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

Seattle-Tacoma · NCEP GFS · lead day 6

KSEA · gfs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC4.85 [3.03, 6.84]4.32+2.95 [-0.10, 6.30]6.20 [3.64, 8.46]12% [0%, 29%]25%33%+0.06+0.162026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC4.85 [2.75, 6.80]4.32+2.95 [-0.37, 6.41]6.20 [3.33, 8.49]12% [0%, 33%]25%33%+0.06+0.162026-08-07 → 2026-08-30
tmax00Zbilinear365d24 1 QC4.85 [2.68, 6.99]4.32+2.95 [-0.49, 6.55]6.20 [3.29, 8.66]12% [0%, 33%]25%33%+0.06+0.162026-08-07 → 2026-08-30
tmax00Zbilinearall24 1 QC4.85 [2.56, 7.07]4.32+2.95 [-0.63, 6.50]6.20 [3.14, 8.71]12% [0%, 33%]25%33%+0.06+0.162026-08-07 → 2026-08-30
tmax00Znearest30d24 1 QC4.77 [2.97, 6.63]4.35+2.65 [-0.34, 5.95]6.05 [3.68, 8.13]17% [4%, 32%]25%33%+0.08+0.162026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC4.77 [2.70, 6.62]4.35+2.65 [-0.59, 6.01]6.05 [3.40, 8.14]17% [0%, 32%]25%33%+0.08+0.162026-08-07 → 2026-08-30
tmax00Znearest365d24 1 QC4.77 [2.67, 6.81]4.35+2.65 [-0.66, 6.22]6.05 [3.31, 8.24]17% [0%, 34%]25%33%+0.08+0.162026-08-07 → 2026-08-30
tmax00Znearestall24 1 QC4.77 [2.53, 6.80]4.35+2.65 [-0.79, 6.19]6.05 [3.20, 8.34]17% [0%, 33%]25%33%+0.08+0.162026-08-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC4.54 [3.26, 5.90]4.01+2.53 [-0.21, 5.12]5.44 [3.71, 6.81]8% [0%, 21%]17%33%+0.12+0.222026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC4.54 [3.20, 6.16]4.01+2.53 [-0.34, 5.66]5.44 [3.57, 6.99]8% [0%, 22%]17%33%+0.12+0.222026-08-07 → 2026-08-30
tmax12Zbilinear365d24 1 QC4.54 [3.06, 6.20]4.01+2.53 [-1.16, 5.67]5.44 [3.30, 7.04]8% [0%, 24%]17%33%+0.12+0.222026-08-07 → 2026-08-30
tmax12Zbilinearall24 1 QC4.54 [3.07, 6.19]4.01+2.53 [-0.81, 5.68]5.44 [3.38, 7.01]8% [0%, 21%]17%33%+0.12+0.222026-08-07 → 2026-08-30
tmax12Znearest30d24 1 QC4.58 [3.54, 5.85]4.21+1.99 [-0.92, 4.80]5.42 [4.17, 6.63]12% [0%, 27%]21%29%+0.11+0.192026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC4.58 [3.54, 6.03]4.21+1.99 [-1.03, 5.28]5.42 [4.09, 6.81]12% [0%, 27%]21%29%+0.11+0.192026-08-07 → 2026-08-30
tmax12Znearest365d24 1 QC4.58 [3.43, 6.08]4.21+1.99 [-1.83, 5.31]5.42 [3.94, 6.84]12% [0%, 29%]21%29%+0.11+0.192026-08-07 → 2026-08-30
tmax12Znearestall24 1 QC4.58 [3.44, 6.02]4.21+1.99 [-1.47, 5.36]5.42 [3.99, 6.82]12% [0%, 29%]21%29%+0.11+0.192026-08-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC2.56 [2.04, 3.33]2.47-1.10 [-2.78, 0.21]3.14 [2.67, 3.79]25% [4%, 47%]42%67%-0.18-0.142026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC2.56 [1.93, 3.58]2.47-1.10 [-3.24, 0.32]3.14 [2.58, 3.95]25% [0%, 50%]42%67%-0.18-0.142026-08-07 → 2026-08-30
tmin00Zbilinear365d24 1 QC2.56 [1.92, 3.57]2.47-1.10 [-3.19, 0.41]3.14 [2.54, 3.89]25% [0%, 50%]42%67%-0.18-0.142026-08-07 → 2026-08-30
tmin00Zbilinearall24 1 QC2.56 [1.91, 3.81]2.47-1.10 [-3.57, 0.40]3.14 [2.53, 4.11]25% [0%, 50%]42%67%-0.18-0.142026-08-07 → 2026-08-30
tmin00Znearest30d24 1 QC2.51 [2.03, 3.12]2.47+0.49 [-1.24, 1.86]3.04 [2.41, 3.72]25% [13%, 37%]46%71%-0.16-0.142026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC2.51 [2.03, 3.15]2.47+0.49 [-1.79, 2.02]3.04 [2.40, 3.78]25% [12%, 40%]46%71%-0.16-0.142026-08-07 → 2026-08-30
tmin00Znearest365d24 1 QC2.51 [2.01, 3.19]2.47+0.49 [-1.74, 2.10]3.04 [2.40, 3.79]25% [13%, 38%]46%71%-0.16-0.142026-08-07 → 2026-08-30
tmin00Znearestall24 1 QC2.51 [1.99, 3.28]2.47+0.49 [-2.10, 2.09]3.04 [2.36, 3.86]25% [12%, 38%]46%71%-0.16-0.142026-08-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC1.94 [1.55, 2.48]1.68-0.92 [-2.18, 0.15]2.34 [1.82, 2.86]25% [12%, 40%]62%79%+0.11+0.232026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC1.94 [1.52, 2.58]1.68-0.92 [-2.54, 0.32]2.34 [1.73, 2.96]25% [12%, 41%]62%79%+0.11+0.232026-08-07 → 2026-08-30
tmin12Zbilinear365d24 1 QC1.94 [1.51, 2.61]1.68-0.92 [-2.61, 0.31]2.34 [1.72, 2.98]25% [10%, 43%]62%79%+0.11+0.232026-08-07 → 2026-08-30
tmin12Zbilinearall24 1 QC1.94 [1.49, 2.72]1.68-0.92 [-2.52, 0.31]2.34 [1.69, 3.05]25% [11%, 43%]62%79%+0.11+0.232026-08-07 → 2026-08-30
tmin12Znearest30d24 1 QC1.82 [1.35, 2.35]1.75+0.61 [-0.88, 1.83]2.43 [1.78, 2.93]42% [18%, 60%]58%71%+0.16+0.192026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC1.82 [1.31, 2.50]1.75+0.61 [-1.31, 2.06]2.43 [1.75, 2.95]42% [12%, 62%]58%71%+0.16+0.192026-08-07 → 2026-08-30
tmin12Znearest365d24 1 QC1.82 [1.24, 2.46]1.75+0.61 [-1.41, 2.05]2.43 [1.64, 2.93]42% [13%, 64%]58%71%+0.16+0.192026-08-07 → 2026-08-30
tmin12Znearestall24 1 QC1.82 [1.22, 2.48]1.75+0.61 [-1.33, 2.05]2.43 [1.61, 2.98]42% [14%, 62%]58%71%+0.16+0.192026-08-07 → 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 6, 00Z bilinear tmax+20+100-10-202026-08-07: -0.67 °F2026-08-08: +5.69 °F2026-08-09: +2.25 °F2026-08-10: +10.38 °F2026-08-11: +5.14 °F2026-08-12: +5.21 °F2026-08-13: +1.12 °F2026-08-14: +17.55 °F2026-08-15: +10.99 °F2026-08-16: +7.27 °F2026-08-17: +3.06 °F2026-08-18: +8.5 °F2026-08-19: -3 °F2026-08-20: -3.5 °F2026-08-21: +4.57 °F2026-08-22: -4.7 °F2026-08-23: +4.31 °F2026-08-24: +1.18 °F2026-08-25: -0.69 °F2026-08-26: -6.15 °F2026-08-27: -3.46 °F2026-08-28: +4.55 °F2026-08-29: -0.66 °F2026-08-30: +1.91 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.91
2026-08-29-0.66
2026-08-28+4.55
2026-08-27-3.46
2026-08-26-6.15
2026-08-25-0.69
2026-08-24+1.18
2026-08-23+4.31
2026-08-22-4.70
2026-08-21+4.57
2026-08-20-3.50
2026-08-19-3.00
2026-08-18+8.50
2026-08-17+3.06
2026-08-16+7.27
2026-08-15+10.99
2026-08-14+17.55
2026-08-13+1.12
2026-08-12+5.21
2026-08-11+5.14
2026-08-10+10.38
2026-08-09+2.25
2026-08-08+5.69
2026-08-07-0.67

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 6-20 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: 1 day-6 to -4 °F: 1 day-4 to -2 °F: 3 days-2 to 0 °F: 3 days0 to 2 °F: 3 days2 to 4 °F: 2 days4 to 6 °F: 6 days6 to 8 °F: 1 day8 to 10 °F: 1 day10 to 12 °F: 2 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 1 day18 to 20 °F: 0 daysdashed: P50 |e| 4.43 · P90 |e| 9.81 °F-200+20 °Fn = 24 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
-8.00-6.001
-6.00-4.001
-4.00-2.003
-2.00+0.003
+0.00+2.003
+2.00+4.002
+4.00+6.006
+6.00+8.001
+8.00+10.001
+10.00+12.002
+12.00+14.000
+14.00+16.000
+16.00+18.001
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08244.85 +2.95

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24

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 24 -0.63 [-3.65, 2.80] no
GraphCast (IFS init) 24 -1.82 [-4.89, 1.02] no
ECMWF IFS HRES 19 -0.12 [-2.41, 1.94] no
Persistence (baseline) 24 -0.31 [-4.63, 2.59] no

Cite this page

ShortCastCheck, KSEA gfs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model gfs, lead day 6. 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/6/

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