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

Trenton Mercer · GraphCast (IFS init) · lead day 6

KTTN · graphcast_ifs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC2.25 [1.95, 2.72]1.77-1.58 [-2.42, -0.81]2.64 [2.26, 3.12]25% [16%, 33%]46%62%+0.39+0.512026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC2.25 [1.91, 2.89]1.77-1.58 [-2.62, -0.72]2.64 [2.24, 3.27]25% [17%, 33%]46%62%+0.39+0.512026-08-07 → 2026-08-30
tmax00Zbilinear365d30 1 QC3.05 [2.05, 4.97]2.78-0.76 [-2.24, 1.52]4.26 [2.40, 6.75]20% [8%, 29%]40%57%+0.49+0.562026-01-07 → 2026-08-30
tmax00Zbilinearall30 1 QC3.05 [2.04, 5.17]2.78-0.76 [-2.31, 1.73]4.26 [2.42, 7.02]20% [7%, 29%]40%57%+0.49+0.562026-01-07 → 2026-08-30
tmax00Znearest30d24 1 QC2.20 [1.91, 2.63]1.81-1.43 [-2.25, -0.67]2.57 [2.24, 3.01]29% [18%, 40%]42%62%+0.40+0.502026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC2.20 [1.89, 2.79]1.81-1.43 [-2.45, -0.58]2.57 [2.21, 3.16]29% [17%, 42%]42%62%+0.40+0.502026-08-07 → 2026-08-30
tmax00Znearest365d30 1 QC3.03 [2.02, 5.00]2.83-0.59 [-2.08, 1.75]4.29 [2.35, 6.89]23% [8%, 36%]37%57%+0.50+0.552026-01-07 → 2026-08-30
tmax00Znearestall30 1 QC3.03 [2.02, 5.20]2.83-0.59 [-2.14, 1.95]4.29 [2.37, 7.15]23% [8%, 36%]37%57%+0.50+0.552026-01-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC2.40 [1.78, 3.20]2.03-1.52 [-2.53, -0.67]3.02 [2.26, 3.89]29% [17%, 42%]50%67%+0.35+0.442026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC2.40 [1.79, 3.38]2.03-1.52 [-2.75, -0.63]3.02 [2.23, 4.09]29% [17%, 43%]50%67%+0.35+0.442026-08-07 → 2026-08-30
tmax12Zbilinear365d29 1 QC2.91 [1.95, 4.62]2.72-0.59 [-2.17, 1.93]4.03 [2.43, 6.12]28% [17%, 39%]48%66%+0.53+0.582026-01-07 → 2026-08-30
tmax12Zbilinearall29 1 QC2.91 [1.96, 4.65]2.72-0.59 [-2.12, 2.08]4.03 [2.43, 6.23]28% [16%, 39%]48%66%+0.53+0.582026-01-07 → 2026-08-30
tmax12Znearest30d24 1 QC2.34 [1.73, 3.14]2.02-1.38 [-2.40, -0.53]2.95 [2.19, 3.81]29% [17%, 42%]54%67%+0.36+0.442026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC2.34 [1.74, 3.31]2.02-1.38 [-2.63, -0.49]2.95 [2.16, 3.99]29% [17%, 43%]54%67%+0.36+0.442026-08-07 → 2026-08-30
tmax12Znearest365d29 1 QC2.88 [1.90, 4.69]2.76-0.43 [-2.00, 2.13]4.05 [2.38, 6.24]28% [17%, 40%]52%66%+0.53+0.572026-01-07 → 2026-08-30
tmax12Znearestall29 1 QC2.88 [1.89, 4.70]2.76-0.43 [-1.99, 2.26]4.05 [2.37, 6.35]28% [17%, 40%]52%66%+0.53+0.572026-01-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC4.18 [3.04, 5.44]2.43+4.02 [2.68, 5.44]4.98 [3.68, 6.18]12% [0%, 23%]25%42%-0.17+0.282026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC4.18 [3.00, 5.74]2.43+4.02 [2.61, 5.74]4.98 [3.57, 6.48]12% [0%, 24%]25%42%-0.17+0.282026-08-07 → 2026-08-30
tmin00Zbilinear365d30 1 QC4.54 [3.21, 6.09]2.70+4.41 [2.88, 6.09]5.53 [3.87, 7.21]13% [0%, 25%]27%40%+0.11+0.482026-01-07 → 2026-08-30
tmin00Zbilinearall30 1 QC4.54 [3.25, 6.11]2.70+4.41 [2.93, 6.11]5.53 [3.85, 7.20]13% [0%, 24%]27%40%+0.11+0.482026-01-07 → 2026-08-30
tmin00Znearest30d24 1 QC4.36 [3.19, 5.66]2.42+4.23 [2.90, 5.65]5.16 [3.85, 6.36]12% [0%, 23%]21%42%-0.22+0.282026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC4.36 [3.15, 5.94]2.42+4.23 [2.83, 5.94]5.16 [3.74, 6.71]12% [0%, 24%]21%42%-0.22+0.282026-08-07 → 2026-08-30
tmin00Znearest365d30 1 QC4.73 [3.35, 6.32]2.69+4.63 [3.10, 6.32]5.72 [4.04, 7.41]10% [0%, 21%]23%40%+0.07+0.482026-01-07 → 2026-08-30
tmin00Znearestall30 1 QC4.73 [3.41, 6.32]2.69+4.63 [3.15, 6.32]5.72 [4.03, 7.42]10% [0%, 20%]23%40%+0.07+0.482026-01-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC4.30 [3.04, 5.71]2.77+3.80 [2.10, 5.55]5.11 [3.52, 6.42]4% [0%, 12%]21%42%-0.20+0.172026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC4.30 [3.06, 5.88]2.77+3.80 [2.13, 5.73]5.11 [3.51, 6.58]4% [0%, 12%]21%42%-0.20+0.172026-08-07 → 2026-08-30
tmin12Zbilinear365d29 1 QC4.75 [3.18, 6.65]3.00+4.33 [2.38, 6.59]5.86 [3.63, 7.95]3% [0%, 10%]21%38%+0.09+0.442026-01-07 → 2026-08-30
tmin12Zbilinearall29 1 QC4.75 [3.24, 6.68]3.00+4.33 [2.39, 6.55]5.86 [3.74, 8.04]3% [0%, 10%]21%38%+0.09+0.442026-01-07 → 2026-08-30
tmin12Znearest30d24 1 QC4.45 [3.14, 5.88]2.78+4.00 [2.31, 5.74]5.26 [3.69, 6.58]8% [0%, 19%]21%33%-0.24+0.172026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC4.45 [3.15, 6.06]2.78+4.00 [2.34, 5.92]5.26 [3.67, 6.73]8% [0%, 19%]21%33%-0.24+0.172026-08-07 → 2026-08-30
tmin12Znearest365d29 1 QC4.90 [3.32, 6.85]3.01+4.53 [2.60, 6.80]6.00 [3.81, 8.10]7% [0%, 17%]21%31%+0.06+0.442026-01-07 → 2026-08-30
tmin12Znearestall29 1 QC4.90 [3.35, 6.85]3.01+4.53 [2.60, 6.75]6.00 [3.88, 8.19]7% [0%, 17%]21%31%+0.06+0.442026-01-07 → 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 6, 00Z bilinear tmax+5+2.50-2.5-52026-08-07: -4.38 °F2026-08-08: -4.06 °F2026-08-09: -2.3 °F2026-08-10: -0.49 °F2026-08-11: -4.34 °F2026-08-12: -1.25 °F2026-08-13: +0.24 °F2026-08-14: -4.42 °F2026-08-15: -1.88 °F2026-08-16: +2.43 °F2026-08-17: +0.74 °F2026-08-18: -3.33 °F2026-08-19: -1.97 °F2026-08-20: +1.45 °F2026-08-21: -2.51 °F2026-08-22: -0.86 °F2026-08-23: -3.31 °F2026-08-24: -2.5 °F2026-08-25: -0.48 °F2026-08-26: -3.09 °F2026-08-27: -1.04 °F2026-08-28: -3.66 °F2026-08-29: +3.15 °F2026-08-30: +0.04 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+0.04
2026-08-29+3.15
2026-08-28-3.66
2026-08-27-1.04
2026-08-26-3.09
2026-08-25-0.48
2026-08-24-2.50
2026-08-23-3.31
2026-08-22-0.86
2026-08-21-2.51
2026-08-20+1.45
2026-08-19-1.97
2026-08-18-3.33
2026-08-17+0.74
2026-08-16+2.43
2026-08-15-1.88
2026-08-14-4.42
2026-08-13+0.24
2026-08-12-1.25
2026-08-11-4.34
2026-08-10-0.49
2026-08-09-2.30
2026-08-08-4.06
2026-08-07-4.38

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KTTN, lead day 6-20 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: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 0 days-6 to -4 °F: 5 days-4 to -2 °F: 9 days-2 to 0 °F: 7 days0 to 2 °F: 5 days2 to 4 °F: 2 days4 to 6 °F: 0 days6 to 8 °F: 0 days8 to 10 °F: 1 day10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 1 day16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 2.5 · P90 |e| 4.43 °F-200+20 °Fn = 30 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
-12.00-10.000
-10.00-8.000
-8.00-6.000
-6.00-4.005
-4.00-2.009
-2.00+0.007
+0.00+2.005
+2.00+4.002
+4.00+6.000
+6.00+8.000
+8.00+10.001
+10.00+12.000
+12.00+14.000
+14.00+16.001
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08242.25 -1.58
2026-0166.27 +2.51

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-07 → 2026-08-30 30
GraphCast (IFS init)2026-01-07 → 2026-08-30 30
GraphCast (IFS init)2026-01-07 → 2026-08-30 29
GraphCast (IFS init)2026-01-07 → 2026-08-30 29

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 24 +0.33 [-0.32, 0.98] no
NCEP GFS 24 -1.45 [-2.40, -0.15] yes
ECMWF IFS HRES 19 -1.99 [-3.96, -0.40] yes
Persistence (baseline) 24 -1.42 [-2.38, -0.31] yes

Cite this page

ShortCastCheck, KTTN graphcast_ifs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/graphcast_ifs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model graphcast_ifs, lead day 6. 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/6/

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