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

Seattle-Tacoma · NCEP GFS · lead day 4

KSEA · gfs · lead 4

Target day = initialization date + 4 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
tmax00Zbilinear30d26 1 QC4.43 [3.19, 5.74]3.16+3.66 [1.38, 5.67]5.44 [3.85, 6.63]15% [3%, 28%]23%42%+0.31+0.512026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC4.43 [3.08, 5.85]3.16+3.66 [1.22, 5.80]5.44 [3.78, 6.67]15% [0%, 29%]23%42%+0.31+0.512026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC4.43 [2.96, 5.97]3.16+3.66 [0.93, 5.95]5.44 [3.68, 6.80]15% [0%, 29%]23%42%+0.31+0.512026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC4.43 [2.92, 5.89]3.16+3.66 [0.87, 5.89]5.44 [3.56, 6.75]15% [0%, 29%]23%42%+0.31+0.512026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC4.28 [3.12, 5.42]3.25+3.31 [1.00, 5.31]5.24 [3.93, 6.30]15% [4%, 27%]27%42%+0.34+0.492026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC4.28 [3.07, 5.50]3.25+3.31 [0.82, 5.46]5.24 [3.87, 6.35]15% [3%, 30%]27%42%+0.34+0.492026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC4.28 [2.87, 5.64]3.25+3.31 [0.49, 5.60]5.24 [3.61, 6.46]15% [0%, 31%]27%42%+0.34+0.492026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC4.28 [2.94, 5.54]3.25+3.31 [0.37, 5.54]5.24 [3.58, 6.42]15% [0%, 29%]27%42%+0.34+0.492026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC4.65 [3.40, 6.01]3.98+2.43 [-0.16, 4.70]5.54 [4.13, 6.71]15% [7%, 25%]23%35%+0.28+0.382026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC4.65 [3.26, 6.12]3.98+2.43 [-0.43, 4.85]5.54 [3.98, 6.74]15% [5%, 27%]23%35%+0.28+0.382026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC4.65 [3.17, 6.27]3.98+2.43 [-0.59, 4.92]5.54 [3.87, 6.84]15% [4%, 26%]23%35%+0.28+0.382026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC4.65 [3.15, 6.21]3.98+2.43 [-0.72, 4.92]5.54 [3.80, 6.83]15% [4%, 27%]23%35%+0.28+0.382026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC4.75 [3.63, 5.95]4.18+2.20 [-0.29, 4.41]5.63 [4.44, 6.69]15% [7%, 25%]23%38%+0.27+0.352026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC4.75 [3.49, 6.07]4.18+2.20 [-0.62, 4.49]5.63 [4.31, 6.73]15% [5%, 27%]23%38%+0.27+0.352026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC4.75 [3.41, 6.27]4.18+2.20 [-0.72, 4.61]5.63 [4.22, 6.89]15% [4%, 26%]23%38%+0.27+0.352026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC4.75 [3.37, 6.18]4.18+2.20 [-0.87, 4.62]5.63 [4.06, 6.86]15% [4%, 27%]23%38%+0.27+0.352026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.90 [1.45, 2.37]1.71-1.00 [-2.05, -0.16]2.38 [1.81, 2.87]35% [23%, 46%]58%77%+0.10+0.192026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.90 [1.43, 2.47]1.71-1.00 [-2.33, -0.08]2.38 [1.76, 2.96]35% [20%, 47%]58%77%+0.10+0.192026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC1.90 [1.35, 2.45]1.71-1.00 [-2.38, -0.11]2.38 [1.66, 2.95]35% [20%, 50%]58%77%+0.10+0.192026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC1.90 [1.39, 2.51]1.71-1.00 [-2.42, -0.06]2.38 [1.70, 2.98]35% [21%, 47%]58%77%+0.10+0.192026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC1.77 [1.46, 2.01]1.75+0.58 [-0.58, 1.54]2.22 [1.77, 2.50]31% [12%, 50%]65%85%+0.16+0.182026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC1.77 [1.45, 2.00]1.75+0.58 [-0.83, 1.60]2.22 [1.75, 2.52]31% [8%, 50%]65%85%+0.16+0.182026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC1.77 [1.44, 2.01]1.75+0.58 [-0.90, 1.60]2.22 [1.70, 2.51]31% [0%, 54%]65%85%+0.16+0.182026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC1.77 [1.36, 2.02]1.75+0.58 [-0.86, 1.64]2.22 [1.63, 2.52]31% [7%, 52%]65%85%+0.16+0.182026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC1.45 [1.18, 1.75]1.48-0.45 [-1.24, 0.28]1.72 [1.35, 2.04]31% [17%, 46%]77%92%+0.31+0.302026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC1.45 [1.16, 1.78]1.48-0.45 [-1.34, 0.30]1.72 [1.29, 2.08]31% [16%, 48%]77%92%+0.31+0.302026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC1.45 [1.13, 1.80]1.48-0.45 [-1.46, 0.35]1.72 [1.24, 2.09]31% [14%, 50%]77%92%+0.31+0.302026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC1.45 [1.14, 1.88]1.48-0.45 [-1.55, 0.36]1.72 [1.28, 2.15]31% [14%, 48%]77%92%+0.31+0.302026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC1.82 [1.30, 2.36]1.57+1.10 [0.12, 2.04]2.14 [1.58, 2.56]35% [17%, 52%]54%81%+0.14+0.262026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC1.82 [1.23, 2.35]1.57+1.10 [0.01, 2.07]2.14 [1.54, 2.57]35% [17%, 54%]54%81%+0.14+0.262026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC1.82 [1.24, 2.44]1.57+1.10 [-0.17, 2.18]2.14 [1.50, 2.65]35% [14%, 53%]54%81%+0.14+0.262026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC1.82 [1.21, 2.39]1.57+1.10 [-0.27, 2.13]2.14 [1.44, 2.60]35% [15%, 55%]54%81%+0.14+0.262026-08-05 → 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 4, 00Z bilinear tmax+20+100-10-202026-08-05: +1.53 °F2026-08-06: +7.56 °F2026-08-07: +2.02 °F2026-08-08: +2.79 °F2026-08-09: +7.59 °F2026-08-10: +10.81 °F2026-08-11: +5.06 °F2026-08-12: +3.5 °F2026-08-13: +3.22 °F2026-08-14: +10.03 °F2026-08-15: +7.14 °F2026-08-16: +11.07 °F2026-08-17: +4.77 °F2026-08-18: -0.25 °F2026-08-19: -0.16 °F2026-08-20: +2.73 °F2026-08-21: +1.89 °F2026-08-22: -5.87 °F2026-08-23: +2.54 °F2026-08-24: -2.49 °F2026-08-25: -0.87 °F2026-08-26: +5.82 °F2026-08-27: +3.72 °F2026-08-28: -0.44 °F2026-08-29: +7.44 °F2026-08-30: +3.92 °F2026-08-052026-08-30°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 (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+3.92
2026-08-29+7.44
2026-08-28-0.44
2026-08-27+3.72
2026-08-26+5.82
2026-08-25-0.87
2026-08-24-2.49
2026-08-23+2.54
2026-08-22-5.87
2026-08-21+1.89
2026-08-20+2.73
2026-08-19-0.16
2026-08-18-0.25
2026-08-17+4.77
2026-08-16+11.07
2026-08-15+7.14
2026-08-14+10.03
2026-08-13+3.22
2026-08-12+3.50
2026-08-11+5.06
2026-08-10+10.81
2026-08-09+7.59
2026-08-08+2.79
2026-08-07+2.02
2026-08-06+7.56
2026-08-05+1.53

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 4-20 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: 1 day-2 to 0 °F: 4 days0 to 2 °F: 2 days2 to 4 °F: 8 days4 to 6 °F: 3 days6 to 8 °F: 4 days8 to 10 °F: 0 days10 to 12 °F: 3 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.61 · P90 |e| 8.81 °F-200+20 °Fn = 26 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
-4.00-2.001
-2.00+0.004
+0.00+2.002
+2.00+4.008
+4.00+6.003
+6.00+8.004
+8.00+10.000
+10.00+12.003
+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
2026-08264.43 +3.66

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26

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 26 -0.32 [-3.18, 2.18] no
GraphCast (IFS init) 25 -0.67 [-3.08, 1.51] no
ECMWF IFS HRES 20 +1.08 [-0.56, 2.92] no
Persistence (baseline) 26 -2.03 [-5.96, 0.37] no

Cite this page

ShortCastCheck, KSEA gfs lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/4/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model gfs, lead day 4. 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/4/

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