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

Seattle-Tacoma · NCEP GFS · lead day 0

KSEA · gfs · lead 0

Target day = initialization date + 0 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
tmax00Zbilinear30d30 1 QC3.85 [2.77, 5.09]2.40+3.14 [1.43, 4.85]4.60 [3.36, 5.84]10% [3%, 17%]27%37%——2026-08-01 → 2026-08-30
tmax00Zbilinear90d30 1 QC3.85 [2.52, 4.98]2.40+3.14 [1.17, 4.69]4.60 [3.13, 5.77]10% [0%, 19%]27%37%——2026-08-01 → 2026-08-30
tmax00Zbilinear365d30 1 QC3.85 [2.43, 5.04]2.40+3.14 [1.08, 4.83]4.60 [3.02, 5.84]10% [0%, 20%]27%37%——2026-08-01 → 2026-08-30
tmax00Zbilinearall30 1 QC3.85 [2.53, 5.05]2.40+3.14 [1.08, 4.93]4.60 [3.20, 5.83]10% [0%, 19%]27%37%——2026-08-01 → 2026-08-30
tmax00Znearest30d30 1 QC3.62 [2.65, 4.79]2.52+2.90 [1.22, 4.60]4.50 [3.31, 5.75]17% [3%, 30%]30%47%——2026-08-01 → 2026-08-30
tmax00Znearest90d30 1 QC3.62 [2.39, 4.72]2.52+2.90 [0.94, 4.45]4.50 [3.06, 5.67]17% [0%, 30%]30%47%——2026-08-01 → 2026-08-30
tmax00Znearest365d30 1 QC3.62 [2.27, 4.78]2.52+2.90 [0.93, 4.54]4.50 [2.99, 5.76]17% [0%, 31%]30%47%——2026-08-01 → 2026-08-30
tmax00Znearestall30 1 QC3.62 [2.44, 4.77]2.52+2.90 [0.88, 4.70]4.50 [3.13, 5.76]17% [0%, 30%]30%47%——2026-08-01 → 2026-08-30
tmin00Zbilinear30d30 1 QC1.35 [0.89, 1.93]1.26-0.67 [-1.60, 0.21]1.75 [1.13, 2.41]53% [37%, 70%]73%90%——2026-08-01 → 2026-08-30
tmin00Zbilinear90d30 1 QC1.35 [0.83, 2.00]1.26-0.67 [-1.80, 0.18]1.75 [1.06, 2.50]53% [35%, 73%]73%90%——2026-08-01 → 2026-08-30
tmin00Zbilinear365d30 1 QC1.35 [0.79, 2.02]1.26-0.67 [-1.74, 0.27]1.75 [0.99, 2.47]53% [33%, 75%]73%90%——2026-08-01 → 2026-08-30
tmin00Zbilinearall30 1 QC1.35 [0.84, 2.14]1.26-0.67 [-1.95, 0.19]1.75 [1.05, 2.56]53% [32%, 73%]73%90%——2026-08-01 → 2026-08-30
tmin00Znearest30d30 1 QC1.59 [1.12, 2.03]1.45+0.74 [-0.32, 1.74]1.93 [1.36, 2.35]37% [17%, 60%]70%90%——2026-08-01 → 2026-08-30
tmin00Znearest90d30 1 QC1.59 [0.98, 2.03]1.45+0.74 [-0.47, 1.73]1.93 [1.16, 2.35]37% [13%, 65%]70%90%——2026-08-01 → 2026-08-30
tmin00Znearest365d30 1 QC1.59 [0.93, 2.04]1.45+0.74 [-0.37, 1.81]1.93 [1.09, 2.35]37% [14%, 70%]70%90%——2026-08-01 → 2026-08-30
tmin00Znearestall30 1 QC1.59 [0.97, 2.07]1.45+0.74 [-0.68, 1.77]1.93 [1.13, 2.37]37% [13%, 67%]70%90%——2026-08-01 → 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 0, 00Z bilinear tmax+20+100-10-202026-08-01: +2.75 °F2026-08-02: -6.71 °F2026-08-03: +1.77 °F2026-08-04: +3.71 °F2026-08-05: +2.98 °F2026-08-06: +4.74 °F2026-08-07: +4.64 °F2026-08-08: +3.6 °F2026-08-09: +4.97 °F2026-08-10: +9.16 °F2026-08-11: +3.1 °F2026-08-12: +0.87 °F2026-08-13: +3.8 °F2026-08-14: +9.02 °F2026-08-15: +10.42 °F2026-08-16: +5.44 °F2026-08-17: +3.54 °F2026-08-18: +5.22 °F2026-08-19: +3.28 °F2026-08-20: +1.19 °F2026-08-21: +4.64 °F2026-08-22: +3.6 °F2026-08-23: +0.31 °F2026-08-24: -1.07 °F2026-08-25: +3.25 °F2026-08-26: +6.31 °F2026-08-27: -1.03 °F2026-08-28: +0.38 °F2026-08-29: -1.8 °F2026-08-30: +2.17 °F2026-08-012026-08-30°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 (30 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+2.17
2026-08-29-1.80
2026-08-28+0.38
2026-08-27-1.03
2026-08-26+6.31
2026-08-25+3.25
2026-08-24-1.07
2026-08-23+0.31
2026-08-22+3.60
2026-08-21+4.64
2026-08-20+1.19
2026-08-19+3.28
2026-08-18+5.22
2026-08-17+3.54
2026-08-16+5.44
2026-08-15+10.42
2026-08-14+9.02
2026-08-13+3.80
2026-08-12+0.87
2026-08-11+3.10
2026-08-10+9.16
2026-08-09+4.97
2026-08-08+3.60
2026-08-07+4.64
2026-08-06+4.74
2026-08-05+2.98
2026-08-04+3.71
2026-08-03+1.77
2026-08-02-6.71
2026-08-01+2.75

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 0-20 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: 0 days-4 to -2 °F: 0 days-2 to 0 °F: 3 days0 to 2 °F: 5 days2 to 4 °F: 11 days4 to 6 °F: 6 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| 3.57 · P90 |e| 6.94 °F-200+20 °Fn = 30 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
-6.00-4.000
-4.00-2.000
-2.00+0.003
+0.00+2.005
+2.00+4.0011
+4.00+6.006
+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
2026-08303.85 +3.14

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-01 → 2026-08-30 30
NCEP GFS2026-08-01 → 2026-08-30 30

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 30 -1.81 [-3.56, -0.15] yes
Aurora (GFS init) 2 -3.11 [-4.85, -1.38] yes
Aurora (IFS init) 3 -1.88 [-2.94, 0.25] no
FourCastNet v2 (GFS init) 2 -1.74 [-4.59, 1.11] no
FourCastNet v2 (IFS init) 3 -0.71 [-2.07, 2.02] no
GraphCast (GFS init) 2 -4.14 [-6.26, -2.02] yes
GraphCast (IFS init) 28 -0.47 [-2.52, 1.10] no
ECMWF IFS HRES 25 +2.05 [0.45, 3.56] yes
Pangu-Weather (GFS init) 2 -1.79 [-2.16, -1.43] yes
Pangu-Weather (IFS init) 3 -0.33 [-1.10, 1.20] no

Cite this page

ShortCastCheck, KSEA gfs lead 0, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/0/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model gfs, lead day 0. 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/0/

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

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