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 2

KSEA · gfs · lead 2

Target day = initialization date + 2 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
tmax00Zbilinear30d28 1 QC4.41 [3.39, 5.38]3.62+2.86 [0.71, 5.02]5.30 [4.16, 6.27]7% [0%, 14%]29%43%+0.18+0.322026-08-03 → 2026-08-30
tmax00Zbilinear90d28 1 QC4.41 [3.21, 5.29]3.62+2.86 [0.27, 4.92]5.30 [3.99, 6.19]7% [0%, 15%]29%43%+0.18+0.322026-08-03 → 2026-08-30
tmax00Zbilinear365d28 1 QC4.41 [3.27, 5.39]3.62+2.86 [-0.04, 5.09]5.30 [3.90, 6.26]7% [0%, 15%]29%43%+0.18+0.322026-08-03 → 2026-08-30
tmax00Zbilinearall28 1 QC4.41 [3.23, 5.33]3.62+2.86 [0.28, 5.02]5.30 [3.87, 6.23]7% [0%, 15%]29%43%+0.18+0.322026-08-03 → 2026-08-30
tmax00Znearest30d28 1 QC4.28 [3.23, 5.19]3.68+2.54 [0.37, 4.74]5.21 [4.05, 6.16]18% [10%, 31%]29%39%+0.20+0.312026-08-03 → 2026-08-30
tmax00Znearest90d28 1 QC4.28 [3.07, 5.12]3.68+2.54 [-0.06, 4.62]5.21 [3.78, 6.06]18% [10%, 33%]29%39%+0.20+0.312026-08-03 → 2026-08-30
tmax00Znearest365d28 1 QC4.28 [3.10, 5.19]3.68+2.54 [-0.35, 4.81]5.21 [3.80, 6.18]18% [9%, 33%]29%39%+0.20+0.312026-08-03 → 2026-08-30
tmax00Znearestall28 1 QC4.28 [3.00, 5.18]3.68+2.54 [-0.13, 4.73]5.21 [3.62, 6.16]18% [9%, 33%]29%39%+0.20+0.312026-08-03 → 2026-08-30
tmax12Zbilinear30d28 1 QC4.48 [3.55, 5.48]3.73+2.40 [-0.44, 5.15]5.39 [4.11, 6.44]7% [0%, 13%]21%32%+0.16+0.302026-08-03 → 2026-08-30
tmax12Zbilinear90d28 1 QC4.48 [3.36, 5.38]3.73+2.40 [-0.92, 5.09]5.39 [3.65, 6.37]7% [0%, 14%]21%32%+0.16+0.302026-08-03 → 2026-08-30
tmax12Zbilinear365d28 1 QC4.48 [3.31, 5.49]3.73+2.40 [-1.23, 5.22]5.39 [3.58, 6.48]7% [0%, 14%]21%32%+0.16+0.302026-08-03 → 2026-08-30
tmax12Zbilinearall28 1 QC4.48 [3.30, 5.49]3.73+2.40 [-0.93, 5.18]5.39 [3.57, 6.45]7% [0%, 14%]21%32%+0.16+0.302026-08-03 → 2026-08-30
tmax12Znearest30d28 1 QC4.44 [3.56, 5.30]3.84+2.12 [-0.77, 4.89]5.40 [4.16, 6.40]11% [3%, 18%]21%32%+0.17+0.282026-08-03 → 2026-08-30
tmax12Znearest90d28 1 QC4.44 [3.39, 5.22]3.84+2.12 [-1.28, 4.84]5.40 [3.76, 6.29]11% [0%, 20%]21%32%+0.17+0.282026-08-03 → 2026-08-30
tmax12Znearest365d28 1 QC4.44 [3.51, 5.30]3.84+2.12 [-1.59, 4.98]5.40 [3.86, 6.41]11% [0%, 20%]21%32%+0.17+0.282026-08-03 → 2026-08-30
tmax12Znearestall28 1 QC4.44 [3.33, 5.33]3.84+2.12 [-1.20, 4.91]5.40 [3.69, 6.37]11% [0%, 22%]21%32%+0.17+0.282026-08-03 → 2026-08-30
tmin00Zbilinear30d28 1 QC1.37 [1.03, 1.77]1.20-0.70 [-1.45, -0.06]1.71 [1.32, 2.10]43% [25%, 62%]79%89%+0.29+0.382026-08-03 → 2026-08-30
tmin00Zbilinear90d28 1 QC1.37 [0.96, 1.88]1.20-0.70 [-1.67, -0.03]1.71 [1.26, 2.20]43% [21%, 67%]79%89%+0.29+0.382026-08-03 → 2026-08-30
tmin00Zbilinear365d28 1 QC1.37 [0.94, 1.87]1.20-0.70 [-1.58, 0.03]1.71 [1.21, 2.17]43% [21%, 70%]79%89%+0.29+0.382026-08-03 → 2026-08-30
tmin00Zbilinearall28 1 QC1.37 [0.92, 1.99]1.20-0.70 [-1.74, -0.01]1.71 [1.21, 2.30]43% [22%, 69%]79%89%+0.29+0.382026-08-03 → 2026-08-30
tmin00Znearest30d28 1 QC1.41 [1.13, 1.70]1.25+0.83 [0.04, 1.54]1.81 [1.39, 2.27]39% [28%, 52%]75%96%+0.27+0.362026-08-03 → 2026-08-30
tmin00Znearest90d28 1 QC1.41 [1.07, 1.70]1.25+0.83 [-0.11, 1.57]1.81 [1.35, 2.25]39% [25%, 55%]75%96%+0.27+0.362026-08-03 → 2026-08-30
tmin00Znearest365d28 1 QC1.41 [1.04, 1.73]1.25+0.83 [-0.05, 1.64]1.81 [1.33, 2.27]39% [25%, 57%]75%96%+0.27+0.362026-08-03 → 2026-08-30
tmin00Znearestall28 1 QC1.41 [1.04, 1.71]1.25+0.83 [-0.34, 1.59]1.81 [1.31, 2.28]39% [26%, 57%]75%96%+0.27+0.362026-08-03 → 2026-08-30
tmin12Zbilinear30d28 1 QC1.49 [1.16, 1.93]1.14-1.04 [-1.82, -0.29]1.82 [1.41, 2.29]46% [33%, 60%]68%93%+0.23+0.422026-08-03 → 2026-08-30
tmin12Zbilinear90d28 1 QC1.49 [1.09, 2.03]1.14-1.04 [-1.97, -0.28]1.82 [1.33, 2.36]46% [29%, 62%]68%93%+0.23+0.422026-08-03 → 2026-08-30
tmin12Zbilinear365d28 1 QC1.49 [1.09, 1.99]1.14-1.04 [-1.92, -0.18]1.82 [1.31, 2.34]46% [31%, 63%]68%93%+0.23+0.422026-08-03 → 2026-08-30
tmin12Zbilinearall28 1 QC1.49 [1.06, 2.16]1.14-1.04 [-2.10, -0.26]1.82 [1.28, 2.48]46% [29%, 64%]68%93%+0.23+0.422026-08-03 → 2026-08-30
tmin12Znearest30d28 1 QC1.28 [0.91, 1.63]1.17+0.60 [-0.33, 1.44]1.67 [1.12, 2.16]50% [36%, 67%]79%96%+0.34+0.402026-08-03 → 2026-08-30
tmin12Znearest90d28 1 QC1.28 [0.79, 1.65]1.17+0.60 [-0.49, 1.43]1.67 [1.00, 2.13]50% [33%, 69%]79%96%+0.34+0.402026-08-03 → 2026-08-30
tmin12Znearest365d28 1 QC1.28 [0.75, 1.69]1.17+0.60 [-0.41, 1.52]1.67 [0.88, 2.19]50% [31%, 71%]79%96%+0.34+0.402026-08-03 → 2026-08-30
tmin12Znearestall28 1 QC1.28 [0.76, 1.70]1.17+0.60 [-0.58, 1.50]1.67 [0.96, 2.20]50% [33%, 71%]79%96%+0.34+0.402026-08-03 → 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 2, 00Z bilinear tmax+20+100-10-202026-08-03: +1.29 °F2026-08-04: +4.93 °F2026-08-05: +2.87 °F2026-08-06: +5.48 °F2026-08-07: +5.04 °F2026-08-08: +3.5 °F2026-08-09: +6.23 °F2026-08-10: +8.67 °F2026-08-11: +3.79 °F2026-08-12: -1.06 °F2026-08-13: +2.87 °F2026-08-14: +8.5 °F2026-08-15: +10.3 °F2026-08-16: +9.21 °F2026-08-17: +5.31 °F2026-08-18: +2.49 °F2026-08-19: -1.67 °F2026-08-20: +0.5 °F2026-08-21: +5.97 °F2026-08-22: -7.91 °F2026-08-23: -1.55 °F2026-08-24: -1.73 °F2026-08-25: +9.68 °F2026-08-26: +4.12 °F2026-08-27: -0.28 °F2026-08-28: -2.37 °F2026-08-29: -5.05 °F2026-08-30: +1.03 °F2026-08-032026-08-30°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 (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.03
2026-08-29-5.05
2026-08-28-2.37
2026-08-27-0.28
2026-08-26+4.12
2026-08-25+9.68
2026-08-24-1.73
2026-08-23-1.55
2026-08-22-7.91
2026-08-21+5.97
2026-08-20+0.50
2026-08-19-1.67
2026-08-18+2.49
2026-08-17+5.31
2026-08-16+9.21
2026-08-15+10.30
2026-08-14+8.50
2026-08-13+2.87
2026-08-12-1.06
2026-08-11+3.79
2026-08-10+8.67
2026-08-09+6.23
2026-08-08+3.50
2026-08-07+5.04
2026-08-06+5.48
2026-08-05+2.87
2026-08-04+4.93
2026-08-03+1.29

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 2-20 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: 1 day-2 to 0 °F: 5 days0 to 2 °F: 3 days2 to 4 °F: 5 days4 to 6 °F: 6 days6 to 8 °F: 1 day8 to 10 °F: 4 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| 8.83 °F-200+20 °Fn = 28 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
-4.00-2.001
-2.00+0.005
+0.00+2.003
+2.00+4.005
+4.00+6.006
+6.00+8.001
+8.00+10.004
+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
2026-08284.41 +2.86

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28

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 28 -1.00 [-3.07, 0.84] no
Aurora (IFS init) 1 -1.36 [-1.36, -1.36] yes
FourCastNet v2 (IFS init) 1 -0.50 [-0.50, -0.50] yes
GraphCast (IFS init) 26 -0.23 [-2.05, 1.29] no
ECMWF IFS HRES 23 +2.11 [0.75, 3.63] yes
Pangu-Weather (IFS init) 1 -1.26 [-1.26, -1.26] yes
Persistence (baseline) 28 -0.95 [-2.69, 0.81] no

Cite this page

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

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

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