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

Washington Reagan · GraphCast (IFS init) · lead day 8

KDCA · graphcast_ifs · lead 8

Target day = initialization date + 8 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
tmax00Zbilinear30d22 1 QC6.42 [4.79, 8.56]4.44-4.67 [-8.02, -2.34]7.28 [5.63, 9.25]9% [0%, 23%]9%18%-0.53-0.082026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC6.42 [4.68, 9.51]4.44-4.67 [-9.51, -2.31]7.28 [5.37, 9.95]9% [0%, 23%]9%18%-0.53-0.082026-08-09 → 2026-08-30
tmax00Zbilinear365d28 1 QC6.13 [4.69, 8.00]4.94-4.04 [-7.10, -1.51]7.25 [5.64, 9.02]18% [0%, 38%]18%25%-0.14+0.102026-01-09 → 2026-08-30
tmax00Zbilinearall28 1 QC6.13 [4.70, 8.16]4.94-4.04 [-7.30, -1.48]7.25 [5.76, 8.97]18% [0%, 40%]18%25%-0.14+0.102026-01-09 → 2026-08-30
tmax00Znearest30d22 1 QC6.40 [4.79, 8.55]4.45-4.61 [-8.00, -2.26]7.26 [5.61, 9.18]9% [0%, 23%]14%18%-0.53-0.082026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC6.40 [4.65, 9.44]4.45-4.61 [-9.44, -2.28]7.26 [5.38, 9.88]9% [0%, 23%]14%18%-0.53-0.082026-08-09 → 2026-08-30
tmax00Znearest365d28 1 QC6.16 [4.71, 8.05]5.02-3.88 [-6.97, -1.29]7.24 [5.63, 8.98]18% [0%, 38%]21%25%-0.14+0.082026-01-09 → 2026-08-30
tmax00Znearestall28 1 QC6.16 [4.71, 8.10]5.02-3.88 [-7.18, -1.24]7.24 [5.76, 8.93]18% [0%, 40%]21%25%-0.14+0.082026-01-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC5.47 [3.85, 7.60]3.37-4.77 [-7.25, -3.22]6.45 [4.71, 8.51]5% [0%, 12%]18%32%-0.31+0.182026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC5.47 [3.70, 8.49]3.37-4.77 [-8.49, -3.09]6.45 [4.45, 9.10]5% [0%, 13%]18%32%-0.31+0.182026-08-09 → 2026-08-30
tmax12Zbilinear365d27 1 QC5.80 [4.14, 8.13]4.38-3.50 [-6.53, 0.09]6.93 [5.04, 9.06]7% [0%, 18%]19%33%-0.05+0.232026-01-09 → 2026-08-30
tmax12Zbilinearall27 1 QC5.80 [4.02, 8.25]4.38-3.50 [-6.63, 0.24]6.93 [4.88, 9.19]7% [0%, 18%]19%33%-0.05+0.232026-01-09 → 2026-08-30
tmax12Znearest30d22 1 QC5.38 [3.81, 7.52]3.34-4.65 [-7.12, -3.12]6.36 [4.49, 8.42]5% [0%, 12%]23%32%-0.29+0.182026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC5.38 [3.63, 8.38]3.34-4.65 [-8.38, -3.02]6.36 [4.37, 9.02]5% [0%, 13%]23%32%-0.29+0.182026-08-09 → 2026-08-30
tmax12Znearest365d27 1 QC5.71 [4.08, 8.06]4.37-3.33 [-6.37, 0.35]6.85 [4.85, 9.02]7% [0%, 18%]22%33%-0.03+0.232026-01-09 → 2026-08-30
tmax12Znearestall27 1 QC5.71 [3.90, 8.17]4.37-3.33 [-6.47, 0.50]6.85 [4.74, 9.15]7% [0%, 18%]22%33%-0.03+0.232026-01-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC3.57 [2.44, 4.81]3.59+0.09 [-2.23, 2.41]4.46 [2.95, 5.75]18% [5%, 33%]41%50%+0.26+0.242026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC3.57 [2.38, 4.97]3.59+0.09 [-2.51, 2.64]4.46 [2.89, 5.87]18% [5%, 38%]41%50%+0.26+0.242026-08-09 → 2026-08-30
tmin00Zbilinear365d28 1 QC3.45 [2.48, 4.53]3.46+0.06 [-1.97, 2.06]4.23 [2.92, 5.44]14% [0%, 29%]39%54%+0.38+0.382026-01-09 → 2026-08-30
tmin00Zbilinearall28 1 QC3.45 [2.50, 4.53]3.46+0.06 [-2.12, 2.24]4.23 [2.91, 5.46]14% [0%, 27%]39%54%+0.38+0.382026-01-09 → 2026-08-30
tmin00Znearest30d22 1 QC3.39 [2.22, 4.79]3.50+0.69 [-1.64, 2.97]4.40 [2.75, 5.85]18% [5%, 33%]41%55%+0.30+0.262026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC3.39 [2.11, 4.95]3.50+0.69 [-1.90, 3.18]4.40 [2.55, 5.94]18% [5%, 38%]41%55%+0.30+0.262026-08-09 → 2026-08-30
tmin00Znearest365d28 1 QC3.24 [2.17, 4.44]3.39+0.69 [-1.32, 2.61]4.20 [2.70, 5.54]14% [0%, 29%]43%57%+0.42+0.392026-01-09 → 2026-08-30
tmin00Znearestall28 1 QC3.24 [2.14, 4.49]3.39+0.69 [-1.44, 2.83]4.20 [2.63, 5.55]14% [0%, 27%]43%57%+0.42+0.392026-01-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC3.10 [2.30, 3.93]3.06+0.32 [-2.32, 2.51]3.91 [2.85, 4.87]23% [12%, 32%]36%59%+0.36+0.352026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC3.10 [2.31, 4.05]3.06+0.32 [-3.15, 2.75]3.91 [2.83, 5.02]23% [11%, 32%]36%59%+0.36+0.352026-08-09 → 2026-08-30
tmin12Zbilinear365d27 1 QC3.62 [2.46, 5.36]3.47+1.19 [-1.68, 4.06]4.61 [2.99, 6.41]19% [5%, 29%]30%56%+0.33+0.362026-01-09 → 2026-08-30
tmin12Zbilinearall27 1 QC3.62 [2.50, 5.46]3.47+1.19 [-1.74, 3.90]4.61 [3.05, 6.48]19% [0%, 29%]30%56%+0.33+0.362026-01-09 → 2026-08-30
tmin12Znearest30d22 1 QC3.19 [2.26, 4.03]3.05+0.90 [-1.70, 3.07]3.97 [2.91, 4.73]18% [0%, 33%]41%50%+0.34+0.362026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC3.19 [2.21, 4.06]3.05+0.90 [-2.54, 3.32]3.97 [2.86, 4.82]18% [0%, 33%]41%50%+0.34+0.362026-08-09 → 2026-08-30
tmin12Znearest365d27 1 QC3.75 [2.52, 5.56]3.48+1.79 [-1.02, 4.64]4.75 [3.11, 6.52]15% [0%, 29%]37%44%+0.31+0.362026-01-09 → 2026-08-30
tmin12Znearestall27 1 QC3.75 [2.46, 5.66]3.48+1.79 [-1.09, 4.52]4.75 [3.17, 6.64]15% [0%, 30%]37%44%+0.31+0.362026-01-09 → 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 8, 00Z bilinear tmax+20+100-10-202026-08-09: -5.99 °F2026-08-10: -6.87 °F2026-08-11: +3.48 °F2026-08-12: -5.63 °F2026-08-13: -2.19 °F2026-08-14: +0.49 °F2026-08-15: -7.1 °F2026-08-16: -0.54 °F2026-08-17: -10.04 °F2026-08-18: -10.03 °F2026-08-19: -6.31 °F2026-08-20: -2.04 °F2026-08-21: +6.12 °F2026-08-22: +9.08 °F2026-08-23: -3.52 °F2026-08-24: -6.39 °F2026-08-25: -7.37 °F2026-08-26: -4.15 °F2026-08-27: -10.35 °F2026-08-28: -12.96 °F2026-08-29: -8.33 °F2026-08-30: -12.18 °F2026-08-092026-08-30°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 (22 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-12.18
2026-08-29-8.33
2026-08-28-12.96
2026-08-27-10.35
2026-08-26-4.15
2026-08-25-7.37
2026-08-24-6.39
2026-08-23-3.52
2026-08-22+9.08
2026-08-21+6.12
2026-08-20-2.04
2026-08-19-6.31
2026-08-18-10.03
2026-08-17-10.04
2026-08-16-0.54
2026-08-15-7.10
2026-08-14+0.49
2026-08-13-2.19
2026-08-12-5.63
2026-08-11+3.48
2026-08-10-6.87
2026-08-09-5.99

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KDCA, lead day 8-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 2 days-12 to -10 °F: 4 days-10 to -8 °F: 2 days-8 to -6 °F: 5 days-6 to -4 °F: 3 days-4 to -2 °F: 3 days-2 to 0 °F: 3 days0 to 2 °F: 2 days2 to 4 °F: 1 day4 to 6 °F: 0 days6 to 8 °F: 1 day8 to 10 °F: 1 day10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 6.35 · P90 |e| 10.57 °F-200+20 °Fn = 28 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
-14.00-12.002
-12.00-10.004
-10.00-8.002
-8.00-6.005
-6.00-4.003
-4.00-2.003
-2.00+0.003
+0.00+2.002
+2.00+4.001
+4.00+6.000
+6.00+8.001
+8.00+10.001
+10.00+12.001
+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
2026-08226.42 -4.67
2026-0165.09 -1.72

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 27
GraphCast (IFS init)2026-01-09 → 2026-08-30 27

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 22 +1.89 [0.55, 3.56] yes
NCEP GFS 22 +0.81 [-0.36, 3.55] no
ECMWF IFS HRES 17 +4.03 [2.71, 6.35] yes
Persistence (baseline) 22 +2.23 [0.54, 4.56] yes

Cite this page

ShortCastCheck, KDCA graphcast_ifs lead 8, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDCA/model/graphcast_ifs/lead/8/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDCA (Washington Reagan), model graphcast_ifs, lead day 8. 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/8/

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