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

Trenton Mercer · GraphCast (IFS init) · lead day 9

KTTN · graphcast_ifs · 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, 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
tmax00Zbilinear30d21 1 QC4.15 [2.71, 5.49]4.10-0.28 [-3.21, 2.64]5.18 [3.47, 6.50]14% [4%, 25%]33%43%-0.07-0.642026-08-10 → 2026-08-30
tmax00Zbilinear90d21 1 QC4.15 [2.36, 5.54]4.10-0.28 [-3.25, 2.82]5.18 [3.13, 6.55]14% [0%, 27%]33%43%-0.07-0.642026-08-10 → 2026-08-30
tmax00Zbilinear365d27 1 QC4.78 [3.25, 6.52]4.53-1.35 [-4.75, 1.81]5.72 [4.07, 7.21]11% [0%, 20%]26%33%+0.19+0.242026-01-10 → 2026-08-30
tmax00Zbilinearall27 1 QC4.78 [3.20, 6.57]4.53-1.35 [-4.91, 1.94]5.72 [3.92, 7.24]11% [0%, 20%]26%33%+0.19+0.242026-01-10 → 2026-08-30
tmax00Znearest30d21 1 QC4.13 [2.65, 5.52]4.11-0.14 [-3.06, 2.76]5.19 [3.45, 6.57]19% [5%, 40%]33%43%-0.07-0.642026-08-10 → 2026-08-30
tmax00Znearest90d21 1 QC4.13 [2.28, 5.55]4.11-0.14 [-3.12, 2.94]5.19 [3.09, 6.59]19% [3%, 49%]33%43%-0.07-0.642026-08-10 → 2026-08-30
tmax00Znearest365d27 1 QC4.72 [3.19, 6.37]4.52-1.18 [-4.52, 1.92]5.66 [4.02, 7.07]15% [0%, 33%]26%33%+0.20+0.252026-01-10 → 2026-08-30
tmax00Znearestall27 1 QC4.72 [3.14, 6.49]4.52-1.18 [-4.71, 2.09]5.66 [3.88, 7.06]15% [0%, 32%]26%33%+0.20+0.252026-01-10 → 2026-08-30
tmax12Zbilinear30d21 1 QC4.23 [3.50, 5.31]3.97-2.24 [-4.27, -0.46]5.11 [4.24, 6.25]14% [5%, 24%]29%33%-0.10-0.592026-08-10 → 2026-08-30
tmax12Zbilinear90d21 1 QC4.23 [3.29, 5.48]3.97-2.24 [-4.51, -0.27]5.11 [3.95, 6.41]14% [0%, 25%]29%33%-0.10-0.592026-08-10 → 2026-08-30
tmax12Zbilinear365d26 1 QC4.78 [3.81, 6.53]4.49-2.29 [-4.52, -0.15]5.68 [4.58, 7.25]12% [0%, 21%]23%27%+0.21+0.272026-01-10 → 2026-08-30
tmax12Zbilinearall26 1 QC4.78 [3.82, 6.83]4.49-2.29 [-4.57, -0.39]5.68 [4.66, 7.53]12% [0%, 21%]23%27%+0.21+0.272026-01-10 → 2026-08-30
tmax12Znearest30d21 1 QC4.19 [3.50, 5.29]3.96-2.12 [-4.12, -0.38]5.07 [4.23, 6.23]14% [5%, 24%]29%33%-0.09-0.582026-08-10 → 2026-08-30
tmax12Znearest90d21 1 QC4.19 [3.29, 5.43]3.96-2.12 [-4.36, -0.18]5.07 [3.96, 6.35]14% [0%, 25%]29%33%-0.09-0.582026-08-10 → 2026-08-30
tmax12Znearest365d26 1 QC4.76 [3.78, 6.48]4.49-2.12 [-4.30, -0.02]5.64 [4.57, 7.19]12% [0%, 21%]23%27%+0.22+0.272026-01-10 → 2026-08-30
tmax12Znearestall26 1 QC4.76 [3.82, 6.82]4.49-2.12 [-4.43, -0.18]5.64 [4.64, 7.45]12% [0%, 21%]23%27%+0.22+0.272026-01-10 → 2026-08-30
tmin00Zbilinear30d21 1 QC4.46 [2.81, 6.33]3.60+3.60 [1.30, 5.99]5.79 [3.59, 7.55]14% [0%, 25%]24%48%+0.03-0.062026-08-10 → 2026-08-30
tmin00Zbilinear90d21 1 QC4.46 [2.78, 6.57]3.60+3.60 [1.23, 6.24]5.79 [3.49, 7.75]14% [0%, 24%]24%48%+0.03-0.062026-08-10 → 2026-08-30
tmin00Zbilinear365d27 1 QC4.02 [2.48, 5.77]3.38+2.76 [0.45, 5.18]5.38 [3.33, 7.14]19% [7%, 31%]33%52%+0.33+0.432026-01-10 → 2026-08-30
tmin00Zbilinearall27 1 QC4.02 [2.34, 5.94]3.38+2.76 [0.24, 5.28]5.38 [3.12, 7.29]19% [6%, 30%]33%52%+0.33+0.432026-01-10 → 2026-08-30
tmin00Znearest30d21 1 QC4.58 [2.88, 6.49]3.60+3.81 [1.53, 6.20]5.92 [3.69, 7.71]14% [0%, 25%]24%48%+0.01-0.062026-08-10 → 2026-08-30
tmin00Znearest90d21 1 QC4.58 [2.84, 6.74]3.60+3.81 [1.46, 6.44]5.92 [3.59, 7.90]14% [0%, 24%]24%48%+0.01-0.062026-08-10 → 2026-08-30
tmin00Znearest365d27 1 QC4.14 [2.60, 5.88]3.36+2.98 [0.68, 5.38]5.48 [3.40, 7.29]15% [4%, 23%]33%52%+0.31+0.432026-01-10 → 2026-08-30
tmin00Znearestall27 1 QC4.14 [2.45, 6.07]3.36+2.98 [0.48, 5.49]5.48 [3.17, 7.44]15% [3%, 23%]33%52%+0.31+0.432026-01-10 → 2026-08-30
tmin12Zbilinear30d21 1 QC3.89 [2.62, 5.30]3.47+2.77 [0.79, 5.04]5.02 [3.11, 6.53]14% [0%, 25%]33%48%+0.16-0.022026-08-10 → 2026-08-30
tmin12Zbilinear90d21 1 QC3.89 [2.36, 5.56]3.47+2.77 [0.64, 5.55]5.02 [2.88, 6.71]14% [0%, 25%]33%48%+0.16-0.022026-08-10 → 2026-08-30
tmin12Zbilinear365d26 1 QC3.95 [2.66, 5.46]3.59+2.86 [1.00, 5.08]5.26 [3.29, 6.98]12% [0%, 22%]38%50%+0.35+0.402026-01-10 → 2026-08-30
tmin12Zbilinearall26 1 QC3.95 [2.53, 5.42]3.59+2.86 [0.84, 4.93]5.26 [3.08, 6.89]12% [0%, 23%]38%50%+0.35+0.402026-01-10 → 2026-08-30
tmin12Znearest30d21 1 QC3.97 [2.62, 5.46]3.46+2.98 [1.01, 5.23]5.13 [3.14, 6.66]14% [0%, 25%]38%48%+0.14-0.022026-08-10 → 2026-08-30
tmin12Znearest90d21 1 QC3.97 [2.36, 5.72]3.46+2.98 [0.89, 5.72]5.13 [2.93, 6.86]14% [0%, 25%]38%48%+0.14-0.022026-08-10 → 2026-08-30
tmin12Znearest365d26 1 QC4.01 [2.67, 5.62]3.59+3.08 [1.23, 5.30]5.38 [3.37, 7.14]15% [0%, 29%]42%50%+0.34+0.402026-01-10 → 2026-08-30
tmin12Znearestall26 1 QC4.01 [2.54, 5.55]3.59+3.08 [1.05, 5.16]5.38 [3.15, 7.05]15% [4%, 27%]42%50%+0.34+0.402026-01-10 → 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 GraphCast (IFS init) at KTTN, lead day 9, 00Z bilinear tmax+20+100-10-202026-08-10: -1.07 °F2026-08-11: -0.08 °F2026-08-12: +2.61 °F2026-08-13: -7.17 °F2026-08-14: -2.93 °F2026-08-15: -5.95 °F2026-08-16: +0.08 °F2026-08-17: -7.94 °F2026-08-18: -4.38 °F2026-08-19: -4.06 °F2026-08-20: +5.65 °F2026-08-21: +11.67 °F2026-08-22: +8.95 °F2026-08-23: +1.04 °F2026-08-24: +6.3 °F2026-08-25: -0.21 °F2026-08-26: -3.73 °F2026-08-27: +4.28 °F2026-08-28: -1.32 °F2026-08-29: -1.8 °F2026-08-30: -5.87 °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
2026-08-30-5.87
2026-08-29-1.80
2026-08-28-1.32
2026-08-27+4.28
2026-08-26-3.73
2026-08-25-0.21
2026-08-24+6.30
2026-08-23+1.04
2026-08-22+8.95
2026-08-21+11.67
2026-08-20+5.65
2026-08-19-4.06
2026-08-18-4.38
2026-08-17-7.94
2026-08-16+0.08
2026-08-15-5.95
2026-08-14-2.93
2026-08-13-7.17
2026-08-12+2.61
2026-08-11-0.08
2026-08-10-1.07

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KTTN, lead day 9-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 0 days-12 to -10 °F: 1 day-10 to -8 °F: 2 days-8 to -6 °F: 2 days-6 to -4 °F: 6 days-4 to -2 °F: 2 days-2 to 0 °F: 5 days0 to 2 °F: 2 days2 to 4 °F: 1 day4 to 6 °F: 3 days6 to 8 °F: 1 day8 to 10 °F: 1 day10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 4.61 · P90 |e| 8.82 °F-200+20 °Fn = 27 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
-16.00-14.000
-14.00-12.000
-12.00-10.001
-10.00-8.002
-8.00-6.002
-6.00-4.006
-4.00-2.002
-2.00+0.005
+0.00+2.002
+2.00+4.001
+4.00+6.003
+6.00+8.001
+8.00+10.001
+10.00+12.001
+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
2026-08214.15 -0.28
2026-0167.01 -5.10

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-10 → 2026-08-30 27
GraphCast (IFS init)2026-01-10 → 2026-08-30 27
GraphCast (IFS init)2026-01-10 → 2026-08-30 26
GraphCast (IFS init)2026-01-10 → 2026-08-30 26

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 21 +0.24 [-0.89, 1.47] no
NCEP GFS 21 -1.18 [-3.48, 1.04] no
ECMWF IFS HRES 16 -0.24 [-6.25, 1.86] no
Persistence (baseline) 21 +0.29 [-0.76, 1.55] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model graphcast_ifs, 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/KTTN/model/graphcast_ifs/lead/9/

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