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

Seattle-Tacoma · GraphCast (IFS init) · lead day 7

KSEA · graphcast_ifs · lead 7

Target day = initialization date + 7 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, GRAP_v100, starting 2026-01-01 — 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
tmax00Zbilinear30d23 1 QC6.45 [4.67, 8.38]4.54-5.38 [-8.00, -2.92]7.59 [5.90, 9.12]9% [0%, 20%]17%22%-0.29+0.082026-08-08 → 2026-08-30
tmax00Zbilinear90d23 1 QC6.45 [4.58, 8.63]4.54-5.38 [-8.05, -2.65]7.59 [5.79, 9.25]9% [0%, 23%]17%22%-0.29+0.082026-08-08 → 2026-08-30
tmax00Zbilinear365d29 1 QC6.28 [4.81, 7.99]4.02-5.43 [-7.81, -3.21]7.31 [5.85, 8.75]7% [0%, 18%]14%21%-0.23+0.222026-01-08 → 2026-08-30
tmax00Zbilinearall29 1 QC6.28 [4.82, 8.14]4.02-5.43 [-7.90, -3.27]7.31 [5.84, 8.85]7% [0%, 18%]14%21%-0.23+0.222026-01-08 → 2026-08-30
tmax00Znearest30d23 1 QC6.61 [4.87, 8.57]4.60-5.55 [-8.19, -3.07]7.76 [6.06, 9.31]9% [0%, 17%]17%22%-0.32+0.072026-08-08 → 2026-08-30
tmax00Znearest90d23 1 QC6.61 [4.74, 8.77]4.60-5.55 [-8.27, -2.74]7.76 [5.94, 9.43]9% [0%, 17%]17%22%-0.32+0.072026-08-08 → 2026-08-30
tmax00Znearest365d29 1 QC6.38 [4.88, 8.12]4.09-5.54 [-7.93, -3.32]7.43 [5.97, 8.93]7% [0%, 14%]14%21%-0.25+0.202026-01-08 → 2026-08-30
tmax00Znearestall29 1 QC6.38 [4.90, 8.20]4.09-5.54 [-7.94, -3.34]7.43 [5.94, 8.98]7% [0%, 14%]14%21%-0.25+0.202026-01-08 → 2026-08-30
tmax12Zbilinear30d23 1 QC5.85 [3.62, 7.88]3.64-4.97 [-7.75, -1.48]6.84 [4.13, 8.70]4% [0%, 17%]17%17%-0.17+0.262026-08-08 → 2026-08-30
tmax12Zbilinear90d23 1 QC5.85 [3.28, 7.97]3.64-4.97 [-7.87, -0.63]6.84 [3.68, 8.84]4% [0%, 22%]17%17%-0.17+0.262026-08-08 → 2026-08-30
tmax12Zbilinear365d28 1 QC5.26 [2.92, 7.46]3.37-4.55 [-7.43, -1.30]6.33 [3.39, 8.28]7% [0%, 22%]25%25%-0.10+0.302026-01-08 → 2026-08-30
tmax12Zbilinearall28 1 QC5.26 [2.74, 7.37]3.37-4.55 [-7.22, -1.40]6.33 [3.21, 8.37]7% [0%, 22%]25%25%-0.10+0.302026-01-08 → 2026-08-30
tmax12Znearest30d23 1 QC6.02 [3.72, 8.06]3.71-5.14 [-7.98, -1.62]7.00 [4.27, 8.88]0% [0%, 0%]17%17%-0.20+0.252026-08-08 → 2026-08-30
tmax12Znearest90d23 1 QC6.02 [3.43, 8.15]3.71-5.14 [-8.07, -0.64]7.00 [3.80, 9.00]0% [0%, 0%]17%17%-0.20+0.252026-08-08 → 2026-08-30
tmax12Znearest365d28 1 QC5.39 [2.95, 7.62]3.46-4.64 [-7.59, -1.28]6.47 [3.38, 8.48]4% [0%, 14%]21%25%-0.13+0.292026-01-08 → 2026-08-30
tmax12Znearestall28 1 QC5.39 [2.75, 7.51]3.46-4.64 [-7.44, -1.33]6.47 [3.20, 8.53]4% [0%, 16%]21%25%-0.13+0.292026-01-08 → 2026-08-30
tmin00Zbilinear30d23 1 QC2.38 [1.80, 3.03]1.61+1.97 [1.12, 2.96]2.83 [2.26, 3.42]17% [0%, 33%]39%70%-0.05+0.292026-08-08 → 2026-08-30
tmin00Zbilinear90d23 1 QC2.38 [1.78, 3.21]1.61+1.97 [1.03, 3.18]2.83 [2.22, 3.62]17% [0%, 35%]39%70%-0.05+0.292026-08-08 → 2026-08-30
tmin00Zbilinear365d29 1 QC2.98 [2.00, 4.47]2.78+0.51 [-2.54, 2.68]3.85 [2.44, 5.41]21% [0%, 37%]38%62%-0.07+0.012026-01-08 → 2026-08-30
tmin00Zbilinearall29 1 QC2.98 [2.01, 4.65]2.78+0.51 [-3.19, 2.57]3.85 [2.49, 5.66]21% [0%, 38%]38%62%-0.07+0.012026-01-08 → 2026-08-30
tmin00Znearest30d23 1 QC2.18 [1.68, 2.77]1.63+1.57 [0.67, 2.63]2.62 [2.11, 3.20]30% [13%, 50%]48%70%+0.04+0.282026-08-08 → 2026-08-30
tmin00Znearest90d23 1 QC2.18 [1.66, 2.93]1.63+1.57 [0.52, 2.90]2.62 [2.09, 3.37]30% [12%, 50%]48%70%+0.04+0.282026-08-08 → 2026-08-30
tmin00Znearest365d29 1 QC2.84 [1.87, 4.42]2.79+0.14 [-2.86, 2.32]3.82 [2.29, 5.53]31% [15%, 50%]45%62%-0.02+0.012026-01-08 → 2026-08-30
tmin00Znearestall29 1 QC2.84 [1.86, 4.64]2.79+0.14 [-3.47, 2.24]3.82 [2.29, 5.84]31% [14%, 48%]45%62%-0.02+0.012026-01-08 → 2026-08-30
tmin12Zbilinear30d23 1 QC2.24 [1.64, 3.13]1.32+2.04 [1.28, 3.09]2.59 [1.92, 3.42]22% [6%, 38%]52%65%+0.01+0.422026-08-08 → 2026-08-30
tmin12Zbilinear90d23 1 QC2.24 [1.53, 3.50]1.32+2.04 [1.21, 3.50]2.59 [1.81, 3.72]22% [0%, 38%]52%65%+0.01+0.422026-08-08 → 2026-08-30
tmin12Zbilinear365d28 1 QC2.32 [1.70, 3.14]1.75+1.40 [-0.16, 2.75]2.69 [1.96, 3.49]21% [7%, 36%]46%68%+0.07+0.302026-01-08 → 2026-08-30
tmin12Zbilinearall28 1 QC2.32 [1.70, 3.14]1.75+1.40 [-0.45, 2.66]2.69 [1.98, 3.48]21% [7%, 35%]46%68%+0.07+0.302026-01-08 → 2026-08-30
tmin12Znearest30d23 1 QC1.98 [1.36, 2.76]1.33+1.69 [0.93, 2.74]2.33 [1.67, 3.07]26% [11%, 42%]57%74%+0.13+0.412026-08-08 → 2026-08-30
tmin12Znearest90d23 1 QC1.98 [1.24, 3.11]1.33+1.69 [0.86, 3.11]2.33 [1.56, 3.34]26% [9%, 43%]57%74%+0.13+0.412026-08-08 → 2026-08-30
tmin12Znearest365d28 1 QC2.06 [1.45, 2.82]1.69+1.09 [-0.38, 2.40]2.45 [1.75, 3.17]25% [11%, 38%]54%75%+0.18+0.332026-01-08 → 2026-08-30
tmin12Znearestall28 1 QC2.06 [1.43, 2.81]1.69+1.09 [-0.68, 2.32]2.45 [1.76, 3.19]25% [11%, 38%]54%75%+0.18+0.332026-01-08 → 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 GraphCast (IFS init) at KSEA, lead day 7, 00Z bilinear tmax+20+100-10-202026-08-08: -11.13 °F2026-08-09: +2.52 °F2026-08-10: +4.54 °F2026-08-11: -0.96 °F2026-08-12: -5.08 °F2026-08-13: -13.03 °F2026-08-14: -1.46 °F2026-08-15: -0.15 °F2026-08-16: +4.28 °F2026-08-17: -3.22 °F2026-08-18: -8.26 °F2026-08-19: -10.51 °F2026-08-20: -14.26 °F2026-08-21: -5.45 °F2026-08-22: -11.65 °F2026-08-23: -9 °F2026-08-24: -9.14 °F2026-08-25: -9.11 °F2026-08-26: -7.31 °F2026-08-27: +1 °F2026-08-28: -4.2 °F2026-08-29: -7.89 °F2026-08-30: -4.13 °F2026-08-082026-08-30°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 (23 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.13
2026-08-29-7.89
2026-08-28-4.20
2026-08-27+1.00
2026-08-26-7.31
2026-08-25-9.11
2026-08-24-9.14
2026-08-23-9.00
2026-08-22-11.65
2026-08-21-5.45
2026-08-20-14.26
2026-08-19-10.51
2026-08-18-8.26
2026-08-17-3.22
2026-08-16+4.28
2026-08-15-0.15
2026-08-14-1.46
2026-08-13-13.03
2026-08-12-5.08
2026-08-11-0.96
2026-08-10+4.54
2026-08-09+2.52
2026-08-08-11.13

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 7-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 1 day-12 to -10 °F: 3 days-10 to -8 °F: 6 days-8 to -6 °F: 2 days-6 to -4 °F: 6 days-4 to -2 °F: 3 days-2 to 0 °F: 3 days0 to 2 °F: 1 day2 to 4 °F: 1 day4 to 6 °F: 2 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| 5.45 · P90 |e| 11.24 °F-200+20 °Fn = 29 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
-16.00-14.001
-14.00-12.001
-12.00-10.003
-10.00-8.006
-8.00-6.002
-6.00-4.006
-4.00-2.003
-2.00+0.003
+0.00+2.001
+2.00+4.001
+4.00+6.002
+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
2026-08236.45 -5.38
2026-0165.65 -5.65

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-08 → 2026-08-30 29
GraphCast (IFS init)2026-01-08 → 2026-08-30 29
GraphCast (IFS init)2026-01-08 → 2026-08-30 28
GraphCast (IFS init)2026-01-08 → 2026-08-30 28

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 23 +0.67 [-0.47, 3.00] no
NCEP GFS 23 +1.79 [-1.57, 5.14] no
ECMWF IFS HRES 18 +2.07 [-1.02, 6.03] no
Persistence (baseline) 23 +1.45 [-1.55, 5.12] no

Cite this page

ShortCastCheck, KSEA graphcast_ifs lead 7, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/graphcast_ifs/lead/7/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model graphcast_ifs, lead day 7. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KSEA/model/graphcast_ifs/lead/7/

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