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 5

KATL · gfs · lead 5

Target day = initialization date + 5 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
tmax00Zbilinear30d25 1 QC4.02 [2.45, 5.85]4.00-0.60 [-3.86, 2.28]5.29 [3.00, 7.21]8% [0%, 19%]40%56%-0.24-0.242026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC4.02 [2.32, 6.06]4.00-0.60 [-4.24, 2.60]5.29 [2.85, 7.47]8% [0%, 22%]40%56%-0.24-0.242026-08-06 → 2026-08-30
tmax00Zbilinear365d25 1 QC4.02 [2.23, 6.28]4.00-0.60 [-4.31, 2.79]5.29 [2.69, 7.59]8% [0%, 22%]40%56%-0.24-0.242026-08-06 → 2026-08-30
tmax00Zbilinearall25 1 QC4.02 [2.20, 6.26]4.00-0.60 [-4.25, 2.63]5.29 [2.60, 7.48]8% [0%, 22%]40%56%-0.24-0.242026-08-06 → 2026-08-30
tmax00Znearest30d25 1 QC3.96 [2.79, 5.33]3.96+0.07 [-2.99, 2.86]5.18 [3.59, 6.70]16% [7%, 26%]36%48%-0.22-0.232026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC3.96 [2.69, 5.44]3.96+0.07 [-3.15, 3.29]5.18 [3.45, 6.85]16% [3%, 29%]36%48%-0.22-0.232026-08-06 → 2026-08-30
tmax00Znearest365d25 1 QC3.96 [2.53, 5.57]3.96+0.07 [-3.44, 3.40]5.18 [3.23, 6.93]16% [0%, 29%]36%48%-0.22-0.232026-08-06 → 2026-08-30
tmax00Znearestall25 1 QC3.96 [2.52, 5.66]3.96+0.07 [-3.35, 3.29]5.18 [3.18, 6.98]16% [4%, 29%]36%48%-0.22-0.232026-08-06 → 2026-08-30
tmax12Zbilinear30d25 1 QC3.11 [1.84, 4.29]3.12-0.29 [-2.72, 1.73]4.16 [2.26, 5.45]24% [5%, 42%]44%60%+0.04+0.032026-08-06 → 2026-08-30
tmax12Zbilinear90d25 1 QC3.11 [1.70, 4.41]3.12-0.29 [-2.91, 1.90]4.16 [2.07, 5.54]24% [0%, 46%]44%60%+0.04+0.032026-08-06 → 2026-08-30
tmax12Zbilinear365d25 1 QC3.11 [1.61, 4.51]3.12-0.29 [-3.07, 2.01]4.16 [2.01, 5.76]24% [0%, 45%]44%60%+0.04+0.032026-08-06 → 2026-08-30
tmax12Zbilinearall25 1 QC3.11 [1.64, 4.51]3.12-0.29 [-3.09, 2.06]4.16 [2.01, 5.68]24% [0%, 45%]44%60%+0.04+0.032026-08-06 → 2026-08-30
tmax12Znearest30d25 1 QC3.32 [2.30, 4.23]3.30+0.12 [-2.39, 2.27]4.29 [2.75, 5.38]20% [5%, 33%]44%56%-0.02-0.022026-08-06 → 2026-08-30
tmax12Znearest90d25 1 QC3.32 [2.18, 4.36]3.30+0.12 [-2.64, 2.40]4.29 [2.58, 5.44]20% [0%, 36%]44%56%-0.02-0.022026-08-06 → 2026-08-30
tmax12Znearest365d25 1 QC3.32 [2.06, 4.40]3.30+0.12 [-2.74, 2.54]4.29 [2.47, 5.57]20% [0%, 35%]44%56%-0.02-0.022026-08-06 → 2026-08-30
tmax12Znearestall25 1 QC3.32 [2.11, 4.36]3.30+0.12 [-2.85, 2.57]4.29 [2.50, 5.53]20% [0%, 36%]44%56%-0.02-0.022026-08-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC2.97 [1.81, 4.02]2.40+2.01 [0.54, 3.50]3.60 [2.19, 4.60]20% [4%, 40%]36%64%-0.26-0.022026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC2.97 [1.62, 4.11]2.40+2.01 [0.25, 3.70]3.60 [1.76, 4.71]20% [0%, 43%]36%64%-0.26-0.022026-08-06 → 2026-08-30
tmin00Zbilinear365d25 1 QC2.97 [1.56, 4.25]2.40+2.01 [0.05, 3.89]3.60 [1.75, 4.79]20% [0%, 43%]36%64%-0.26-0.022026-08-06 → 2026-08-30
tmin00Zbilinearall25 1 QC2.97 [1.59, 4.12]2.40+2.01 [0.12, 3.56]3.60 [1.75, 4.68]20% [0%, 44%]36%64%-0.26-0.022026-08-06 → 2026-08-30
tmin00Znearest30d25 1 QC3.92 [2.41, 5.29]2.68+3.27 [1.59, 5.01]4.68 [2.97, 5.98]12% [0%, 22%]28%40%-0.66-0.132026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC3.92 [2.07, 5.48]2.68+3.27 [1.29, 5.21]4.68 [2.48, 6.11]12% [0%, 24%]28%40%-0.66-0.132026-08-06 → 2026-08-30
tmin00Znearest365d25 1 QC3.92 [2.01, 5.64]2.68+3.27 [1.11, 5.45]4.68 [2.45, 6.27]12% [0%, 25%]28%40%-0.66-0.132026-08-06 → 2026-08-30
tmin00Znearestall25 1 QC3.92 [2.02, 5.43]2.68+3.27 [1.17, 5.15]4.68 [2.39, 6.07]12% [0%, 24%]28%40%-0.66-0.132026-08-06 → 2026-08-30
tmin12Zbilinear30d25 1 QC2.92 [1.60, 4.19]2.77+1.85 [0.41, 3.34]3.75 [2.16, 5.03]28% [9%, 53%]40%56%-0.24-0.172026-08-06 → 2026-08-30
tmin12Zbilinear90d25 1 QC2.92 [1.30, 4.28]2.77+1.85 [0.02, 3.55]3.75 [1.74, 5.10]28% [7%, 62%]40%56%-0.24-0.172026-08-06 → 2026-08-30
tmin12Zbilinear365d25 1 QC2.92 [1.40, 4.48]2.77+1.85 [-0.01, 3.76]3.75 [1.76, 5.26]28% [5%, 60%]40%56%-0.24-0.172026-08-06 → 2026-08-30
tmin12Zbilinearall25 1 QC2.92 [1.21, 4.34]2.77+1.85 [-0.11, 3.44]3.75 [1.56, 5.09]28% [5%, 62%]40%56%-0.24-0.172026-08-06 → 2026-08-30
tmin12Znearest30d25 1 QC3.73 [2.38, 5.12]2.87+3.06 [1.53, 4.66]4.62 [2.89, 6.12]12% [0%, 23%]36%56%-0.58-0.222026-08-06 → 2026-08-30
tmin12Znearest90d25 1 QC3.73 [2.02, 5.28]2.87+3.06 [1.21, 4.87]4.62 [2.44, 6.18]12% [0%, 24%]36%56%-0.58-0.222026-08-06 → 2026-08-30
tmin12Znearest365d25 1 QC3.73 [1.95, 5.46]2.87+3.06 [1.11, 5.05]4.62 [2.29, 6.37]12% [0%, 24%]36%56%-0.58-0.222026-08-06 → 2026-08-30
tmin12Znearestall25 1 QC3.73 [1.69, 5.19]2.87+3.06 [1.09, 4.78]4.62 [1.86, 6.17]12% [0%, 25%]36%56%-0.58-0.222026-08-06 → 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 5, 00Z bilinear tmax+20+100-10-202026-08-06: +1.73 °F2026-08-07: +6.44 °F2026-08-08: -1.3 °F2026-08-09: -1.57 °F2026-08-10: -2.54 °F2026-08-11: -2.01 °F2026-08-12: +1.76 °F2026-08-13: -1.26 °F2026-08-14: +1.32 °F2026-08-15: +1.24 °F2026-08-16: +4.35 °F2026-08-17: +2.49 °F2026-08-18: +7.06 °F2026-08-19: +6.12 °F2026-08-20: +3.45 °F2026-08-21: -2.31 °F2026-08-22: -1.63 °F2026-08-23: +0.19 °F2026-08-24: -13.1 °F2026-08-25: -7.27 °F2026-08-26: -7.2 °F2026-08-27: -12.81 °F2026-08-28: -4.03 °F2026-08-29: +6.56 °F2026-08-30: -0.72 °F2026-08-062026-08-30°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 (25 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.72
2026-08-29+6.56
2026-08-28-4.03
2026-08-27-12.81
2026-08-26-7.20
2026-08-25-7.27
2026-08-24-13.10
2026-08-23+0.19
2026-08-22-1.63
2026-08-21-2.31
2026-08-20+3.45
2026-08-19+6.12
2026-08-18+7.06
2026-08-17+2.49
2026-08-16+4.35
2026-08-15+1.24
2026-08-14+1.32
2026-08-13-1.26
2026-08-12+1.76
2026-08-11-2.01
2026-08-10-2.54
2026-08-09-1.57
2026-08-08-1.30
2026-08-07+6.44
2026-08-06+1.73

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KATL, lead day 5-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 2 days-12 to -10 °F: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 2 days-6 to -4 °F: 1 day-4 to -2 °F: 3 days-2 to 0 °F: 5 days0 to 2 °F: 5 days2 to 4 °F: 2 days4 to 6 °F: 1 day6 to 8 °F: 4 days8 to 10 °F: 0 days10 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| 2.49 · P90 |e| 7.24 °F-200+20 °Fn = 25 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
-14.00-12.002
-12.00-10.000
-10.00-8.000
-8.00-6.002
-6.00-4.001
-4.00-2.003
-2.00+0.005
+0.00+2.005
+2.00+4.002
+4.00+6.001
+6.00+8.004
+8.00+10.000
+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
2026-08254.02 -0.60

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25

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 25 -0.75 [-3.08, 1.06] no
GraphCast (IFS init) 25 -1.02 [-3.60, 1.31] no
ECMWF IFS HRES 18 +0.61 [-2.69, 2.69] no
Persistence (baseline) 25 +0.78 [-1.96, 3.27] no

Cite this page

ShortCastCheck, KATL gfs lead 5, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KATL/model/gfs/lead/5/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KATL (Atlanta Hartsfield), model gfs, lead day 5. 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/5/

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