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CastCheck methodology v0.2 · data through 2026-08-30

Atlanta Hartsfield · GraphCast (IFS init) · lead day 1

KATL · graphcast_ifs · lead 1

Target day = initialization date + 1 day. 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, GRAP_v100, starting 2026-01-01 — 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
tmax00Zbilinear30d27 1 QC5.93 [5.30, 6.54]1.21-5.93 [-6.54, -5.30]6.14 [5.52, 6.70]0% [0%, 0%]4%4%-1.76+0.442026-08-02 → 2026-08-30
tmax00Zbilinear90d27 1 QC5.93 [5.22, 6.72]1.21-5.93 [-6.72, -5.22]6.14 [5.35, 6.89]0% [0%, 0%]4%4%-1.76+0.442026-08-02 → 2026-08-30
tmax00Zbilinear365d33 1 QC5.85 [5.17, 6.53]1.55-5.85 [-6.53, -5.17]6.20 [5.41, 6.84]3% [0%, 11%]6%6%-1.27+0.412026-01-02 → 2026-08-30
tmax00Zbilinearall33 1 QC5.85 [5.12, 6.47]1.55-5.85 [-6.47, -5.12]6.20 [5.38, 6.79]3% [0%, 11%]6%6%-1.27+0.412026-01-02 → 2026-08-30
tmax00Znearest30d27 1 QC5.91 [5.22, 6.56]1.29-5.91 [-6.56, -5.22]6.13 [5.44, 6.75]0% [0%, 0%]4%4%-1.75+0.402026-08-02 → 2026-08-30
tmax00Znearest90d27 1 QC5.91 [5.07, 6.76]1.29-5.91 [-6.76, -5.07]6.13 [5.23, 6.98]0% [0%, 0%]4%4%-1.75+0.402026-08-02 → 2026-08-30
tmax00Znearest365d33 1 QC5.85 [5.09, 6.55]1.58-5.85 [-6.55, -5.09]6.20 [5.34, 6.89]3% [0%, 11%]6%6%-1.27+0.392026-01-02 → 2026-08-30
tmax00Znearestall33 1 QC5.85 [5.08, 6.50]1.58-5.85 [-6.50, -5.08]6.20 [5.30, 6.83]3% [0%, 11%]6%6%-1.27+0.392026-01-02 → 2026-08-30
tmax12Zbilinear30d27 1 QC6.61 [6.02, 7.25]1.24-6.61 [-7.25, -6.02]6.80 [6.24, 7.41]0% [0%, 0%]0%4%-2.07+0.422026-08-02 → 2026-08-30
tmax12Zbilinear90d27 1 QC6.61 [6.04, 7.36]1.24-6.61 [-7.36, -6.04]6.80 [6.20, 7.52]0% [0%, 0%]0%4%-2.07+0.422026-08-02 → 2026-08-30
tmax12Zbilinear365d32 1 QC6.59 [5.97, 7.24]1.56-6.59 [-7.24, -5.97]6.92 [6.24, 7.59]3% [0%, 12%]3%6%-1.74+0.352026-01-02 → 2026-08-30
tmax12Zbilinearall32 1 QC6.59 [5.96, 7.24]1.56-6.59 [-7.24, -5.96]6.92 [6.25, 7.55]3% [0%, 12%]3%6%-1.74+0.352026-01-02 → 2026-08-30
tmax12Znearest30d27 1 QC6.60 [6.00, 7.24]1.22-6.60 [-7.24, -6.00]6.80 [6.19, 7.39]0% [0%, 0%]0%4%-2.07+0.432026-08-02 → 2026-08-30
tmax12Znearest90d27 1 QC6.60 [6.01, 7.34]1.22-6.60 [-7.34, -6.01]6.80 [6.15, 7.49]0% [0%, 0%]0%4%-2.07+0.432026-08-02 → 2026-08-30
tmax12Znearest365d32 1 QC6.61 [5.97, 7.26]1.53-6.61 [-7.26, -5.97]6.94 [6.22, 7.60]3% [0%, 12%]3%6%-1.75+0.362026-01-02 → 2026-08-30
tmax12Znearestall32 1 QC6.61 [5.92, 7.25]1.53-6.61 [-7.25, -5.92]6.94 [6.22, 7.56]3% [0%, 12%]3%6%-1.75+0.362026-01-02 → 2026-08-30
tmin00Zbilinear30d27 1 QC1.63 [1.04, 2.21]1.47-0.60 [-1.68, 0.27]2.09 [1.33, 2.61]41% [20%, 62%]67%81%+0.14+0.222026-08-02 → 2026-08-30
tmin00Zbilinear90d27 1 QC1.63 [0.93, 2.24]1.47-0.60 [-1.95, 0.27]2.09 [1.12, 2.64]41% [14%, 68%]67%81%+0.14+0.222026-08-02 → 2026-08-30
tmin00Zbilinear365d33 1 QC1.60 [1.11, 2.17]1.48-0.48 [-1.52, 0.29]2.00 [1.34, 2.56]39% [17%, 59%]70%85%+0.32+0.402026-01-02 → 2026-08-30
tmin00Zbilinearall33 1 QC1.60 [1.11, 2.15]1.48-0.48 [-1.54, 0.26]2.00 [1.30, 2.53]39% [17%, 59%]70%85%+0.32+0.402026-01-02 → 2026-08-30
tmin00Znearest30d27 1 QC1.69 [1.08, 2.29]1.51-0.67 [-1.81, 0.22]2.15 [1.37, 2.71]41% [20%, 62%]70%81%+0.11+0.202026-08-02 → 2026-08-30
tmin00Znearest90d27 1 QC1.69 [0.96, 2.32]1.51-0.67 [-1.95, 0.21]2.15 [1.15, 2.75]41% [14%, 68%]70%81%+0.11+0.202026-08-02 → 2026-08-30
tmin00Znearest365d33 1 QC1.65 [1.15, 2.24]1.51-0.57 [-1.61, 0.20]2.06 [1.38, 2.64]36% [11%, 57%]73%85%+0.30+0.392026-01-02 → 2026-08-30
tmin00Znearestall33 1 QC1.65 [1.12, 2.21]1.51-0.57 [-1.67, 0.19]2.06 [1.32, 2.62]36% [13%, 58%]73%85%+0.30+0.392026-01-02 → 2026-08-30
tmin12Zbilinear30d27 1 QC1.69 [1.18, 2.15]1.37-0.84 [-1.77, -0.10]1.99 [1.41, 2.41]26% [5%, 55%]70%89%+0.10+0.272026-08-02 → 2026-08-30
tmin12Zbilinear90d27 1 QC1.69 [1.06, 2.20]1.37-0.84 [-2.04, -0.13]1.99 [1.27, 2.45]26% [0%, 62%]70%89%+0.10+0.272026-08-02 → 2026-08-30
tmin12Zbilinear365d32 1 QC1.65 [1.20, 2.13]1.42-0.78 [-1.69, -0.12]1.95 [1.44, 2.41]28% [6%, 55%]69%91%+0.24+0.362026-01-02 → 2026-08-30
tmin12Zbilinearall32 1 QC1.65 [1.13, 2.13]1.42-0.78 [-1.71, -0.16]1.95 [1.39, 2.39]28% [7%, 57%]69%91%+0.24+0.362026-01-02 → 2026-08-30
tmin12Znearest30d27 1 QC1.76 [1.19, 2.27]1.38-0.96 [-1.96, -0.19]2.07 [1.45, 2.57]26% [5%, 55%]63%89%+0.07+0.272026-08-02 → 2026-08-30
tmin12Znearest90d27 1 QC1.76 [1.06, 2.32]1.38-0.96 [-2.14, -0.22]2.07 [1.29, 2.60]26% [0%, 62%]63%89%+0.07+0.272026-08-02 → 2026-08-30
tmin12Znearest365d32 1 QC1.70 [1.20, 2.25]1.41-0.93 [-1.91, -0.23]2.03 [1.48, 2.55]28% [6%, 55%]62%91%+0.21+0.362026-01-02 → 2026-08-30
tmin12Znearestall32 1 QC1.70 [1.15, 2.24]1.41-0.93 [-1.90, -0.27]2.03 [1.44, 2.53]28% [7%, 57%]62%91%+0.21+0.362026-01-02 → 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 GraphCast (IFS init) at KATL, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-02: -9.24 °F2026-08-03: -6.25 °F2026-08-04: -3.89 °F2026-08-05: -7.84 °F2026-08-06: -6.89 °F2026-08-07: -4.85 °F2026-08-08: -6.48 °F2026-08-09: -6.46 °F2026-08-10: -9.16 °F2026-08-11: -5.51 °F2026-08-12: -6.32 °F2026-08-13: -8.15 °F2026-08-14: -5.54 °F2026-08-15: -6.63 °F2026-08-16: -6.89 °F2026-08-17: -4.43 °F2026-08-18: -1.64 °F2026-08-19: -5.97 °F2026-08-20: -4.73 °F2026-08-21: -6.09 °F2026-08-22: -6.23 °F2026-08-23: -4.66 °F2026-08-24: -5.08 °F2026-08-25: -6.71 °F2026-08-26: -4.03 °F2026-08-29: -4.9 °F2026-08-30: -5.56 °F2026-08-022026-08-30°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 (29 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-5.56
2026-08-29-4.90
2026-08-28—
2026-08-27—
2026-08-26-4.03
2026-08-25-6.71
2026-08-24-5.08
2026-08-23-4.66
2026-08-22-6.23
2026-08-21-6.09
2026-08-20-4.73
2026-08-19-5.97
2026-08-18-1.64
2026-08-17-4.43
2026-08-16-6.89
2026-08-15-6.63
2026-08-14-5.54
2026-08-13-8.15
2026-08-12-6.32
2026-08-11-5.51
2026-08-10-9.16
2026-08-09-6.46
2026-08-08-6.48
2026-08-07-4.85
2026-08-06-6.89
2026-08-05-7.84
2026-08-04-3.89
2026-08-03-6.25
2026-08-02-9.24

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KATL, lead day 1-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 0 days-12 to -10 °F: 1 day-10 to -8 °F: 4 days-8 to -6 °F: 11 days-6 to -4 °F: 12 days-4 to -2 °F: 3 days-2 to 0 °F: 2 days0 to 2 °F: 0 days2 to 4 °F: 0 days4 to 6 °F: 0 days6 to 8 °F: 0 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| 5.97 · P90 |e| 8.31 °F-200+20 °Fn = 33 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
-14.00-12.000
-12.00-10.001
-10.00-8.004
-8.00-6.0011
-6.00-4.0012
-4.00-2.003
-2.00+0.002
+0.00+2.000
+2.00+4.000
+4.00+6.000
+6.00+8.000
+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
2026-08275.93 -5.93
2026-0165.47 -5.47

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 32
GraphCast (IFS init)2026-01-02 → 2026-08-30 32

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means GraphCast (IFS init) has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 27 +1.62 [1.00, 2.27] yes
Aurora (GFS init) 1 -1.55 [-1.55, -1.55] yes
Aurora (IFS init) 2 -1.03 [-1.42, -0.63] yes
FourCastNet v2 (GFS init) 1 +2.13 [2.13, 2.13] yes
FourCastNet v2 (IFS init) 2 +2.45 [1.96, 2.94] yes
NCEP GFS 27 +3.64 [2.42, 4.61] yes
GraphCast (GFS init) 1 -0.62 [-0.62, -0.62] yes
ECMWF IFS HRES 21 +3.92 [2.99, 4.48] yes
Pangu-Weather (GFS init) 1 +1.58 [1.58, 1.58] yes
Pangu-Weather (IFS init) 2 +2.37 [2.16, 2.58] yes
Persistence (baseline) 27 +3.78 [2.76, 4.89] yes

Cite this page

ShortCastCheck, KATL graphcast_ifs lead 1, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KATL/model/graphcast_ifs/lead/1/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KATL (Atlanta Hartsfield), model graphcast_ifs, lead day 1. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KATL/model/graphcast_ifs/lead/1/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

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