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

Trenton Mercer · GraphCast (IFS init) · lead day 5

KTTN · graphcast_ifs · lead 5

Target day = initialization date + 5 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
tmax00Zbilinear30d25 1 QC2.33 [1.75, 3.00]2.09-1.45 [-2.43, -0.44]2.97 [2.12, 3.66]24% [12%, 33%]48%76%+0.38+0.442026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC2.33 [1.72, 3.17]2.09-1.45 [-2.57, -0.14]2.97 [2.06, 3.72]24% [10%, 33%]48%76%+0.38+0.442026-08-06 → 2026-08-30
tmax00Zbilinear365d31 1 QC2.72 [1.94, 3.84]2.68-0.61 [-2.22, 1.52]3.55 [2.37, 4.72]23% [12%, 31%]45%68%+0.54+0.562026-01-06 → 2026-08-30
tmax00Zbilinearall31 1 QC2.72 [1.96, 3.92]2.68-0.61 [-1.98, 1.65]3.55 [2.47, 4.77]23% [12%, 30%]45%68%+0.54+0.562026-01-06 → 2026-08-30
tmax00Znearest30d25 1 QC2.28 [1.71, 2.95]2.11-1.29 [-2.26, -0.29]2.91 [2.05, 3.59]28% [12%, 42%]48%76%+0.39+0.432026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC2.28 [1.67, 3.08]2.11-1.29 [-2.40, -0.00]2.91 [1.99, 3.65]28% [10%, 41%]48%76%+0.39+0.432026-08-06 → 2026-08-30
tmax00Znearest365d31 1 QC2.72 [1.86, 3.93]2.70-0.43 [-2.06, 1.76]3.57 [2.32, 4.83]26% [12%, 38%]45%68%+0.54+0.552026-01-06 → 2026-08-30
tmax00Znearestall31 1 QC2.72 [1.93, 4.01]2.70-0.43 [-1.83, 1.88]3.57 [2.43, 4.91]26% [12%, 38%]45%68%+0.54+0.552026-01-06 → 2026-08-30
tmax12Zbilinear30d25 1 QC3.01 [2.04, 4.23]2.72-2.00 [-3.44, -0.97]3.81 [2.63, 5.03]20% [12%, 29%]40%56%+0.20+0.272026-08-06 → 2026-08-30
tmax12Zbilinear90d25 1 QC3.01 [1.95, 4.41]2.72-2.00 [-3.76, -0.88]3.81 [2.50, 5.24]20% [11%, 29%]40%56%+0.20+0.272026-08-06 → 2026-08-30
tmax12Zbilinear365d30 1 QC3.02 [2.12, 4.04]2.85-1.38 [-2.83, 0.35]3.79 [2.67, 4.82]17% [6%, 26%]37%60%+0.50+0.542026-01-06 → 2026-08-30
tmax12Zbilinearall30 1 QC3.02 [2.09, 4.05]2.85-1.38 [-2.92, 0.38]3.79 [2.60, 4.87]17% [6%, 27%]37%60%+0.50+0.542026-01-06 → 2026-08-30
tmax12Znearest30d25 1 QC2.98 [2.02, 4.15]2.71-1.86 [-3.29, -0.84]3.75 [2.57, 4.93]20% [12%, 29%]44%56%+0.21+0.272026-08-06 → 2026-08-30
tmax12Znearest90d25 1 QC2.98 [1.93, 4.31]2.71-1.86 [-3.60, -0.76]3.75 [2.46, 5.15]20% [11%, 29%]44%56%+0.21+0.272026-08-06 → 2026-08-30
tmax12Znearest365d30 1 QC3.01 [2.13, 3.98]2.87-1.23 [-2.68, 0.53]3.76 [2.64, 4.74]17% [6%, 26%]40%57%+0.50+0.532026-01-06 → 2026-08-30
tmax12Znearestall30 1 QC3.01 [2.10, 4.01]2.87-1.23 [-2.76, 0.56]3.76 [2.59, 4.80]17% [6%, 27%]40%57%+0.50+0.532026-01-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC4.08 [2.77, 5.43]2.58+3.73 [2.06, 5.31]4.89 [3.50, 6.19]12% [0%, 23%]32%40%-0.34+0.072026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC4.08 [2.76, 5.84]2.58+3.73 [2.06, 5.71]4.89 [3.42, 6.55]12% [0%, 24%]32%40%-0.34+0.072026-08-06 → 2026-08-30
tmin00Zbilinear365d31 1 QC4.33 [2.97, 5.85]2.58+4.05 [2.36, 5.78]5.32 [3.65, 6.94]10% [0%, 20%]29%39%+0.05+0.462026-01-06 → 2026-08-30
tmin00Zbilinearall31 1 QC4.33 [2.95, 5.81]2.58+4.05 [2.36, 5.71]5.32 [3.65, 6.91]10% [0%, 21%]29%39%+0.05+0.462026-01-06 → 2026-08-30
tmin00Znearest30d25 1 QC4.25 [2.90, 5.61]2.57+3.95 [2.29, 5.52]5.05 [3.65, 6.36]12% [0%, 23%]28%40%-0.40+0.082026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC4.25 [2.87, 6.03]2.57+3.95 [2.30, 5.91]5.05 [3.58, 6.72]12% [0%, 24%]28%40%-0.40+0.082026-08-06 → 2026-08-30
tmin00Znearest365d31 1 QC4.50 [3.11, 6.05]2.57+4.26 [2.60, 5.97]5.47 [3.80, 7.10]10% [0%, 20%]26%35%+0.01+0.462026-01-06 → 2026-08-30
tmin00Znearestall31 1 QC4.50 [3.07, 5.97]2.57+4.26 [2.59, 5.88]5.47 [3.80, 7.09]10% [0%, 21%]26%35%+0.01+0.462026-01-06 → 2026-08-30
tmin12Zbilinear30d25 1 QC3.91 [2.80, 5.11]2.44+3.64 [2.20, 5.04]4.74 [3.39, 5.81]12% [0%, 20%]32%40%-0.29+0.122026-08-06 → 2026-08-30
tmin12Zbilinear90d25 1 QC3.91 [2.78, 5.30]2.44+3.64 [2.18, 5.30]4.74 [3.32, 6.08]12% [0%, 20%]32%40%-0.29+0.122026-08-06 → 2026-08-30
tmin12Zbilinear365d30 1 QC4.42 [3.03, 6.24]2.64+4.19 [2.51, 6.24]5.35 [3.53, 7.09]10% [0%, 18%]27%37%+0.01+0.432026-01-06 → 2026-08-30
tmin12Zbilinearall30 1 QC4.42 [3.03, 6.28]2.64+4.19 [2.40, 6.28]5.35 [3.60, 7.17]10% [0%, 19%]27%37%+0.01+0.432026-01-06 → 2026-08-30
tmin12Znearest30d25 1 QC4.08 [2.92, 5.31]2.45+3.85 [2.43, 5.24]4.90 [3.55, 5.98]12% [0%, 20%]28%40%-0.34+0.122026-08-06 → 2026-08-30
tmin12Znearest90d25 1 QC4.08 [2.87, 5.50]2.45+3.85 [2.39, 5.50]4.90 [3.47, 6.25]12% [0%, 20%]28%40%-0.34+0.122026-08-06 → 2026-08-30
tmin12Znearest365d30 1 QC4.58 [3.20, 6.42]2.63+4.39 [2.73, 6.42]5.51 [3.71, 7.25]10% [0%, 18%]23%33%-0.03+0.442026-01-06 → 2026-08-30
tmin12Znearestall30 1 QC4.58 [3.17, 6.47]2.63+4.39 [2.62, 6.47]5.51 [3.74, 7.34]10% [0%, 19%]23%33%-0.03+0.442026-01-06 → 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 5, 00Z bilinear tmax+10+50-5-102026-08-06: -2.75 °F2026-08-07: -4.76 °F2026-08-08: -4.76 °F2026-08-09: -2.93 °F2026-08-10: +0.04 °F2026-08-11: +2.09 °F2026-08-12: -6.32 °F2026-08-13: +1.01 °F2026-08-14: -0.26 °F2026-08-15: -6.78 °F2026-08-16: -1.11 °F2026-08-17: -0.18 °F2026-08-18: -2.95 °F2026-08-19: -3.25 °F2026-08-20: -0.83 °F2026-08-21: -2.52 °F2026-08-22: +1.19 °F2026-08-23: +0.48 °F2026-08-24: -1.55 °F2026-08-25: -1.37 °F2026-08-26: -2.52 °F2026-08-27: +0.31 °F2026-08-28: -2.43 °F2026-08-29: +4.37 °F2026-08-30: +1.56 °F2026-08-062026-08-30°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 (25 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.56
2026-08-29+4.37
2026-08-28-2.43
2026-08-27+0.31
2026-08-26-2.52
2026-08-25-1.37
2026-08-24-1.55
2026-08-23+0.48
2026-08-22+1.19
2026-08-21-2.52
2026-08-20-0.83
2026-08-19-3.25
2026-08-18-2.95
2026-08-17-0.18
2026-08-16-1.11
2026-08-15-6.78
2026-08-14-0.26
2026-08-13+1.01
2026-08-12-6.32
2026-08-11+2.09
2026-08-10+0.04
2026-08-09-2.93
2026-08-08-4.76
2026-08-07-4.76
2026-08-06-2.75

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KTTN, lead day 5-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 2 days-6 to -5 °F: 0 days-5 to -4 °F: 3 days-4 to -3 °F: 1 day-3 to -2 °F: 6 days-2 to -1 °F: 3 days-1 to 0 °F: 3 days0 to 1 °F: 4 days1 to 2 °F: 4 days2 to 3 °F: 1 day3 to 4 °F: 0 days4 to 5 °F: 2 days5 to 6 °F: 1 day6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 1 daydashed: P50 |e| 2.43 · P90 |e| 5.48 °F-100+10 °Fn = 31 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
-7.00-6.002
-6.00-5.000
-5.00-4.003
-4.00-3.001
-3.00-2.006
-2.00-1.003
-1.00+0.003
+0.00+1.004
+1.00+2.004
+2.00+3.001
+3.00+4.000
+4.00+5.002
+5.00+6.001
+6.00+7.000
+7.00+8.000
+8.00+9.000
+9.00+10.001

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08252.33 -1.45
2026-0164.35 +2.89

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-06 → 2026-08-30 31
GraphCast (IFS init)2026-01-06 → 2026-08-30 31
GraphCast (IFS init)2026-01-06 → 2026-08-30 30
GraphCast (IFS init)2026-01-06 → 2026-08-30 30

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 25 +0.65 [-0.07, 1.85] no
NCEP GFS 25 -1.94 [-3.68, 0.20] no
ECMWF IFS HRES 18 -1.15 [-3.06, 0.20] no
Persistence (baseline) 25 -1.43 [-2.34, -0.23] yes

Cite this page

ShortCastCheck, KTTN graphcast_ifs lead 5, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/graphcast_ifs/lead/5/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model graphcast_ifs, lead day 5. 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/5/

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