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

Atlanta Hartsfield · NCEP GFS · lead day 4

KATL · 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, 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
tmax00Zbilinear30d26 1 QC3.26 [2.20, 4.53]3.37-0.72 [-2.89, 1.21]4.71 [2.78, 6.44]23% [15%, 31%]46%62%-0.18-0.232026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.26 [2.12, 4.61]3.37-0.72 [-3.06, 1.21]4.71 [2.62, 6.50]23% [14%, 32%]46%62%-0.18-0.232026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC3.26 [2.10, 4.80]3.37-0.72 [-3.49, 1.44]4.71 [2.61, 6.85]23% [14%, 33%]46%62%-0.18-0.232026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC3.26 [2.12, 4.73]3.37-0.72 [-3.30, 1.33]4.71 [2.59, 6.77]23% [14%, 33%]46%62%-0.18-0.232026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC3.02 [2.11, 4.03]2.97+0.23 [-2.02, 2.01]4.27 [2.48, 5.78]19% [7%, 29%]50%69%-0.09-0.082026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC3.02 [2.03, 4.03]2.97+0.23 [-2.10, 2.11]4.27 [2.37, 5.81]19% [7%, 30%]50%69%-0.09-0.082026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC3.02 [2.03, 4.23]2.97+0.23 [-2.57, 2.22]4.27 [2.38, 6.10]19% [6%, 29%]50%69%-0.09-0.082026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC3.02 [2.01, 4.16]2.97+0.23 [-2.33, 2.10]4.27 [2.36, 6.05]19% [4%, 30%]50%69%-0.09-0.082026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.03 [2.05, 4.02]2.99+0.11 [-2.42, 2.18]3.98 [2.59, 5.02]19% [0%, 36%]38%69%-0.09-0.092026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.03 [1.85, 4.01]2.99+0.11 [-2.82, 2.27]3.98 [2.18, 5.03]19% [0%, 38%]38%69%-0.09-0.092026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC3.03 [1.80, 4.13]2.99+0.11 [-3.21, 2.36]3.98 [2.16, 5.19]19% [0%, 38%]38%69%-0.09-0.092026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC3.03 [1.82, 4.10]2.99+0.11 [-2.93, 2.35]3.98 [2.15, 5.14]19% [0%, 36%]38%69%-0.09-0.092026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC3.18 [2.46, 3.88]2.87+0.76 [-1.74, 2.82]3.91 [2.91, 4.68]19% [8%, 28%]35%54%-0.15-0.052026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC3.18 [2.36, 3.90]2.87+0.76 [-2.16, 2.89]3.91 [2.70, 4.70]19% [7%, 29%]35%54%-0.15-0.052026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC3.18 [2.33, 3.92]2.87+0.76 [-2.82, 2.98]3.91 [2.67, 4.75]19% [7%, 29%]35%54%-0.15-0.052026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC3.18 [2.35, 3.90]2.87+0.76 [-2.25, 2.99]3.91 [2.64, 4.71]19% [0%, 29%]35%54%-0.15-0.052026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC2.56 [1.77, 3.39]2.19+1.60 [0.60, 2.77]3.30 [2.07, 4.33]27% [16%, 39%]46%65%-0.19-0.012026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC2.56 [1.72, 3.41]2.19+1.60 [0.40, 2.79]3.30 [2.01, 4.32]27% [14%, 41%]46%65%-0.19-0.012026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC2.56 [1.67, 3.52]2.19+1.60 [0.29, 2.99]3.30 [1.98, 4.47]27% [14%, 43%]46%65%-0.19-0.012026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC2.56 [1.71, 3.42]2.19+1.60 [0.33, 2.82]3.30 [1.98, 4.41]27% [13%, 40%]46%65%-0.19-0.012026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC3.34 [2.43, 4.33]2.23+2.59 [1.53, 3.95]4.06 [2.68, 5.24]8% [0%, 16%]27%58%-0.55-0.032026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC3.34 [2.31, 4.37]2.23+2.59 [1.32, 4.01]4.06 [2.54, 5.24]8% [0%, 15%]27%58%-0.55-0.032026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC3.34 [2.23, 4.49]2.23+2.59 [1.18, 4.20]4.06 [2.43, 5.38]8% [0%, 15%]27%58%-0.55-0.032026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC3.34 [2.31, 4.37]2.23+2.59 [1.20, 4.03]4.06 [2.52, 5.27]8% [0%, 15%]27%58%-0.55-0.032026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC2.66 [1.63, 3.63]2.35+1.92 [0.21, 3.38]3.43 [2.09, 4.45]31% [18%, 47%]42%62%-0.24-0.082026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC2.66 [1.51, 3.62]2.35+1.92 [-0.22, 3.35]3.43 [1.96, 4.41]31% [18%, 50%]42%62%-0.24-0.082026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC2.66 [1.45, 3.78]2.35+1.92 [-0.58, 3.58]3.43 [1.92, 4.52]31% [16%, 50%]42%62%-0.24-0.082026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC2.66 [1.41, 3.69]2.35+1.92 [-0.44, 3.50]3.43 [1.88, 4.48]31% [16%, 50%]42%62%-0.24-0.082026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC3.49 [1.96, 4.90]2.53+3.17 [1.21, 4.87]4.40 [2.60, 5.67]27% [7%, 48%]42%46%-0.62-0.162026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC3.49 [1.64, 4.85]2.53+3.17 [0.66, 4.84]4.40 [2.07, 5.63]27% [7%, 53%]42%46%-0.62-0.162026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC3.49 [1.38, 5.09]2.53+3.17 [0.19, 5.09]4.40 [1.84, 5.80]27% [0%, 57%]42%46%-0.62-0.162026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC3.49 [1.56, 5.02]2.53+3.17 [0.57, 5.02]4.40 [1.85, 5.77]27% [0%, 54%]42%46%-0.62-0.162026-08-05 → 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 KATL, lead day 4, 00Z bilinear tmax+20+100-10-202026-08-05: +2.59 °F2026-08-06: +3.24 °F2026-08-07: -4.09 °F2026-08-08: +0.1 °F2026-08-09: -2.38 °F2026-08-10: +0.33 °F2026-08-11: +1.51 °F2026-08-12: +1.01 °F2026-08-13: -2.45 °F2026-08-14: +3.61 °F2026-08-15: -5.76 °F2026-08-16: +0.3 °F2026-08-17: +1.1 °F2026-08-18: +8.8 °F2026-08-19: +3.8 °F2026-08-20: +1.71 °F2026-08-21: -0.72 °F2026-08-22: -3.17 °F2026-08-23: -0.84 °F2026-08-24: +2.78 °F2026-08-25: -15.73 °F2026-08-26: -8.36 °F2026-08-27: +1.64 °F2026-08-28: -1.77 °F2026-08-29: -6.52 °F2026-08-30: +0.51 °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+0.51
2026-08-29-6.52
2026-08-28-1.77
2026-08-27+1.64
2026-08-26-8.36
2026-08-25-15.73
2026-08-24+2.78
2026-08-23-0.84
2026-08-22-3.17
2026-08-21-0.72
2026-08-20+1.71
2026-08-19+3.80
2026-08-18+8.80
2026-08-17+1.10
2026-08-16+0.30
2026-08-15-5.76
2026-08-14+3.61
2026-08-13-2.45
2026-08-12+1.01
2026-08-11+1.51
2026-08-10+0.33
2026-08-09-2.38
2026-08-08+0.10
2026-08-07-4.09
2026-08-06+3.24
2026-08-05+2.59

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KATL, lead day 4-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 0 days-12 to -10 °F: 0 days-10 to -8 °F: 1 day-8 to -6 °F: 1 day-6 to -4 °F: 2 days-4 to -2 °F: 3 days-2 to 0 °F: 3 days0 to 2 °F: 9 days2 to 4 °F: 5 days4 to 6 °F: 0 days6 to 8 °F: 0 days8 to 10 °F: 1 day10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 2.42 · P90 |e| 7.44 °F-200+20 °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
-20.00-18.000
-18.00-16.000
-16.00-14.001
-14.00-12.000
-12.00-10.000
-10.00-8.001
-8.00-6.001
-6.00-4.002
-4.00-2.003
-2.00+0.003
+0.00+2.009
+2.00+4.005
+4.00+6.000
+6.00+8.000
+8.00+10.001
+10.00+12.000
+12.00+14.000
+14.00+16.000
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08263.26 -0.72

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 -0.95 [-2.76, 0.53] no
GraphCast (IFS init) 25 -1.76 [-3.87, 0.21] no
ECMWF IFS HRES 20 -0.55 [-3.28, 1.15] no
Persistence (baseline) 26 +0.49 [-1.17, 1.97] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KATL (Atlanta Hartsfield), 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/KATL/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