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 · NCEP GFS · lead day 7

KSEA · gfs · lead 7

Target day = initialization date + 7 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, gfs-0p25, starting 2026-08-01 — 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
tmax00Zbilinear30d23 1 QC4.66 [2.50, 6.56]4.41+1.38 [-0.92, 4.17]6.16 [3.11, 8.01]17% [10%, 29%]30%52%+0.07+0.112026-08-08 → 2026-08-30
tmax00Zbilinear90d23 1 QC4.66 [2.21, 6.63]4.41+1.38 [-0.96, 4.65]6.16 [2.64, 8.12]17% [10%, 33%]30%52%+0.07+0.112026-08-08 → 2026-08-30
tmax00Zbilinear365d23 1 QC4.66 [2.20, 6.73]4.41+1.38 [-1.27, 4.80]6.16 [2.64, 8.27]17% [10%, 30%]30%52%+0.07+0.112026-08-08 → 2026-08-30
tmax00Zbilinearall23 1 QC4.66 [2.21, 6.84]4.41+1.38 [-1.10, 4.86]6.16 [2.68, 8.29]17% [10%, 33%]30%52%+0.07+0.112026-08-08 → 2026-08-30
tmax00Znearest30d23 1 QC4.30 [2.16, 6.28]4.18+0.96 [-1.24, 3.77]5.80 [2.78, 7.63]22% [4%, 43%]43%48%+0.14+0.162026-08-08 → 2026-08-30
tmax00Znearest90d23 1 QC4.30 [1.85, 6.34]4.18+0.96 [-1.34, 4.32]5.80 [2.37, 7.72]22% [0%, 50%]43%48%+0.14+0.162026-08-08 → 2026-08-30
tmax00Znearest365d23 1 QC4.30 [1.90, 6.46]4.18+0.96 [-1.63, 4.48]5.80 [2.33, 7.86]22% [0%, 50%]43%48%+0.14+0.162026-08-08 → 2026-08-30
tmax00Znearestall23 1 QC4.30 [1.89, 6.59]4.18+0.96 [-1.47, 4.49]5.80 [2.33, 7.96]22% [0%, 50%]43%48%+0.14+0.162026-08-08 → 2026-08-30
tmax12Zbilinear30d23 1 QC3.49 [2.08, 5.58]3.36+1.77 [-0.35, 4.81]4.51 [2.75, 6.48]26% [5%, 47%]39%43%+0.30+0.322026-08-08 → 2026-08-30
tmax12Zbilinear90d23 1 QC3.49 [1.94, 6.12]3.36+1.77 [-0.44, 5.78]4.51 [2.64, 6.94]26% [0%, 50%]39%43%+0.30+0.322026-08-08 → 2026-08-30
tmax12Zbilinear365d23 1 QC3.49 [1.97, 6.12]3.36+1.77 [-0.67, 5.30]4.51 [2.64, 6.83]26% [0%, 50%]39%43%+0.30+0.322026-08-08 → 2026-08-30
tmax12Zbilinearall23 1 QC3.49 [1.94, 6.12]3.36+1.77 [-0.70, 5.56]4.51 [2.60, 6.90]26% [0%, 50%]39%43%+0.30+0.322026-08-08 → 2026-08-30
tmax12Znearest30d23 1 QC3.52 [2.32, 5.33]3.43+1.38 [-0.69, 4.41]4.43 [2.89, 6.32]17% [0%, 38%]35%43%+0.30+0.312026-08-08 → 2026-08-30
tmax12Znearest90d23 1 QC3.52 [2.19, 5.85]3.43+1.38 [-0.81, 5.39]4.43 [2.75, 6.79]17% [0%, 39%]35%43%+0.30+0.312026-08-08 → 2026-08-30
tmax12Znearest365d23 1 QC3.52 [2.24, 5.82]3.43+1.38 [-0.92, 4.92]4.43 [2.79, 6.62]17% [0%, 43%]35%43%+0.30+0.312026-08-08 → 2026-08-30
tmax12Znearestall23 1 QC3.52 [2.18, 5.82]3.43+1.38 [-1.00, 5.19]4.43 [2.74, 6.72]17% [0%, 43%]35%43%+0.30+0.312026-08-08 → 2026-08-30
tmin00Zbilinear30d23 1 QC2.83 [1.71, 4.07]2.59-0.70 [-3.08, 1.40]3.59 [2.28, 4.75]26% [4%, 56%]48%61%-0.25-0.152026-08-08 → 2026-08-30
tmin00Zbilinear90d23 1 QC2.83 [1.31, 4.44]2.59-0.70 [-3.54, 1.49]3.59 [1.70, 5.03]26% [0%, 62%]48%61%-0.25-0.152026-08-08 → 2026-08-30
tmin00Zbilinear365d23 1 QC2.83 [1.41, 4.54]2.59-0.70 [-3.64, 1.77]3.59 [1.81, 5.05]26% [0%, 67%]48%61%-0.25-0.152026-08-08 → 2026-08-30
tmin00Zbilinearall23 1 QC2.83 [1.36, 4.68]2.59-0.70 [-3.68, 1.76]3.59 [1.79, 5.23]26% [0%, 67%]48%61%-0.25-0.152026-08-08 → 2026-08-30
tmin00Znearest30d23 1 QC2.58 [1.54, 3.62]2.45+0.82 [-1.53, 2.96]3.41 [2.02, 4.41]22% [10%, 35%]52%65%-0.14-0.082026-08-08 → 2026-08-30
tmin00Znearest90d23 1 QC2.58 [1.32, 3.76]2.45+0.82 [-2.03, 3.02]3.41 [1.59, 4.51]22% [8%, 36%]52%65%-0.14-0.082026-08-08 → 2026-08-30
tmin00Znearest365d23 1 QC2.58 [1.30, 3.80]2.45+0.82 [-2.09, 3.20]3.41 [1.53, 4.53]22% [7%, 38%]52%65%-0.14-0.082026-08-08 → 2026-08-30
tmin00Znearestall23 1 QC2.58 [1.20, 3.86]2.45+0.82 [-2.26, 3.28]3.41 [1.45, 4.60]22% [8%, 37%]52%65%-0.14-0.082026-08-08 → 2026-08-30
tmin12Zbilinear30d23 1 QC2.46 [1.52, 3.31]2.21-1.22 [-2.86, 0.26]3.10 [2.05, 3.81]30% [11%, 53%]43%57%-0.09+0.032026-08-08 → 2026-08-30
tmin12Zbilinear90d23 1 QC2.46 [1.24, 3.39]2.21-1.22 [-3.27, 0.26]3.10 [1.65, 3.82]30% [9%, 56%]43%57%-0.09+0.032026-08-08 → 2026-08-30
tmin12Zbilinear365d23 1 QC2.46 [1.22, 3.42]2.21-1.22 [-3.29, 0.43]3.10 [1.69, 3.85]30% [8%, 57%]43%57%-0.09+0.032026-08-08 → 2026-08-30
tmin12Zbilinearall23 1 QC2.46 [1.22, 3.41]2.21-1.22 [-3.36, 0.43]3.10 [1.70, 3.83]30% [7%, 57%]43%57%-0.09+0.032026-08-08 → 2026-08-30
tmin12Znearest30d23 1 QC2.32 [1.59, 3.04]2.35+0.37 [-1.47, 1.94]3.00 [1.86, 3.99]22% [5%, 41%]52%87%-0.03-0.042026-08-08 → 2026-08-30
tmin12Znearest90d23 1 QC2.32 [1.56, 3.03]2.35+0.37 [-1.90, 1.98]3.00 [1.87, 4.02]22% [0%, 46%]52%87%-0.03-0.042026-08-08 → 2026-08-30
tmin12Znearest365d23 1 QC2.32 [1.59, 3.11]2.35+0.37 [-1.92, 2.12]3.00 [1.88, 4.25]22% [0%, 46%]52%87%-0.03-0.042026-08-08 → 2026-08-30
tmin12Znearestall23 1 QC2.32 [1.43, 3.08]2.35+0.37 [-2.00, 2.09]3.00 [1.67, 4.10]22% [0%, 46%]52%87%-0.03-0.042026-08-08 → 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 NCEP GFS at KSEA, lead day 7, 00Z bilinear tmax+20+100-10-202026-08-08: +0.19 °F2026-08-09: +5.61 °F2026-08-10: +8.91 °F2026-08-11: +5.82 °F2026-08-12: +7.19 °F2026-08-13: -2.76 °F2026-08-14: +11.88 °F2026-08-15: -0.95 °F2026-08-16: +8.06 °F2026-08-17: -14.35 °F2026-08-18: +2.65 °F2026-08-19: -12.67 °F2026-08-20: +2.36 °F2026-08-21: -2.03 °F2026-08-22: +5.7 °F2026-08-23: +0.68 °F2026-08-24: +1.44 °F2026-08-25: -2.69 °F2026-08-26: +3.18 °F2026-08-27: -1.37 °F2026-08-28: +1.3 °F2026-08-29: -0.84 °F2026-08-30: +4.5 °F2026-08-082026-08-30°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 (23 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+4.50
2026-08-29-0.84
2026-08-28+1.30
2026-08-27-1.37
2026-08-26+3.18
2026-08-25-2.69
2026-08-24+1.44
2026-08-23+0.68
2026-08-22+5.70
2026-08-21-2.03
2026-08-20+2.36
2026-08-19-12.67
2026-08-18+2.65
2026-08-17-14.35
2026-08-16+8.06
2026-08-15-0.95
2026-08-14+11.88
2026-08-13-2.76
2026-08-12+7.19
2026-08-11+5.82
2026-08-10+8.91
2026-08-09+5.61
2026-08-08+0.19

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 7-20 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: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 0 days-6 to -4 °F: 0 days-4 to -2 °F: 3 days-2 to 0 °F: 3 days0 to 2 °F: 4 days2 to 4 °F: 3 days4 to 6 °F: 4 days6 to 8 °F: 1 day8 to 10 °F: 2 days10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 2.76 · P90 |e| 11.29 °F-200+20 °Fn = 23 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
-12.00-10.000
-10.00-8.000
-8.00-6.000
-6.00-4.000
-4.00-2.003
-2.00+0.003
+0.00+2.004
+2.00+4.003
+4.00+6.004
+6.00+8.001
+8.00+10.002
+10.00+12.001
+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
2026-08234.66 +1.38

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 23 -1.12 [-4.66, 2.92] no
GraphCast (IFS init) 23 -1.79 [-5.14, 1.57] no
ECMWF IFS HRES 18 -0.45 [-2.55, 2.59] no
Persistence (baseline) 23 -0.34 [-4.01, 2.05] no

Cite this page

ShortCastCheck, KSEA gfs lead 7, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/7/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model gfs, lead day 7. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/7/

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