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

Chicago O'Hare · GraphCast (IFS init) · lead day 1

KORD · 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 QC3.52 [2.66, 4.36]1.45-3.49 [-4.35, -2.65]3.92 [2.98, 4.70]7% [0%, 14%]22%44%-0.16+0.512026-08-02 → 2026-08-30
tmax00Zbilinear90d27 1 QC3.52 [2.70, 4.55]1.45-3.49 [-4.53, -2.70]3.92 [3.02, 4.87]7% [0%, 14%]22%44%-0.16+0.512026-08-02 → 2026-08-30
tmax00Zbilinear365d33 1 QC3.57 [2.86, 4.37]1.42-3.55 [-4.33, -2.85]3.94 [3.18, 4.63]6% [0%, 12%]21%42%-0.09+0.542026-01-02 → 2026-08-30
tmax00Zbilinearall33 1 QC3.57 [2.86, 4.41]1.42-3.55 [-4.40, -2.84]3.94 [3.16, 4.71]6% [0%, 12%]21%42%-0.09+0.542026-01-02 → 2026-08-30
tmax00Znearest30d27 1 QC3.50 [2.64, 4.38]1.47-3.49 [-4.36, -2.63]3.91 [2.95, 4.72]7% [0%, 14%]22%41%-0.15+0.512026-08-02 → 2026-08-30
tmax00Znearest90d27 1 QC3.50 [2.66, 4.55]1.47-3.49 [-4.53, -2.66]3.91 [2.98, 4.89]7% [0%, 14%]22%41%-0.15+0.512026-08-02 → 2026-08-30
tmax00Znearest365d33 1 QC3.57 [2.84, 4.36]1.43-3.56 [-4.35, -2.83]3.94 [3.17, 4.65]6% [0%, 12%]21%39%-0.09+0.542026-01-02 → 2026-08-30
tmax00Znearestall33 1 QC3.57 [2.85, 4.42]1.43-3.56 [-4.42, -2.84]3.94 [3.15, 4.71]6% [0%, 12%]21%39%-0.09+0.542026-01-02 → 2026-08-30
tmax12Zbilinear30d27 1 QC4.01 [3.07, 4.92]1.40-4.01 [-4.92, -3.07]4.33 [3.37, 5.10]4% [0%, 11%]11%33%-0.32+0.532026-08-02 → 2026-08-30
tmax12Zbilinear90d27 1 QC4.01 [3.00, 5.07]1.40-4.01 [-5.07, -3.00]4.33 [3.26, 5.24]4% [0%, 10%]11%33%-0.32+0.532026-08-02 → 2026-08-30
tmax12Zbilinear365d32 1 QC3.98 [3.15, 4.85]1.36-3.98 [-4.85, -3.15]4.29 [3.44, 5.04]3% [0%, 9%]12%31%-0.19+0.572026-01-02 → 2026-08-30
tmax12Zbilinearall32 1 QC3.98 [3.14, 4.92]1.36-3.98 [-4.92, -3.14]4.29 [3.42, 5.09]3% [0%, 10%]12%31%-0.19+0.572026-01-02 → 2026-08-30
tmax12Znearest30d27 1 QC3.98 [3.02, 4.92]1.45-3.98 [-4.92, -3.02]4.31 [3.31, 5.11]4% [0%, 11%]11%33%-0.31+0.522026-08-02 → 2026-08-30
tmax12Znearest90d27 1 QC3.98 [2.99, 5.08]1.45-3.98 [-5.08, -2.99]4.31 [3.19, 5.25]4% [0%, 10%]11%33%-0.31+0.522026-08-02 → 2026-08-30
tmax12Znearest365d32 1 QC3.97 [3.12, 4.84]1.39-3.97 [-4.84, -3.12]4.28 [3.44, 5.04]3% [0%, 9%]12%31%-0.19+0.562026-01-02 → 2026-08-30
tmax12Znearestall32 1 QC3.97 [3.11, 4.90]1.39-3.97 [-4.90, -3.11]4.28 [3.40, 5.12]3% [0%, 10%]12%31%-0.19+0.562026-01-02 → 2026-08-30
tmin00Zbilinear30d27 1 QC1.47 [1.10, 1.93]1.39+0.57 [-0.08, 1.10]1.87 [1.46, 2.31]44% [30%, 57%]63%89%+0.48+0.522026-08-02 → 2026-08-30
tmin00Zbilinear90d27 1 QC1.47 [1.03, 2.03]1.39+0.57 [-0.20, 1.18]1.87 [1.35, 2.40]44% [28%, 58%]63%89%+0.48+0.522026-08-02 → 2026-08-30
tmin00Zbilinear365d33 1 QC1.60 [1.14, 2.19]1.59+0.10 [-1.13, 0.95]2.04 [1.50, 2.62]42% [27%, 57%]61%85%+0.48+0.492026-01-02 → 2026-08-30
tmin00Zbilinearall33 1 QC1.60 [1.12, 2.21]1.59+0.10 [-0.94, 0.92]2.04 [1.50, 2.62]42% [25%, 57%]61%85%+0.48+0.492026-01-02 → 2026-08-30
tmin00Znearest30d27 1 QC1.45 [1.09, 1.85]1.43+0.24 [-0.43, 0.78]1.81 [1.40, 2.22]44% [25%, 61%]74%85%+0.49+0.502026-08-02 → 2026-08-30
tmin00Znearest90d27 1 QC1.45 [1.01, 1.95]1.43+0.24 [-0.54, 0.84]1.81 [1.28, 2.33]44% [24%, 61%]74%85%+0.49+0.502026-08-02 → 2026-08-30
tmin00Znearest365d33 1 QC1.64 [1.15, 2.31]1.64-0.25 [-1.52, 0.61]2.10 [1.46, 2.86]42% [24%, 59%]70%79%+0.46+0.472026-01-02 → 2026-08-30
tmin00Znearestall33 1 QC1.64 [1.13, 2.33]1.64-0.25 [-1.35, 0.61]2.10 [1.44, 2.82]42% [23%, 59%]70%79%+0.46+0.472026-01-02 → 2026-08-30
tmin12Zbilinear30d27 1 QC1.40 [1.09, 1.77]1.39+0.08 [-0.74, 0.68]1.81 [1.40, 2.30]44% [27%, 59%]70%93%+0.50+0.522026-08-02 → 2026-08-30
tmin12Zbilinear90d27 1 QC1.40 [1.04, 1.79]1.39+0.08 [-0.80, 0.74]1.81 [1.31, 2.29]44% [25%, 60%]70%93%+0.50+0.522026-08-02 → 2026-08-30
tmin12Zbilinear365d32 1 QC1.50 [1.09, 1.96]1.51-0.24 [-1.37, 0.52]1.91 [1.41, 2.41]41% [22%, 57%]69%91%+0.52+0.512026-01-02 → 2026-08-30
tmin12Zbilinearall32 1 QC1.50 [1.12, 1.96]1.51-0.24 [-1.19, 0.52]1.91 [1.44, 2.36]41% [21%, 57%]69%91%+0.52+0.512026-01-02 → 2026-08-30
tmin12Znearest30d27 1 QC1.42 [1.07, 1.86]1.42-0.28 [-1.09, 0.30]1.83 [1.36, 2.36]37% [21%, 53%]78%89%+0.50+0.502026-08-02 → 2026-08-30
tmin12Znearest90d27 1 QC1.42 [1.00, 1.88]1.42-0.28 [-1.15, 0.36]1.83 [1.27, 2.38]37% [19%, 54%]78%89%+0.50+0.502026-08-02 → 2026-08-30
tmin12Znearest365d32 1 QC1.57 [1.09, 2.14]1.55-0.60 [-1.75, 0.19]1.99 [1.41, 2.64]34% [19%, 52%]72%84%+0.49+0.502026-01-02 → 2026-08-30
tmin12Znearestall32 1 QC1.57 [1.12, 2.09]1.55-0.60 [-1.59, 0.17]1.99 [1.45, 2.52]34% [18%, 50%]72%84%+0.49+0.502026-01-02 → 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 KORD, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-02: -2.68 °F2026-08-03: -6.77 °F2026-08-04: -4.8 °F2026-08-05: -5.99 °F2026-08-06: -5.06 °F2026-08-07: -5.17 °F2026-08-08: -3.25 °F2026-08-09: +0.32 °F2026-08-10: -6.95 °F2026-08-11: -3.61 °F2026-08-12: -2.99 °F2026-08-13: -2.13 °F2026-08-14: -2.98 °F2026-08-15: -2.42 °F2026-08-16: -2.8 °F2026-08-17: -3.33 °F2026-08-18: -0.71 °F2026-08-19: -1.97 °F2026-08-20: -1.79 °F2026-08-21: -1.36 °F2026-08-22: -4.91 °F2026-08-23: -3.76 °F2026-08-24: -4.57 °F2026-08-25: -5.28 °F2026-08-26: -3.47 °F2026-08-29: -1.22 °F2026-08-30: -4.71 °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
2026-08-30-4.71
2026-08-29-1.22
2026-08-28—
2026-08-27—
2026-08-26-3.47
2026-08-25-5.28
2026-08-24-4.57
2026-08-23-3.76
2026-08-22-4.91
2026-08-21-1.36
2026-08-20-1.79
2026-08-19-1.97
2026-08-18-0.71
2026-08-17-3.33
2026-08-16-2.80
2026-08-15-2.42
2026-08-14-2.98
2026-08-13-2.13
2026-08-12-2.99
2026-08-11-3.61
2026-08-10-6.95
2026-08-09+0.32
2026-08-08-3.25
2026-08-07-5.17
2026-08-06-5.06
2026-08-05-5.99
2026-08-04-4.80
2026-08-03-6.77
2026-08-02-2.68

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KORD, lead day 1-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 2 days-6 to -5 °F: 4 days-5 to -4 °F: 8 days-4 to -3 °F: 5 days-3 to -2 °F: 7 days-2 to -1 °F: 5 days-1 to 0 °F: 1 day0 to 1 °F: 1 day1 to 2 °F: 0 days2 to 3 °F: 0 days3 to 4 °F: 0 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 3.47 · P90 |e| 5.26 °F-100+10 °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
-10.00-9.000
-9.00-8.000
-8.00-7.000
-7.00-6.002
-6.00-5.004
-5.00-4.008
-4.00-3.005
-3.00-2.007
-2.00-1.005
-1.00+0.001
+0.00+1.001
+1.00+2.000
+2.00+3.000
+3.00+4.000
+4.00+5.000
+5.00+6.000
+6.00+7.000
+7.00+8.000
+8.00+9.000
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08273.52 -3.49
2026-0163.81 -3.81

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 +0.21 [-0.31, 0.92] no
Aurora (GFS init) 1 -1.98 [-1.98, -1.98] yes
Aurora (IFS init) 2 +0.27 [-1.48, 2.01] no
FourCastNet v2 (GFS init) 1 +2.09 [2.09, 2.09] yes
FourCastNet v2 (IFS init) 2 +0.51 [-1.49, 2.52] no
NCEP GFS 27 +0.83 [0.18, 1.70] yes
GraphCast (GFS init) 1 -2.23 [-2.23, -2.23] yes
ECMWF IFS HRES 21 +0.00 [-0.68, 0.62] no
Pangu-Weather (GFS init) 1 +0.48 [0.48, 0.48] yes
Pangu-Weather (IFS init) 2 -1.06 [-2.99, 0.88] no
Persistence (baseline) 27 +0.48 [-0.49, 1.55] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KORD (Chicago O'Hare), 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/KORD/model/graphcast_ifs/lead/1/

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