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

Chicago O'Hare · ECMWF AIFS Single · lead day 4

KORD · aifs_single · lead 4

Target day = initialization date + 4 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
tmax00Zbilinear30d26 1 QC3.19 [2.60, 3.84]2.11-2.87 [-3.67, -2.12]3.83 [3.10, 4.52]15% [4%, 28%]38%54%-0.04+0.312026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.19 [2.54, 3.96]2.11-2.87 [-3.77, -2.02]3.83 [2.98, 4.57]15% [0%, 29%]38%54%-0.04+0.312026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC3.19 [2.53, 3.80]2.11-2.87 [-3.67, -1.92]3.83 [2.95, 4.47]15% [0%, 29%]38%54%-0.04+0.312026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC3.19 [2.48, 3.88]2.11-2.87 [-3.78, -1.92]3.83 [2.85, 4.51]15% [0%, 30%]38%54%-0.04+0.312026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC2.94 [2.39, 3.56]2.10-2.42 [-3.24, -1.65]3.53 [2.81, 4.24]19% [4%, 33%]38%62%+0.05+0.312026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC2.94 [2.33, 3.65]2.10-2.42 [-3.39, -1.53]3.53 [2.66, 4.34]19% [0%, 36%]38%62%+0.05+0.312026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC2.94 [2.31, 3.53]2.10-2.42 [-3.28, -1.49]3.53 [2.63, 4.24]19% [0%, 38%]38%62%+0.05+0.312026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC2.94 [2.29, 3.62]2.10-2.42 [-3.32, -1.44]3.53 [2.54, 4.27]19% [0%, 36%]38%62%+0.05+0.312026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.11 [2.53, 3.79]1.87-2.76 [-3.56, -1.92]3.63 [2.85, 4.41]12% [0%, 24%]35%54%-0.01+0.392026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.11 [2.50, 3.91]1.87-2.76 [-3.82, -1.76]3.63 [2.75, 4.53]12% [0%, 25%]35%54%-0.01+0.392026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC3.11 [2.46, 3.76]1.87-2.76 [-3.69, -1.73]3.63 [2.72, 4.46]12% [0%, 25%]35%54%-0.01+0.392026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC3.11 [2.46, 3.86]1.87-2.76 [-3.77, -1.71]3.63 [2.72, 4.49]12% [0%, 27%]35%54%-0.01+0.392026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC2.79 [2.19, 3.57]1.89-2.28 [-3.17, -1.40]3.33 [2.51, 4.16]15% [4%, 27%]38%65%+0.09+0.382026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC2.79 [2.17, 3.70]1.89-2.28 [-3.46, -1.17]3.33 [2.44, 4.27]15% [4%, 27%]38%65%+0.09+0.382026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC2.79 [2.17, 3.58]1.89-2.28 [-3.31, -1.06]3.33 [2.41, 4.21]15% [0%, 29%]38%65%+0.09+0.382026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC2.79 [2.16, 3.67]1.89-2.28 [-3.38, -1.12]3.33 [2.45, 4.24]15% [0%, 29%]38%65%+0.09+0.382026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.94 [1.33, 2.56]1.93+0.53 [-0.79, 1.78]2.56 [1.72, 3.26]38% [24%, 55%]65%73%+0.46+0.472026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.94 [1.20, 2.60]1.93+0.53 [-1.06, 1.88]2.56 [1.56, 3.33]38% [26%, 57%]65%73%+0.46+0.472026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC1.94 [1.26, 2.62]1.93+0.53 [-1.33, 1.94]2.56 [1.62, 3.36]38% [24%, 57%]65%73%+0.46+0.472026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC1.94 [1.11, 2.54]1.93+0.53 [-1.11, 1.81]2.56 [1.49, 3.29]38% [25%, 60%]65%73%+0.46+0.472026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC2.02 [1.47, 2.55]2.00-0.11 [-1.50, 1.17]2.57 [1.92, 3.09]35% [22%, 48%]58%77%+0.44+0.452026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC2.02 [1.27, 2.57]2.00-0.11 [-1.82, 1.30]2.57 [1.57, 3.14]35% [22%, 50%]58%77%+0.44+0.452026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC2.02 [1.30, 2.58]2.00-0.11 [-2.13, 1.35]2.57 [1.60, 3.15]35% [22%, 50%]58%77%+0.44+0.452026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC2.02 [1.23, 2.56]2.00-0.11 [-1.81, 1.18]2.57 [1.46, 3.11]35% [20%, 50%]58%77%+0.44+0.452026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC1.74 [1.31, 2.15]1.68+0.60 [-0.51, 1.48]2.29 [1.75, 2.77]42% [27%, 60%]69%85%+0.52+0.532026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC1.74 [1.22, 2.17]1.68+0.60 [-0.76, 1.59]2.29 [1.66, 2.80]42% [29%, 63%]69%85%+0.52+0.532026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC1.74 [1.24, 2.20]1.68+0.60 [-1.08, 1.54]2.29 [1.68, 2.85]42% [28%, 64%]69%85%+0.52+0.532026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC1.74 [1.12, 2.14]1.68+0.60 [-0.76, 1.49]2.29 [1.50, 2.78]42% [29%, 67%]69%85%+0.52+0.532026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC1.76 [1.30, 2.15]1.76-0.03 [-1.22, 0.87]2.28 [1.77, 2.67]35% [23%, 48%]73%81%+0.51+0.512026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC1.76 [1.20, 2.18]1.76-0.03 [-1.49, 0.95]2.28 [1.65, 2.68]35% [22%, 50%]73%81%+0.51+0.512026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC1.76 [1.27, 2.18]1.76-0.03 [-1.79, 0.95]2.28 [1.69, 2.72]35% [21%, 50%]73%81%+0.51+0.512026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC1.76 [1.16, 2.16]1.76-0.03 [-1.49, 0.87]2.28 [1.63, 2.69]35% [21%, 50%]73%81%+0.51+0.512026-08-05 → 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 4, 00Z bilinear tmax+10+50-5-102026-08-05: -2.19 °F2026-08-06: -6.62 °F2026-08-07: -5.51 °F2026-08-08: -0.79 °F2026-08-09: +0.33 °F2026-08-10: -4 °F2026-08-11: -7.12 °F2026-08-12: -6.51 °F2026-08-13: +0.09 °F2026-08-14: -1.36 °F2026-08-15: -1.84 °F2026-08-16: -2.59 °F2026-08-17: -4.61 °F2026-08-18: -1.84 °F2026-08-19: -3.05 °F2026-08-20: +1.91 °F2026-08-21: +0.34 °F2026-08-22: -3.6 °F2026-08-23: -2.37 °F2026-08-24: -5.05 °F2026-08-25: -5.63 °F2026-08-26: -2.07 °F2026-08-27: -3.29 °F2026-08-28: -6.86 °F2026-08-29: -1.81 °F2026-08-30: +1.48 °F2026-08-052026-08-30°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 (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.48
2026-08-29-1.81
2026-08-28-6.86
2026-08-27-3.29
2026-08-26-2.07
2026-08-25-5.63
2026-08-24-5.05
2026-08-23-2.37
2026-08-22-3.60
2026-08-21+0.34
2026-08-20+1.91
2026-08-19-3.05
2026-08-18-1.84
2026-08-17-4.61
2026-08-16-2.59
2026-08-15-1.84
2026-08-14-1.36
2026-08-13+0.09
2026-08-12-6.51
2026-08-11-7.12
2026-08-10-4.00
2026-08-09+0.33
2026-08-08-0.79
2026-08-07-5.51
2026-08-06-6.62
2026-08-05-2.19

Error distribution

Distribution of the signed daily error in °F for ECMWF AIFS Single at KORD, lead day 4-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 1 day-7 to -6 °F: 3 days-6 to -5 °F: 3 days-5 to -4 °F: 2 days-4 to -3 °F: 3 days-3 to -2 °F: 4 days-2 to -1 °F: 4 days-1 to 0 °F: 1 day0 to 1 °F: 3 days1 to 2 °F: 2 days2 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| 2.48 · P90 |e| 6.56 °F-100+10 °Fn = 26 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
-8.00-7.001
-7.00-6.003
-6.00-5.003
-5.00-4.002
-4.00-3.003
-3.00-2.004
-2.00-1.004
-1.00+0.001
+0.00+1.003
+1.00+2.002
+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
2026-08263.19 -2.87

Availability

ModelScored period DaysCoverage
ECMWF AIFS Single2026-08-05 → 2026-08-30 26
ECMWF AIFS Single2026-08-05 → 2026-08-30 26
ECMWF AIFS Single2026-08-05 → 2026-08-30 26
ECMWF AIFS Single2026-08-05 → 2026-08-30 26

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 26 +0.04 [-1.67, 1.92] no
GraphCast (IFS init) 25 -0.83 [-1.51, -0.24] yes
ECMWF IFS HRES 20 +0.68 [0.08, 1.61] yes
Persistence (baseline) 26 +0.11 [-1.03, 1.05] no

Cite this page

ShortCastCheck, KORD aifs_single lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KORD/model/aifs_single/lead/4/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KORD (Chicago O'Hare), model aifs_single, lead day 4. 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/4/

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