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 1

KSEA · gfs · 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, 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
tmax00Zbilinear30d29 1 QC4.28 [3.14, 5.59]2.88+3.22 [1.31, 5.02]4.93 [3.57, 6.25]7% [0%, 14%]17%31%-0.38+0.072026-08-02 → 2026-08-30
tmax00Zbilinear90d29 1 QC4.28 [2.94, 5.54]2.88+3.22 [0.79, 4.87]4.93 [3.40, 6.17]7% [0%, 19%]17%31%-0.38+0.072026-08-02 → 2026-08-30
tmax00Zbilinear365d29 1 QC4.28 [2.88, 5.63]2.88+3.22 [0.72, 5.06]4.93 [3.28, 6.30]7% [0%, 20%]17%31%-0.38+0.072026-08-02 → 2026-08-30
tmax00Zbilinearall29 1 QC4.28 [2.92, 5.60]2.88+3.22 [0.77, 5.07]4.93 [3.34, 6.20]7% [0%, 19%]17%31%-0.38+0.072026-08-02 → 2026-08-30
tmax00Znearest30d29 1 QC4.22 [3.10, 5.39]3.04+3.02 [1.04, 4.86]4.88 [3.48, 6.14]3% [0%, 11%]21%34%-0.36+0.022026-08-02 → 2026-08-30
tmax00Znearest90d29 1 QC4.22 [3.01, 5.36]3.04+3.02 [0.44, 4.70]4.88 [3.43, 6.07]3% [0%, 14%]21%34%-0.36+0.022026-08-02 → 2026-08-30
tmax00Znearest365d29 1 QC4.22 [2.83, 5.47]3.04+3.02 [0.44, 4.89]4.88 [3.22, 6.20]3% [0%, 13%]21%34%-0.36+0.022026-08-02 → 2026-08-30
tmax00Znearestall29 1 QC4.22 [2.79, 5.41]3.04+3.02 [0.49, 4.90]4.88 [3.17, 6.14]3% [0%, 15%]21%34%-0.36+0.022026-08-02 → 2026-08-30
tmax12Zbilinear30d29 1 QC3.87 [2.75, 5.17]2.74+2.94 [1.03, 4.72]4.69 [3.40, 5.97]14% [3%, 30%]28%34%-0.25+0.122026-08-02 → 2026-08-30
tmax12Zbilinear90d29 1 QC3.87 [2.47, 5.11]2.74+2.94 [0.57, 4.58]4.69 [3.26, 5.93]14% [0%, 36%]28%34%-0.25+0.122026-08-02 → 2026-08-30
tmax12Zbilinear365d29 1 QC3.87 [2.49, 5.27]2.74+2.94 [0.32, 4.71]4.69 [3.27, 6.08]14% [0%, 40%]28%34%-0.25+0.122026-08-02 → 2026-08-30
tmax12Zbilinearall29 1 QC3.87 [2.49, 5.18]2.74+2.94 [0.44, 4.72]4.69 [3.25, 5.97]14% [0%, 36%]28%34%-0.25+0.122026-08-02 → 2026-08-30
tmax12Znearest30d29 1 QC3.82 [2.86, 5.03]2.86+2.60 [0.64, 4.37]4.64 [3.38, 5.86]17% [3%, 36%]28%41%-0.23+0.082026-08-02 → 2026-08-30
tmax12Znearest90d29 1 QC3.82 [2.75, 4.96]2.86+2.60 [0.04, 4.23]4.64 [3.32, 5.83]17% [4%, 40%]28%41%-0.23+0.082026-08-02 → 2026-08-30
tmax12Znearest365d29 1 QC3.82 [2.72, 5.14]2.86+2.60 [-0.03, 4.35]4.64 [3.27, 5.97]17% [3%, 43%]28%41%-0.23+0.082026-08-02 → 2026-08-30
tmax12Znearestall29 1 QC3.82 [2.69, 5.03]2.86+2.60 [-0.01, 4.42]4.64 [3.19, 5.87]17% [0%, 41%]28%41%-0.23+0.082026-08-02 → 2026-08-30
tmin00Zbilinear30d29 1 QC1.38 [0.99, 1.98]1.06-0.95 [-1.85, -0.14]1.72 [1.17, 2.38]45% [32%, 57%]79%90%+0.15+0.352026-08-02 → 2026-08-30
tmin00Zbilinear90d29 1 QC1.38 [0.95, 2.15]1.06-0.95 [-2.10, -0.15]1.72 [1.12, 2.51]45% [28%, 60%]79%90%+0.15+0.352026-08-02 → 2026-08-30
tmin00Zbilinear365d29 1 QC1.38 [0.93, 2.10]1.06-0.95 [-2.00, -0.07]1.72 [1.11, 2.49]45% [29%, 62%]79%90%+0.15+0.352026-08-02 → 2026-08-30
tmin00Zbilinearall29 1 QC1.38 [0.91, 2.30]1.06-0.95 [-2.28, -0.12]1.72 [1.09, 2.65]45% [26%, 60%]79%90%+0.15+0.352026-08-02 → 2026-08-30
tmin00Znearest30d29 1 QC1.29 [0.78, 1.71]1.21+0.63 [-0.41, 1.56]1.65 [1.06, 2.09]45% [24%, 69%]79%97%+0.21+0.262026-08-02 → 2026-08-30
tmin00Znearest90d29 1 QC1.29 [0.64, 1.76]1.21+0.63 [-0.57, 1.51]1.65 [0.88, 2.10]45% [21%, 76%]79%97%+0.21+0.262026-08-02 → 2026-08-30
tmin00Znearest365d29 1 QC1.29 [0.53, 1.79]1.21+0.63 [-0.46, 1.61]1.65 [0.70, 2.13]45% [21%, 81%]79%97%+0.21+0.262026-08-02 → 2026-08-30
tmin00Znearestall29 1 QC1.29 [0.66, 1.80]1.21+0.63 [-0.81, 1.55]1.65 [0.87, 2.15]45% [21%, 78%]79%97%+0.21+0.262026-08-02 → 2026-08-30
tmin12Zbilinear30d29 1 QC1.22 [0.81, 1.90]1.18-0.69 [-1.70, 0.10]1.65 [1.03, 2.41]55% [39%, 70%]79%90%+0.25+0.282026-08-02 → 2026-08-30
tmin12Zbilinear90d29 1 QC1.22 [0.74, 2.08]1.18-0.69 [-1.94, 0.12]1.65 [0.97, 2.56]55% [35%, 73%]79%90%+0.25+0.282026-08-02 → 2026-08-30
tmin12Zbilinear365d29 1 QC1.22 [0.71, 2.03]1.18-0.69 [-1.82, 0.20]1.65 [0.92, 2.52]55% [35%, 74%]79%90%+0.25+0.282026-08-02 → 2026-08-30
tmin12Zbilinearall29 1 QC1.22 [0.73, 2.21]1.18-0.69 [-2.12, 0.16]1.65 [0.94, 2.68]55% [32%, 73%]79%90%+0.25+0.282026-08-02 → 2026-08-30
tmin12Znearest30d29 1 QC1.45 [0.99, 1.85]1.15+0.82 [-0.21, 1.68]1.75 [1.24, 2.11]38% [17%, 59%]69%93%+0.10+0.302026-08-02 → 2026-08-30
tmin12Znearest90d29 1 QC1.45 [0.84, 1.90]1.15+0.82 [-0.43, 1.67]1.75 [1.02, 2.15]38% [14%, 70%]69%93%+0.10+0.302026-08-02 → 2026-08-30
tmin12Znearest365d29 1 QC1.45 [0.76, 1.89]1.15+0.82 [-0.31, 1.77]1.75 [0.90, 2.17]38% [14%, 71%]69%93%+0.10+0.302026-08-02 → 2026-08-30
tmin12Znearestall29 1 QC1.45 [0.85, 1.93]1.15+0.82 [-0.67, 1.78]1.75 [1.04, 2.18]38% [14%, 67%]69%93%+0.10+0.302026-08-02 → 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 NCEP GFS at KSEA, lead day 1, 00Z bilinear tmax+20+100-10-202026-08-02: -4.27 °F2026-08-03: +1.27 °F2026-08-04: +4.45 °F2026-08-05: +2.81 °F2026-08-06: +5.92 °F2026-08-07: +4.34 °F2026-08-08: +3.79 °F2026-08-09: +6.73 °F2026-08-10: +7.94 °F2026-08-11: +4.38 °F2026-08-12: -2.72 °F2026-08-13: +4.85 °F2026-08-14: +8.41 °F2026-08-15: +10.85 °F2026-08-16: +8.87 °F2026-08-17: +3.56 °F2026-08-18: +3.52 °F2026-08-19: +1.66 °F2026-08-20: +2.86 °F2026-08-21: +5.57 °F2026-08-22: +0.98 °F2026-08-23: +2.48 °F2026-08-24: -1.11 °F2026-08-25: +4.07 °F2026-08-26: +5.96 °F2026-08-27: +3.33 °F2026-08-28: -3.95 °F2026-08-29: -3.27 °F2026-08-30: +0.05 °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+0.05
2026-08-29-3.27
2026-08-28-3.95
2026-08-27+3.33
2026-08-26+5.96
2026-08-25+4.07
2026-08-24-1.11
2026-08-23+2.48
2026-08-22+0.98
2026-08-21+5.57
2026-08-20+2.86
2026-08-19+1.66
2026-08-18+3.52
2026-08-17+3.56
2026-08-16+8.87
2026-08-15+10.85
2026-08-14+8.41
2026-08-13+4.85
2026-08-12-2.72
2026-08-11+4.38
2026-08-10+7.94
2026-08-09+6.73
2026-08-08+3.79
2026-08-07+4.34
2026-08-06+5.92
2026-08-05+2.81
2026-08-04+4.45
2026-08-03+1.27
2026-08-02-4.27

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 1-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 0 days-12 to -10 °F: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 0 days-6 to -4 °F: 1 day-4 to -2 °F: 3 days-2 to 0 °F: 1 day0 to 2 °F: 4 days2 to 4 °F: 7 days4 to 6 °F: 8 days6 to 8 °F: 2 days8 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| 3.95 · P90 |e| 8.04 °F-200+20 °Fn = 29 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
-16.00-14.000
-14.00-12.000
-12.00-10.000
-10.00-8.000
-8.00-6.000
-6.00-4.001
-4.00-2.003
-2.00+0.001
+0.00+2.004
+2.00+4.007
+4.00+6.008
+6.00+8.002
+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
2026-08294.27 +3.22

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29

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 29 -1.04 [-2.85, 0.61] no
Aurora (GFS init) 1 -4.45 [-4.45, -4.45] yes
Aurora (IFS init) 2 -2.25 [-3.09, -1.41] yes
FourCastNet v2 (GFS init) 1 -1.69 [-1.69, -1.69] yes
FourCastNet v2 (IFS init) 2 -0.04 [-0.08, -0.01] yes
GraphCast (GFS init) 1 -4.38 [-4.38, -4.38] yes
GraphCast (IFS init) 27 -0.16 [-2.05, 1.40] no
ECMWF IFS HRES 22 +1.91 [0.77, 3.24] yes
Pangu-Weather (GFS init) 1 -2.37 [-2.37, -2.37] yes
Pangu-Weather (IFS init) 2 -1.40 [-1.63, -1.18] yes
Persistence (baseline) 29 +1.17 [-0.38, 2.77] no

Cite this page

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

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

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

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