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 5

KORD · 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 QC3.40 [2.06, 4.73]3.36-1.22 [-2.64, 0.33]4.55 [2.60, 6.10]20% [7%, 36%]40%56%+0.08+0.092026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC3.40 [1.83, 4.93]3.36-1.22 [-2.59, 0.59]4.55 [2.29, 6.41]20% [4%, 38%]40%56%+0.08+0.092026-08-06 → 2026-08-30
tmax00Zbilinear365d25 1 QC3.40 [1.55, 4.95]3.36-1.22 [-2.64, 0.66]4.55 [1.93, 6.32]20% [0%, 43%]40%56%+0.08+0.092026-08-06 → 2026-08-30
tmax00Zbilinearall25 1 QC3.40 [1.65, 4.94]3.36-1.22 [-2.79, 0.76]4.55 [2.05, 6.17]20% [3%, 43%]40%56%+0.08+0.092026-08-06 → 2026-08-30
tmax00Znearest30d25 1 QC3.11 [1.91, 4.36]3.14-1.11 [-2.58, 0.39]4.30 [2.35, 5.90]24% [12%, 37%]36%60%+0.15+0.152026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC3.11 [1.68, 4.48]3.14-1.11 [-2.63, 0.61]4.30 [2.07, 6.15]24% [10%, 39%]36%60%+0.15+0.152026-08-06 → 2026-08-30
tmax00Znearest365d25 1 QC3.11 [1.52, 4.51]3.14-1.11 [-2.66, 0.74]4.30 [1.94, 6.12]24% [9%, 43%]36%60%+0.15+0.152026-08-06 → 2026-08-30
tmax00Znearestall25 1 QC3.11 [1.49, 4.47]3.14-1.11 [-2.69, 0.84]4.30 [1.97, 5.98]24% [10%, 43%]36%60%+0.15+0.152026-08-06 → 2026-08-30
tmax12Zbilinear30d25 1 QC2.83 [2.10, 3.60]2.62-1.37 [-2.44, -0.05]3.51 [2.62, 4.29]24% [14%, 35%]44%68%+0.23+0.292026-08-06 → 2026-08-30
tmax12Zbilinear90d25 1 QC2.83 [2.04, 3.69]2.62-1.37 [-2.57, -0.00]3.51 [2.57, 4.41]24% [12%, 36%]44%68%+0.23+0.292026-08-06 → 2026-08-30
tmax12Zbilinear365d25 1 QC2.83 [1.87, 3.92]2.62-1.37 [-2.51, 0.24]3.51 [2.31, 4.53]24% [12%, 36%]44%68%+0.23+0.292026-08-06 → 2026-08-30
tmax12Zbilinearall25 1 QC2.83 [2.08, 3.74]2.62-1.37 [-2.63, 0.16]3.51 [2.56, 4.37]24% [12%, 35%]44%68%+0.23+0.292026-08-06 → 2026-08-30
tmax12Znearest30d25 1 QC2.72 [2.06, 3.37]2.43-1.45 [-2.40, -0.34]3.38 [2.57, 4.10]24% [14%, 35%]36%72%+0.26+0.342026-08-06 → 2026-08-30
tmax12Znearest90d25 1 QC2.72 [2.01, 3.47]2.43-1.45 [-2.54, -0.28]3.38 [2.52, 4.19]24% [12%, 36%]36%72%+0.26+0.342026-08-06 → 2026-08-30
tmax12Znearest365d25 1 QC2.72 [1.94, 3.58]2.43-1.45 [-2.50, -0.02]3.38 [2.31, 4.30]24% [12%, 36%]36%72%+0.26+0.342026-08-06 → 2026-08-30
tmax12Znearestall25 1 QC2.72 [2.04, 3.47]2.43-1.45 [-2.53, -0.07]3.38 [2.50, 4.19]24% [13%, 35%]36%72%+0.26+0.342026-08-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC3.20 [2.30, 3.85]3.21+1.30 [-0.15, 2.60]4.34 [3.26, 5.02]28% [18%, 40%]56%56%+0.25+0.242026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC3.20 [2.21, 3.83]3.21+1.30 [-0.14, 2.61]4.34 [2.99, 5.05]28% [17%, 42%]56%56%+0.25+0.242026-08-06 → 2026-08-30
tmin00Zbilinear365d25 1 QC3.20 [2.05, 3.90]3.21+1.30 [-0.25, 2.76]4.34 [2.67, 5.09]28% [14%, 43%]56%56%+0.25+0.242026-08-06 → 2026-08-30
tmin00Zbilinearall25 1 QC3.20 [2.04, 3.83]3.21+1.30 [-0.32, 2.83]4.34 [2.64, 5.00]28% [15%, 42%]56%56%+0.25+0.242026-08-06 → 2026-08-30
tmin00Znearest30d25 1 QC3.26 [2.23, 3.99]3.30+0.89 [-0.53, 2.21]4.37 [3.17, 5.13]24% [10%, 42%]52%64%+0.23+0.222026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC3.26 [2.13, 4.01]3.30+0.89 [-0.50, 2.23]4.37 [2.91, 5.20]24% [10%, 45%]52%64%+0.23+0.222026-08-06 → 2026-08-30
tmin00Znearest365d25 1 QC3.26 [1.88, 4.09]3.30+0.89 [-0.67, 2.34]4.37 [2.57, 5.26]24% [9%, 50%]52%64%+0.23+0.222026-08-06 → 2026-08-30
tmin00Znearestall25 1 QC3.26 [1.96, 4.01]3.30+0.89 [-0.69, 2.39]4.37 [2.66, 5.14]24% [10%, 50%]52%64%+0.23+0.222026-08-06 → 2026-08-30
tmin12Zbilinear30d25 1 QC2.45 [1.53, 3.13]2.13+0.86 [-0.26, 1.99]2.97 [1.84, 3.66]24% [7%, 50%]52%68%+0.42+0.502026-08-06 → 2026-08-30
tmin12Zbilinear90d25 1 QC2.45 [1.31, 3.22]2.13+0.86 [-0.21, 2.17]2.97 [1.55, 3.69]24% [6%, 60%]52%68%+0.42+0.502026-08-06 → 2026-08-30
tmin12Zbilinear365d25 1 QC2.45 [1.38, 3.22]2.13+0.86 [-0.27, 2.16]2.97 [1.60, 3.73]24% [5%, 57%]52%68%+0.42+0.502026-08-06 → 2026-08-30
tmin12Zbilinearall25 1 QC2.45 [1.29, 3.16]2.13+0.86 [-0.41, 2.25]2.97 [1.53, 3.63]24% [5%, 60%]52%68%+0.42+0.502026-08-06 → 2026-08-30
tmin12Znearest30d25 1 QC2.33 [1.40, 3.05]2.21+0.45 [-0.61, 1.53]2.96 [1.88, 3.70]32% [12%, 58%]48%72%+0.45+0.482026-08-06 → 2026-08-30
tmin12Znearest90d25 1 QC2.33 [1.15, 3.08]2.21+0.45 [-0.55, 1.67]2.96 [1.53, 3.73]32% [12%, 63%]48%72%+0.45+0.482026-08-06 → 2026-08-30
tmin12Znearest365d25 1 QC2.33 [1.23, 3.17]2.21+0.45 [-0.57, 1.71]2.96 [1.58, 3.80]32% [7%, 60%]48%72%+0.45+0.482026-08-06 → 2026-08-30
tmin12Znearestall25 1 QC2.33 [1.10, 3.10]2.21+0.45 [-0.72, 1.75]2.96 [1.50, 3.74]32% [10%, 65%]48%72%+0.45+0.482026-08-06 → 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 KORD, lead day 5, 00Z bilinear tmax+20+100-10-202026-08-06: +0.73 °F2026-08-07: -1.08 °F2026-08-08: +3.55 °F2026-08-09: +4.39 °F2026-08-10: -4.64 °F2026-08-11: -2.51 °F2026-08-12: -9.28 °F2026-08-13: -3.82 °F2026-08-14: -4.68 °F2026-08-15: +5.2 °F2026-08-16: -1.28 °F2026-08-17: -0.82 °F2026-08-18: -1.68 °F2026-08-19: -3.19 °F2026-08-20: +2.93 °F2026-08-21: -0.43 °F2026-08-22: +0.01 °F2026-08-23: +1.37 °F2026-08-24: +2.68 °F2026-08-25: +0.49 °F2026-08-26: -2.31 °F2026-08-27: -9.41 °F2026-08-28: -12.57 °F2026-08-29: +1.68 °F2026-08-30: +4.24 °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+4.24
2026-08-29+1.68
2026-08-28-12.57
2026-08-27-9.41
2026-08-26-2.31
2026-08-25+0.49
2026-08-24+2.68
2026-08-23+1.37
2026-08-22+0.01
2026-08-21-0.43
2026-08-20+2.93
2026-08-19-3.19
2026-08-18-1.68
2026-08-17-0.82
2026-08-16-1.28
2026-08-15+5.20
2026-08-14-4.68
2026-08-13-3.82
2026-08-12-9.28
2026-08-11-2.51
2026-08-10-4.64
2026-08-09+4.39
2026-08-08+3.55
2026-08-07-1.08
2026-08-06+0.73

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KORD, 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: 1 day-12 to -10 °F: 0 days-10 to -8 °F: 2 days-8 to -6 °F: 0 days-6 to -4 °F: 2 days-4 to -2 °F: 4 days-2 to 0 °F: 5 days0 to 2 °F: 5 days2 to 4 °F: 3 days4 to 6 °F: 3 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| 2.68 · P90 |e| 7.65 °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
-14.00-12.001
-12.00-10.000
-10.00-8.002
-8.00-6.000
-6.00-4.002
-4.00-2.004
-2.00+0.005
+0.00+2.005
+2.00+4.003
+4.00+6.003
+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
2026-08253.40 -1.22

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 -0.07 [-1.76, 1.18] no
GraphCast (IFS init) 25 -0.27 [-2.18, 1.32] no
ECMWF IFS HRES 18 +0.65 [-1.74, 3.32] no
Persistence (baseline) 25 -0.28 [-2.33, 1.69] no

Cite this page

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

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