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

Trenton Mercer · GraphCast (IFS init) · lead day 1

KTTN · graphcast_ifs · 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 2026-01-01 — 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
tmax00Zbilinear30d27 1 QC2.41 [1.56, 3.52]1.43-2.38 [-3.52, -1.50]2.94 [1.97, 3.90]26% [4%, 48%]44%70%-0.03+0.382026-08-02 → 2026-08-30
tmax00Zbilinear90d27 1 QC2.41 [1.51, 3.72]1.43-2.38 [-3.72, -1.46]2.94 [1.85, 4.05]26% [3%, 50%]44%70%-0.03+0.382026-08-02 → 2026-08-30
tmax00Zbilinear365d33 1 QC2.17 [1.26, 3.21]1.65-1.82 [-3.02, -0.51]2.73 [1.64, 3.67]33% [11%, 58%]52%76%+0.21+0.422026-01-02 → 2026-08-30
tmax00Zbilinearall33 1 QC2.17 [1.29, 3.32]1.65-1.82 [-3.21, -0.58]2.73 [1.64, 3.73]33% [9%, 57%]52%76%+0.21+0.422026-01-02 → 2026-08-30
tmax00Znearest30d27 1 QC2.26 [1.44, 3.36]1.45-2.20 [-3.34, -1.31]2.80 [1.86, 3.75]30% [11%, 52%]52%70%+0.03+0.372026-08-02 → 2026-08-30
tmax00Znearest90d27 1 QC2.26 [1.39, 3.54]1.45-2.20 [-3.54, -1.28]2.80 [1.75, 3.91]30% [9%, 52%]52%70%+0.03+0.372026-08-02 → 2026-08-30
tmax00Znearest365d33 1 QC2.07 [1.27, 3.09]1.68-1.63 [-2.85, -0.32]2.62 [1.60, 3.54]33% [14%, 53%]58%73%+0.25+0.412026-01-02 → 2026-08-30
tmax00Znearestall33 1 QC2.07 [1.26, 3.18]1.68-1.63 [-3.04, -0.39]2.62 [1.60, 3.59]33% [14%, 53%]58%73%+0.25+0.412026-01-02 → 2026-08-30
tmax12Zbilinear30d27 1 QC2.09 [1.41, 2.93]1.17-2.07 [-2.91, -1.37]2.49 [1.78, 3.23]26% [4%, 50%]52%63%+0.11+0.502026-08-02 → 2026-08-30
tmax12Zbilinear90d27 1 QC2.09 [1.39, 3.06]1.17-2.07 [-3.05, -1.35]2.49 [1.74, 3.34]26% [0%, 49%]52%63%+0.11+0.502026-08-02 → 2026-08-30
tmax12Zbilinear365d32 1 QC1.92 [1.22, 2.72]1.34-1.66 [-2.60, -0.63]2.34 [1.55, 3.06]28% [9%, 50%]56%69%+0.23+0.462026-01-02 → 2026-08-30
tmax12Zbilinearall32 1 QC1.92 [1.27, 2.81]1.34-1.66 [-2.68, -0.67]2.34 [1.58, 3.11]28% [8%, 48%]56%69%+0.23+0.462026-01-02 → 2026-08-30
tmax12Znearest30d27 1 QC1.95 [1.32, 2.74]1.18-1.86 [-2.71, -1.15]2.33 [1.66, 3.04]30% [8%, 50%]56%70%+0.16+0.492026-08-02 → 2026-08-30
tmax12Znearest90d27 1 QC1.95 [1.30, 2.87]1.18-1.86 [-2.84, -1.13]2.33 [1.61, 3.14]30% [0%, 52%]56%70%+0.16+0.492026-08-02 → 2026-08-30
tmax12Znearest365d32 1 QC1.82 [1.19, 2.57]1.36-1.45 [-2.37, -0.42]2.21 [1.48, 2.89]34% [14%, 55%]59%75%+0.27+0.452026-01-02 → 2026-08-30
tmax12Znearestall32 1 QC1.82 [1.21, 2.66]1.36-1.45 [-2.46, -0.47]2.21 [1.50, 2.95]34% [12%, 55%]59%75%+0.27+0.452026-01-02 → 2026-08-30
tmin00Zbilinear30d27 1 QC3.31 [2.70, 4.02]1.60+3.27 [2.68, 3.97]3.88 [3.20, 4.59]19% [5%, 29%]22%41%-0.13+0.442026-08-02 → 2026-08-30
tmin00Zbilinear90d27 1 QC3.31 [2.69, 4.19]1.60+3.27 [2.67, 4.16]3.88 [3.21, 4.66]19% [3%, 29%]22%41%-0.13+0.442026-08-02 → 2026-08-30
tmin00Zbilinear365d33 1 QC3.11 [2.46, 3.93]1.50+3.08 [2.46, 3.89]3.66 [2.89, 4.43]18% [6%, 28%]21%48%+0.03+0.532026-01-02 → 2026-08-30
tmin00Zbilinearall33 1 QC3.11 [2.51, 3.89]1.50+3.08 [2.51, 3.86]3.66 [2.94, 4.40]18% [7%, 27%]21%48%+0.03+0.532026-01-02 → 2026-08-30
tmin00Znearest30d27 1 QC3.51 [2.92, 4.21]1.60+3.50 [2.91, 4.20]4.08 [3.40, 4.81]19% [5%, 29%]22%37%-0.20+0.442026-08-02 → 2026-08-30
tmin00Znearest90d27 1 QC3.51 [2.91, 4.39]1.60+3.50 [2.91, 4.38]4.08 [3.41, 4.87]19% [3%, 29%]22%37%-0.20+0.442026-08-02 → 2026-08-30
tmin00Znearest365d33 1 QC3.30 [2.66, 4.12]1.51+3.30 [2.65, 4.11]3.85 [3.07, 4.64]18% [6%, 28%]21%45%-0.03+0.532026-01-02 → 2026-08-30
tmin00Znearestall33 1 QC3.30 [2.71, 4.09]1.51+3.30 [2.71, 4.08]3.85 [3.12, 4.61]18% [7%, 27%]21%45%-0.03+0.532026-01-02 → 2026-08-30
tmin12Zbilinear30d27 1 QC3.34 [2.63, 4.16]1.74+3.34 [2.63, 4.16]3.94 [3.14, 4.73]15% [0%, 29%]33%48%-0.14+0.392026-08-02 → 2026-08-30
tmin12Zbilinear90d27 1 QC3.34 [2.63, 4.31]1.74+3.34 [2.63, 4.31]3.94 [3.13, 4.80]15% [0%, 30%]33%48%-0.14+0.392026-08-02 → 2026-08-30
tmin12Zbilinear365d32 1 QC3.20 [2.51, 4.08]1.62+3.20 [2.51, 4.08]3.77 [2.95, 4.59]16% [0%, 29%]34%47%-0.06+0.462026-01-02 → 2026-08-30
tmin12Zbilinearall32 1 QC3.20 [2.54, 4.07]1.62+3.20 [2.54, 4.07]3.77 [2.98, 4.58]16% [0%, 28%]34%47%-0.06+0.462026-01-02 → 2026-08-30
tmin12Znearest30d27 1 QC3.59 [2.88, 4.39]1.74+3.59 [2.88, 4.39]4.15 [3.34, 4.94]11% [0%, 24%]33%41%-0.23+0.392026-08-02 → 2026-08-30
tmin12Znearest90d27 1 QC3.59 [2.88, 4.53]1.74+3.59 [2.88, 4.53]4.15 [3.33, 5.01]11% [0%, 25%]33%41%-0.23+0.392026-08-02 → 2026-08-30
tmin12Znearest365d32 1 QC3.43 [2.72, 4.31]1.62+3.43 [2.72, 4.31]3.96 [3.11, 4.79]12% [0%, 24%]34%41%-0.13+0.462026-01-02 → 2026-08-30
tmin12Znearestall32 1 QC3.43 [2.76, 4.28]1.62+3.43 [2.76, 4.28]3.96 [3.15, 4.80]12% [0%, 25%]34%41%-0.13+0.462026-01-02 → 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 (IFS init) at KTTN, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-02: -4.24 °F2026-08-03: -5.42 °F2026-08-04: -3.94 °F2026-08-05: -4.64 °F2026-08-06: -4.19 °F2026-08-07: -5.86 °F2026-08-08: -2.66 °F2026-08-09: -0.68 °F2026-08-10: -0.08 °F2026-08-11: +0.4 °F2026-08-12: -2.15 °F2026-08-13: -0.11 °F2026-08-14: -0.82 °F2026-08-15: -3.3 °F2026-08-16: -0.6 °F2026-08-17: -1.51 °F2026-08-18: -1.37 °F2026-08-19: -2.05 °F2026-08-20: -5.32 °F2026-08-21: -2.83 °F2026-08-22: -2.97 °F2026-08-23: -1.2 °F2026-08-24: -1.8 °F2026-08-25: -1.21 °F2026-08-26: -2.38 °F2026-08-29: -0.86 °F2026-08-30: -2.56 °F2026-08-022026-08-30°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 (29 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.56
2026-08-29-0.86
2026-08-28—
2026-08-27—
2026-08-26-2.38
2026-08-25-1.21
2026-08-24-1.80
2026-08-23-1.20
2026-08-22-2.97
2026-08-21-2.83
2026-08-20-5.32
2026-08-19-2.05
2026-08-18-1.37
2026-08-17-1.51
2026-08-16-0.60
2026-08-15-3.30
2026-08-14-0.82
2026-08-13-0.11
2026-08-12-2.15
2026-08-11+0.40
2026-08-10-0.08
2026-08-09-0.68
2026-08-08-2.66
2026-08-07-5.86
2026-08-06-4.19
2026-08-05-4.64
2026-08-04-3.94
2026-08-03-5.42
2026-08-02-4.24

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KTTN, 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: 0 days-6 to -5 °F: 3 days-5 to -4 °F: 3 days-4 to -3 °F: 2 days-3 to -2 °F: 7 days-2 to -1 °F: 5 days-1 to 0 °F: 7 days0 to 1 °F: 4 days1 to 2 °F: 1 day2 to 3 °F: 1 day3 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| 1.8 · P90 |e| 4.56 °F-100+10 °Fn = 33 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
-7.00-6.000
-6.00-5.003
-5.00-4.003
-4.00-3.002
-3.00-2.007
-2.00-1.005
-1.00+0.007
+0.00+1.004
+1.00+2.001
+2.00+3.001
+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
2026-08272.41 -2.38
2026-0161.05 +0.74

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 32
GraphCast (IFS init)2026-01-02 → 2026-08-30 32

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 27 +0.59 [-0.64, 2.00] no
Aurora (GFS init) 1 +0.13 [0.13, 0.13] yes
Aurora (IFS init) 2 +1.17 [0.76, 1.57] yes
FourCastNet v2 (GFS init) 1 +1.36 [1.36, 1.36] yes
FourCastNet v2 (IFS init) 2 -0.95 [-2.46, 0.57] no
NCEP GFS 27 -0.35 [-1.15, 0.72] no
GraphCast (GFS init) 1 -0.88 [-0.88, -0.88] yes
ECMWF IFS HRES 21 -0.57 [-1.39, 0.97] no
Pangu-Weather (GFS init) 1 +0.10 [0.10, 0.10] yes
Pangu-Weather (IFS init) 2 -1.10 [-3.21, 1.02] no
Persistence (baseline) 27 +0.08 [-1.15, 1.61] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model graphcast_ifs, 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/KTTN/model/graphcast_ifs/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