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

Chicago O'Hare · GraphCast (GFS init) · lead day 1

KORD · graphcast_gfs · lead 1

Target day = initialization date + 1 day. 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, GRAP_v100, starting 2026-08-28 — 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
tmax00Zbilinear30d1 1 QC6.94 [6.94, 6.94]0.00-6.94 [-6.94, -6.94]6.94 [6.94, 6.94]0% [0%, 0%]0%0%-5.94—2026-08-30 → 2026-08-30
tmax00Zbilinear90d1 1 QC6.94 [6.94, 6.94]0.00-6.94 [-6.94, -6.94]6.94 [6.94, 6.94]0% [0%, 0%]0%0%-5.94—2026-08-30 → 2026-08-30
tmax00Zbilinear365d1 1 QC6.94 [6.94, 6.94]0.00-6.94 [-6.94, -6.94]6.94 [6.94, 6.94]0% [0%, 0%]0%0%-5.94—2026-08-30 → 2026-08-30
tmax00Zbilinearall1 1 QC6.94 [6.94, 6.94]0.00-6.94 [-6.94, -6.94]6.94 [6.94, 6.94]0% [0%, 0%]0%0%-5.94—2026-08-30 → 2026-08-30
tmax00Znearest30d1 1 QC6.83 [6.83, 6.83]0.00-6.83 [-6.83, -6.83]6.83 [6.83, 6.83]0% [0%, 0%]0%0%-5.83—2026-08-30 → 2026-08-30
tmax00Znearest90d1 1 QC6.83 [6.83, 6.83]0.00-6.83 [-6.83, -6.83]6.83 [6.83, 6.83]0% [0%, 0%]0%0%-5.83—2026-08-30 → 2026-08-30
tmax00Znearest365d1 1 QC6.83 [6.83, 6.83]0.00-6.83 [-6.83, -6.83]6.83 [6.83, 6.83]0% [0%, 0%]0%0%-5.83—2026-08-30 → 2026-08-30
tmax00Znearestall1 1 QC6.83 [6.83, 6.83]0.00-6.83 [-6.83, -6.83]6.83 [6.83, 6.83]0% [0%, 0%]0%0%-5.83—2026-08-30 → 2026-08-30
tmax12Zbilinear30d2 1 QC3.06 [1.82, 4.30]1.24-3.06 [-4.30, -1.82]3.30 [1.82, 4.30]0% [0%, 0%]50%50%-1.04+0.172026-08-29 → 2026-08-30
tmax12Zbilinear90d2 1 QC3.06 [1.82, 4.30]1.24-3.06 [-4.30, -1.82]3.30 [1.82, 4.30]0% [0%, 0%]50%50%-1.04+0.172026-08-29 → 2026-08-30
tmax12Zbilinear365d2 1 QC3.06 [1.82, 4.30]1.24-3.06 [-4.30, -1.82]3.30 [1.82, 4.30]0% [0%, 0%]50%50%-1.04+0.172026-08-29 → 2026-08-30
tmax12Zbilinearall2 1 QC3.06 [1.82, 4.30]1.24-3.06 [-4.30, -1.82]3.30 [1.82, 4.30]0% [0%, 0%]50%50%-1.04+0.172026-08-29 → 2026-08-30
tmax12Znearest30d2 1 QC2.87 [1.85, 3.88]1.02-2.87 [-3.88, -1.85]3.04 [1.85, 3.88]0% [0%, 0%]50%50%-0.91+0.322026-08-29 → 2026-08-30
tmax12Znearest90d2 1 QC2.87 [1.85, 3.88]1.02-2.87 [-3.88, -1.85]3.04 [1.85, 3.88]0% [0%, 0%]50%50%-0.91+0.322026-08-29 → 2026-08-30
tmax12Znearest365d2 1 QC2.87 [1.85, 3.88]1.02-2.87 [-3.88, -1.85]3.04 [1.85, 3.88]0% [0%, 0%]50%50%-0.91+0.322026-08-29 → 2026-08-30
tmax12Znearestall2 1 QC2.87 [1.85, 3.88]1.02-2.87 [-3.88, -1.85]3.04 [1.85, 3.88]0% [0%, 0%]50%50%-0.91+0.322026-08-29 → 2026-08-30
tmin00Zbilinear30d1 1 QC0.90 [0.90, 0.90]0.00+0.90 [0.90, 0.90]0.90 [0.90, 0.90]100% [100%, 100%]100%100%+0.78—2026-08-30 → 2026-08-30
tmin00Zbilinear90d1 1 QC0.90 [0.90, 0.90]0.00+0.90 [0.90, 0.90]0.90 [0.90, 0.90]100% [100%, 100%]100%100%+0.78—2026-08-30 → 2026-08-30
tmin00Zbilinear365d1 1 QC0.90 [0.90, 0.90]0.00+0.90 [0.90, 0.90]0.90 [0.90, 0.90]100% [100%, 100%]100%100%+0.78—2026-08-30 → 2026-08-30
tmin00Zbilinearall1 1 QC0.90 [0.90, 0.90]0.00+0.90 [0.90, 0.90]0.90 [0.90, 0.90]100% [100%, 100%]100%100%+0.78—2026-08-30 → 2026-08-30
tmin00Znearest30d1 1 QC0.59 [0.59, 0.59]0.00+0.59 [0.59, 0.59]0.59 [0.59, 0.59]100% [100%, 100%]100%100%+0.85—2026-08-30 → 2026-08-30
tmin00Znearest90d1 1 QC0.59 [0.59, 0.59]0.00+0.59 [0.59, 0.59]0.59 [0.59, 0.59]100% [100%, 100%]100%100%+0.85—2026-08-30 → 2026-08-30
tmin00Znearest365d1 1 QC0.59 [0.59, 0.59]0.00+0.59 [0.59, 0.59]0.59 [0.59, 0.59]100% [100%, 100%]100%100%+0.85—2026-08-30 → 2026-08-30
tmin00Znearestall1 1 QC0.59 [0.59, 0.59]0.00+0.59 [0.59, 0.59]0.59 [0.59, 0.59]100% [100%, 100%]100%100%+0.85—2026-08-30 → 2026-08-30
tmin12Zbilinear30d2 1 QC1.87 [1.72, 2.03]0.15+1.87 [1.72, 2.03]1.88 [1.72, 2.03]0% [0%, 0%]50%100%+0.25+0.942026-08-29 → 2026-08-30
tmin12Zbilinear90d2 1 QC1.87 [1.72, 2.03]0.15+1.87 [1.72, 2.03]1.88 [1.72, 2.03]0% [0%, 0%]50%100%+0.25+0.942026-08-29 → 2026-08-30
tmin12Zbilinear365d2 1 QC1.87 [1.72, 2.03]0.15+1.87 [1.72, 2.03]1.88 [1.72, 2.03]0% [0%, 0%]50%100%+0.25+0.942026-08-29 → 2026-08-30
tmin12Zbilinearall2 1 QC1.87 [1.72, 2.03]0.15+1.87 [1.72, 2.03]1.88 [1.72, 2.03]0% [0%, 0%]50%100%+0.25+0.942026-08-29 → 2026-08-30
tmin12Znearest30d2 1 QC1.40 [1.31, 1.49]0.09+1.40 [1.31, 1.49]1.40 [1.31, 1.49]0% [0%, 0%]100%100%+0.44+0.962026-08-29 → 2026-08-30
tmin12Znearest90d2 1 QC1.40 [1.31, 1.49]0.09+1.40 [1.31, 1.49]1.40 [1.31, 1.49]0% [0%, 0%]100%100%+0.44+0.962026-08-29 → 2026-08-30
tmin12Znearest365d2 1 QC1.40 [1.31, 1.49]0.09+1.40 [1.31, 1.49]1.40 [1.31, 1.49]0% [0%, 0%]100%100%+0.44+0.962026-08-29 → 2026-08-30
tmin12Znearestall2 1 QC1.40 [1.31, 1.49]0.09+1.40 [1.31, 1.49]1.40 [1.31, 1.49]0% [0%, 0%]100%100%+0.44+0.962026-08-29 → 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 GraphCast (GFS init) at KORD, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-30: -6.94 °F2026-08-30°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 (1 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.94

Error distribution

Distribution of the signed daily error in °F for GraphCast (GFS init) at KORD, lead day 1-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 1 day-6 to -5 °F: 0 days-5 to -4 °F: 0 days-4 to -3 °F: 0 days-3 to -2 °F: 0 days-2 to -1 °F: 0 days-1 to 0 °F: 0 days0 to 1 °F: 0 days1 to 2 °F: 0 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| 6.94 · P90 |e| 6.94 °F-100+10 °Fn = 1 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
-8.00-7.000
-7.00-6.001
-6.00-5.000
-5.00-4.000
-4.00-3.000
-3.00-2.000
-2.00-1.000
-1.00+0.000
+0.00+1.000
+1.00+2.000
+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
2026-0816.94 -6.94

Availability

ModelScored period DaysCoverage
GraphCast (GFS init)2026-08-30 → 2026-08-30 1
GraphCast (GFS init)2026-08-30 → 2026-08-30 1
GraphCast (GFS init)2026-08-29 → 2026-08-30 2
GraphCast (GFS init)2026-08-29 → 2026-08-30 2

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 1 +4.27 [4.27, 4.27] yes
Aurora (GFS init) 1 +0.25 [0.25, 0.25] yes
Aurora (IFS init) 1 +4.24 [4.24, 4.24] yes
FourCastNet v2 (GFS init) 1 +4.32 [4.32, 4.32] yes
FourCastNet v2 (IFS init) 1 +4.75 [4.75, 4.75] yes
NCEP GFS 1 +4.48 [4.48, 4.48] yes
GraphCast (IFS init) 1 +2.23 [2.23, 2.23] yes
ECMWF IFS HRES 1 +4.70 [4.70, 4.70] yes
Pangu-Weather (GFS init) 1 +2.71 [2.71, 2.71] yes
Pangu-Weather (IFS init) 1 +3.11 [3.11, 3.11] yes
Persistence (baseline) 1 +5.94 [5.94, 5.94] yes

Cite this page

ShortCastCheck, KORD graphcast_gfs lead 1, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KORD/model/graphcast_gfs/lead/1/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KORD (Chicago O'Hare), model graphcast_gfs, lead day 1. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KORD/model/graphcast_gfs/lead/1/

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