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

Seattle-Tacoma · GraphCast (IFS init) · lead day 8

KSEA · 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 QC6.57 [4.30, 7.98]3.36-6.36 [-7.92, -3.83]7.57 [5.42, 8.70]0% [0%, 0%]18%27%-0.19+0.392026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC6.57 [3.47, 8.04]3.36-6.36 [-8.03, -2.59]7.57 [4.24, 8.78]0% [0%, 0%]18%27%-0.19+0.392026-08-09 → 2026-08-30
tmax00Zbilinear365d28 1 QC6.78 [4.92, 8.01]3.28-6.62 [-8.01, -4.62]7.75 [6.10, 8.77]0% [0%, 0%]14%21%-0.18+0.432026-01-09 → 2026-08-30
tmax00Zbilinearall28 1 QC6.78 [5.10, 8.11]3.28-6.62 [-8.10, -4.77]7.75 [6.33, 8.79]0% [0%, 0%]14%21%-0.18+0.432026-01-09 → 2026-08-30
tmax00Znearest30d22 1 QC6.78 [4.53, 8.20]3.38-6.57 [-8.17, -4.06]7.77 [5.58, 8.93]0% [0%, 0%]14%27%-0.23+0.382026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC6.78 [3.59, 8.28]3.38-6.57 [-8.27, -2.65]7.77 [4.29, 9.02]0% [0%, 0%]14%27%-0.23+0.382026-08-09 → 2026-08-30
tmax00Znearest365d28 1 QC6.91 [5.09, 8.15]3.36-6.75 [-8.15, -4.76]7.89 [6.18, 8.92]0% [0%, 0%]11%21%-0.20+0.422026-01-09 → 2026-08-30
tmax00Znearestall28 1 QC6.91 [5.20, 8.22]3.36-6.75 [-8.18, -4.93]7.89 [6.42, 8.97]0% [0%, 0%]11%21%-0.20+0.422026-01-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC7.68 [5.44, 9.60]4.70-6.29 [-9.22, -1.63]8.64 [6.24, 10.18]5% [0%, 13%]5%14%-0.40+0.152026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC7.68 [4.83, 9.64]4.70-6.29 [-9.31, -0.47]8.64 [5.49, 10.23]5% [0%, 14%]5%14%-0.40+0.152026-08-09 → 2026-08-30
tmax12Zbilinear365d27 1 QC7.42 [5.27, 9.32]4.19-6.28 [-9.14, -2.60]8.32 [5.95, 9.93]4% [0%, 11%]4%11%-0.32+0.262026-01-09 → 2026-08-30
tmax12Zbilinearall27 1 QC7.42 [5.35, 9.23]4.19-6.28 [-9.01, -2.65]8.32 [6.02, 9.88]4% [0%, 11%]4%11%-0.32+0.262026-01-09 → 2026-08-30
tmax12Znearest30d22 1 QC7.91 [5.68, 9.80]4.76-6.49 [-9.44, -1.80]8.86 [6.45, 10.40]5% [0%, 13%]5%14%-0.44+0.132026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC7.91 [5.04, 9.85]4.76-6.49 [-9.53, -0.66]8.86 [5.70, 10.42]5% [0%, 14%]5%14%-0.44+0.132026-08-09 → 2026-08-30
tmax12Znearest365d27 1 QC7.53 [5.31, 9.45]4.27-6.38 [-9.28, -2.56]8.46 [5.98, 10.13]4% [0%, 11%]4%15%-0.34+0.242026-01-09 → 2026-08-30
tmax12Znearestall27 1 QC7.53 [5.43, 9.39]4.27-6.38 [-9.19, -2.62]8.46 [6.01, 10.05]4% [0%, 11%]4%15%-0.34+0.242026-01-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC2.35 [1.55, 3.15]1.64+1.71 [0.58, 3.06]2.85 [1.73, 3.63]14% [0%, 28%]50%77%-0.05+0.262026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC2.35 [1.50, 3.32]1.64+1.71 [0.45, 3.32]2.85 [1.69, 3.69]14% [0%, 30%]50%77%-0.05+0.262026-08-09 → 2026-08-30
tmin00Zbilinear365d28 1 QC3.61 [1.95, 6.28]3.72-0.42 [-4.88, 2.53]4.79 [2.35, 7.35]11% [0%, 24%]39%61%-0.18-0.192026-01-09 → 2026-08-30
tmin00Zbilinearall28 1 QC3.61 [1.92, 7.14]3.72-0.42 [-6.00, 2.48]4.79 [2.41, 7.91]11% [0%, 25%]39%61%-0.18-0.192026-01-09 → 2026-08-30
tmin00Znearest30d22 1 QC2.22 [1.52, 2.92]1.73+1.35 [0.13, 2.79]2.73 [1.71, 3.45]18% [4%, 33%]50%82%+0.00+0.222026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC2.22 [1.47, 3.14]1.73+1.35 [-0.00, 3.08]2.73 [1.67, 3.52]18% [0%, 33%]50%82%+0.00+0.222026-08-09 → 2026-08-30
tmin00Znearest365d28 1 QC3.55 [1.84, 6.34]3.70-0.74 [-5.09, 2.23]4.81 [2.23, 7.49]14% [0%, 27%]39%68%-0.15-0.182026-01-09 → 2026-08-30
tmin00Znearestall28 1 QC3.55 [1.86, 7.22]3.70-0.74 [-6.18, 2.16]4.81 [2.33, 8.06]14% [0%, 29%]39%68%-0.15-0.182026-01-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC2.29 [1.39, 3.52]2.00+1.73 [0.55, 3.35]3.06 [1.85, 4.31]32% [12%, 50%]59%73%-0.03+0.112026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC2.29 [1.28, 3.98]2.00+1.73 [0.50, 3.92]3.06 [1.65, 4.76]32% [11%, 53%]59%73%-0.03+0.112026-08-09 → 2026-08-30
tmin12Zbilinear365d27 1 QC3.08 [1.74, 5.45]3.03+0.21 [-3.37, 2.75]4.24 [2.36, 6.46]30% [12%, 47%]52%63%-0.05-0.012026-01-09 → 2026-08-30
tmin12Zbilinearall27 1 QC3.08 [1.67, 5.82]3.03+0.21 [-4.15, 2.62]4.24 [2.25, 6.87]30% [12%, 47%]52%63%-0.05-0.012026-01-09 → 2026-08-30
tmin12Znearest30d22 1 QC2.19 [1.44, 3.23]2.00+1.38 [0.16, 3.00]2.88 [1.79, 3.99]32% [12%, 50%]55%77%+0.01+0.102026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC2.19 [1.35, 3.68]2.00+1.38 [0.12, 3.55]2.88 [1.62, 4.41]32% [11%, 53%]55%77%+0.01+0.102026-08-09 → 2026-08-30
tmin12Znearest365d27 1 QC3.03 [1.76, 5.26]3.04-0.09 [-3.56, 2.40]4.16 [2.26, 6.42]30% [12%, 47%]48%67%-0.03-0.022026-01-09 → 2026-08-30
tmin12Znearestall27 1 QC3.03 [1.65, 5.90]3.04-0.09 [-4.35, 2.30]4.16 [2.15, 6.88]30% [12%, 47%]48%67%-0.03-0.022026-01-09 → 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 KSEA, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: -6.51 °F2026-08-10: +2.28 °F2026-08-11: -1.42 °F2026-08-12: -7.47 °F2026-08-13: -10.47 °F2026-08-14: -9.58 °F2026-08-15: -5.03 °F2026-08-16: -3.78 °F2026-08-17: -11.94 °F2026-08-18: -1.74 °F2026-08-19: -9.1 °F2026-08-20: -10.99 °F2026-08-21: -7.45 °F2026-08-22: -6.15 °F2026-08-23: -5.6 °F2026-08-24: -10.32 °F2026-08-25: -14.57 °F2026-08-26: -8.58 °F2026-08-27: -6.27 °F2026-08-28: -1.71 °F2026-08-29: -2.02 °F2026-08-30: -1.56 °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
2026-08-30-1.56
2026-08-29-2.02
2026-08-28-1.71
2026-08-27-6.27
2026-08-26-8.58
2026-08-25-14.57
2026-08-24-10.32
2026-08-23-5.60
2026-08-22-6.15
2026-08-21-7.45
2026-08-20-10.99
2026-08-19-9.10
2026-08-18-1.74
2026-08-17-11.94
2026-08-16-3.78
2026-08-15-5.03
2026-08-14-9.58
2026-08-13-10.47
2026-08-12-7.47
2026-08-11-1.42
2026-08-10+2.28
2026-08-09-6.51

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 8-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 1 day-12 to -10 °F: 5 days-10 to -8 °F: 3 days-8 to -6 °F: 6 days-6 to -4 °F: 4 days-4 to -2 °F: 3 days-2 to 0 °F: 4 days0 to 2 °F: 0 days2 to 4 °F: 1 day4 to 6 °F: 0 days6 to 8 °F: 0 days8 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| 6.39 · P90 |e| 11.65 °F-200+20 °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
-20.00-18.000
-18.00-16.000
-16.00-14.001
-14.00-12.001
-12.00-10.005
-10.00-8.003
-8.00-6.006
-6.00-4.004
-4.00-2.003
-2.00+0.004
+0.00+2.000
+2.00+4.001
+4.00+6.000
+6.00+8.000
+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
2026-08226.57 -6.36
2026-0167.56 -7.56

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 +0.18 [-1.92, 1.84] no
NCEP GFS 22 -0.72 [-3.87, 2.94] no
ECMWF IFS HRES 17 +0.52 [-2.11, 2.63] no
Persistence (baseline) 22 +1.07 [-3.79, 3.93] no

Cite this page

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

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