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

Seattle-Tacoma · GraphCast (IFS init) · lead day 6

KSEA · 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 QC6.67 [5.25, 8.49]4.03-5.92 [-8.38, -3.68]7.82 [6.29, 9.47]12% [5%, 19%]12%29%-0.29+0.222026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC6.67 [5.21, 8.78]4.03-5.92 [-8.67, -3.46]7.82 [6.20, 9.75]12% [0%, 19%]12%29%-0.29+0.222026-08-07 → 2026-08-30
tmax00Zbilinear365d30 1 QC5.76 [3.62, 7.82]4.10-5.10 [-7.62, -2.68]7.11 [4.80, 8.96]20% [9%, 35%]20%37%-0.14+0.192026-01-07 → 2026-08-30
tmax00Zbilinearall30 1 QC5.76 [3.39, 7.84]4.10-5.10 [-7.60, -2.54]7.11 [4.68, 9.01]20% [9%, 38%]20%37%-0.14+0.192026-01-07 → 2026-08-30
tmax00Znearest30d24 1 QC6.84 [5.37, 8.67]4.10-6.08 [-8.57, -3.84]7.98 [6.46, 9.61]12% [5%, 19%]12%29%-0.32+0.212026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC6.84 [5.35, 8.93]4.10-6.08 [-8.86, -3.62]7.98 [6.40, 9.92]12% [0%, 19%]12%29%-0.32+0.212026-08-07 → 2026-08-30
tmax00Znearest365d30 1 QC5.87 [3.62, 7.98]4.18-5.23 [-7.78, -2.74]7.25 [4.97, 9.09]20% [9%, 35%]20%37%-0.17+0.172026-01-07 → 2026-08-30
tmax00Znearestall30 1 QC5.87 [3.39, 7.93]4.18-5.23 [-7.73, -2.60]7.25 [4.77, 9.13]20% [9%, 38%]20%37%-0.17+0.172026-01-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC5.03 [3.37, 6.64]3.31-4.68 [-6.60, -2.47]6.23 [4.16, 7.88]12% [0%, 28%]21%33%+0.03+0.362026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC5.03 [3.25, 6.85]3.31-4.68 [-6.79, -2.30]6.23 [3.88, 8.00]12% [0%, 29%]21%33%+0.03+0.362026-08-07 → 2026-08-30
tmax12Zbilinear365d29 1 QC4.61 [2.91, 6.38]3.05-4.32 [-6.37, -2.36]5.81 [3.47, 7.56]14% [0%, 29%]28%38%+0.06+0.372026-01-07 → 2026-08-30
tmax12Zbilinearall29 1 QC4.61 [2.89, 6.34]3.05-4.32 [-6.33, -2.39]5.81 [3.33, 7.48]14% [0%, 29%]28%38%+0.06+0.372026-01-07 → 2026-08-30
tmax12Znearest30d24 1 QC5.15 [3.48, 6.75]3.35-4.80 [-6.71, -2.58]6.34 [4.26, 7.99]12% [0%, 28%]21%33%+0.00+0.352026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC5.15 [3.34, 6.98]3.35-4.80 [-6.92, -2.38]6.34 [3.95, 8.11]12% [0%, 29%]21%33%+0.00+0.352026-08-07 → 2026-08-30
tmax12Znearest365d29 1 QC4.73 [3.03, 6.49]3.08-4.45 [-6.49, -2.45]5.92 [3.52, 7.67]10% [0%, 25%]24%38%+0.03+0.372026-01-07 → 2026-08-30
tmax12Znearestall29 1 QC4.73 [2.99, 6.46]3.08-4.45 [-6.44, -2.49]5.92 [3.37, 7.60]10% [0%, 25%]24%38%+0.03+0.372026-01-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC2.23 [1.56, 2.91]1.49+2.06 [1.28, 2.82]2.71 [1.92, 3.31]29% [12%, 46%]46%67%-0.03+0.312026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC2.23 [1.49, 2.99]1.49+2.06 [1.18, 2.93]2.71 [1.84, 3.39]29% [11%, 48%]46%67%-0.03+0.312026-08-07 → 2026-08-30
tmin00Zbilinear365d30 1 QC2.06 [1.42, 2.78]1.61+1.58 [0.40, 2.62]2.54 [1.73, 3.19]30% [14%, 46%]50%73%+0.25+0.412026-01-07 → 2026-08-30
tmin00Zbilinearall30 1 QC2.06 [1.39, 2.78]1.61+1.58 [0.23, 2.66]2.54 [1.71, 3.20]30% [15%, 46%]50%73%+0.25+0.412026-01-07 → 2026-08-30
tmin00Znearest30d24 1 QC2.10 [1.53, 2.68]1.51+1.72 [0.89, 2.53]2.50 [1.77, 3.05]25% [13%, 38%]54%71%+0.03+0.312026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC2.10 [1.47, 2.76]1.51+1.72 [0.80, 2.62]2.50 [1.70, 3.13]25% [11%, 40%]54%71%+0.03+0.312026-08-07 → 2026-08-30
tmin00Znearest365d30 1 QC1.96 [1.41, 2.59]1.64+1.26 [0.07, 2.34]2.37 [1.67, 2.96]30% [17%, 46%]57%73%+0.28+0.402026-01-07 → 2026-08-30
tmin00Znearestall30 1 QC1.96 [1.40, 2.56]1.64+1.26 [-0.11, 2.37]2.37 [1.65, 2.96]30% [16%, 50%]57%73%+0.28+0.402026-01-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC1.79 [1.27, 2.32]1.24+1.71 [1.17, 2.27]2.21 [1.72, 2.63]38% [15%, 59%]58%71%+0.17+0.432026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC1.79 [1.24, 2.40]1.24+1.71 [1.12, 2.34]2.21 [1.63, 2.69]38% [12%, 62%]58%71%+0.17+0.432026-08-07 → 2026-08-30
tmin12Zbilinear365d29 1 QC1.72 [1.24, 2.28]1.18+1.56 [0.98, 2.21]2.11 [1.57, 2.60]34% [12%, 57%]66%76%+0.34+0.542026-01-07 → 2026-08-30
tmin12Zbilinearall29 1 QC1.72 [1.23, 2.26]1.18+1.56 [0.95, 2.18]2.11 [1.52, 2.56]34% [12%, 56%]66%76%+0.34+0.542026-01-07 → 2026-08-30
tmin12Znearest30d24 1 QC1.65 [1.19, 2.12]1.29+1.38 [0.79, 1.96]2.00 [1.53, 2.39]38% [21%, 52%]58%75%+0.24+0.402026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC1.65 [1.12, 2.18]1.29+1.38 [0.74, 2.05]2.00 [1.44, 2.44]38% [20%, 55%]58%75%+0.24+0.402026-08-07 → 2026-08-30
tmin12Znearest365d29 1 QC1.60 [1.17, 2.09]1.25+1.24 [0.62, 1.92]1.92 [1.44, 2.36]34% [18%, 50%]66%79%+0.39+0.522026-01-07 → 2026-08-30
tmin12Znearestall29 1 QC1.60 [1.16, 2.07]1.25+1.24 [0.59, 1.90]1.92 [1.43, 2.33]34% [18%, 50%]66%79%+0.39+0.522026-01-07 → 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 KSEA, lead day 6, 00Z bilinear tmax+20+100-10-202026-08-07: -12.51 °F2026-08-08: -2.63 °F2026-08-09: +0.4 °F2026-08-10: +6.12 °F2026-08-11: -2.72 °F2026-08-12: -10.28 °F2026-08-13: -6.92 °F2026-08-14: -5.64 °F2026-08-15: +2.6 °F2026-08-16: -0.27 °F2026-08-17: -8.39 °F2026-08-18: -9.45 °F2026-08-19: -14.99 °F2026-08-20: -14.09 °F2026-08-21: -6.9 °F2026-08-22: -9.93 °F2026-08-23: -5.86 °F2026-08-24: -6.42 °F2026-08-25: -10.34 °F2026-08-26: -0.03 °F2026-08-27: -7.1 °F2026-08-28: -2.71 °F2026-08-29: -7.87 °F2026-08-30: -6.02 °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
2026-08-30-6.02
2026-08-29-7.87
2026-08-28-2.71
2026-08-27-7.10
2026-08-26-0.03
2026-08-25-10.34
2026-08-24-6.42
2026-08-23-5.86
2026-08-22-9.93
2026-08-21-6.90
2026-08-20-14.09
2026-08-19-14.99
2026-08-18-9.45
2026-08-17-8.39
2026-08-16-0.27
2026-08-15+2.60
2026-08-14-5.64
2026-08-13-6.92
2026-08-12-10.28
2026-08-11-2.72
2026-08-10+6.12
2026-08-09+0.40
2026-08-08-2.63
2026-08-07-12.51

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 6-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 2 days-14 to -12 °F: 1 day-12 to -10 °F: 2 days-10 to -8 °F: 3 days-8 to -6 °F: 6 days-6 to -4 °F: 3 days-4 to -2 °F: 5 days-2 to 0 °F: 3 days0 to 2 °F: 3 days2 to 4 °F: 1 day4 to 6 °F: 0 days6 to 8 °F: 1 day8 to 10 °F: 0 days10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 5.94 · P90 |e| 10.56 °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
-16.00-14.002
-14.00-12.001
-12.00-10.002
-10.00-8.003
-8.00-6.006
-6.00-4.003
-4.00-2.005
-2.00+0.003
+0.00+2.003
+2.00+4.001
+4.00+6.000
+6.00+8.001
+8.00+10.000
+10.00+12.000
+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
2026-08246.67 -5.92
2026-0162.09 -1.85

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 +1.20 [0.43, 2.59] yes
NCEP GFS 24 +1.82 [-1.02, 4.89] no
ECMWF IFS HRES 19 +2.52 [0.47, 7.17] yes
Persistence (baseline) 24 +1.51 [-2.64, 4.80] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), 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/KSEA/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