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

Trenton Mercer · GraphCast (IFS init) · lead day 2

KTTN · graphcast_ifs · lead 2

Target day = initialization date + 2 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
tmax00Zbilinear30d26 1 QC2.58 [1.92, 3.39]1.74-2.20 [-3.23, -1.20]3.10 [2.28, 3.85]19% [7%, 32%]42%65%+0.09+0.362026-08-03 → 2026-08-30
tmax00Zbilinear90d26 1 QC2.58 [1.75, 3.53]1.74-2.20 [-3.48, -0.99]3.10 [2.04, 3.95]19% [6%, 35%]42%65%+0.09+0.362026-08-03 → 2026-08-30
tmax00Zbilinear365d32 1 QC2.37 [1.59, 3.13]1.80-1.79 [-2.88, -0.54]2.89 [1.88, 3.62]22% [10%, 38%]47%72%+0.38+0.552026-01-03 → 2026-08-30
tmax00Zbilinearall32 1 QC2.37 [1.65, 3.17]1.80-1.79 [-2.96, -0.65]2.89 [1.93, 3.65]22% [10%, 36%]47%72%+0.38+0.552026-01-03 → 2026-08-30
tmax00Znearest30d26 1 QC2.49 [1.85, 3.28]1.77-2.03 [-3.09, -1.03]3.00 [2.22, 3.71]23% [12%, 35%]38%73%+0.12+0.352026-08-03 → 2026-08-30
tmax00Znearest90d26 1 QC2.49 [1.68, 3.39]1.77-2.03 [-3.33, -0.80]3.00 [1.98, 3.81]23% [9%, 39%]38%73%+0.12+0.352026-08-03 → 2026-08-30
tmax00Znearest365d32 1 QC2.29 [1.53, 3.01]1.84-1.62 [-2.73, -0.33]2.80 [1.82, 3.49]25% [13%, 39%]47%78%+0.40+0.552026-01-03 → 2026-08-30
tmax00Znearestall32 1 QC2.29 [1.60, 3.06]1.84-1.62 [-2.79, -0.44]2.80 [1.88, 3.50]25% [13%, 38%]47%78%+0.40+0.552026-01-03 → 2026-08-30
tmax12Zbilinear30d26 1 QC2.58 [1.78, 3.47]1.64-2.36 [-3.41, -1.36]3.11 [2.19, 3.86]15% [3%, 29%]54%65%+0.09+0.402026-08-03 → 2026-08-30
tmax12Zbilinear90d26 1 QC2.58 [1.67, 3.63]1.64-2.36 [-3.60, -1.28]3.11 [1.97, 4.00]15% [0%, 32%]54%65%+0.09+0.402026-08-03 → 2026-08-30
tmax12Zbilinear365d31 1 QC2.39 [1.50, 3.23]1.71-1.93 [-3.11, -0.54]2.92 [1.74, 3.67]16% [3%, 30%]58%71%+0.34+0.552026-01-03 → 2026-08-30
tmax12Zbilinearall31 1 QC2.39 [1.55, 3.24]1.71-1.93 [-3.15, -0.67]2.92 [1.78, 3.69]16% [4%, 29%]58%71%+0.34+0.552026-01-03 → 2026-08-30
tmax12Znearest30d26 1 QC2.48 [1.72, 3.35]1.68-2.19 [-3.25, -1.18]3.01 [2.12, 3.72]15% [0%, 31%]54%65%+0.13+0.382026-08-03 → 2026-08-30
tmax12Znearest90d26 1 QC2.48 [1.58, 3.49]1.68-2.19 [-3.44, -1.09]3.01 [1.80, 3.86]15% [0%, 33%]54%65%+0.13+0.382026-08-03 → 2026-08-30
tmax12Znearest365d31 1 QC2.31 [1.46, 3.11]1.75-1.75 [-2.94, -0.33]2.83 [1.68, 3.55]19% [5%, 36%]58%71%+0.37+0.542026-01-03 → 2026-08-30
tmax12Znearestall31 1 QC2.31 [1.49, 3.12]1.75-1.75 [-3.00, -0.47]2.83 [1.72, 3.58]19% [4%, 36%]58%71%+0.37+0.542026-01-03 → 2026-08-30
tmin00Zbilinear30d26 1 QC3.55 [2.90, 4.27]1.72+3.46 [2.80, 4.21]4.06 [3.34, 4.74]8% [0%, 15%]27%38%+0.03+0.532026-08-03 → 2026-08-30
tmin00Zbilinear90d26 1 QC3.55 [2.92, 4.38]1.72+3.46 [2.83, 4.33]4.06 [3.39, 4.90]8% [0%, 16%]27%38%+0.03+0.532026-08-03 → 2026-08-30
tmin00Zbilinear365d32 1 QC3.45 [2.83, 4.20]1.62+3.37 [2.75, 4.15]3.93 [3.22, 4.65]6% [0%, 14%]28%41%+0.13+0.592026-01-03 → 2026-08-30
tmin00Zbilinearall32 1 QC3.45 [2.88, 4.13]1.62+3.37 [2.80, 4.08]3.93 [3.30, 4.61]6% [0%, 13%]28%41%+0.13+0.592026-01-03 → 2026-08-30
tmin00Znearest30d26 1 QC3.76 [3.12, 4.48]1.74+3.68 [3.02, 4.44]4.26 [3.54, 4.96]8% [0%, 15%]27%31%-0.03+0.532026-08-03 → 2026-08-30
tmin00Znearest90d26 1 QC3.76 [3.13, 4.59]1.74+3.68 [3.05, 4.54]4.26 [3.57, 5.11]8% [0%, 16%]27%31%-0.03+0.532026-08-03 → 2026-08-30
tmin00Znearest365d32 1 QC3.65 [3.02, 4.41]1.64+3.58 [2.96, 4.36]4.12 [3.40, 4.86]6% [0%, 14%]28%34%+0.08+0.592026-01-03 → 2026-08-30
tmin00Znearestall32 1 QC3.65 [3.08, 4.33]1.64+3.58 [3.00, 4.29]4.12 [3.48, 4.82]6% [0%, 13%]28%34%+0.08+0.592026-01-03 → 2026-08-30
tmin12Zbilinear30d26 1 QC3.52 [2.83, 4.30]1.73+3.50 [2.82, 4.27]4.09 [3.30, 4.88]12% [4%, 18%]31%35%+0.04+0.532026-08-03 → 2026-08-30
tmin12Zbilinear90d26 1 QC3.52 [2.89, 4.39]1.73+3.50 [2.88, 4.38]4.09 [3.34, 5.00]12% [0%, 18%]31%35%+0.04+0.532026-08-03 → 2026-08-30
tmin12Zbilinear365d31 1 QC3.37 [2.75, 4.17]1.60+3.35 [2.74, 4.14]3.91 [3.11, 4.76]10% [0%, 15%]32%39%+0.15+0.602026-01-03 → 2026-08-30
tmin12Zbilinearall31 1 QC3.37 [2.77, 4.12]1.60+3.35 [2.76, 4.09]3.91 [3.16, 4.73]10% [0%, 16%]32%39%+0.15+0.602026-01-03 → 2026-08-30
tmin12Znearest30d26 1 QC3.74 [3.06, 4.51]1.73+3.73 [3.05, 4.50]4.29 [3.49, 5.08]8% [0%, 16%]27%31%-0.02+0.532026-08-03 → 2026-08-30
tmin12Znearest90d26 1 QC3.74 [3.12, 4.60]1.73+3.73 [3.11, 4.60]4.29 [3.53, 5.21]8% [0%, 17%]27%31%-0.02+0.532026-08-03 → 2026-08-30
tmin12Znearest365d31 1 QC3.57 [2.95, 4.38]1.61+3.57 [2.94, 4.37]4.10 [3.30, 4.97]6% [0%, 14%]29%35%+0.10+0.592026-01-03 → 2026-08-30
tmin12Znearestall31 1 QC3.57 [2.97, 4.32]1.61+3.57 [2.96, 4.31]4.10 [3.33, 4.92]6% [0%, 15%]29%35%+0.10+0.592026-01-03 → 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 2, 00Z bilinear tmax+10+50-5-102026-08-03: -4.18 °F2026-08-04: -3.99 °F2026-08-05: -2.6 °F2026-08-06: -4.81 °F2026-08-07: -6.97 °F2026-08-08: -3.16 °F2026-08-09: -1.18 °F2026-08-10: +0.17 °F2026-08-11: +2.27 °F2026-08-12: -1.48 °F2026-08-13: +0.67 °F2026-08-14: -2.81 °F2026-08-15: -3.6 °F2026-08-16: -0.15 °F2026-08-17: -1.87 °F2026-08-18: -1.38 °F2026-08-19: -2.32 °F2026-08-20: -5.81 °F2026-08-21: -2.57 °F2026-08-22: -4.93 °F2026-08-23: -1.16 °F2026-08-24: -2.64 °F2026-08-25: -0.59 °F2026-08-26: -3.03 °F2026-08-27: +1.88 °F2026-08-30: -0.9 °F2026-08-032026-08-30°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 (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.90
2026-08-29—
2026-08-28—
2026-08-27+1.88
2026-08-26-3.03
2026-08-25-0.59
2026-08-24-2.64
2026-08-23-1.16
2026-08-22-4.93
2026-08-21-2.57
2026-08-20-5.81
2026-08-19-2.32
2026-08-18-1.38
2026-08-17-1.87
2026-08-16-0.15
2026-08-15-3.60
2026-08-14-2.81
2026-08-13+0.67
2026-08-12-1.48
2026-08-11+2.27
2026-08-10+0.17
2026-08-09-1.18
2026-08-08-3.16
2026-08-07-6.97
2026-08-06-4.81
2026-08-05-2.60
2026-08-04-3.99
2026-08-03-4.18

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KTTN, lead day 2-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 1 day-6 to -5 °F: 1 day-5 to -4 °F: 3 days-4 to -3 °F: 4 days-3 to -2 °F: 6 days-2 to -1 °F: 6 days-1 to 0 °F: 4 days0 to 1 °F: 3 days1 to 2 °F: 2 days2 to 3 °F: 2 days3 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| 2.19 · P90 |e| 4.74 °F-100+10 °Fn = 32 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
-7.00-6.001
-6.00-5.001
-5.00-4.003
-4.00-3.004
-3.00-2.006
-2.00-1.006
-1.00+0.004
+0.00+1.003
+1.00+2.002
+2.00+3.002
+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
2026-08262.58 -2.20
2026-0161.46 -0.03

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 31
GraphCast (IFS init)2026-01-03 → 2026-08-30 31

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 26 +0.34 [-0.51, 1.37] no
Aurora (IFS init) 1 +0.59 [0.59, 0.59] yes
FourCastNet v2 (IFS init) 1 -0.17 [-0.17, -0.17] yes
NCEP GFS 26 -0.41 [-1.47, 0.37] no
ECMWF IFS HRES 20 -0.10 [-0.91, 0.56] no
Pangu-Weather (IFS init) 1 -1.21 [-1.21, -1.21] yes
Persistence (baseline) 26 -0.27 [-0.90, 0.59] no

Cite this page

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

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

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