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 · ECMWF AIFS Single · lead day 5

KSEA · aifs_single · 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, aifs-single-gpid5, 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 QC5.55 [4.13, 7.11]2.74-5.16 [-6.98, -3.38]6.25 [4.71, 7.65]0% [0%, 0%]12%20%+0.06+0.522026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC5.55 [3.93, 7.24]2.74-5.16 [-7.14, -3.06]6.25 [4.51, 7.77]0% [0%, 0%]12%20%+0.06+0.522026-08-06 → 2026-08-30
tmax00Zbilinear365d25 1 QC5.55 [3.74, 7.46]2.74-5.16 [-7.44, -2.89]6.25 [4.21, 7.97]0% [0%, 0%]12%20%+0.06+0.522026-08-06 → 2026-08-30
tmax00Zbilinearall25 1 QC5.55 [3.96, 7.19]2.74-5.16 [-7.14, -3.06]6.25 [4.49, 7.76]0% [0%, 0%]12%20%+0.06+0.522026-08-06 → 2026-08-30
tmax00Znearest30d25 1 QC5.30 [3.93, 6.84]2.76-4.85 [-6.70, -3.04]6.00 [4.47, 7.39]4% [0%, 11%]8%28%+0.10+0.512026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC5.30 [3.72, 6.95]2.76-4.85 [-6.86, -2.76]6.00 [4.27, 7.52]4% [0%, 12%]8%28%+0.10+0.512026-08-06 → 2026-08-30
tmax00Znearest365d25 1 QC5.30 [3.64, 7.17]2.76-4.85 [-7.16, -2.56]6.00 [4.04, 7.72]4% [0%, 12%]8%28%+0.10+0.512026-08-06 → 2026-08-30
tmax00Znearestall25 1 QC5.30 [3.73, 6.93]2.76-4.85 [-6.85, -2.77]6.00 [4.28, 7.50]4% [0%, 12%]8%28%+0.10+0.512026-08-06 → 2026-08-30
tmax12Zbilinear30d24 1 QC4.83 [3.55, 6.15]2.09-4.73 [-6.13, -3.30]5.50 [4.04, 6.82]8% [0%, 22%]12%17%+0.14+0.622026-08-06 → 2026-08-30
tmax12Zbilinear90d24 1 QC4.83 [3.35, 6.30]2.09-4.73 [-6.26, -3.01]5.50 [3.78, 7.01]8% [0%, 25%]12%17%+0.14+0.622026-08-06 → 2026-08-30
tmax12Zbilinear365d24 1 QC4.83 [3.29, 6.52]2.09-4.73 [-6.52, -2.92]5.50 [3.71, 7.10]8% [0%, 25%]12%17%+0.14+0.622026-08-06 → 2026-08-30
tmax12Zbilinearall24 1 QC4.83 [3.30, 6.40]2.09-4.73 [-6.39, -2.89]5.50 [3.74, 6.98]8% [0%, 25%]12%17%+0.14+0.622026-08-06 → 2026-08-30
tmax12Znearest30d24 1 QC4.54 [3.28, 5.88]2.13-4.40 [-5.85, -2.97]5.23 [3.74, 6.59]8% [0%, 17%]12%25%+0.19+0.612026-08-06 → 2026-08-30
tmax12Znearest90d24 1 QC4.54 [3.10, 6.06]2.13-4.40 [-5.97, -2.69]5.23 [3.46, 6.79]8% [0%, 17%]12%25%+0.19+0.612026-08-06 → 2026-08-30
tmax12Znearest365d24 1 QC4.54 [3.03, 6.23]2.13-4.40 [-6.23, -2.62]5.23 [3.42, 6.85]8% [0%, 18%]12%25%+0.19+0.612026-08-06 → 2026-08-30
tmax12Znearestall24 1 QC4.54 [3.09, 6.11]2.13-4.40 [-6.09, -2.61]5.23 [3.48, 6.74]8% [0%, 18%]12%25%+0.19+0.612026-08-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC1.19 [0.78, 1.55]1.16+0.33 [-0.32, 0.90]1.49 [1.08, 1.82]44% [28%, 67%]80%96%+0.49+0.502026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC1.19 [0.73, 1.58]1.16+0.33 [-0.46, 1.00]1.49 [1.02, 1.85]44% [25%, 73%]80%96%+0.49+0.502026-08-06 → 2026-08-30
tmin00Zbilinear365d25 1 QC1.19 [0.75, 1.59]1.16+0.33 [-0.49, 1.01]1.49 [1.00, 1.86]44% [25%, 73%]80%96%+0.49+0.502026-08-06 → 2026-08-30
tmin00Zbilinearall25 1 QC1.19 [0.72, 1.61]1.16+0.33 [-0.52, 0.99]1.49 [1.00, 1.87]44% [24%, 73%]80%96%+0.49+0.502026-08-06 → 2026-08-30
tmin00Znearest30d25 1 QC1.28 [0.87, 1.65]1.24+0.39 [-0.28, 0.93]1.57 [1.15, 1.91]40% [27%, 60%]80%96%+0.45+0.472026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC1.28 [0.82, 1.67]1.24+0.39 [-0.41, 1.00]1.57 [1.09, 1.92]40% [25%, 65%]80%96%+0.45+0.472026-08-06 → 2026-08-30
tmin00Znearest365d25 1 QC1.28 [0.85, 1.68]1.24+0.39 [-0.46, 1.04]1.57 [1.12, 1.95]40% [24%, 64%]80%96%+0.45+0.472026-08-06 → 2026-08-30
tmin00Znearestall25 1 QC1.28 [0.81, 1.69]1.24+0.39 [-0.51, 1.07]1.57 [1.09, 1.95]40% [24%, 67%]80%96%+0.45+0.472026-08-06 → 2026-08-30
tmin12Zbilinear30d24 1 QC1.16 [0.93, 1.36]1.13-0.12 [-0.78, 0.43]1.35 [1.08, 1.57]46% [32%, 60%]88%100%+0.49+0.502026-08-06 → 2026-08-30
tmin12Zbilinear90d24 1 QC1.16 [0.87, 1.39]1.13-0.12 [-0.95, 0.52]1.35 [1.02, 1.61]46% [29%, 62%]88%100%+0.49+0.502026-08-06 → 2026-08-30
tmin12Zbilinear365d24 1 QC1.16 [0.88, 1.39]1.13-0.12 [-0.97, 0.53]1.35 [0.99, 1.59]46% [29%, 62%]88%100%+0.49+0.502026-08-06 → 2026-08-30
tmin12Zbilinearall24 1 QC1.16 [0.88, 1.40]1.13-0.12 [-1.09, 0.54]1.35 [1.00, 1.61]46% [28%, 63%]88%100%+0.49+0.502026-08-06 → 2026-08-30
tmin12Znearest30d24 1 QC1.17 [0.93, 1.38]1.17-0.07 [-0.71, 0.46]1.38 [1.09, 1.61]46% [32%, 60%]88%100%+0.48+0.482026-08-06 → 2026-08-30
tmin12Znearest90d24 1 QC1.17 [0.88, 1.41]1.17-0.07 [-0.88, 0.54]1.38 [1.04, 1.63]46% [29%, 62%]88%100%+0.48+0.482026-08-06 → 2026-08-30
tmin12Znearest365d24 1 QC1.17 [0.90, 1.41]1.17-0.07 [-0.94, 0.57]1.38 [1.02, 1.64]46% [29%, 62%]88%100%+0.48+0.482026-08-06 → 2026-08-30
tmin12Znearestall24 1 QC1.17 [0.88, 1.44]1.17-0.07 [-0.99, 0.57]1.38 [1.01, 1.66]46% [29%, 63%]88%100%+0.48+0.482026-08-06 → 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 ECMWF AIFS Single at KSEA, lead day 5, 00Z bilinear tmax+20+100-10-202026-08-06: -4.76 °F2026-08-07: -8.3 °F2026-08-08: -6.1 °F2026-08-09: +1.8 °F2026-08-10: +2.07 °F2026-08-11: -5.67 °F2026-08-12: -5.87 °F2026-08-13: -1.15 °F2026-08-14: -3.26 °F2026-08-15: -3.2 °F2026-08-16: -2.62 °F2026-08-17: -10.5 °F2026-08-18: -6.77 °F2026-08-19: -11.89 °F2026-08-20: -9.68 °F2026-08-21: -6.95 °F2026-08-22: -8.79 °F2026-08-23: -4.33 °F2026-08-24: -4.3 °F2026-08-25: -8.25 °F2026-08-26: -7.17 °F2026-08-27: -4.18 °F2026-08-28: -4.81 °F2026-08-29: -5.38 °F2026-08-30: +1 °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+1.00
2026-08-29-5.38
2026-08-28-4.81
2026-08-27-4.18
2026-08-26-7.17
2026-08-25-8.25
2026-08-24-4.30
2026-08-23-4.33
2026-08-22-8.79
2026-08-21-6.95
2026-08-20-9.68
2026-08-19-11.89
2026-08-18-6.77
2026-08-17-10.50
2026-08-16-2.62
2026-08-15-3.20
2026-08-14-3.26
2026-08-13-1.15
2026-08-12-5.87
2026-08-11-5.67
2026-08-10+2.07
2026-08-09+1.80
2026-08-08-6.10
2026-08-07-8.30
2026-08-06-4.76

Error distribution

Distribution of the signed daily error in °F for ECMWF AIFS Single 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: 2 days-10 to -8 °F: 4 days-8 to -6 °F: 4 days-6 to -4 °F: 8 days-4 to -2 °F: 3 days-2 to 0 °F: 1 day0 to 2 °F: 2 days2 to 4 °F: 1 day4 to 6 °F: 0 days6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 5.38 · P90 |e| 9.32 °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
-12.00-10.002
-10.00-8.004
-8.00-6.004
-6.00-4.008
-4.00-2.003
-2.00+0.001
+0.00+2.002
+2.00+4.001
+4.00+6.000
+6.00+8.000
+8.00+10.000
+10.00+12.000
+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
2026-08255.55 -5.16

Availability

ModelScored period DaysCoverage
ECMWF AIFS Single2026-08-06 → 2026-08-30 25
ECMWF AIFS Single2026-08-06 → 2026-08-30 25
ECMWF AIFS Single2026-08-06 → 2026-08-30 24
ECMWF AIFS Single2026-08-06 → 2026-08-30 24

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means ECMWF AIFS Single has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
NCEP GFS 25 +1.37 [-2.01, 4.76] no
GraphCast (IFS init) 25 -0.05 [-0.67, 0.64] no
ECMWF IFS HRES 18 +1.24 [0.15, 2.43] yes
Persistence (baseline) 25 -0.37 [-5.91, 2.86] no

Cite this page

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

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