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 7

KORD · gfs · lead 7

Target day = initialization date + 7 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
tmax00Zbilinear30d23 1 QC5.61 [4.82, 6.57]5.03-3.56 [-5.65, -1.17]6.88 [6.08, 7.81]22% [10%, 31%]26%30%-0.47-0.312026-08-08 → 2026-08-30
tmax00Zbilinear90d23 1 QC5.61 [4.78, 6.58]5.03-3.56 [-5.81, -0.87]6.88 [6.05, 7.71]22% [8%, 31%]26%30%-0.47-0.312026-08-08 → 2026-08-30
tmax00Zbilinear365d23 1 QC5.61 [4.75, 6.62]5.03-3.56 [-6.00, -0.81]6.88 [6.05, 7.80]22% [9%, 31%]26%30%-0.47-0.312026-08-08 → 2026-08-30
tmax00Zbilinearall23 1 QC5.61 [4.67, 6.69]5.03-3.56 [-6.14, -0.87]6.88 [6.04, 7.85]22% [7%, 32%]26%30%-0.47-0.312026-08-08 → 2026-08-30
tmax00Znearest30d23 1 QC5.60 [4.72, 6.69]5.09-3.49 [-5.43, -1.18]6.94 [6.01, 7.98]13% [0%, 25%]22%26%-0.46-0.332026-08-08 → 2026-08-30
tmax00Znearest90d23 1 QC5.60 [4.69, 6.75]5.09-3.49 [-5.59, -0.87]6.94 [5.96, 7.92]13% [0%, 25%]22%26%-0.46-0.332026-08-08 → 2026-08-30
tmax00Znearest365d23 1 QC5.60 [4.68, 6.76]5.09-3.49 [-5.75, -0.75]6.94 [5.93, 7.95]13% [0%, 29%]22%26%-0.46-0.332026-08-08 → 2026-08-30
tmax00Znearestall23 1 QC5.60 [4.62, 6.83]5.09-3.49 [-5.88, -0.81]6.94 [5.91, 8.06]13% [0%, 29%]22%26%-0.46-0.332026-08-08 → 2026-08-30
tmax12Zbilinear30d23 1 QC4.18 [2.99, 5.85]3.42-2.97 [-5.58, -1.00]5.19 [3.70, 7.05]13% [0%, 25%]26%39%-0.09+0.112026-08-08 → 2026-08-30
tmax12Zbilinear90d23 1 QC4.18 [2.83, 6.34]3.42-2.97 [-6.31, -0.76]5.19 [3.45, 7.54]13% [0%, 27%]26%39%-0.09+0.112026-08-08 → 2026-08-30
tmax12Zbilinear365d23 1 QC4.18 [2.75, 6.37]3.42-2.97 [-6.29, -0.66]5.19 [3.27, 7.58]13% [0%, 29%]26%39%-0.09+0.112026-08-08 → 2026-08-30
tmax12Zbilinearall23 1 QC4.18 [2.73, 6.69]3.42-2.97 [-6.69, -0.74]5.19 [3.27, 7.69]13% [0%, 29%]26%39%-0.09+0.112026-08-08 → 2026-08-30
tmax12Znearest30d23 1 QC4.30 [2.93, 6.02]3.28-3.17 [-5.76, -1.19]5.28 [3.60, 7.19]13% [0%, 26%]17%39%-0.12+0.142026-08-08 → 2026-08-30
tmax12Znearest90d23 1 QC4.30 [2.82, 6.52]3.28-3.17 [-6.46, -0.92]5.28 [3.44, 7.63]13% [0%, 27%]17%39%-0.12+0.142026-08-08 → 2026-08-30
tmax12Znearest365d23 1 QC4.30 [2.66, 6.56]3.28-3.17 [-6.43, -0.85]5.28 [3.19, 7.65]13% [0%, 29%]17%39%-0.12+0.142026-08-08 → 2026-08-30
tmax12Znearestall23 1 QC4.30 [2.71, 6.88]3.28-3.17 [-6.88, -0.91]5.28 [3.19, 7.81]13% [0%, 29%]17%39%-0.12+0.142026-08-08 → 2026-08-30
tmin00Zbilinear30d23 1 QC3.64 [2.63, 4.44]3.63-0.27 [-2.65, 1.91]4.65 [3.30, 5.42]17% [7%, 29%]39%48%+0.22+0.232026-08-08 → 2026-08-30
tmin00Zbilinear90d23 1 QC3.64 [2.35, 4.36]3.63-0.27 [-2.64, 2.22]4.65 [2.88, 5.39]17% [6%, 29%]39%48%+0.22+0.232026-08-08 → 2026-08-30
tmin00Zbilinear365d23 1 QC3.64 [2.36, 4.42]3.63-0.27 [-2.86, 2.28]4.65 [2.92, 5.46]17% [0%, 29%]39%48%+0.22+0.232026-08-08 → 2026-08-30
tmin00Zbilinearall23 1 QC3.64 [2.39, 4.41]3.63-0.27 [-3.00, 2.60]4.65 [2.91, 5.47]17% [0%, 29%]39%48%+0.22+0.232026-08-08 → 2026-08-30
tmin00Znearest30d23 1 QC3.61 [2.58, 4.41]3.51-0.71 [-3.00, 1.46]4.64 [3.15, 5.53]17% [9%, 26%]39%43%+0.22+0.262026-08-08 → 2026-08-30
tmin00Znearest90d23 1 QC3.61 [2.30, 4.34]3.51-0.71 [-2.95, 1.73]4.64 [2.74, 5.48]17% [8%, 29%]39%43%+0.22+0.262026-08-08 → 2026-08-30
tmin00Znearest365d23 1 QC3.61 [2.27, 4.39]3.51-0.71 [-3.15, 1.79]4.64 [2.74, 5.51]17% [9%, 29%]39%43%+0.22+0.262026-08-08 → 2026-08-30
tmin00Znearestall23 1 QC3.61 [2.32, 4.37]3.51-0.71 [-3.32, 2.07]4.64 [2.78, 5.52]17% [8%, 29%]39%43%+0.22+0.262026-08-08 → 2026-08-30
tmin12Zbilinear30d23 1 QC3.27 [2.09, 4.11]3.26+0.38 [-2.04, 2.59]4.64 [2.82, 5.56]30% [17%, 47%]39%65%+0.30+0.312026-08-08 → 2026-08-30
tmin12Zbilinear90d23 1 QC3.27 [1.75, 4.11]3.26+0.38 [-2.13, 2.86]4.64 [2.42, 5.59]30% [14%, 55%]39%65%+0.30+0.312026-08-08 → 2026-08-30
tmin12Zbilinear365d23 1 QC3.27 [1.91, 4.12]3.26+0.38 [-2.23, 2.82]4.64 [2.57, 5.60]30% [14%, 50%]39%65%+0.30+0.312026-08-08 → 2026-08-30
tmin12Zbilinearall23 1 QC3.27 [1.82, 4.16]3.26+0.38 [-2.48, 3.12]4.64 [2.49, 5.59]30% [14%, 50%]39%65%+0.30+0.312026-08-08 → 2026-08-30
tmin12Znearest30d23 1 QC3.22 [2.02, 4.10]3.23-0.07 [-2.44, 2.10]4.66 [2.74, 5.64]35% [17%, 53%]39%65%+0.31+0.322026-08-08 → 2026-08-30
tmin12Znearest90d23 1 QC3.22 [1.70, 4.08]3.23-0.07 [-2.51, 2.35]4.66 [2.51, 5.65]35% [15%, 60%]39%65%+0.31+0.322026-08-08 → 2026-08-30
tmin12Znearest365d23 1 QC3.22 [1.88, 4.12]3.23-0.07 [-2.62, 2.36]4.66 [2.56, 5.67]35% [14%, 58%]39%65%+0.31+0.322026-08-08 → 2026-08-30
tmin12Znearestall23 1 QC3.22 [1.78, 4.13]3.23-0.07 [-2.85, 2.61]4.66 [2.51, 5.67]35% [14%, 60%]39%65%+0.31+0.322026-08-08 → 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 7, 00Z bilinear tmax+20+100-10-202026-08-08: +5.22 °F2026-08-09: -3.84 °F2026-08-10: -7.31 °F2026-08-11: -7.27 °F2026-08-12: -10.3 °F2026-08-13: +0.72 °F2026-08-14: -5.92 °F2026-08-15: -7.96 °F2026-08-16: -8.58 °F2026-08-17: -4.62 °F2026-08-18: +0.94 °F2026-08-19: +7.82 °F2026-08-20: +2.21 °F2026-08-21: -12.62 °F2026-08-22: +0.29 °F2026-08-23: +5.26 °F2026-08-24: -1.53 °F2026-08-25: +0.61 °F2026-08-26: -14.51 °F2026-08-27: -3.42 °F2026-08-28: -6.89 °F2026-08-29: +0.54 °F2026-08-30: -10.7 °F2026-08-082026-08-30°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 (23 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-10.70
2026-08-29+0.54
2026-08-28-6.89
2026-08-27-3.42
2026-08-26-14.51
2026-08-25+0.61
2026-08-24-1.53
2026-08-23+5.26
2026-08-22+0.29
2026-08-21-12.62
2026-08-20+2.21
2026-08-19+7.82
2026-08-18+0.94
2026-08-17-4.62
2026-08-16-8.58
2026-08-15-7.96
2026-08-14-5.92
2026-08-13+0.72
2026-08-12-10.30
2026-08-11-7.27
2026-08-10-7.31
2026-08-09-3.84
2026-08-08+5.22

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KORD, lead day 7-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 1 day-12 to -10 °F: 2 days-10 to -8 °F: 1 day-8 to -6 °F: 4 days-6 to -4 °F: 2 days-4 to -2 °F: 2 days-2 to 0 °F: 1 day0 to 2 °F: 5 days2 to 4 °F: 1 day4 to 6 °F: 2 days6 to 8 °F: 1 day8 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| 5.26 · P90 |e| 10.62 °F-200+20 °Fn = 23 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
-16.00-14.001
-14.00-12.001
-12.00-10.002
-10.00-8.001
-8.00-6.004
-6.00-4.002
-4.00-2.002
-2.00+0.001
+0.00+2.005
+2.00+4.001
+4.00+6.002
+6.00+8.001
+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
2026-08235.61 -3.56

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23

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 23 +0.95 [-0.84, 2.66] no
GraphCast (IFS init) 23 +1.39 [-0.60, 2.82] no
ECMWF IFS HRES 18 +2.13 [1.13, 4.20] yes
Persistence (baseline) 23 +1.79 [0.17, 3.04] yes

Cite this page

ShortCastCheck, KORD gfs lead 7, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KORD/model/gfs/lead/7/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KORD (Chicago O'Hare), model gfs, lead day 7. 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/7/

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