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

Washington Reagan · GraphCast (IFS init) · lead day 9

KDCA · graphcast_ifs · lead 9

Target day = initialization date + 9 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
tmax00Zbilinear30d21 1 QC6.46 [5.11, 8.09]4.60-4.17 [-7.42, -1.25]7.47 [6.12, 8.90]5% [0%, 12%]19%19%-0.56-0.162026-08-10 → 2026-08-30
tmax00Zbilinear90d21 1 QC6.46 [4.73, 8.53]4.60-4.17 [-7.90, -0.93]7.47 [5.67, 9.20]5% [0%, 14%]19%19%-0.56-0.162026-08-10 → 2026-08-30
tmax00Zbilinear365d27 1 QC6.78 [5.53, 8.40]4.76-4.29 [-7.19, -1.39]7.69 [6.50, 8.99]4% [0%, 11%]15%15%-0.22+0.152026-01-10 → 2026-08-30
tmax00Zbilinearall27 1 QC6.78 [5.57, 8.36]4.76-4.29 [-7.48, -1.33]7.69 [6.49, 9.01]4% [0%, 11%]15%15%-0.22+0.152026-01-10 → 2026-08-30
tmax00Znearest30d21 1 QC6.42 [5.04, 8.04]4.57-4.13 [-7.33, -1.28]7.42 [6.08, 8.83]10% [0%, 17%]19%19%-0.55-0.152026-08-10 → 2026-08-30
tmax00Znearest90d21 1 QC6.42 [4.69, 8.46]4.57-4.13 [-7.80, -0.98]7.42 [5.63, 9.10]10% [0%, 15%]19%19%-0.55-0.152026-08-10 → 2026-08-30
tmax00Znearest365d27 1 QC6.64 [5.45, 8.13]4.68-4.17 [-7.01, -1.38]7.54 [6.36, 8.73]7% [0%, 14%]15%19%-0.19+0.162026-01-10 → 2026-08-30
tmax00Znearestall27 1 QC6.64 [5.46, 8.06]4.68-4.17 [-7.23, -1.28]7.54 [6.35, 8.78]7% [0%, 14%]15%19%-0.19+0.162026-01-10 → 2026-08-30
tmax12Zbilinear30d21 1 QC7.02 [5.87, 8.83]4.29-5.42 [-8.47, -2.85]7.98 [6.71, 9.98]5% [0%, 16%]5%14%-0.69-0.082026-08-10 → 2026-08-30
tmax12Zbilinear90d21 1 QC7.02 [5.67, 9.15]4.29-5.42 [-8.94, -2.69]7.98 [6.47, 10.37]5% [0%, 20%]5%14%-0.69-0.082026-08-10 → 2026-08-30
tmax12Zbilinear365d26 1 QC7.21 [6.12, 9.09]5.19-4.91 [-7.60, -1.91]8.38 [6.99, 10.47]8% [0%, 20%]12%19%-0.29+0.072026-01-10 → 2026-08-30
tmax12Zbilinearall26 1 QC7.21 [6.03, 8.98]5.19-4.91 [-7.95, -2.07]8.38 [7.01, 10.52]8% [0%, 21%]12%19%-0.29+0.072026-01-10 → 2026-08-30
tmax12Znearest30d21 1 QC6.94 [5.78, 8.82]4.28-5.35 [-8.37, -2.84]7.92 [6.63, 9.99]5% [0%, 16%]5%14%-0.67-0.082026-08-10 → 2026-08-30
tmax12Znearest90d21 1 QC6.94 [5.58, 9.15]4.28-5.35 [-8.93, -2.68]7.92 [6.39, 10.37]5% [0%, 20%]5%14%-0.67-0.082026-08-10 → 2026-08-30
tmax12Znearest365d26 1 QC7.14 [6.02, 9.09]5.20-4.77 [-7.48, -1.84]8.31 [6.95, 10.37]8% [0%, 20%]8%19%-0.28+0.072026-01-10 → 2026-08-30
tmax12Znearestall26 1 QC7.14 [5.95, 8.97]5.20-4.77 [-7.80, -1.89]8.31 [6.97, 10.38]8% [0%, 21%]8%19%-0.28+0.072026-01-10 → 2026-08-30
tmin00Zbilinear30d21 1 QC4.49 [3.61, 5.23]4.37-0.55 [-3.48, 2.45]5.22 [4.02, 6.27]5% [0%, 12%]14%29%-0.10-0.102026-08-10 → 2026-08-30
tmin00Zbilinear90d21 1 QC4.49 [3.53, 5.29]4.37-0.55 [-3.90, 3.03]5.22 [3.96, 6.32]5% [0%, 14%]14%29%-0.10-0.102026-08-10 → 2026-08-30
tmin00Zbilinear365d27 1 QC4.37 [3.42, 5.18]4.15-1.01 [-3.54, 1.89]5.29 [4.04, 6.31]7% [0%, 17%]19%33%+0.17+0.212026-01-10 → 2026-08-30
tmin00Zbilinearall27 1 QC4.37 [3.35, 5.18]4.15-1.01 [-3.67, 2.14]5.29 [3.96, 6.39]7% [0%, 17%]19%33%+0.17+0.212026-01-10 → 2026-08-30
tmin00Znearest30d21 1 QC4.29 [3.28, 5.22]4.30+0.04 [-2.85, 3.05]5.12 [3.69, 6.38]5% [0%, 12%]14%29%-0.05-0.082026-08-10 → 2026-08-30
tmin00Znearest90d21 1 QC4.29 [3.19, 5.29]4.30+0.04 [-3.27, 3.64]5.12 [3.54, 6.47]5% [0%, 14%]14%29%-0.05-0.082026-08-10 → 2026-08-30
tmin00Znearest365d27 1 QC4.18 [3.18, 5.14]4.11-0.39 [-2.88, 2.51]5.13 [3.68, 6.26]4% [0%, 11%]22%37%+0.21+0.222026-01-10 → 2026-08-30
tmin00Znearestall27 1 QC4.18 [3.08, 5.14]4.11-0.39 [-3.04, 2.75]5.13 [3.61, 6.33]4% [0%, 11%]22%37%+0.21+0.222026-01-10 → 2026-08-30
tmin12Zbilinear30d21 1 QC4.39 [3.44, 5.64]4.44-0.48 [-4.14, 2.98]5.33 [4.33, 6.34]14% [5%, 24%]24%38%-0.07-0.122026-08-10 → 2026-08-30
tmin12Zbilinear90d21 1 QC4.39 [3.43, 5.93]4.44-0.48 [-5.19, 3.73]5.33 [4.26, 6.59]14% [0%, 24%]24%38%-0.07-0.122026-08-10 → 2026-08-30
tmin12Zbilinear365d26 1 QC4.44 [3.50, 5.66]4.44-0.20 [-3.76, 3.25]5.44 [4.36, 6.59]12% [0%, 21%]23%42%+0.13+0.132026-01-10 → 2026-08-30
tmin12Zbilinearall26 1 QC4.44 [3.51, 5.82]4.44-0.20 [-3.73, 3.12]5.44 [4.35, 6.63]12% [0%, 20%]23%42%+0.13+0.132026-01-10 → 2026-08-30
tmin12Znearest30d21 1 QC4.38 [3.40, 5.45]4.36+0.12 [-3.48, 3.53]5.22 [4.16, 6.16]14% [5%, 24%]24%43%-0.07-0.102026-08-10 → 2026-08-30
tmin12Znearest90d21 1 QC4.38 [3.41, 5.65]4.36+0.12 [-4.53, 4.27]5.22 [4.12, 6.23]14% [0%, 24%]24%43%-0.07-0.102026-08-10 → 2026-08-30
tmin12Znearest365d26 1 QC4.40 [3.36, 5.54]4.37+0.44 [-3.06, 3.82]5.38 [4.11, 6.56]15% [0%, 25%]27%42%+0.14+0.152026-01-10 → 2026-08-30
tmin12Znearestall26 1 QC4.40 [3.32, 5.64]4.37+0.44 [-3.09, 3.75]5.38 [4.06, 6.56]15% [5%, 25%]27%42%+0.14+0.152026-01-10 → 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 KDCA, lead day 9, 00Z bilinear tmax+20+100-10-202026-08-10: -4.36 °F2026-08-11: -4.16 °F2026-08-12: +1.47 °F2026-08-13: -8.67 °F2026-08-14: -1.1 °F2026-08-15: -10.16 °F2026-08-16: -3.31 °F2026-08-17: -10.78 °F2026-08-18: -7.9 °F2026-08-19: -7.21 °F2026-08-20: -3.15 °F2026-08-21: +9.77 °F2026-08-22: +12.47 °F2026-08-23: -4.14 °F2026-08-24: +0.35 °F2026-08-25: -7.28 °F2026-08-26: -7.15 °F2026-08-27: -1.6 °F2026-08-28: -8.52 °F2026-08-29: -8.8 °F2026-08-30: -13.36 °F2026-08-102026-08-30°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 (21 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-13.36
2026-08-29-8.80
2026-08-28-8.52
2026-08-27-1.60
2026-08-26-7.15
2026-08-25-7.28
2026-08-24+0.35
2026-08-23-4.14
2026-08-22+12.47
2026-08-21+9.77
2026-08-20-3.15
2026-08-19-7.21
2026-08-18-7.90
2026-08-17-10.78
2026-08-16-3.31
2026-08-15-10.16
2026-08-14-1.10
2026-08-13-8.67
2026-08-12+1.47
2026-08-11-4.16
2026-08-10-4.36

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KDCA, lead day 9-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 1 day-12 to -10 °F: 4 days-10 to -8 °F: 4 days-8 to -6 °F: 4 days-6 to -4 °F: 4 days-4 to -2 °F: 3 days-2 to 0 °F: 2 days0 to 2 °F: 2 days2 to 4 °F: 0 days4 to 6 °F: 0 days6 to 8 °F: 0 days8 to 10 °F: 2 days10 to 12 °F: 0 days12 to 14 °F: 1 day14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 7.28 · P90 |e| 10.81 °F-200+20 °Fn = 27 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
-14.00-12.001
-12.00-10.004
-10.00-8.004
-8.00-6.004
-6.00-4.004
-4.00-2.003
-2.00+0.002
+0.00+2.002
+2.00+4.000
+4.00+6.000
+6.00+8.000
+8.00+10.002
+10.00+12.000
+12.00+14.001
+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
2026-08216.46 -4.17
2026-0167.89 -4.72

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-10 → 2026-08-30 27
GraphCast (IFS init)2026-01-10 → 2026-08-30 27
GraphCast (IFS init)2026-01-10 → 2026-08-30 26
GraphCast (IFS init)2026-01-10 → 2026-08-30 26

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 21 +1.91 [0.76, 3.46] yes
NCEP GFS 21 -0.81 [-2.49, 2.05] no
ECMWF IFS HRES 16 +2.53 [0.24, 5.55] yes
Persistence (baseline) 21 +2.32 [1.13, 3.96] yes

Cite this page

ShortCastCheck, KDCA graphcast_ifs lead 9, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDCA/model/graphcast_ifs/lead/9/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDCA (Washington Reagan), model graphcast_ifs, lead day 9. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KDCA/model/graphcast_ifs/lead/9/

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

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