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

Seattle-Tacoma · GraphCast (IFS init) · lead day 2

KSEA · graphcast_ifs · 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, 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
tmax00Zbilinear30d26 1 QC4.69 [3.56, 5.82]1.94-4.50 [-5.80, -3.26]5.17 [3.87, 6.26]4% [0%, 11%]4%23%+0.15+0.652026-08-03 → 2026-08-30
tmax00Zbilinear90d26 1 QC4.69 [3.49, 5.96]1.94-4.50 [-5.94, -3.08]5.17 [3.79, 6.32]4% [0%, 11%]4%23%+0.15+0.652026-08-03 → 2026-08-30
tmax00Zbilinear365d32 1 QC4.31 [3.08, 5.60]2.00-4.17 [-5.54, -2.89]4.87 [3.51, 6.00]9% [0%, 23%]12%31%+0.20+0.632026-01-03 → 2026-08-30
tmax00Zbilinearall32 1 QC4.31 [3.05, 5.56]2.00-4.17 [-5.54, -2.88]4.87 [3.45, 6.05]9% [0%, 23%]12%31%+0.20+0.632026-01-03 → 2026-08-30
tmax00Znearest30d26 1 QC4.77 [3.55, 5.99]1.96-4.60 [-5.98, -3.26]5.26 [3.85, 6.40]4% [0%, 11%]8%27%+0.13+0.642026-08-03 → 2026-08-30
tmax00Znearest90d26 1 QC4.77 [3.46, 6.11]1.96-4.60 [-6.09, -3.09]5.26 [3.75, 6.48]4% [0%, 11%]8%27%+0.13+0.642026-08-03 → 2026-08-30
tmax00Znearest365d32 1 QC4.45 [3.27, 5.76]1.97-4.32 [-5.68, -3.05]4.99 [3.62, 6.16]3% [0%, 9%]12%31%+0.17+0.632026-01-03 → 2026-08-30
tmax00Znearestall32 1 QC4.45 [3.24, 5.76]1.97-4.32 [-5.75, -3.07]4.99 [3.60, 6.22]3% [0%, 9%]12%31%+0.17+0.632026-01-03 → 2026-08-30
tmax12Zbilinear30d26 1 QC5.34 [4.39, 6.31]1.86-5.28 [-6.31, -4.29]5.81 [4.78, 6.72]4% [0%, 11%]8%12%+0.03+0.662026-08-03 → 2026-08-30
tmax12Zbilinear90d26 1 QC5.34 [4.35, 6.28]1.86-5.28 [-6.28, -4.24]5.81 [4.64, 6.71]4% [0%, 11%]8%12%+0.03+0.662026-08-03 → 2026-08-30
tmax12Zbilinear365d31 1 QC4.89 [3.46, 5.97]2.00-4.84 [-5.97, -3.43]5.48 [4.04, 6.45]10% [0%, 25%]13%19%+0.12+0.642026-01-03 → 2026-08-30
tmax12Zbilinearall31 1 QC4.89 [3.41, 6.01]2.00-4.84 [-5.98, -3.39]5.48 [3.98, 6.46]10% [0%, 25%]13%19%+0.12+0.642026-01-03 → 2026-08-30
tmax12Znearest30d26 1 QC5.39 [4.38, 6.39]1.87-5.34 [-6.39, -4.31]5.86 [4.76, 6.81]4% [0%, 11%]4%12%+0.02+0.662026-08-03 → 2026-08-30
tmax12Znearest90d26 1 QC5.39 [4.32, 6.37]1.87-5.34 [-6.37, -4.23]5.86 [4.58, 6.79]4% [0%, 11%]4%12%+0.02+0.662026-08-03 → 2026-08-30
tmax12Znearest365d31 1 QC4.99 [3.67, 6.08]1.92-4.95 [-6.08, -3.64]5.55 [4.14, 6.54]6% [0%, 15%]10%19%+0.10+0.652026-01-03 → 2026-08-30
tmax12Znearestall31 1 QC4.99 [3.62, 6.09]1.92-4.95 [-6.09, -3.58]5.55 [4.04, 6.55]6% [0%, 14%]10%19%+0.10+0.652026-01-03 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.90 [0.90, 2.78]1.28+1.84 [0.79, 2.76]2.39 [1.19, 3.12]38% [13%, 68%]58%73%-0.01+0.332026-08-03 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.90 [0.74, 2.78]1.28+1.84 [0.63, 2.76]2.39 [0.99, 3.10]38% [12%, 75%]58%73%-0.01+0.332026-08-03 → 2026-08-30
tmin00Zbilinear365d32 1 QC1.73 [0.74, 2.54]1.31+1.50 [0.19, 2.50]2.20 [0.95, 2.92]38% [14%, 62%]66%78%+0.24+0.432026-01-03 → 2026-08-30
tmin00Zbilinearall32 1 QC1.73 [0.79, 2.56]1.31+1.50 [0.31, 2.46]2.20 [0.97, 2.95]38% [15%, 64%]66%78%+0.24+0.432026-01-03 → 2026-08-30
tmin00Znearest30d26 1 QC1.68 [0.80, 2.51]1.41+1.41 [0.21, 2.44]2.18 [1.04, 2.88]35% [12%, 58%]65%81%+0.11+0.262026-08-03 → 2026-08-30
tmin00Znearest90d26 1 QC1.68 [0.65, 2.49]1.41+1.41 [0.00, 2.44]2.18 [0.80, 2.85]35% [11%, 64%]65%81%+0.11+0.262026-08-03 → 2026-08-30
tmin00Znearest365d32 1 QC1.53 [0.71, 2.26]1.42+1.06 [-0.31, 2.15]2.01 [0.90, 2.69]41% [17%, 68%]72%84%+0.33+0.382026-01-03 → 2026-08-30
tmin00Znearestall32 1 QC1.53 [0.71, 2.32]1.42+1.06 [-0.24, 2.12]2.01 [0.86, 2.71]41% [18%, 68%]72%84%+0.33+0.382026-01-03 → 2026-08-30
tmin12Zbilinear30d26 1 QC1.75 [0.80, 2.67]1.46+1.49 [0.27, 2.62]2.30 [1.02, 3.11]42% [13%, 74%]65%77%+0.07+0.232026-08-03 → 2026-08-30
tmin12Zbilinear90d26 1 QC1.75 [0.68, 2.67]1.46+1.49 [0.10, 2.60]2.30 [0.86, 3.08]42% [12%, 81%]65%77%+0.07+0.232026-08-03 → 2026-08-30
tmin12Zbilinear365d31 1 QC1.64 [0.75, 2.45]1.45+1.28 [0.05, 2.32]2.16 [0.93, 2.93]42% [16%, 73%]71%81%+0.25+0.352026-01-03 → 2026-08-30
tmin12Zbilinearall31 1 QC1.64 [0.74, 2.48]1.45+1.28 [0.03, 2.32]2.16 [0.94, 2.96]42% [15%, 75%]71%81%+0.25+0.352026-01-03 → 2026-08-30
tmin12Znearest30d26 1 QC1.75 [0.97, 2.54]1.60+1.11 [-0.26, 2.36]2.21 [1.15, 2.97]35% [12%, 61%]65%81%+0.07+0.162026-08-03 → 2026-08-30
tmin12Znearest90d26 1 QC1.75 [0.86, 2.52]1.60+1.11 [-0.47, 2.34]2.21 [1.01, 2.91]35% [10%, 67%]65%81%+0.07+0.162026-08-03 → 2026-08-30
tmin12Znearest365d31 1 QC1.63 [0.88, 2.33]1.55+0.90 [-0.39, 2.03]2.08 [1.02, 2.76]35% [14%, 64%]71%84%+0.26+0.302026-01-03 → 2026-08-30
tmin12Znearestall31 1 QC1.63 [0.91, 2.37]1.55+0.90 [-0.43, 2.03]2.08 [1.04, 2.81]35% [12%, 64%]71%84%+0.26+0.302026-01-03 → 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 GraphCast (IFS init) at KSEA, lead day 2, 00Z bilinear tmax+10+50-5-102026-08-03: -4.07 °F2026-08-04: -2.15 °F2026-08-05: -3.2 °F2026-08-06: -3.94 °F2026-08-07: -5.98 °F2026-08-08: -4.59 °F2026-08-09: -0.74 °F2026-08-10: +2.35 °F2026-08-11: -3.07 °F2026-08-12: -7.61 °F2026-08-13: -5.24 °F2026-08-14: -2.05 °F2026-08-15: -2.82 °F2026-08-16: -3.3 °F2026-08-17: -6.93 °F2026-08-18: -8.63 °F2026-08-19: -9.69 °F2026-08-20: -7.7 °F2026-08-21: -4.58 °F2026-08-22: -5.68 °F2026-08-23: -4.37 °F2026-08-24: -6.92 °F2026-08-25: -5.64 °F2026-08-26: -2.9 °F2026-08-27: -4.59 °F2026-08-30: -3.08 °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
2026-08-30-3.08
2026-08-29—
2026-08-28—
2026-08-27-4.59
2026-08-26-2.90
2026-08-25-5.64
2026-08-24-6.92
2026-08-23-4.37
2026-08-22-5.68
2026-08-21-4.58
2026-08-20-7.70
2026-08-19-9.69
2026-08-18-8.63
2026-08-17-6.93
2026-08-16-3.30
2026-08-15-2.82
2026-08-14-2.05
2026-08-13-5.24
2026-08-12-7.61
2026-08-11-3.07
2026-08-10+2.35
2026-08-09-0.74
2026-08-08-4.59
2026-08-07-5.98
2026-08-06-3.94
2026-08-05-3.20
2026-08-04-2.15
2026-08-03-4.07

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSEA, lead day 2-10 to -9 °F: 1 day-9 to -8 °F: 1 day-8 to -7 °F: 2 days-7 to -6 °F: 3 days-6 to -5 °F: 4 days-5 to -4 °F: 5 days-4 to -3 °F: 6 days-3 to -2 °F: 5 days-2 to -1 °F: 1 day-1 to 0 °F: 3 days0 to 1 °F: 0 days1 to 2 °F: 0 days2 to 3 °F: 1 day3 to 4 °F: 0 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 4.01 · P90 |e| 7.55 °F-100+10 °Fn = 32 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
-10.00-9.001
-9.00-8.001
-8.00-7.002
-7.00-6.003
-6.00-5.004
-5.00-4.005
-4.00-3.006
-3.00-2.005
-2.00-1.001
-1.00+0.003
+0.00+1.000
+1.00+2.000
+2.00+3.001
+3.00+4.000
+4.00+5.000
+5.00+6.000
+6.00+7.000
+7.00+8.000
+8.00+9.000
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08264.69 -4.50
2026-0162.70 -2.70

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 31
GraphCast (IFS init)2026-01-03 → 2026-08-30 31

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 26 -0.66 [-1.16, 0.17] no
Aurora (IFS init) 1 +0.70 [0.70, 0.70] yes
FourCastNet v2 (IFS init) 1 +1.55 [1.55, 1.55] yes
NCEP GFS 26 +0.23 [-1.29, 2.05] no
ECMWF IFS HRES 21 +2.18 [1.06, 3.12] yes
Pangu-Weather (IFS init) 1 +0.80 [0.80, 0.80] yes
Persistence (baseline) 26 -0.81 [-3.07, 1.06] no

Cite this page

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

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