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

Chicago O'Hare · NCEP GFS · lead day 1

KORD · gfs · 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, 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
tmax00Zbilinear30d29 1 QC2.57 [1.97, 3.26]1.98-1.96 [-2.98, -0.81]3.28 [2.47, 4.03]24% [11%, 38%]48%62%+0.12+0.322026-08-02 → 2026-08-30
tmax00Zbilinear90d29 1 QC2.57 [1.84, 3.34]1.98-1.96 [-3.13, -0.55]3.28 [2.27, 4.06]24% [11%, 38%]48%62%+0.12+0.322026-08-02 → 2026-08-30
tmax00Zbilinear365d29 1 QC2.57 [1.86, 3.34]1.98-1.96 [-3.13, -0.62]3.28 [2.31, 4.05]24% [9%, 40%]48%62%+0.12+0.322026-08-02 → 2026-08-30
tmax00Zbilinearall29 1 QC2.57 [1.87, 3.38]1.98-1.96 [-3.22, -0.61]3.28 [2.36, 4.05]24% [9%, 38%]48%62%+0.12+0.322026-08-02 → 2026-08-30
tmax00Znearest30d29 1 QC2.80 [2.31, 3.38]1.98-2.06 [-3.14, -0.85]3.49 [2.72, 4.25]14% [4%, 21%]48%72%+0.05+0.322026-08-02 → 2026-08-30
tmax00Znearest90d29 1 QC2.80 [2.23, 3.38]1.98-2.06 [-3.23, -0.61]3.49 [2.60, 4.26]14% [4%, 23%]48%72%+0.05+0.322026-08-02 → 2026-08-30
tmax00Znearest365d29 1 QC2.80 [2.26, 3.38]1.98-2.06 [-3.22, -0.63]3.49 [2.61, 4.26]14% [0%, 22%]48%72%+0.05+0.322026-08-02 → 2026-08-30
tmax00Znearestall29 1 QC2.80 [2.29, 3.41]1.98-2.06 [-3.23, -0.67]3.49 [2.63, 4.29]14% [4%, 22%]48%72%+0.05+0.322026-08-02 → 2026-08-30
tmax12Zbilinear30d29 1 QC2.12 [1.47, 2.96]1.64-1.73 [-2.67, -0.91]3.00 [1.70, 4.21]21% [7%, 34%]55%90%+0.28+0.432026-08-02 → 2026-08-30
tmax12Zbilinear90d29 1 QC2.12 [1.35, 3.00]1.64-1.73 [-2.71, -0.72]3.00 [1.55, 4.21]21% [8%, 33%]55%90%+0.28+0.432026-08-02 → 2026-08-30
tmax12Zbilinear365d29 1 QC2.12 [1.31, 3.06]1.64-1.73 [-2.79, -0.63]3.00 [1.51, 4.30]21% [7%, 35%]55%90%+0.28+0.432026-08-02 → 2026-08-30
tmax12Zbilinearall29 1 QC2.12 [1.38, 3.06]1.64-1.73 [-2.77, -0.73]3.00 [1.59, 4.29]21% [5%, 33%]55%90%+0.28+0.432026-08-02 → 2026-08-30
tmax12Znearest30d29 1 QC2.32 [1.72, 3.04]1.61-1.89 [-2.75, -1.02]3.09 [1.95, 4.23]21% [7%, 34%]55%76%+0.21+0.452026-08-02 → 2026-08-30
tmax12Znearest90d29 1 QC2.32 [1.62, 3.06]1.61-1.89 [-2.72, -0.92]3.09 [1.83, 4.21]21% [6%, 36%]55%76%+0.21+0.452026-08-02 → 2026-08-30
tmax12Znearest365d29 1 QC2.32 [1.61, 3.08]1.61-1.89 [-2.84, -0.88]3.09 [1.81, 4.29]21% [5%, 36%]55%76%+0.21+0.452026-08-02 → 2026-08-30
tmax12Znearestall29 1 QC2.32 [1.64, 3.16]1.61-1.89 [-2.85, -0.96]3.09 [1.83, 4.33]21% [4%, 35%]55%76%+0.21+0.452026-08-02 → 2026-08-30
tmin00Zbilinear30d29 1 QC1.65 [1.42, 1.90]1.55+0.41 [-0.18, 0.98]2.13 [1.77, 2.48]41% [28%, 53%]72%83%+0.42+0.462026-08-02 → 2026-08-30
tmin00Zbilinear90d29 1 QC1.65 [1.32, 1.97]1.55+0.41 [-0.28, 1.13]2.13 [1.67, 2.53]41% [25%, 55%]72%83%+0.42+0.462026-08-02 → 2026-08-30
tmin00Zbilinear365d29 1 QC1.65 [1.33, 1.97]1.55+0.41 [-0.34, 1.14]2.13 [1.66, 2.51]41% [25%, 55%]72%83%+0.42+0.462026-08-02 → 2026-08-30
tmin00Zbilinearall29 1 QC1.65 [1.36, 2.04]1.55+0.41 [-0.27, 1.16]2.13 [1.72, 2.60]41% [22%, 57%]72%83%+0.42+0.462026-08-02 → 2026-08-30
tmin00Znearest30d29 1 QC1.54 [1.33, 1.76]1.55-0.07 [-0.71, 0.46]2.02 [1.63, 2.47]45% [31%, 60%]72%86%+0.46+0.462026-08-02 → 2026-08-30
tmin00Znearest90d29 1 QC1.54 [1.29, 1.76]1.55-0.07 [-0.84, 0.58]2.02 [1.56, 2.46]45% [29%, 62%]72%86%+0.46+0.462026-08-02 → 2026-08-30
tmin00Znearest365d29 1 QC1.54 [1.29, 1.75]1.55-0.07 [-0.90, 0.61]2.02 [1.56, 2.49]45% [27%, 64%]72%86%+0.46+0.462026-08-02 → 2026-08-30
tmin00Znearestall29 1 QC1.54 [1.33, 1.79]1.55-0.07 [-0.83, 0.61]2.02 [1.59, 2.50]45% [27%, 62%]72%86%+0.46+0.462026-08-02 → 2026-08-30
tmin12Zbilinear30d29 1 QC1.75 [1.22, 2.27]1.68+0.44 [-0.09, 0.96]2.22 [1.63, 2.78]38% [17%, 60%]66%90%+0.38+0.412026-08-02 → 2026-08-30
tmin12Zbilinear90d29 1 QC1.75 [1.17, 2.30]1.68+0.44 [-0.20, 1.03]2.22 [1.52, 2.76]38% [14%, 60%]66%90%+0.38+0.412026-08-02 → 2026-08-30
tmin12Zbilinear365d29 1 QC1.75 [1.12, 2.31]1.68+0.44 [-0.23, 1.09]2.22 [1.43, 2.85]38% [14%, 62%]66%90%+0.38+0.412026-08-02 → 2026-08-30
tmin12Zbilinearall29 1 QC1.75 [1.13, 2.33]1.68+0.44 [-0.19, 1.06]2.22 [1.46, 2.84]38% [12%, 62%]66%90%+0.38+0.412026-08-02 → 2026-08-30
tmin12Znearest30d29 1 QC1.57 [1.19, 1.97]1.59-0.11 [-0.66, 0.36]2.14 [1.53, 2.79]48% [30%, 66%]76%90%+0.44+0.442026-08-02 → 2026-08-30
tmin12Znearest90d29 1 QC1.57 [1.17, 1.98]1.59-0.11 [-0.71, 0.45]2.14 [1.47, 2.79]48% [28%, 66%]76%90%+0.44+0.442026-08-02 → 2026-08-30
tmin12Znearest365d29 1 QC1.57 [1.12, 2.01]1.59-0.11 [-0.76, 0.45]2.14 [1.42, 2.83]48% [27%, 67%]76%90%+0.44+0.442026-08-02 → 2026-08-30
tmin12Znearestall29 1 QC1.57 [1.14, 2.03]1.59-0.11 [-0.76, 0.45]2.14 [1.44, 2.82]48% [29%, 67%]76%90%+0.44+0.442026-08-02 → 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 NCEP GFS at KORD, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-02: -3.06 °F2026-08-03: -3.65 °F2026-08-04: -2.25 °F2026-08-05: -0.01 °F2026-08-06: -7.21 °F2026-08-07: -3.14 °F2026-08-08: +0.75 °F2026-08-09: -7.16 °F2026-08-10: -3.55 °F2026-08-11: -4.39 °F2026-08-12: -1.84 °F2026-08-13: -4.18 °F2026-08-14: -1.19 °F2026-08-15: -2.03 °F2026-08-16: -1.48 °F2026-08-17: +0.55 °F2026-08-18: -3.79 °F2026-08-19: +1.11 °F2026-08-20: +3.99 °F2026-08-21: -0.15 °F2026-08-22: -0.85 °F2026-08-23: -0.55 °F2026-08-24: -1.69 °F2026-08-25: -2.02 °F2026-08-26: -7.74 °F2026-08-27: -1.32 °F2026-08-28: -0.57 °F2026-08-29: -1.76 °F2026-08-30: +2.46 °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+2.46
2026-08-29-1.76
2026-08-28-0.57
2026-08-27-1.32
2026-08-26-7.74
2026-08-25-2.02
2026-08-24-1.69
2026-08-23-0.55
2026-08-22-0.85
2026-08-21-0.15
2026-08-20+3.99
2026-08-19+1.11
2026-08-18-3.79
2026-08-17+0.55
2026-08-16-1.48
2026-08-15-2.03
2026-08-14-1.19
2026-08-13-4.18
2026-08-12-1.84
2026-08-11-4.39
2026-08-10-3.55
2026-08-09-7.16
2026-08-08+0.75
2026-08-07-3.14
2026-08-06-7.21
2026-08-05-0.01
2026-08-04-2.25
2026-08-03-3.65
2026-08-02-3.06

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KORD, lead day 1-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 3 days-7 to -6 °F: 0 days-6 to -5 °F: 0 days-5 to -4 °F: 2 days-4 to -3 °F: 5 days-3 to -2 °F: 3 days-2 to -1 °F: 6 days-1 to 0 °F: 5 days0 to 1 °F: 2 days1 to 2 °F: 1 day2 to 3 °F: 1 day3 to 4 °F: 1 day4 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| 2.02 · P90 |e| 4.95 °F-100+10 °Fn = 29 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
-8.00-7.003
-7.00-6.000
-6.00-5.000
-5.00-4.002
-4.00-3.005
-3.00-2.003
-2.00-1.006
-1.00+0.005
+0.00+1.002
+1.00+2.001
+2.00+3.001
+3.00+4.001
+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
2026-08292.57 -1.96

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29

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 29 -0.72 [-1.14, -0.35] yes
Aurora (GFS init) 1 -4.23 [-4.23, -4.23] yes
Aurora (IFS init) 2 -0.59 [-0.94, -0.24] yes
FourCastNet v2 (GFS init) 1 -0.17 [-0.17, -0.17] yes
FourCastNet v2 (IFS init) 2 -0.34 [-0.95, 0.26] no
GraphCast (GFS init) 1 -4.48 [-4.48, -4.48] yes
GraphCast (IFS init) 27 -0.83 [-1.70, -0.18] yes
ECMWF IFS HRES 23 -0.48 [-1.12, 0.80] no
Pangu-Weather (GFS init) 1 -1.77 [-1.77, -1.77] yes
Pangu-Weather (IFS init) 2 -1.91 [-2.45, -1.37] yes
Persistence (baseline) 29 -0.36 [-1.21, 0.61] no

Cite this page

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

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