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

Seattle-Tacoma · GraphCast (IFS init) · lead day 0

KSEA · graphcast_ifs · lead 0

Target day = initialization date + 0 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
tmax00Zbilinear30d28 1 QC4.33 [3.71, 5.01]1.61-4.30 [-5.01, -3.62]4.69 [4.15, 5.24]4% [0%, 10%]14%25%——2026-08-01 → 2026-08-30
tmax00Zbilinear90d28 1 QC4.33 [3.63, 5.01]1.61-4.30 [-5.01, -3.56]4.69 [4.07, 5.23]4% [0%, 11%]14%25%——2026-08-01 → 2026-08-30
tmax00Zbilinear365d34 1 QC4.15 [3.43, 4.86]1.76-4.12 [-4.85, -3.39]4.58 [3.97, 5.14]6% [0%, 14%]18%32%——2026-01-01 → 2026-08-30
tmax00Zbilinearall34 1 QC4.15 [3.42, 4.86]1.76-4.12 [-4.86, -3.38]4.58 [3.95, 5.13]6% [0%, 13%]18%32%——2026-01-01 → 2026-08-30
tmax00Znearest30d28 1 QC4.47 [3.81, 5.19]1.62-4.44 [-5.19, -3.74]4.83 [4.27, 5.42]4% [0%, 10%]18%25%——2026-08-01 → 2026-08-30
tmax00Znearest90d28 1 QC4.47 [3.74, 5.20]1.62-4.44 [-5.20, -3.68]4.83 [4.20, 5.44]4% [0%, 11%]18%25%——2026-08-01 → 2026-08-30
tmax00Znearest365d34 1 QC4.30 [3.59, 5.06]1.73-4.27 [-5.05, -3.55]4.71 [4.10, 5.33]6% [0%, 14%]21%29%——2026-01-01 → 2026-08-30
tmax00Znearestall34 1 QC4.30 [3.57, 5.06]1.73-4.27 [-5.06, -3.55]4.71 [4.05, 5.33]6% [0%, 13%]21%29%——2026-01-01 → 2026-08-30
tmin00Zbilinear30d28 1 QC2.47 [1.50, 3.46]1.34+2.42 [1.40, 3.45]2.89 [1.77, 3.70]21% [3%, 46%]46%64%——2026-08-01 → 2026-08-30
tmin00Zbilinear90d28 1 QC2.47 [1.36, 3.41]1.34+2.42 [1.26, 3.39]2.89 [1.57, 3.67]21% [4%, 50%]46%64%——2026-08-01 → 2026-08-30
tmin00Zbilinear365d34 1 QC2.25 [1.29, 3.17]1.52+1.93 [0.44, 3.06]2.69 [1.52, 3.47]26% [7%, 50%]53%71%——2026-01-01 → 2026-08-30
tmin00Zbilinearall34 1 QC2.25 [1.26, 3.16]1.52+1.93 [0.51, 3.09]2.69 [1.48, 3.49]26% [7%, 52%]53%71%——2026-01-01 → 2026-08-30
tmin00Znearest30d28 1 QC2.15 [1.25, 3.10]1.48+1.93 [0.82, 3.07]2.59 [1.48, 3.37]25% [7%, 43%]50%68%——2026-08-01 → 2026-08-30
tmin00Znearest90d28 1 QC2.15 [1.11, 3.07]1.48+1.93 [0.70, 3.00]2.59 [1.27, 3.33]25% [8%, 50%]50%68%——2026-08-01 → 2026-08-30
tmin00Znearest365d34 1 QC2.00 [1.15, 2.85]1.60+1.48 [-0.02, 2.68]2.43 [1.34, 3.15]29% [12%, 50%]56%74%——2026-01-01 → 2026-08-30
tmin00Znearestall34 1 QC2.00 [1.12, 2.85]1.60+1.48 [0.07, 2.67]2.43 [1.29, 3.18]29% [12%, 50%]56%74%——2026-01-01 → 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 0, 00Z bilinear tmax+10+50-5-102026-08-01: -2.84 °F2026-08-02: -5.82 °F2026-08-03: -3.36 °F2026-08-04: -1.88 °F2026-08-05: -4.9 °F2026-08-06: -5.26 °F2026-08-07: -6 °F2026-08-08: -4.51 °F2026-08-09: -1.52 °F2026-08-10: +0.46 °F2026-08-11: -5.12 °F2026-08-12: -5.91 °F2026-08-13: -1.98 °F2026-08-14: -2.06 °F2026-08-15: -4.24 °F2026-08-16: -5.73 °F2026-08-17: -5.17 °F2026-08-18: -3.48 °F2026-08-19: -6.31 °F2026-08-20: -6.91 °F2026-08-21: -3.78 °F2026-08-22: -6.35 °F2026-08-23: -3.19 °F2026-08-24: -5.93 °F2026-08-25: -6.71 °F2026-08-28: -3.25 °F2026-08-29: -6.39 °F2026-08-30: -2.3 °F2026-08-012026-08-30°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 (30 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.30
2026-08-29-6.39
2026-08-28-3.25
2026-08-27—
2026-08-26—
2026-08-25-6.71
2026-08-24-5.93
2026-08-23-3.19
2026-08-22-6.35
2026-08-21-3.78
2026-08-20-6.91
2026-08-19-6.31
2026-08-18-3.48
2026-08-17-5.17
2026-08-16-5.73
2026-08-15-4.24
2026-08-14-2.06
2026-08-13-1.98
2026-08-12-5.91
2026-08-11-5.12
2026-08-10+0.46
2026-08-09-1.52
2026-08-08-4.51
2026-08-07-6.00
2026-08-06-5.26
2026-08-05-4.90
2026-08-04-1.88
2026-08-03-3.36
2026-08-02-5.82
2026-08-01-2.84

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 0-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 7 days-6 to -5 °F: 8 days-5 to -4 °F: 3 days-4 to -3 °F: 5 days-3 to -2 °F: 5 days-2 to -1 °F: 4 days-1 to 0 °F: 1 day0 to 1 °F: 1 day1 to 2 °F: 0 days2 to 3 °F: 0 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| 4.38 · P90 |e| 6.4 °F-100+10 °Fn = 34 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
-7.00-6.007
-6.00-5.008
-5.00-4.003
-4.00-3.005
-3.00-2.005
-2.00-1.004
-1.00+0.001
+0.00+1.001
+1.00+2.000
+2.00+3.000
+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
2026-08284.33 -4.30
2026-0163.27 -3.27

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-01 → 2026-08-30 34
GraphCast (IFS init)2026-01-01 → 2026-08-30 34

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 28 -1.39 [-2.13, -0.32] yes
Aurora (GFS init) 2 -0.75 [-1.24, -0.26] yes
Aurora (IFS init) 3 +0.65 [0.33, 0.81] yes
FourCastNet v2 (GFS init) 2 +0.62 [0.00, 1.24] yes
FourCastNet v2 (IFS init) 3 +1.82 [1.57, 2.15] yes
NCEP GFS 28 +0.47 [-1.10, 2.52] no
GraphCast (GFS init) 2 -1.78 [-1.89, -1.67] yes
ECMWF IFS HRES 23 +2.53 [1.80, 3.19] yes
Pangu-Weather (GFS init) 2 +0.57 [-1.29, 2.42] no
Pangu-Weather (IFS init) 3 +2.20 [1.33, 2.63] yes

Cite this page

ShortCastCheck, KSEA graphcast_ifs lead 0, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/graphcast_ifs/lead/0/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model graphcast_ifs, lead day 0. 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/0/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

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