2026-08-30
tmax12Znearest90d26 2 QC3.49 [3.02, 3.92]1.00-0.97 [-1.72, 0.09]4.47 [3.91, 4.95]22% [19%, 25%]38%52%+0.10+0.312026-08-05 → 2026-08-30
tmax12Znearest365d26 2 QC3.49 [3.01, 3.95]1.00-0.97 [-1.77, 0.09]4.47 [3.91, 4.97]22% [19%, 25%]38%52%+0.10+0.312026-08-05 → 2026-08-30
tmax12Znearestall26 2 QC3.49 [3.02, 3.98]1.00-0.97 [-1.79, 0.06]4.47 [3.91, 5.00]22% [19%, 25%]38%52%+0.10+0.312026-08-05 → 2026-08-30
tmin00Zbilinear30d26 2 QC3.26 [3.09, 3.43]0.71+1.93 [1.40, 2.41]4.09 [3.88, 4.31]20% [18%, 23%]36%53%-0.05+0.092026-08-05 → 2026-08-30
tmin00Zbilinear90d26 2 QC3.26 [3.09, 3.46]0.71+1.93 [1.41, 2.46]4.09 [3.85, 4.34]20% [18%, 23%]36%53%-0.05+0.092026-08-05 → 2026-08-30
tmin00Zbilinear365d26 2 QC3.26 [3.08, 3.47]0.71+1.93 [1.34, 2.48]4.09 [3.85, 4.34]20% [17%, 23%]36%53%-0.05+0.092026-08-05 → 2026-08-30
tmin00Zbilinearall26 2 QC3.26 [3.06, 3.47]0.71+1.93 [1.33, 2.52]4.09 [3.84, 4.33]20% [17%, 23%]36%53%-0.05+0.092026-08-05 → 2026-08-30
tmin00Znearest30d26 2 QC3.42 [3.24, 3.59]0.75+2.03 [1.51, 2.51]4.27 [4.01, 4.52]16% [14%, 19%]36%51%-0.10+0.032026-08-05 → 2026-08-30
tmin00Znearest90d26 2 QC3.42 [3.23, 3.62]0.75+2.03 [1.51, 2.58]4.27 [4.00, 4.55]16% [14%, 20%]36%51%-0.10+0.032026-08-05 → 2026-08-30
tmin00Znearest365d26 2 QC3.42 [3.22, 3.62]0.75+2.03 [1.44, 2.60]4.27 [3.97, 4.56]16% [14%, 21%]36%51%-0.10+0.032026-08-05 → 2026-08-30
tmin00Znearestall26 2 QC3.42 [3.22, 3.63]0.75+2.03 [1.40, 2.61]4.27 [3.96, 4.55]16% [14%, 21%]36%51%-0.10+0.032026-08-05 → 2026-08-30
tmin12Zbilinear30d26 2 QC3.09 [2.97, 3.23]0.65+1.85 [1.45, 2.18]3.91 [3.74, 4.10]22% [20%, 24%]40%55%+0.00+0.172026-08-05 → 2026-08-30
tmin12Zbilinear90d26 2 QC3.09 [2.97, 3.25]0.65+1.85 [1.45, 2.21]3.91 [3.74, 4.13]22% [20%, 24%]40%55%+0.00+0.172026-08-05 → 2026-08-30
tmin12Zbilinear365d26 2 QC3.09 [2.97, 3.25]0.65+1.85 [1.43, 2.22]3.91 [3.74, 4.13]22% [20%, 24%]40%55%+0.00+0.172026-08-05 → 2026-08-30
tmin12Zbilinearall26 2 QC3.09 [2.96, 3.25]0.65+1.85 [1.41, 2.21]3.91 [3.74, 4.15]22% [20%, 25%]40%55%+0.00+0.172026-08-05 → 2026-08-30
tmin12Znearest30d26 2 QC3.25 [3.11, 3.41]0.70+1.97 [1.58, 2.33]4.10 [3.91, 4.31]21% [18%, 25%]38%53%-0.05+0.102026-08-05 → 2026-08-30
tmin12Znearest90d26 2 QC3.25 [3.11, 3.42]0.70+1.97 [1.57, 2.36]4.10 [3.91, 4.33]21% [18%, 25%]38%53%-0.05+0.102026-08-05 → 2026-08-30
tmin12Znearest365d26 2 QC3.25 [3.11, 3.43]0.70+1.97 [1.53, 2.38]4.10 [3.91, 4.36]21% [17%, 25%]38%53%-0.05+0.102026-08-05 → 2026-08-30
tmin12Znearestall26 2 QC3.25 [3.10, 3.43]0.70+1.97 [1.51, 2.37]4.10 [3.89, 4.35]21% [17%, 25%]38%53%-0.05+0.102026-08-05 → 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 4, 00Z bilinear tmax+5+2.50-2.5-52026-08-05: -0.67 °F2026-08-06: +0.28 °F2026-08-07: -0.21 °F2026-08-08: -0.8 °F2026-08-09: +0.21 °F2026-08-10: +0.23 °F2026-08-11: -0.87 °F2026-08-12: -1.42 °F2026-08-13: -1.81 °F2026-08-14: -2.43 °F2026-08-15: -1.9 °F2026-08-16: +0.62 °F2026-08-17: -1.73 °F2026-08-18: -0.72 °F2026-08-19: -0.2 °F2026-08-20: -2.97 °F2026-08-21: -1.92 °F2026-08-22: -0.71 °F2026-08-23: -1.25 °F2026-08-24: -3.03 °F2026-08-25: -0.39 °F2026-08-26: -1.49 °F2026-08-27: -0.85 °F2026-08-28: -1.05 °F2026-08-29: -1.7 °F2026-08-30: +0.02 °F2026-08-052026-08-30°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 (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+0.02
2026-08-29-1.70
2026-08-28-1.05
2026-08-27-0.85
2026-08-26-1.49
2026-08-25-0.39
2026-08-24-3.03
2026-08-23-1.25
2026-08-22-0.71
2026-08-21-1.92
2026-08-20-2.97
2026-08-19-0.20
2026-08-18-0.72
2026-08-17-1.73
2026-08-16+0.62
2026-08-15-1.90
2026-08-14-2.43
2026-08-13-1.81
2026-08-12-1.42
2026-08-11-0.87
2026-08-10+0.23
2026-08-09+0.21
2026-08-08-0.80
2026-08-07-0.21
2026-08-06+0.28
2026-08-05-0.67

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at ALL, lead day 4-5 to -4.5 °F: 0 days-4.5 to -4 °F: 0 days-4 to -3.5 °F: 0 days-3.5 to -3 °F: 1 day-3 to -2.5 °F: 1 day-2.5 to -2 °F: 1 day-2 to -1.5 °F: 5 days-1.5 to -1 °F: 4 days-1 to -0.5 °F: 6 days-0.5 to 0 °F: 3 days0 to 0.5 °F: 4 days0.5 to 1 °F: 1 day1 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| 0.86 · P90 |e| 2.17 °F-50+5 °Fn = 26 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
-4.00-3.500
-3.50-3.001
-3.00-2.501
-2.50-2.001
-2.00-1.505
-1.50-1.004
-1.00-0.506
-0.50+0.003
+0.00+0.504
+0.50+1.001
+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
2026-08261.13 -1.03

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26

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 26 -0.42 [-0.68, -0.20] yes
GraphCast (IFS init) 25 -2.06 [-2.42, -1.75] yes
ECMWF IFS HRES 20 -0.28 [-0.48, -0.00] yes
Persistence (baseline) 26 -0.61 [-1.30, -0.16] yes

Cite this page

ShortCastCheck, ALL gfs lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/ALL/model/gfs/lead/4/

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 4. 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/4/

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