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

Chicago O'Hare · ECMWF AIFS Single · lead day 9

KORD · aifs_single · lead 9

Target day = initialization date + 9 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, aifs-single-gpid5, 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
tmax00Zbilinear30d21 1 QC5.28 [4.28, 6.28]3.67-4.26 [-6.14, -2.29]6.28 [5.14, 7.28]10% [0%, 17%]19%33%-0.40+0.012026-08-10 → 2026-08-30
tmax00Zbilinear90d21 1 QC5.28 [4.39, 6.26]3.67-4.26 [-6.25, -2.23]6.28 [5.24, 7.25]10% [0%, 17%]19%33%-0.40+0.012026-08-10 → 2026-08-30
tmax00Zbilinear365d21 1 QC5.28 [4.22, 6.30]3.67-4.26 [-6.30, -2.23]6.28 [4.97, 7.31]10% [0%, 17%]19%33%-0.40+0.012026-08-10 → 2026-08-30
tmax00Zbilinearall21 1 QC5.28 [4.32, 6.36]3.67-4.26 [-6.36, -2.18]6.28 [5.15, 7.35]10% [0%, 17%]19%33%-0.40+0.012026-08-10 → 2026-08-30
tmax00Znearest30d21 1 QC5.16 [4.25, 5.99]3.84-3.84 [-5.77, -1.80]6.12 [5.01, 7.10]10% [0%, 17%]19%33%-0.37-0.042026-08-10 → 2026-08-30
tmax00Znearest90d21 1 QC5.16 [4.30, 5.95]3.84-3.84 [-5.89, -1.76]6.12 [5.14, 7.04]10% [0%, 17%]19%33%-0.37-0.042026-08-10 → 2026-08-30
tmax00Znearest365d21 1 QC5.16 [4.21, 5.96]3.84-3.84 [-5.95, -1.76]6.12 [4.88, 7.12]10% [0%, 17%]19%33%-0.37-0.042026-08-10 → 2026-08-30
tmax00Znearestall21 1 QC5.16 [4.21, 6.05]3.84-3.84 [-6.03, -1.58]6.12 [5.02, 7.18]10% [0%, 17%]19%33%-0.37-0.042026-08-10 → 2026-08-30
tmax12Zbilinear30d21 1 QC5.71 [4.91, 7.22]3.31-5.03 [-7.12, -3.73]6.59 [5.70, 7.84]10% [0%, 25%]14%19%-0.52+0.112026-08-10 → 2026-08-30
tmax12Zbilinear90d21 1 QC5.71 [4.91, 7.91]3.31-5.03 [-7.91, -3.71]6.59 [5.69, 8.27]10% [0%, 27%]14%19%-0.52+0.112026-08-10 → 2026-08-30
tmax12Zbilinear365d21 1 QC5.71 [4.85, 7.80]3.31-5.03 [-7.80, -3.51]6.59 [5.54, 8.16]10% [0%, 27%]14%19%-0.52+0.112026-08-10 → 2026-08-30
tmax12Zbilinearall21 1 QC5.71 [4.85, 8.17]3.31-5.03 [-8.17, -3.60]6.59 [5.54, 8.34]10% [0%, 29%]14%19%-0.52+0.112026-08-10 → 2026-08-30
tmax12Znearest30d21 1 QC5.50 [4.72, 7.01]3.40-4.66 [-6.80, -3.33]6.39 [5.46, 7.65]5% [0%, 13%]19%24%-0.46+0.082026-08-10 → 2026-08-30
tmax12Znearest90d21 1 QC5.50 [4.70, 7.65]3.40-4.66 [-7.65, -3.28]6.39 [5.43, 8.06]5% [0%, 14%]19%24%-0.46+0.082026-08-10 → 2026-08-30
tmax12Znearest365d21 1 QC5.50 [4.61, 7.49]3.40-4.66 [-7.46, -3.05]6.39 [5.21, 8.01]5% [0%, 14%]19%24%-0.46+0.082026-08-10 → 2026-08-30
tmax12Znearestall21 1 QC5.50 [4.61, 7.85]3.40-4.66 [-7.85, -3.19]6.39 [5.23, 8.11]5% [0%, 14%]19%24%-0.46+0.082026-08-10 → 2026-08-30
tmin00Zbilinear30d21 1 QC3.62 [2.60, 4.67]3.57-0.35 [-2.98, 2.01]4.28 [3.06, 5.35]19% [0%, 40%]24%43%+0.27+0.302026-08-10 → 2026-08-30
tmin00Zbilinear90d21 1 QC3.62 [2.43, 4.74]3.57-0.35 [-3.29, 2.40]4.28 [2.94, 5.39]19% [0%, 50%]24%43%+0.27+0.302026-08-10 → 2026-08-30
tmin00Zbilinear365d21 1 QC3.62 [2.49, 4.86]3.57-0.35 [-3.27, 2.35]4.28 [2.98, 5.49]19% [0%, 46%]24%43%+0.27+0.302026-08-10 → 2026-08-30
tmin00Zbilinearall21 1 QC3.62 [2.45, 4.94]3.57-0.35 [-3.56, 2.55]4.28 [2.93, 5.52]19% [0%, 45%]24%43%+0.27+0.302026-08-10 → 2026-08-30
tmin00Znearest30d21 1 QC3.79 [2.81, 4.93]3.63-1.08 [-3.71, 1.22]4.46 [3.36, 5.47]14% [0%, 29%]24%33%+0.23+0.292026-08-10 → 2026-08-30
tmin00Znearest90d21 1 QC3.79 [2.57, 5.06]3.63-1.08 [-4.01, 1.59]4.46 [3.13, 5.55]14% [0%, 33%]24%33%+0.23+0.292026-08-10 → 2026-08-30
tmin00Znearest365d21 1 QC3.79 [2.57, 5.21]3.63-1.08 [-4.01, 1.59]4.46 [3.11, 5.64]14% [0%, 33%]24%33%+0.23+0.292026-08-10 → 2026-08-30
tmin00Znearestall21 1 QC3.79 [2.63, 5.26]3.63-1.08 [-4.28, 1.77]4.46 [3.25, 5.76]14% [0%, 30%]24%33%+0.23+0.292026-08-10 → 2026-08-30
tmin12Zbilinear30d21 1 QC3.58 [2.33, 5.46]3.39-1.66 [-4.70, 0.50]4.82 [2.90, 6.72]29% [13%, 43%]38%57%+0.28+0.342026-08-10 → 2026-08-30
tmin12Zbilinear90d21 1 QC3.58 [2.21, 5.99]3.39-1.66 [-5.23, 0.64]4.82 [2.66, 7.11]29% [10%, 44%]38%57%+0.28+0.342026-08-10 → 2026-08-30
tmin12Zbilinear365d21 1 QC3.58 [2.13, 6.05]3.39-1.66 [-5.66, 0.79]4.82 [2.58, 7.21]29% [12%, 44%]38%57%+0.28+0.342026-08-10 → 2026-08-30
tmin12Zbilinearall21 1 QC3.58 [2.11, 6.31]3.39-1.66 [-5.86, 0.66]4.82 [2.59, 7.47]29% [10%, 44%]38%57%+0.28+0.342026-08-10 → 2026-08-30
tmin12Znearest30d21 1 QC4.01 [2.89, 5.97]3.46-2.45 [-5.56, -0.24]5.20 [3.38, 7.23]24% [6%, 42%]38%43%+0.19+0.322026-08-10 → 2026-08-30
tmin12Znearest90d21 1 QC4.01 [2.89, 6.57]3.46-2.45 [-6.10, -0.08]5.20 [3.33, 7.80]24% [4%, 43%]38%43%+0.19+0.322026-08-10 → 2026-08-30
tmin12Znearest365d21 1 QC4.01 [2.82, 6.75]3.46-2.45 [-6.60, 0.02]5.20 [3.22, 7.86]24% [0%, 43%]38%43%+0.19+0.322026-08-10 → 2026-08-30
tmin12Znearestall21 1 QC4.01 [2.80, 7.18]3.46-2.45 [-6.72, -0.05]5.20 [3.25, 8.16]24% [0%, 43%]38%43%+0.19+0.322026-08-10 → 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 ECMWF AIFS Single at KORD, lead day 9, 00Z bilinear tmax+20+100-10-202026-08-10: -7.33 °F2026-08-11: -1.82 °F2026-08-12: -9.53 °F2026-08-13: -2.69 °F2026-08-14: -6.7 °F2026-08-15: -5.33 °F2026-08-16: -14.36 °F2026-08-17: -4.43 °F2026-08-18: -3.66 °F2026-08-19: +0.39 °F2026-08-20: +1.97 °F2026-08-21: -4.86 °F2026-08-22: -7.73 °F2026-08-23: +2.38 °F2026-08-24: +5.84 °F2026-08-25: -8.52 °F2026-08-26: -4.36 °F2026-08-27: +0.09 °F2026-08-28: -7.8 °F2026-08-29: -8.75 °F2026-08-30: -2.33 °F2026-08-102026-08-30°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 (21 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.33
2026-08-29-8.75
2026-08-28-7.80
2026-08-27+0.09
2026-08-26-4.36
2026-08-25-8.52
2026-08-24+5.84
2026-08-23+2.38
2026-08-22-7.73
2026-08-21-4.86
2026-08-20+1.97
2026-08-19+0.39
2026-08-18-3.66
2026-08-17-4.43
2026-08-16-14.36
2026-08-15-5.33
2026-08-14-6.70
2026-08-13-2.69
2026-08-12-9.53
2026-08-11-1.82
2026-08-10-7.33

Error distribution

Distribution of the signed daily error in °F for ECMWF AIFS Single at KORD, lead day 9-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 0 days-12 to -10 °F: 0 days-10 to -8 °F: 3 days-8 to -6 °F: 4 days-6 to -4 °F: 4 days-4 to -2 °F: 3 days-2 to 0 °F: 1 day0 to 2 °F: 3 days2 to 4 °F: 1 day4 to 6 °F: 1 day6 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| 4.86 · P90 |e| 8.75 °F-200+20 °Fn = 21 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
-14.00-12.000
-12.00-10.000
-10.00-8.003
-8.00-6.004
-6.00-4.004
-4.00-2.003
-2.00+0.001
+0.00+2.003
+2.00+4.001
+4.00+6.001
+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
2026-08215.28 -4.26

Availability

ModelScored period DaysCoverage
ECMWF AIFS Single2026-08-10 → 2026-08-30 21
ECMWF AIFS Single2026-08-10 → 2026-08-30 21
ECMWF AIFS Single2026-08-10 → 2026-08-30 21
ECMWF AIFS Single2026-08-10 → 2026-08-30 21

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means ECMWF AIFS Single has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
NCEP GFS 21 -1.89 [-2.88, -0.36] yes
GraphCast (IFS init) 21 +0.17 [-2.07, 1.22] no
ECMWF IFS HRES 16 -0.43 [-1.79, 2.15] no
Persistence (baseline) 21 +1.52 [-0.60, 2.77] no

Cite this page

ShortCastCheck, KORD aifs_single lead 9, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KORD/model/aifs_single/lead/9/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KORD (Chicago O'Hare), model aifs_single, lead day 9. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KORD/model/aifs_single/lead/9/

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

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