Raw model output on the native 0.25° grid — no MOS, no bias correction, no post-processing. Scores understate operational forecast quality. Read the fairness statement →

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

Seattle-Tacoma · GraphCast (IFS init) · lead day 1

KSEA · graphcast_ifs · lead 1

Target day = initialization date + 1 day. 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
tmax00Zbilinear30d27 1 QC4.49 [3.85, 5.19]1.56-4.41 [-5.18, -3.66]4.86 [4.25, 5.47]0% [0%, 0%]15%26%-0.41+0.512026-08-02 → 2026-08-30
tmax00Zbilinear90d27 1 QC4.49 [3.81, 5.19]1.56-4.41 [-5.19, -3.63]4.86 [4.22, 5.52]0% [0%, 0%]15%26%-0.41+0.512026-08-02 → 2026-08-30
tmax00Zbilinear365d33 1 QC4.23 [3.40, 5.01]1.70-4.16 [-4.99, -3.32]4.67 [3.93, 5.33]3% [0%, 11%]18%30%-0.26+0.502026-01-02 → 2026-08-30
tmax00Zbilinearall33 1 QC4.23 [3.42, 5.01]1.70-4.16 [-5.00, -3.34]4.67 [3.93, 5.32]3% [0%, 10%]18%30%-0.26+0.502026-01-02 → 2026-08-30
tmax00Znearest30d27 1 QC4.58 [3.88, 5.34]1.62-4.52 [-5.34, -3.75]4.98 [4.30, 5.65]4% [0%, 11%]15%19%-0.44+0.502026-08-02 → 2026-08-30
tmax00Znearest90d27 1 QC4.58 [3.82, 5.43]1.62-4.52 [-5.43, -3.70]4.98 [4.24, 5.74]4% [0%, 11%]15%19%-0.44+0.502026-08-02 → 2026-08-30
tmax00Znearest365d33 1 QC4.37 [3.59, 5.17]1.68-4.32 [-5.15, -3.53]4.81 [4.07, 5.51]6% [0%, 14%]18%24%-0.30+0.502026-01-02 → 2026-08-30
tmax00Znearestall33 1 QC4.37 [3.58, 5.15]1.68-4.32 [-5.15, -3.52]4.81 [4.05, 5.49]6% [0%, 13%]18%24%-0.30+0.502026-01-02 → 2026-08-30
tmax12Zbilinear30d27 1 QC5.62 [4.93, 6.34]1.51-5.62 [-6.34, -4.93]5.92 [5.26, 6.55]4% [0%, 11%]4%4%-0.76+0.532026-08-02 → 2026-08-30
tmax12Zbilinear90d27 1 QC5.62 [4.89, 6.32]1.51-5.62 [-6.32, -4.89]5.92 [5.22, 6.55]4% [0%, 11%]4%4%-0.76+0.532026-08-02 → 2026-08-30
tmax12Zbilinear365d32 1 QC5.26 [4.17, 6.14]1.74-5.26 [-6.14, -4.17]5.68 [4.80, 6.40]6% [0%, 14%]9%9%-0.54+0.492026-01-02 → 2026-08-30
tmax12Zbilinearall32 1 QC5.26 [4.15, 6.12]1.74-5.26 [-6.12, -4.15]5.68 [4.79, 6.39]6% [0%, 14%]9%9%-0.54+0.492026-01-02 → 2026-08-30
tmax12Znearest30d27 1 QC5.66 [4.94, 6.42]1.53-5.66 [-6.42, -4.94]5.97 [5.27, 6.64]4% [0%, 11%]4%7%-0.78+0.522026-08-02 → 2026-08-30
tmax12Znearest90d27 1 QC5.66 [4.91, 6.44]1.53-5.66 [-6.44, -4.91]5.97 [5.21, 6.66]4% [0%, 11%]4%7%-0.78+0.522026-08-02 → 2026-08-30
tmax12Znearest365d32 1 QC5.34 [4.30, 6.23]1.71-5.34 [-6.23, -4.30]5.74 [4.85, 6.47]6% [0%, 14%]9%12%-0.57+0.502026-01-02 → 2026-08-30
tmax12Znearestall32 1 QC5.34 [4.29, 6.21]1.71-5.34 [-6.21, -4.29]5.74 [4.86, 6.49]6% [0%, 14%]9%12%-0.57+0.502026-01-02 → 2026-08-30
tmin00Zbilinear30d27 1 QC1.94 [0.96, 2.90]1.28+1.87 [0.82, 2.90]2.45 [1.19, 3.30]37% [10%, 69%]56%78%-0.19+0.222026-08-02 → 2026-08-30
tmin00Zbilinear90d27 1 QC1.94 [0.81, 2.85]1.28+1.87 [0.66, 2.84]2.45 [1.01, 3.23]37% [12%, 80%]56%78%-0.19+0.222026-08-02 → 2026-08-30
tmin00Zbilinear365d33 1 QC1.79 [0.88, 2.65]1.40+1.50 [0.21, 2.53]2.28 [1.07, 3.06]39% [16%, 70%]61%82%+0.08+0.282026-01-02 → 2026-08-30
tmin00Zbilinearall33 1 QC1.79 [0.86, 2.65]1.40+1.50 [0.27, 2.53]2.28 [1.03, 3.10]39% [16%, 74%]61%82%+0.08+0.282026-01-02 → 2026-08-30
tmin00Znearest30d27 1 QC1.72 [0.81, 2.64]1.43+1.41 [0.25, 2.55]2.22 [1.02, 3.02]37% [13%, 60%]63%78%-0.05+0.132026-08-02 → 2026-08-30
tmin00Znearest90d27 1 QC1.72 [0.66, 2.57]1.43+1.41 [0.07, 2.49]2.22 [0.83, 2.97]37% [14%, 67%]63%78%-0.05+0.132026-08-02 → 2026-08-30
tmin00Znearest365d33 1 QC1.62 [0.84, 2.37]1.49+1.06 [-0.23, 2.15]2.08 [0.98, 2.80]33% [13%, 55%]70%82%+0.16+0.242026-01-02 → 2026-08-30
tmin00Znearestall33 1 QC1.62 [0.78, 2.40]1.49+1.06 [-0.21, 2.17]2.08 [0.95, 2.85]33% [14%, 57%]70%82%+0.16+0.242026-01-02 → 2026-08-30
tmin12Zbilinear30d27 1 QC1.64 [0.88, 2.44]1.41+1.21 [0.09, 2.34]2.10 [1.05, 2.87]44% [14%, 73%]70%85%-0.00+0.142026-08-02 → 2026-08-30
tmin12Zbilinear90d27 1 QC1.64 [0.75, 2.42]1.41+1.21 [-0.05, 2.28]2.10 [0.91, 2.82]44% [17%, 80%]70%85%-0.00+0.142026-08-02 → 2026-08-30
tmin12Zbilinear365d32 1 QC1.56 [0.84, 2.28]1.43+1.01 [-0.13, 2.07]2.00 [1.05, 2.74]47% [22%, 73%]72%88%+0.20+0.272026-01-02 → 2026-08-30
tmin12Zbilinearall32 1 QC1.56 [0.83, 2.31]1.43+1.01 [-0.11, 2.04]2.00 [1.03, 2.75]47% [21%, 76%]72%88%+0.20+0.272026-01-02 → 2026-08-30
tmin12Znearest30d27 1 QC1.68 [1.02, 2.44]1.58+0.89 [-0.36, 2.15]2.09 [1.26, 2.80]37% [13%, 65%]63%89%-0.03+0.042026-08-02 → 2026-08-30
tmin12Znearest90d27 1 QC1.68 [0.87, 2.39]1.58+0.89 [-0.48, 2.09]2.09 [1.13, 2.74]37% [14%, 72%]63%89%-0.03+0.042026-08-02 → 2026-08-30
tmin12Znearest365d32 1 QC1.59 [0.92, 2.23]1.56+0.70 [-0.48, 1.87]1.98 [1.15, 2.65]41% [19%, 70%]69%91%+0.18+0.212026-01-02 → 2026-08-30
tmin12Znearestall32 1 QC1.59 [0.94, 2.28]1.56+0.70 [-0.51, 1.84]1.98 [1.16, 2.66]41% [19%, 71%]69%91%+0.18+0.212026-01-02 → 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 1, 00Z bilinear tmax+10+50-5-102026-08-02: -5.25 °F2026-08-03: -3.67 °F2026-08-04: -1.66 °F2026-08-05: -4.26 °F2026-08-06: -4.67 °F2026-08-07: -6.01 °F2026-08-08: -5.25 °F2026-08-09: -1.59 °F2026-08-10: +1.03 °F2026-08-11: -4.19 °F2026-08-12: -7.04 °F2026-08-13: -3.48 °F2026-08-14: -1.65 °F2026-08-15: -4.15 °F2026-08-16: -5.35 °F2026-08-17: -7.14 °F2026-08-18: -4.53 °F2026-08-19: -7.91 °F2026-08-20: -6.95 °F2026-08-21: -2.55 °F2026-08-22: -4.81 °F2026-08-23: -4.4 °F2026-08-24: -6.16 °F2026-08-25: -4.69 °F2026-08-26: -2.91 °F2026-08-29: -7.08 °F2026-08-30: -2.75 °F2026-08-022026-08-30°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 (29 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.75
2026-08-29-7.08
2026-08-28—
2026-08-27—
2026-08-26-2.91
2026-08-25-4.69
2026-08-24-6.16
2026-08-23-4.40
2026-08-22-4.81
2026-08-21-2.55
2026-08-20-6.95
2026-08-19-7.91
2026-08-18-4.53
2026-08-17-7.14
2026-08-16-5.35
2026-08-15-4.15
2026-08-14-1.65
2026-08-13-3.48
2026-08-12-7.04
2026-08-11-4.19
2026-08-10+1.03
2026-08-09-1.59
2026-08-08-5.25
2026-08-07-6.01
2026-08-06-4.67
2026-08-05-4.26
2026-08-04-1.66
2026-08-03-3.67
2026-08-02-5.25

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 1-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 4 days-7 to -6 °F: 4 days-6 to -5 °F: 4 days-5 to -4 °F: 8 days-4 to -3 °F: 3 days-3 to -2 °F: 4 days-2 to -1 °F: 4 days-1 to 0 °F: 0 days0 to 1 °F: 1 day1 to 2 °F: 1 day2 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| 4.4 · P90 |e| 7.02 °F-100+10 °Fn = 33 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
-8.00-7.004
-7.00-6.004
-6.00-5.004
-5.00-4.008
-4.00-3.003
-3.00-2.004
-2.00-1.004
-1.00+0.000
+0.00+1.001
+1.00+2.001
+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
2026-08274.49 -4.41
2026-0163.07 -3.05

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 32
GraphCast (IFS init)2026-01-02 → 2026-08-30 32

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 27 -0.81 [-1.47, 0.29] no
Aurora (GFS init) 1 -1.75 [-1.75, -1.75] yes
Aurora (IFS init) 2 +1.01 [0.71, 1.30] yes
FourCastNet v2 (GFS init) 1 +1.01 [1.01, 1.01] yes
FourCastNet v2 (IFS init) 2 +3.21 [2.62, 3.80] yes
NCEP GFS 27 +0.16 [-1.40, 2.05] no
GraphCast (GFS init) 1 -1.67 [-1.67, -1.67] yes
ECMWF IFS HRES 20 +2.24 [1.22, 3.32] yes
Pangu-Weather (GFS init) 1 +0.34 [0.34, 0.34] yes
Pangu-Weather (IFS init) 2 +1.85 [1.08, 2.63] yes
Persistence (baseline) 27 +1.30 [0.26, 2.40] yes

Cite this page

ShortCastCheck, KSEA graphcast_ifs lead 1, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/graphcast_ifs/lead/1/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model graphcast_ifs, lead day 1. 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/1/

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