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

Washington Reagan · GraphCast (IFS init) · lead day 6

KDCA · graphcast_ifs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC5.01 [4.07, 6.12]2.31-4.57 [-5.86, -3.60]5.46 [4.50, 6.55]4% [0%, 12%]4%25%-0.03+0.532026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC5.01 [3.99, 6.35]2.31-4.57 [-6.17, -3.57]5.46 [4.40, 6.70]4% [0%, 12%]4%25%-0.03+0.532026-08-07 → 2026-08-30
tmax00Zbilinear365d30 1 QC5.37 [4.31, 6.65]3.50-3.37 [-5.53, -0.42]6.09 [4.68, 7.55]7% [0%, 15%]7%27%+0.16+0.452026-01-07 → 2026-08-30
tmax00Zbilinearall30 1 QC5.37 [4.26, 6.80]3.50-3.37 [-5.43, -0.31]6.09 [4.72, 7.68]7% [0%, 15%]7%27%+0.16+0.452026-01-07 → 2026-08-30
tmax00Znearest30d24 1 QC4.92 [4.00, 5.98]2.31-4.46 [-5.74, -3.50]5.36 [4.43, 6.37]0% [0%, 0%]4%25%-0.01+0.532026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC4.92 [3.92, 6.21]2.31-4.46 [-6.03, -3.47]5.36 [4.36, 6.53]0% [0%, 0%]4%25%-0.01+0.532026-08-07 → 2026-08-30
tmax00Znearest365d30 1 QC5.33 [4.20, 6.65]3.53-3.18 [-5.40, -0.14]6.07 [4.61, 7.68]0% [0%, 0%]7%27%+0.16+0.452026-01-07 → 2026-08-30
tmax00Znearestall30 1 QC5.33 [4.19, 6.79]3.53-3.18 [-5.29, 0.02]6.07 [4.65, 7.80]0% [0%, 0%]7%27%+0.16+0.452026-01-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC5.00 [4.09, 6.03]2.79-4.45 [-5.75, -3.39]5.69 [4.84, 6.56]4% [0%, 12%]17%21%-0.03+0.432026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC5.00 [4.02, 6.12]2.79-4.45 [-5.98, -3.35]5.69 [4.74, 6.61]4% [0%, 13%]17%21%-0.03+0.432026-08-07 → 2026-08-30
tmax12Zbilinear365d29 1 QC5.26 [4.23, 6.41]3.84-3.15 [-5.41, 0.08]6.04 [4.94, 7.15]3% [0%, 11%]14%21%+0.20+0.412026-01-07 → 2026-08-30
tmax12Zbilinearall29 1 QC5.26 [4.27, 6.51]3.84-3.15 [-5.30, 0.43]6.04 [4.94, 7.19]3% [0%, 11%]14%21%+0.20+0.412026-01-07 → 2026-08-30
tmax12Znearest30d24 1 QC4.91 [3.98, 5.93]2.78-4.34 [-5.63, -3.27]5.60 [4.76, 6.46]4% [0%, 12%]17%21%-0.01+0.432026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC4.91 [3.90, 5.98]2.78-4.34 [-5.87, -3.20]5.60 [4.66, 6.51]4% [0%, 13%]17%21%-0.01+0.432026-08-07 → 2026-08-30
tmax12Znearest365d29 1 QC5.22 [4.13, 6.40]3.86-3.01 [-5.33, 0.28]6.01 [4.86, 7.25]3% [0%, 11%]14%21%+0.20+0.412026-01-07 → 2026-08-30
tmax12Znearestall29 1 QC5.22 [4.17, 6.48]3.86-3.01 [-5.19, 0.71]6.01 [4.86, 7.25]3% [0%, 11%]14%21%+0.20+0.412026-01-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC2.72 [2.13, 3.39]2.63+0.58 [-0.99, 2.26]3.24 [2.44, 4.05]12% [0%, 24%]42%62%+0.37+0.382026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC2.72 [2.12, 3.47]2.63+0.58 [-1.26, 2.45]3.24 [2.41, 4.09]12% [0%, 25%]42%62%+0.37+0.382026-08-07 → 2026-08-30
tmin00Zbilinear365d30 1 QC3.47 [2.28, 5.21]3.22+1.40 [-0.71, 3.83]4.36 [2.58, 6.19]10% [0%, 21%]37%53%+0.31+0.342026-01-07 → 2026-08-30
tmin00Zbilinearall30 1 QC3.47 [2.30, 5.30]3.22+1.40 [-0.65, 3.78]4.36 [2.66, 6.33]10% [0%, 21%]37%53%+0.31+0.342026-01-07 → 2026-08-30
tmin00Znearest30d24 1 QC2.83 [2.07, 3.73]2.61+1.18 [-0.38, 2.87]3.38 [2.33, 4.38]4% [0%, 12%]46%67%+0.35+0.392026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC2.83 [2.03, 3.79]2.61+1.18 [-0.62, 3.04]3.38 [2.31, 4.44]4% [0%, 12%]46%67%+0.35+0.392026-08-07 → 2026-08-30
tmin00Znearest365d30 1 QC3.62 [2.27, 5.49]3.19+2.00 [-0.11, 4.43]4.54 [2.50, 6.50]3% [0%, 10%]37%57%+0.28+0.352026-01-07 → 2026-08-30
tmin00Znearestall30 1 QC3.62 [2.22, 5.66]3.19+2.00 [-0.04, 4.40]4.54 [2.56, 6.63]3% [0%, 10%]37%57%+0.28+0.352026-01-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC3.26 [2.44, 4.02]3.24+0.31 [-1.62, 2.36]3.88 [2.67, 4.82]12% [0%, 24%]29%50%+0.25+0.242026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC3.26 [2.36, 4.12]3.24+0.31 [-1.69, 2.56]3.88 [2.55, 4.86]12% [0%, 24%]29%50%+0.25+0.242026-08-07 → 2026-08-30
tmin12Zbilinear365d29 1 QC3.65 [2.55, 4.88]3.49+1.21 [-1.21, 4.10]4.61 [2.83, 6.34]10% [0%, 21%]24%48%+0.29+0.312026-01-07 → 2026-08-30
tmin12Zbilinearall29 1 QC3.65 [2.59, 4.89]3.49+1.21 [-1.27, 4.07]4.61 [2.84, 6.28]10% [0%, 21%]24%48%+0.29+0.312026-01-07 → 2026-08-30
tmin12Znearest30d24 1 QC3.26 [2.38, 4.19]3.20+0.92 [-0.98, 2.97]3.92 [2.67, 5.07]12% [0%, 24%]33%50%+0.25+0.252026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC3.26 [2.25, 4.29]3.20+0.92 [-1.07, 3.16]3.92 [2.54, 5.10]12% [0%, 24%]33%50%+0.25+0.252026-08-07 → 2026-08-30
tmin12Znearest365d29 1 QC3.72 [2.49, 5.14]3.43+1.78 [-0.60, 4.57]4.70 [2.87, 6.56]10% [0%, 21%]28%41%+0.28+0.322026-01-07 → 2026-08-30
tmin12Znearestall29 1 QC3.72 [2.52, 5.16]3.43+1.78 [-0.64, 4.61]4.70 [2.86, 6.47]10% [0%, 21%]28%41%+0.28+0.322026-01-07 → 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 6, 00Z bilinear tmax+10+50-5-102026-08-07: -4.36 °F2026-08-08: -6.51 °F2026-08-09: -6.15 °F2026-08-10: -2.22 °F2026-08-11: -2.3 °F2026-08-12: -3.99 °F2026-08-13: -2.51 °F2026-08-14: -2.63 °F2026-08-15: -6.85 °F2026-08-16: +0.87 °F2026-08-17: -7.19 °F2026-08-18: -6.24 °F2026-08-19: -5.08 °F2026-08-20: -3.2 °F2026-08-21: -5.29 °F2026-08-22: +4.33 °F2026-08-23: -3.75 °F2026-08-24: -6.23 °F2026-08-25: -6.61 °F2026-08-26: -5.84 °F2026-08-27: -9.96 °F2026-08-28: -8.7 °F2026-08-29: -2.79 °F2026-08-30: -6.54 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.54
2026-08-29-2.79
2026-08-28-8.70
2026-08-27-9.96
2026-08-26-5.84
2026-08-25-6.61
2026-08-24-6.23
2026-08-23-3.75
2026-08-22+4.33
2026-08-21-5.29
2026-08-20-3.20
2026-08-19-5.08
2026-08-18-6.24
2026-08-17-7.19
2026-08-16+0.87
2026-08-15-6.85
2026-08-14-2.63
2026-08-13-2.51
2026-08-12-3.99
2026-08-11-2.30
2026-08-10-2.22
2026-08-09-6.15
2026-08-08-6.51
2026-08-07-4.36

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KDCA, lead day 6-20 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: 3 days-8 to -6 °F: 8 days-6 to -4 °F: 5 days-4 to -2 °F: 9 days-2 to 0 °F: 0 days0 to 2 °F: 2 days2 to 4 °F: 0 days4 to 6 °F: 1 day6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 1 day12 to 14 °F: 1 day14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 5.19 · P90 |e| 8.88 °F-200+20 °Fn = 30 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
-10.00-8.003
-8.00-6.008
-6.00-4.005
-4.00-2.009
-2.00+0.000
+0.00+2.002
+2.00+4.000
+4.00+6.001
+6.00+8.000
+8.00+10.000
+10.00+12.001
+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
2026-08245.01 -4.57
2026-0166.80 +1.43

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-07 → 2026-08-30 30
GraphCast (IFS init)2026-01-07 → 2026-08-30 30
GraphCast (IFS init)2026-01-07 → 2026-08-30 29
GraphCast (IFS init)2026-01-07 → 2026-08-30 29

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 24 +1.22 [0.18, 2.95] yes
NCEP GFS 24 +1.41 [-0.71, 3.51] no
ECMWF IFS HRES 19 +0.50 [-1.19, 2.12] no
Persistence (baseline) 24 +0.13 [-0.92, 1.17] no

Cite this page

ShortCastCheck, KDCA graphcast_ifs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDCA/model/graphcast_ifs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDCA (Washington Reagan), model graphcast_ifs, lead day 6. 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/6/

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