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

Trenton Mercer · GraphCast (IFS init) · lead day 8

KTTN · graphcast_ifs · lead 8

Target day = initialization date + 8 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
tmax00Zbilinear30d22 1 QC3.44 [2.84, 4.16]3.36-0.95 [-2.93, 0.67]4.03 [3.46, 4.60]14% [0%, 32%]32%50%+0.09-0.072026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC3.44 [2.83, 4.19]3.36-0.95 [-3.48, 0.87]4.03 [3.44, 4.66]14% [0%, 33%]32%50%+0.09-0.072026-08-09 → 2026-08-30
tmax00Zbilinear365d28 1 QC3.47 [2.94, 4.17]3.30-1.22 [-3.09, 0.41]3.99 [3.51, 4.60]14% [0%, 31%]29%43%+0.43+0.472026-01-09 → 2026-08-30
tmax00Zbilinearall28 1 QC3.47 [2.91, 4.13]3.30-1.22 [-3.04, 0.48]3.99 [3.50, 4.52]14% [0%, 30%]29%43%+0.43+0.472026-01-09 → 2026-08-30
tmax00Znearest30d22 1 QC3.46 [2.90, 4.15]3.39-0.82 [-2.86, 0.81]4.02 [3.44, 4.61]14% [0%, 32%]32%50%+0.08-0.082026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC3.46 [2.89, 4.21]3.39-0.82 [-3.42, 1.00]4.02 [3.42, 4.67]14% [0%, 33%]32%50%+0.08-0.082026-08-09 → 2026-08-30
tmax00Znearest365d28 1 QC3.46 [2.97, 4.12]3.31-1.03 [-2.90, 0.57]3.95 [3.44, 4.57]11% [0%, 29%]29%43%+0.44+0.472026-01-09 → 2026-08-30
tmax00Znearestall28 1 QC3.46 [2.95, 4.10]3.31-1.03 [-2.81, 0.65]3.95 [3.44, 4.49]11% [0%, 29%]29%43%+0.44+0.472026-01-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC3.87 [3.26, 4.54]3.40-2.54 [-3.79, -1.43]4.95 [4.13, 5.75]14% [0%, 25%]36%55%-0.02-0.082026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC3.87 [3.24, 4.51]3.40-2.54 [-3.76, -1.36]4.95 [4.01, 5.73]14% [0%, 26%]36%55%-0.02-0.082026-08-09 → 2026-08-30
tmax12Zbilinear365d27 1 QC3.79 [2.99, 4.61]3.57-1.68 [-3.37, 0.77]4.89 [3.92, 5.70]19% [3%, 33%]37%56%+0.36+0.402026-01-09 → 2026-08-30
tmax12Zbilinearall27 1 QC3.79 [3.05, 4.48]3.57-1.68 [-3.37, 0.63]4.89 [4.07, 5.63]19% [5%, 37%]37%56%+0.36+0.402026-01-09 → 2026-08-30
tmax12Znearest30d22 1 QC3.82 [3.23, 4.50]3.42-2.39 [-3.63, -1.29]4.88 [4.04, 5.71]14% [0%, 25%]32%55%-0.01-0.092026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC3.82 [3.21, 4.46]3.42-2.39 [-3.58, -1.22]4.88 [3.89, 5.70]14% [0%, 26%]32%55%-0.01-0.092026-08-09 → 2026-08-30
tmax12Znearest365d27 1 QC3.78 [2.94, 4.67]3.61-1.48 [-3.20, 1.05]4.89 [3.87, 5.76]19% [3%, 33%]33%56%+0.36+0.402026-01-09 → 2026-08-30
tmax12Znearestall27 1 QC3.78 [3.00, 4.54]3.61-1.48 [-3.21, 0.95]4.89 [4.00, 5.69]19% [5%, 37%]33%56%+0.36+0.402026-01-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC4.57 [3.58, 5.60]3.35+3.54 [2.09, 5.03]5.28 [4.23, 6.29]9% [0%, 17%]23%27%+0.04+0.102026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC4.57 [3.59, 5.72]3.35+3.54 [2.24, 5.27]5.28 [4.15, 6.37]9% [0%, 15%]23%27%+0.04+0.102026-08-09 → 2026-08-30
tmin00Zbilinear365d28 1 QC4.17 [3.14, 5.33]3.08+3.36 [2.26, 4.62]4.94 [3.72, 5.98]7% [0%, 14%]32%36%+0.31+0.492026-01-09 → 2026-08-30
tmin00Zbilinearall28 1 QC4.17 [3.02, 5.34]3.08+3.36 [2.14, 4.72]4.94 [3.61, 6.02]7% [0%, 14%]32%36%+0.31+0.492026-01-09 → 2026-08-30
tmin00Znearest30d22 1 QC4.68 [3.69, 5.70]3.33+3.73 [2.30, 5.23]5.41 [4.34, 6.40]9% [0%, 17%]23%27%+0.02+0.102026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC4.68 [3.71, 5.83]3.33+3.73 [2.44, 5.49]5.41 [4.30, 6.50]9% [0%, 16%]23%27%+0.02+0.102026-08-09 → 2026-08-30
tmin00Znearest365d28 1 QC4.30 [3.33, 5.41]3.08+3.56 [2.48, 4.81]5.07 [3.89, 6.11]7% [0%, 14%]29%36%+0.29+0.492026-01-09 → 2026-08-30
tmin00Znearestall28 1 QC4.30 [3.19, 5.44]3.08+3.56 [2.35, 4.91]5.07 [3.81, 6.16]7% [0%, 14%]29%36%+0.29+0.492026-01-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC4.82 [4.06, 5.72]2.68+4.14 [3.28, 5.22]5.36 [4.53, 6.21]0% [0%, 0%]9%27%-0.01+0.282026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC4.82 [4.04, 5.91]2.68+4.14 [3.26, 5.56]5.36 [4.51, 6.35]0% [0%, 0%]9%27%-0.01+0.282026-08-09 → 2026-08-30
tmin12Zbilinear365d27 1 QC5.28 [4.32, 6.77]2.80+4.72 [3.62, 6.64]5.92 [4.77, 7.44]0% [0%, 0%]7%22%+0.09+0.512026-01-09 → 2026-08-30
tmin12Zbilinearall27 1 QC5.28 [4.28, 6.97]2.80+4.72 [3.55, 6.76]5.92 [4.71, 7.61]0% [0%, 0%]7%22%+0.09+0.512026-01-09 → 2026-08-30
tmin12Znearest30d22 1 QC4.99 [4.22, 5.92]2.69+4.36 [3.50, 5.44]5.54 [4.71, 6.41]0% [0%, 0%]9%23%-0.05+0.272026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC4.99 [4.20, 6.11]2.69+4.36 [3.47, 5.80]5.54 [4.69, 6.55]0% [0%, 0%]9%23%-0.05+0.272026-08-09 → 2026-08-30
tmin12Znearest365d27 1 QC5.47 [4.49, 7.01]2.80+4.95 [3.84, 6.91]6.11 [4.94, 7.67]0% [0%, 0%]7%19%+0.06+0.512026-01-09 → 2026-08-30
tmin12Znearestall27 1 QC5.47 [4.46, 7.22]2.80+4.95 [3.76, 7.04]6.11 [4.89, 7.80]0% [0%, 0%]7%19%+0.06+0.512026-01-09 → 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 8, 00Z bilinear tmax+10+50-5-102026-08-09: -4.66 °F2026-08-10: -2.43 °F2026-08-11: +3.95 °F2026-08-12: -4.72 °F2026-08-13: +0.59 °F2026-08-14: +0.71 °F2026-08-15: -5.6 °F2026-08-16: +1.15 °F2026-08-17: +0.3 °F2026-08-18: -6.15 °F2026-08-19: -3.52 °F2026-08-20: +6.36 °F2026-08-21: +3.91 °F2026-08-22: +6.32 °F2026-08-23: +2.77 °F2026-08-24: -1.75 °F2026-08-25: -2.61 °F2026-08-26: -1.64 °F2026-08-27: +1.35 °F2026-08-28: -7.65 °F2026-08-29: -2.77 °F2026-08-30: -4.86 °F2026-08-092026-08-30°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 (22 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.86
2026-08-29-2.77
2026-08-28-7.65
2026-08-27+1.35
2026-08-26-1.64
2026-08-25-2.61
2026-08-24-1.75
2026-08-23+2.77
2026-08-22+6.32
2026-08-21+3.91
2026-08-20+6.36
2026-08-19-3.52
2026-08-18-6.15
2026-08-17+0.30
2026-08-16+1.15
2026-08-15-5.60
2026-08-14+0.71
2026-08-13+0.59
2026-08-12-4.72
2026-08-11+3.95
2026-08-10-2.43
2026-08-09-4.66

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KTTN, lead day 8-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 1 day-7 to -6 °F: 1 day-6 to -5 °F: 2 days-5 to -4 °F: 4 days-4 to -3 °F: 3 days-3 to -2 °F: 3 days-2 to -1 °F: 2 days-1 to 0 °F: 0 days0 to 1 °F: 4 days1 to 2 °F: 2 days2 to 3 °F: 1 day3 to 4 °F: 3 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 2 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 3.56 · P90 |e| 6.2 °F-100+10 °Fn = 28 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
-7.00-6.001
-6.00-5.002
-5.00-4.004
-4.00-3.003
-3.00-2.003
-2.00-1.002
-1.00+0.000
+0.00+1.004
+1.00+2.002
+2.00+3.001
+3.00+4.003
+4.00+5.000
+5.00+6.000
+6.00+7.002
+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
2026-08223.44 -0.95
2026-0163.58 -2.18

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 27
GraphCast (IFS init)2026-01-09 → 2026-08-30 27

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 22 +1.25 [0.24, 2.41] yes
NCEP GFS 22 -1.35 [-2.29, 0.33] no
ECMWF IFS HRES 17 +1.06 [0.51, 1.75] yes
Persistence (baseline) 22 -0.33 [-1.85, 1.88] no

Cite this page

ShortCastCheck, KTTN graphcast_ifs lead 8, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/graphcast_ifs/lead/8/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model graphcast_ifs, lead day 8. 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/8/

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