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

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

KSEA · graphcast_gfs · 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 2026-08-28 — 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
tmax00Zbilinear30d2 1 QC6.13 [4.19, 8.06]1.93-6.13 [-8.06, -4.19]6.42 [4.19, 8.06]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Zbilinear90d2 1 QC6.13 [4.19, 8.06]1.93-6.13 [-8.06, -4.19]6.42 [4.19, 8.06]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Zbilinear365d2 1 QC6.13 [4.19, 8.06]1.93-6.13 [-8.06, -4.19]6.42 [4.19, 8.06]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Zbilinearall2 1 QC6.13 [4.19, 8.06]1.93-6.13 [-8.06, -4.19]6.42 [4.19, 8.06]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Znearest30d2 1 QC6.24 [4.10, 8.38]2.14-6.24 [-8.38, -4.10]6.59 [4.10, 8.38]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Znearest90d2 1 QC6.24 [4.10, 8.38]2.14-6.24 [-8.38, -4.10]6.59 [4.10, 8.38]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Znearest365d2 1 QC6.24 [4.10, 8.38]2.14-6.24 [-8.38, -4.10]6.59 [4.10, 8.38]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmax00Znearestall2 1 QC6.24 [4.10, 8.38]2.14-6.24 [-8.38, -4.10]6.59 [4.10, 8.38]0% [0%, 0%]0%0%——2026-08-29 → 2026-08-30
tmin00Zbilinear30d2 1 QC1.21 [0.73, 1.69]0.48+1.21 [0.73, 1.69]1.30 [0.73, 1.69]50% [0%, 100%]100%100%——2026-08-29 → 2026-08-30
tmin00Zbilinear90d2 1 QC1.21 [0.73, 1.69]0.48+1.21 [0.73, 1.69]1.30 [0.73, 1.69]50% [0%, 100%]100%100%——2026-08-29 → 2026-08-30
tmin00Zbilinear365d2 1 QC1.21 [0.73, 1.69]0.48+1.21 [0.73, 1.69]1.30 [0.73, 1.69]50% [0%, 100%]100%100%——2026-08-29 → 2026-08-30
tmin00Zbilinearall2 1 QC1.21 [0.73, 1.69]0.48+1.21 [0.73, 1.69]1.30 [0.73, 1.69]50% [0%, 100%]100%100%——2026-08-29 → 2026-08-30
tmin00Znearest30d2 1 QC1.30 [1.03, 1.57]0.27+1.30 [1.03, 1.57]1.33 [1.03, 1.57]0% [0%, 0%]100%100%——2026-08-29 → 2026-08-30
tmin00Znearest90d2 1 QC1.30 [1.03, 1.57]0.27+1.30 [1.03, 1.57]1.33 [1.03, 1.57]0% [0%, 0%]100%100%——2026-08-29 → 2026-08-30
tmin00Znearest365d2 1 QC1.30 [1.03, 1.57]0.27+1.30 [1.03, 1.57]1.33 [1.03, 1.57]0% [0%, 0%]100%100%——2026-08-29 → 2026-08-30
tmin00Znearestall2 1 QC1.30 [1.03, 1.57]0.27+1.30 [1.03, 1.57]1.33 [1.03, 1.57]0% [0%, 0%]100%100%——2026-08-29 → 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 (GFS init) at KSEA, lead day 0, 00Z bilinear tmax+10+50-5-102026-08-29: -8.06 °F2026-08-30: -4.19 °F2026-08-292026-08-30°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 (2 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.19
2026-08-29-8.06

Error distribution

Distribution of the signed daily error in °F for GraphCast (GFS init) at KSEA, lead day 0-10 to -9 °F: 0 days-9 to -8 °F: 1 day-8 to -7 °F: 0 days-7 to -6 °F: 0 days-6 to -5 °F: 0 days-5 to -4 °F: 1 day-4 to -3 °F: 0 days-3 to -2 °F: 0 days-2 to -1 °F: 0 days-1 to 0 °F: 0 days0 to 1 °F: 0 days1 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| 6.13 · P90 |e| 7.67 °F-100+10 °Fn = 2 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
-9.00-8.001
-8.00-7.000
-7.00-6.000
-6.00-5.000
-5.00-4.001
-4.00-3.000
-3.00-2.000
-2.00-1.000
-1.00+0.000
+0.00+1.000
+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
2026-0826.13 -6.13

Availability

ModelScored period DaysCoverage
GraphCast (GFS init)2026-08-29 → 2026-08-30 2
GraphCast (GFS init)2026-08-29 → 2026-08-30 2

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means GraphCast (GFS init) has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 2 +1.57 [1.21, 1.92] yes
Aurora (GFS init) 2 +1.03 [0.65, 1.41] yes
Aurora (IFS init) 2 +2.59 [2.27, 2.91] yes
FourCastNet v2 (GFS init) 2 +2.40 [1.67, 3.13] yes
FourCastNet v2 (IFS init) 2 +3.73 [3.41, 4.04] yes
NCEP GFS 2 +4.14 [2.02, 6.26] yes
GraphCast (IFS init) 2 +1.78 [1.67, 1.89] yes
ECMWF IFS HRES 2 +4.36 [1.90, 6.82] yes
Pangu-Weather (GFS init) 2 +2.35 [0.60, 4.10] yes
Pangu-Weather (IFS init) 2 +3.82 [3.22, 4.41] yes

Cite this page

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

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

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