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 5

KSEA · gfs · lead 5

Target day = initialization date + 5 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
tmax00Zbilinear30d25 1 QC4.18 [2.52, 5.77]3.61+2.63 [0.59, 4.82]5.02 [3.37, 6.37]16% [0%, 37%]28%32%+0.29+0.362026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC4.18 [2.41, 5.97]3.61+2.63 [0.45, 5.05]5.02 [3.11, 6.54]16% [0%, 39%]28%32%+0.29+0.362026-08-06 → 2026-08-30
tmax00Zbilinear365d25 1 QC4.18 [2.16, 6.13]3.61+2.63 [0.19, 5.17]5.02 [2.71, 6.63]16% [0%, 43%]28%32%+0.29+0.362026-08-06 → 2026-08-30
tmax00Zbilinearall25 1 QC4.18 [2.11, 6.06]3.61+2.63 [0.06, 5.15]5.02 [2.67, 6.67]16% [0%, 43%]28%32%+0.29+0.362026-08-06 → 2026-08-30
tmax00Znearest30d25 1 QC4.07 [2.44, 5.62]3.61+2.44 [0.43, 4.55]4.92 [3.32, 6.22]12% [0%, 28%]32%40%+0.31+0.362026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC4.07 [2.40, 5.85]3.61+2.44 [0.28, 4.79]4.92 [3.24, 6.40]12% [0%, 29%]32%40%+0.31+0.362026-08-06 → 2026-08-30
tmax00Znearest365d25 1 QC4.07 [2.11, 5.96]3.61+2.44 [-0.01, 4.88]4.92 [2.76, 6.48]12% [0%, 29%]32%40%+0.31+0.362026-08-06 → 2026-08-30
tmax00Znearestall25 1 QC4.07 [2.12, 5.94]3.61+2.44 [-0.12, 4.84]4.92 [2.75, 6.46]12% [0%, 29%]32%40%+0.31+0.362026-08-06 → 2026-08-30
tmax12Zbilinear30d25 1 QC4.97 [3.50, 6.65]4.75+2.14 [-0.13, 4.37]6.06 [4.11, 7.66]12% [0%, 28%]20%32%+0.16+0.162026-08-06 → 2026-08-30
tmax12Zbilinear90d25 1 QC4.97 [3.39, 6.76]4.75+2.14 [0.00, 4.46]6.06 [3.97, 7.76]12% [0%, 31%]20%32%+0.16+0.162026-08-06 → 2026-08-30
tmax12Zbilinear365d25 1 QC4.97 [3.39, 7.02]4.75+2.14 [-0.28, 4.75]6.06 [3.87, 7.94]12% [0%, 30%]20%32%+0.16+0.162026-08-06 → 2026-08-30
tmax12Zbilinearall25 1 QC4.97 [3.40, 7.01]4.75+2.14 [-0.33, 4.65]6.06 [3.93, 7.91]12% [0%, 31%]20%32%+0.16+0.162026-08-06 → 2026-08-30
tmax12Znearest30d25 1 QC4.87 [3.42, 6.58]4.63+1.86 [-0.30, 4.08]5.90 [3.89, 7.58]12% [0%, 28%]16%40%+0.18+0.182026-08-06 → 2026-08-30
tmax12Znearest90d25 1 QC4.87 [3.33, 6.66]4.63+1.86 [-0.29, 4.08]5.90 [3.74, 7.67]12% [0%, 31%]16%40%+0.18+0.182026-08-06 → 2026-08-30
tmax12Znearest365d25 1 QC4.87 [3.29, 6.91]4.63+1.86 [-0.49, 4.35]5.90 [3.65, 7.85]12% [0%, 30%]16%40%+0.18+0.182026-08-06 → 2026-08-30
tmax12Znearestall25 1 QC4.87 [3.31, 6.91]4.63+1.86 [-0.65, 4.41]5.90 [3.68, 7.78]12% [0%, 31%]16%40%+0.18+0.182026-08-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC2.03 [1.53, 2.64]1.65-1.35 [-2.53, -0.32]2.38 [1.89, 2.88]24% [4%, 43%]48%72%+0.12+0.292026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC2.03 [1.50, 2.79]1.65-1.35 [-2.79, -0.26]2.38 [1.86, 2.95]24% [0%, 43%]48%72%+0.12+0.292026-08-06 → 2026-08-30
tmin00Zbilinear365d25 1 QC2.03 [1.47, 2.84]1.65-1.35 [-2.84, -0.17]2.38 [1.83, 2.98]24% [0%, 46%]48%72%+0.12+0.292026-08-06 → 2026-08-30
tmin00Zbilinearall25 1 QC2.03 [1.50, 2.85]1.65-1.35 [-2.85, -0.18]2.38 [1.86, 3.01]24% [0%, 43%]48%72%+0.12+0.292026-08-06 → 2026-08-30
tmin00Znearest30d25 1 QC1.81 [1.45, 2.18]1.80+0.43 [-0.87, 1.55]2.12 [1.60, 2.51]24% [12%, 33%]60%88%+0.22+0.232026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC1.81 [1.39, 2.19]1.80+0.43 [-1.12, 1.64]2.12 [1.48, 2.51]24% [11%, 33%]60%88%+0.22+0.232026-08-06 → 2026-08-30
tmin00Znearest365d25 1 QC1.81 [1.35, 2.19]1.80+0.43 [-1.18, 1.73]2.12 [1.43, 2.53]24% [11%, 33%]60%88%+0.22+0.232026-08-06 → 2026-08-30
tmin00Znearestall25 1 QC1.81 [1.36, 2.21]1.80+0.43 [-1.14, 1.71]2.12 [1.43, 2.56]24% [11%, 33%]60%88%+0.22+0.232026-08-06 → 2026-08-30
tmin12Zbilinear30d25 1 QC1.83 [1.41, 2.33]1.79-0.74 [-1.92, 0.50]2.20 [1.65, 2.71]28% [17%, 43%]60%80%+0.21+0.232026-08-06 → 2026-08-30
tmin12Zbilinear90d25 1 QC1.83 [1.38, 2.45]1.79-0.74 [-2.12, 0.57]2.20 [1.62, 2.84]28% [15%, 47%]60%80%+0.21+0.232026-08-06 → 2026-08-30
tmin12Zbilinear365d25 1 QC1.83 [1.31, 2.53]1.79-0.74 [-2.19, 0.68]2.20 [1.52, 2.88]28% [14%, 50%]60%80%+0.21+0.232026-08-06 → 2026-08-30
tmin12Zbilinearall25 1 QC1.83 [1.36, 2.49]1.79-0.74 [-2.16, 0.67]2.20 [1.56, 2.85]28% [14%, 47%]60%80%+0.21+0.232026-08-06 → 2026-08-30
tmin12Znearest30d25 1 QC2.02 [1.53, 2.54]1.82+0.95 [-0.41, 2.25]2.32 [1.75, 2.80]20% [8%, 33%]52%84%+0.13+0.222026-08-06 → 2026-08-30
tmin12Znearest90d25 1 QC2.02 [1.46, 2.57]1.82+0.95 [-0.58, 2.31]2.32 [1.71, 2.84]20% [7%, 35%]52%84%+0.13+0.222026-08-06 → 2026-08-30
tmin12Znearest365d25 1 QC2.02 [1.46, 2.63]1.82+0.95 [-0.67, 2.41]2.32 [1.67, 2.88]20% [0%, 36%]52%84%+0.13+0.222026-08-06 → 2026-08-30
tmin12Znearestall25 1 QC2.02 [1.44, 2.60]1.82+0.95 [-0.61, 2.44]2.32 [1.63, 2.86]20% [5%, 35%]52%84%+0.13+0.222026-08-06 → 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 5, 00Z bilinear tmax+20+100-10-202026-08-06: -3.65 °F2026-08-07: +5.91 °F2026-08-08: +1.48 °F2026-08-09: +6.53 °F2026-08-10: +10.88 °F2026-08-11: +5.66 °F2026-08-12: +3.27 °F2026-08-13: +3.17 °F2026-08-14: +7.59 °F2026-08-15: +7.07 °F2026-08-16: +5.79 °F2026-08-17: +4.46 °F2026-08-18: -1.45 °F2026-08-19: -0.52 °F2026-08-20: +0.7 °F2026-08-21: +0.98 °F2026-08-22: -1.23 °F2026-08-23: +2.27 °F2026-08-24: +0.39 °F2026-08-25: -3.2 °F2026-08-26: -3.77 °F2026-08-27: +4.32 °F2026-08-28: +4.69 °F2026-08-29: -5.54 °F2026-08-30: +9.98 °F2026-08-062026-08-30°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 (25 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+9.98
2026-08-29-5.54
2026-08-28+4.69
2026-08-27+4.32
2026-08-26-3.77
2026-08-25-3.20
2026-08-24+0.39
2026-08-23+2.27
2026-08-22-1.23
2026-08-21+0.98
2026-08-20+0.70
2026-08-19-0.52
2026-08-18-1.45
2026-08-17+4.46
2026-08-16+5.79
2026-08-15+7.07
2026-08-14+7.59
2026-08-13+3.17
2026-08-12+3.27
2026-08-11+5.66
2026-08-10+10.88
2026-08-09+6.53
2026-08-08+1.48
2026-08-07+5.91
2026-08-06-3.65

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 5-20 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: 3 days0 to 2 °F: 4 days2 to 4 °F: 3 days4 to 6 °F: 6 days6 to 8 °F: 3 days8 to 10 °F: 1 day10 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| 3.77 · P90 |e| 7.38 °F-200+20 °Fn = 25 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+0.003
+0.00+2.004
+2.00+4.003
+4.00+6.006
+6.00+8.003
+8.00+10.001
+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
2026-08254.18 +2.63

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25

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 25 -1.37 [-4.76, 2.01] no
GraphCast (IFS init) 25 -1.43 [-4.94, 2.02] no
ECMWF IFS HRES 18 -0.95 [-3.38, 2.37] no
Persistence (baseline) 25 -1.74 [-5.31, 0.54] no

Cite this page

ShortCastCheck, KSEA gfs lead 5, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/5/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model gfs, lead day 5. 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/5/

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