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 6

KATL · 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, 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
tmax00Zbilinear30d24 1 QC4.91 [3.92, 6.01]4.98-0.67 [-3.25, 2.56]5.93 [4.69, 7.06]8% [0%, 21%]21%38%-0.59-0.592026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC4.91 [3.75, 6.13]4.98-0.67 [-3.35, 3.41]5.93 [4.53, 7.12]8% [0%, 22%]21%38%-0.59-0.592026-08-07 → 2026-08-30
tmax00Zbilinear365d24 1 QC4.91 [3.69, 6.27]4.98-0.67 [-3.60, 3.35]5.93 [4.52, 7.27]8% [0%, 24%]21%38%-0.59-0.592026-08-07 → 2026-08-30
tmax00Zbilinearall24 1 QC4.91 [3.77, 6.26]4.98-0.67 [-3.44, 3.38]5.93 [4.55, 7.29]8% [0%, 22%]21%38%-0.59-0.592026-08-07 → 2026-08-30
tmax00Znearest30d24 1 QC4.81 [3.94, 5.82]4.82-0.08 [-2.50, 3.01]5.71 [4.77, 6.63]8% [0%, 21%]25%33%-0.56-0.542026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC4.81 [3.85, 5.99]4.82-0.08 [-2.64, 3.87]5.71 [4.70, 6.67]8% [0%, 22%]25%33%-0.56-0.542026-08-07 → 2026-08-30
tmax00Znearest365d24 1 QC4.81 [3.86, 6.17]4.82-0.08 [-2.84, 3.64]5.71 [4.63, 6.77]8% [0%, 24%]25%33%-0.56-0.542026-08-07 → 2026-08-30
tmax00Znearestall24 1 QC4.81 [3.84, 6.19]4.82-0.08 [-2.83, 3.80]5.71 [4.52, 6.71]8% [0%, 22%]25%33%-0.56-0.542026-08-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC4.97 [3.30, 6.90]5.05-2.20 [-5.16, 0.52]6.65 [4.25, 8.66]12% [4%, 21%]25%46%-0.61-0.612026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC4.97 [2.87, 7.17]5.05-2.20 [-5.28, 0.93]6.65 [3.27, 8.91]12% [0%, 24%]25%46%-0.61-0.612026-08-07 → 2026-08-30
tmax12Zbilinear365d24 1 QC4.97 [2.87, 7.26]5.05-2.20 [-5.47, 0.97]6.65 [3.18, 9.01]12% [0%, 22%]25%46%-0.61-0.612026-08-07 → 2026-08-30
tmax12Zbilinearall24 1 QC4.97 [2.76, 7.07]5.05-2.20 [-5.46, 0.97]6.65 [3.15, 8.73]12% [0%, 22%]25%46%-0.61-0.612026-08-07 → 2026-08-30
tmax12Znearest30d24 1 QC4.97 [3.39, 6.58]5.05-1.56 [-4.18, 1.11]6.56 [4.14, 8.13]12% [4%, 22%]29%42%-0.61-0.612026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC4.97 [3.12, 6.84]5.05-1.56 [-4.19, 1.67]6.56 [3.69, 8.25]12% [0%, 23%]29%42%-0.61-0.612026-08-07 → 2026-08-30
tmax12Znearest365d24 1 QC4.97 [3.09, 6.95]5.05-1.56 [-4.39, 1.73]6.56 [3.65, 8.25]12% [0%, 23%]29%42%-0.61-0.612026-08-07 → 2026-08-30
tmax12Znearestall24 1 QC4.97 [3.03, 6.74]5.05-1.56 [-4.32, 1.68]6.56 [3.59, 8.23]12% [0%, 23%]29%42%-0.61-0.612026-08-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC2.79 [2.10, 3.60]2.79+1.67 [0.57, 2.95]3.65 [2.70, 4.63]33% [20%, 43%]42%58%-0.17-0.172026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC2.79 [2.04, 3.60]2.79+1.67 [0.55, 3.03]3.65 [2.68, 4.62]33% [19%, 43%]42%58%-0.17-0.172026-08-07 → 2026-08-30
tmin00Zbilinear365d24 1 QC2.79 [2.02, 3.67]2.79+1.67 [0.52, 3.23]3.65 [2.65, 4.73]33% [20%, 43%]42%58%-0.17-0.172026-08-07 → 2026-08-30
tmin00Zbilinearall24 1 QC2.79 [2.00, 3.63]2.79+1.67 [0.41, 3.17]3.65 [2.62, 4.67]33% [18%, 43%]42%58%-0.17-0.172026-08-07 → 2026-08-30
tmin00Znearest30d24 1 QC3.58 [2.63, 4.63]3.04+2.91 [1.75, 4.36]4.65 [3.54, 5.78]21% [4%, 33%]42%58%-0.51-0.282026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC3.58 [2.59, 4.61]3.04+2.91 [1.67, 4.46]4.65 [3.49, 5.80]21% [0%, 36%]42%58%-0.51-0.282026-08-07 → 2026-08-30
tmin00Znearest365d24 1 QC3.58 [2.51, 4.74]3.04+2.91 [1.70, 4.62]4.65 [3.46, 5.84]21% [0%, 36%]42%58%-0.51-0.282026-08-07 → 2026-08-30
tmin00Znearestall24 1 QC3.58 [2.46, 4.73]3.04+2.91 [1.58, 4.51]4.65 [3.38, 5.81]21% [0%, 38%]42%58%-0.51-0.282026-08-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC2.91 [1.94, 3.74]2.56+1.63 [0.56, 2.64]3.49 [2.22, 4.25]17% [5%, 29%]46%54%-0.22-0.072026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC2.91 [1.86, 3.74]2.56+1.63 [0.53, 2.72]3.49 [2.05, 4.24]17% [0%, 29%]46%54%-0.22-0.072026-08-07 → 2026-08-30
tmin12Zbilinear365d24 1 QC2.91 [1.85, 3.84]2.56+1.63 [0.50, 2.83]3.49 [2.02, 4.34]17% [0%, 29%]46%54%-0.22-0.072026-08-07 → 2026-08-30
tmin12Zbilinearall24 1 QC2.91 [1.81, 3.84]2.56+1.63 [0.51, 2.70]3.49 [1.98, 4.32]17% [0%, 29%]46%54%-0.22-0.072026-08-07 → 2026-08-30
tmin12Znearest30d24 1 QC3.54 [2.28, 4.57]2.69+2.62 [1.23, 3.95]4.22 [2.64, 5.27]12% [0%, 23%]29%50%-0.49-0.132026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC3.54 [2.20, 4.54]2.69+2.62 [1.18, 4.04]4.22 [2.47, 5.25]12% [0%, 23%]29%50%-0.49-0.132026-08-07 → 2026-08-30
tmin12Znearest365d24 1 QC3.54 [2.08, 4.74]2.69+2.62 [1.15, 4.17]4.22 [2.37, 5.44]12% [0%, 25%]29%50%-0.49-0.132026-08-07 → 2026-08-30
tmin12Znearestall24 1 QC3.54 [2.11, 4.68]2.69+2.62 [1.11, 4.01]4.22 [2.42, 5.35]12% [0%, 24%]29%50%-0.49-0.132026-08-07 → 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 KATL, lead day 6, 00Z bilinear tmax+20+100-10-202026-08-07: +5.36 °F2026-08-08: +3.57 °F2026-08-09: +0.19 °F2026-08-10: -2.78 °F2026-08-11: -6.85 °F2026-08-12: -0.46 °F2026-08-13: -8.9 °F2026-08-14: -7.25 °F2026-08-15: +2.52 °F2026-08-16: +5.57 °F2026-08-17: +1.53 °F2026-08-18: +10.18 °F2026-08-19: +4.04 °F2026-08-20: +1.38 °F2026-08-21: +3.62 °F2026-08-22: -2.88 °F2026-08-23: +1.71 °F2026-08-24: -8.84 °F2026-08-25: -10.57 °F2026-08-26: -3.85 °F2026-08-27: -12.52 °F2026-08-28: -2.04 °F2026-08-29: +5.23 °F2026-08-30: +6 °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+6.00
2026-08-29+5.23
2026-08-28-2.04
2026-08-27-12.52
2026-08-26-3.85
2026-08-25-10.57
2026-08-24-8.84
2026-08-23+1.71
2026-08-22-2.88
2026-08-21+3.62
2026-08-20+1.38
2026-08-19+4.04
2026-08-18+10.18
2026-08-17+1.53
2026-08-16+5.57
2026-08-15+2.52
2026-08-14-7.25
2026-08-13-8.90
2026-08-12-0.46
2026-08-11-6.85
2026-08-10-2.78
2026-08-09+0.19
2026-08-08+3.57
2026-08-07+5.36

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KATL, lead day 6-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 1 day-12 to -10 °F: 1 day-10 to -8 °F: 2 days-8 to -6 °F: 2 days-6 to -4 °F: 0 days-4 to -2 °F: 4 days-2 to 0 °F: 1 day0 to 2 °F: 4 days2 to 4 °F: 3 days4 to 6 °F: 5 days6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.94 · P90 |e| 9.8 °F-200+20 °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
-20.00-18.000
-18.00-16.000
-16.00-14.000
-14.00-12.001
-12.00-10.001
-10.00-8.002
-8.00-6.002
-6.00-4.000
-4.00-2.004
-2.00+0.001
+0.00+2.004
+2.00+4.003
+4.00+6.005
+6.00+8.000
+8.00+10.000
+10.00+12.001
+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
2026-08244.91 -0.67

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 +0.03 [-1.39, 1.28] no
GraphCast (IFS init) 24 -0.44 [-2.70, 1.24] no
ECMWF IFS HRES 19 +2.35 [1.21, 3.43] yes
Persistence (baseline) 24 +1.83 [0.21, 3.37] yes

Cite this page

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

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