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

Chicago O'Hare · NCEP GFS · lead day 0

KORD · gfs · lead 0

Target day = initialization date + 0 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
tmax00Zbilinear30d30 1 QC2.26 [1.59, 2.78]1.59-2.11 [-2.76, -1.36]3.00 [2.38, 3.52]27% [7%, 50%]53%77%——2026-08-01 → 2026-08-30
tmax00Zbilinear90d30 1 QC2.26 [1.67, 2.87]1.59-2.11 [-2.86, -1.44]3.00 [2.29, 3.64]27% [4%, 48%]53%77%——2026-08-01 → 2026-08-30
tmax00Zbilinear365d30 1 QC2.26 [1.56, 2.85]1.59-2.11 [-2.82, -1.33]3.00 [2.29, 3.58]27% [0%, 50%]53%77%——2026-08-01 → 2026-08-30
tmax00Zbilinearall30 1 QC2.26 [1.61, 2.89]1.59-2.11 [-2.85, -1.42]3.00 [2.31, 3.60]27% [4%, 50%]53%77%——2026-08-01 → 2026-08-30
tmax00Znearest30d30 1 QC2.59 [1.84, 3.17]1.90-2.04 [-2.89, -1.00]3.17 [2.50, 3.60]10% [0%, 23%]47%70%——2026-08-01 → 2026-08-30
tmax00Znearest90d30 1 QC2.59 [1.94, 3.25]1.90-2.04 [-3.05, -1.13]3.17 [2.52, 3.65]10% [0%, 23%]47%70%——2026-08-01 → 2026-08-30
tmax00Znearest365d30 1 QC2.59 [1.84, 3.29]1.90-2.04 [-3.14, -0.98]3.17 [2.44, 3.67]10% [0%, 24%]47%70%——2026-08-01 → 2026-08-30
tmax00Znearestall30 1 QC2.59 [1.88, 3.32]1.90-2.04 [-3.05, -1.07]3.17 [2.48, 3.65]10% [0%, 23%]47%70%——2026-08-01 → 2026-08-30
tmin00Zbilinear30d30 1 QC1.76 [1.37, 2.23]1.68+0.40 [-0.15, 0.93]2.20 [1.66, 2.71]40% [27%, 50%]63%87%——2026-08-01 → 2026-08-30
tmin00Zbilinear90d30 1 QC1.76 [1.33, 2.23]1.68+0.40 [-0.32, 1.02]2.20 [1.56, 2.71]40% [29%, 52%]63%87%——2026-08-01 → 2026-08-30
tmin00Zbilinear365d30 1 QC1.76 [1.31, 2.23]1.68+0.40 [-0.42, 1.08]2.20 [1.50, 2.74]40% [29%, 53%]63%87%——2026-08-01 → 2026-08-30
tmin00Zbilinearall30 1 QC1.76 [1.32, 2.23]1.68+0.40 [-0.32, 1.05]2.20 [1.50, 2.75]40% [27%, 52%]63%87%——2026-08-01 → 2026-08-30
tmin00Znearest30d30 1 QC1.66 [1.27, 2.06]1.67-0.12 [-0.72, 0.37]2.12 [1.55, 2.66]40% [27%, 50%]70%83%——2026-08-01 → 2026-08-30
tmin00Znearest90d30 1 QC1.66 [1.23, 2.10]1.67-0.12 [-0.90, 0.47]2.12 [1.53, 2.65]40% [27%, 52%]70%83%——2026-08-01 → 2026-08-30
tmin00Znearest365d30 1 QC1.66 [1.21, 2.10]1.67-0.12 [-1.00, 0.51]2.12 [1.48, 2.71]40% [27%, 52%]70%83%——2026-08-01 → 2026-08-30
tmin00Znearestall30 1 QC1.66 [1.20, 2.12]1.67-0.12 [-0.87, 0.51]2.12 [1.47, 2.70]40% [29%, 52%]70%83%——2026-08-01 → 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 0, 00Z bilinear tmax+10+50-5-102026-08-01: -5.62 °F2026-08-02: -2.8 °F2026-08-03: -0.22 °F2026-08-04: -2.35 °F2026-08-05: -1.72 °F2026-08-06: -5.61 °F2026-08-07: -1.6 °F2026-08-08: -0.46 °F2026-08-09: -2.19 °F2026-08-10: -1.71 °F2026-08-11: -8.49 °F2026-08-12: -0.08 °F2026-08-13: +0.44 °F2026-08-14: -0.14 °F2026-08-15: -1.09 °F2026-08-16: +0.07 °F2026-08-17: -3.46 °F2026-08-18: -0.44 °F2026-08-19: +0.29 °F2026-08-20: +1.44 °F2026-08-21: -5.43 °F2026-08-22: -2.8 °F2026-08-23: -2.33 °F2026-08-24: -3 °F2026-08-25: -2.01 °F2026-08-26: -1.82 °F2026-08-27: -1.46 °F2026-08-28: -1.56 °F2026-08-29: -4.61 °F2026-08-30: -2.58 °F2026-08-012026-08-30°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 (30 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.58
2026-08-29-4.61
2026-08-28-1.56
2026-08-27-1.46
2026-08-26-1.82
2026-08-25-2.01
2026-08-24-3.00
2026-08-23-2.33
2026-08-22-2.80
2026-08-21-5.43
2026-08-20+1.44
2026-08-19+0.29
2026-08-18-0.44
2026-08-17-3.46
2026-08-16+0.07
2026-08-15-1.09
2026-08-14-0.14
2026-08-13+0.44
2026-08-12-0.08
2026-08-11-8.49
2026-08-10-1.71
2026-08-09-2.19
2026-08-08-0.46
2026-08-07-1.60
2026-08-06-5.61
2026-08-05-1.72
2026-08-04-2.35
2026-08-03-0.22
2026-08-02-2.80
2026-08-01-5.62

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KORD, lead day 0-10 to -9 °F: 0 days-9 to -8 °F: 1 day-8 to -7 °F: 0 days-7 to -6 °F: 0 days-6 to -5 °F: 3 days-5 to -4 °F: 1 day-4 to -3 °F: 2 days-3 to -2 °F: 7 days-2 to -1 °F: 7 days-1 to 0 °F: 5 days0 to 1 °F: 3 days1 to 2 °F: 1 day2 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| 1.77 · P90 |e| 5.44 °F-100+10 °Fn = 30 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
-9.00-8.001
-8.00-7.000
-7.00-6.000
-6.00-5.003
-5.00-4.001
-4.00-3.002
-3.00-2.007
-2.00-1.007
-1.00+0.005
+0.00+1.003
+1.00+2.001
+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
2026-08302.26 -2.11

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-01 → 2026-08-30 30
NCEP GFS2026-08-01 → 2026-08-30 30

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 30 -0.94 [-1.53, -0.22] yes
Aurora (GFS init) 2 -1.51 [-4.63, 1.61] no
Aurora (IFS init) 3 -0.04 [-2.10, 1.00] no
FourCastNet v2 (GFS init) 2 +2.08 [0.84, 3.31] yes
FourCastNet v2 (IFS init) 3 -0.45 [-3.43, 1.05] no
GraphCast (GFS init) 2 +0.08 [-1.91, 2.07] no
GraphCast (IFS init) 28 -1.24 [-1.95, -0.60] yes
ECMWF IFS HRES 24 -0.19 [-0.88, 1.14] no
Pangu-Weather (GFS init) 2 +1.24 [0.43, 2.05] yes
Pangu-Weather (IFS init) 3 +0.21 [-1.72, 1.17] no

Cite this page

ShortCastCheck, KORD gfs lead 0, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KORD/model/gfs/lead/0/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KORD (Chicago O'Hare), model gfs, lead day 0. 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/0/

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

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