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

Denver Intl · GraphCast (IFS init) · lead day 8

KDEN · 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 QC9.47 [8.11, 10.80]4.78-9.15 [-10.65, -7.29]10.90 [9.53, 12.13]5% [0%, 12%]5%14%-0.23+0.352026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC9.47 [7.86, 10.93]4.78-9.15 [-10.81, -7.09]10.90 [9.25, 12.32]5% [0%, 12%]5%14%-0.23+0.352026-08-09 → 2026-08-30
tmax00Zbilinear365d28 1 QC9.28 [7.76, 10.45]5.09-8.76 [-10.33, -6.37]10.77 [9.10, 11.90]7% [0%, 18%]7%14%-0.12+0.312026-01-09 → 2026-08-30
tmax00Zbilinearall28 1 QC9.28 [7.74, 10.49]5.09-8.76 [-10.27, -6.42]10.77 [9.30, 11.87]7% [0%, 19%]7%14%-0.12+0.312026-01-09 → 2026-08-30
tmax00Znearest30d22 1 QC9.51 [8.09, 10.90]4.78-9.17 [-10.70, -7.25]10.94 [9.50, 12.23]0% [0%, 0%]5%14%-0.24+0.352026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC9.51 [7.88, 10.99]4.78-9.17 [-10.89, -7.04]10.94 [9.27, 12.40]0% [0%, 0%]5%14%-0.24+0.352026-08-09 → 2026-08-30
tmax00Znearest365d28 1 QC9.27 [7.65, 10.53]5.11-8.67 [-10.30, -6.11]10.75 [9.05, 11.95]0% [0%, 0%]7%14%-0.12+0.312026-01-09 → 2026-08-30
tmax00Znearestall28 1 QC9.27 [7.68, 10.49]5.11-8.67 [-10.26, -6.12]10.75 [9.18, 11.86]0% [0%, 0%]7%14%-0.12+0.312026-01-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC9.80 [7.65, 11.46]4.49-9.65 [-11.45, -7.13]11.05 [8.47, 12.69]0% [0%, 0%]5%5%-0.28+0.392026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC9.80 [7.07, 11.86]4.49-9.65 [-11.86, -6.31]11.05 [7.75, 13.01]0% [0%, 0%]5%5%-0.28+0.392026-08-09 → 2026-08-30
tmax12Zbilinear365d27 1 QC9.89 [7.48, 11.73]4.70-9.76 [-11.72, -7.08]11.25 [8.57, 12.97]0% [0%, 0%]7%7%-0.17+0.392026-01-09 → 2026-08-30
tmax12Zbilinearall27 1 QC9.89 [7.52, 11.74]4.70-9.76 [-11.73, -6.94]11.25 [8.36, 13.05]0% [0%, 0%]7%7%-0.17+0.392026-01-09 → 2026-08-30
tmax12Znearest30d22 1 QC9.76 [7.55, 11.42]4.47-9.63 [-11.42, -7.15]11.02 [8.42, 12.64]0% [0%, 0%]5%9%-0.27+0.402026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC9.76 [6.93, 11.83]4.47-9.63 [-11.83, -6.33]11.02 [7.70, 12.99]0% [0%, 0%]5%9%-0.27+0.402026-08-09 → 2026-08-30
tmax12Znearest365d27 1 QC9.80 [7.33, 11.58]4.70-9.70 [-11.57, -7.05]11.17 [8.43, 12.84]0% [0%, 0%]7%11%-0.16+0.392026-01-09 → 2026-08-30
tmax12Znearestall27 1 QC9.80 [7.43, 11.66]4.70-9.70 [-11.64, -6.95]11.17 [8.30, 12.96]0% [0%, 0%]7%11%-0.16+0.392026-01-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC3.27 [2.86, 3.79]2.98+1.08 [-0.48, 2.64]3.73 [3.32, 4.19]5% [0%, 12%]41%45%+0.43+0.482026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC3.27 [2.85, 3.84]2.98+1.08 [-0.86, 2.78]3.73 [3.27, 4.21]5% [0%, 12%]41%45%+0.43+0.482026-08-09 → 2026-08-30
tmin00Zbilinear365d28 1 QC3.54 [3.01, 4.32]3.28+1.10 [-0.62, 2.90]4.19 [3.48, 5.13]7% [0%, 15%]39%46%+0.50+0.532026-01-09 → 2026-08-30
tmin00Zbilinearall28 1 QC3.54 [2.98, 4.32]3.28+1.10 [-0.67, 2.79]4.19 [3.44, 5.27]7% [0%, 17%]39%46%+0.50+0.532026-01-09 → 2026-08-30
tmin00Znearest30d22 1 QC3.15 [2.72, 3.74]2.95+0.74 [-0.75, 2.24]3.61 [3.11, 4.15]9% [0%, 15%]41%50%+0.45+0.492026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC3.15 [2.69, 3.84]2.95+0.74 [-1.12, 2.40]3.61 [3.05, 4.25]9% [0%, 15%]41%50%+0.45+0.492026-08-09 → 2026-08-30
tmin00Znearest365d28 1 QC3.43 [2.86, 4.24]3.26+0.77 [-0.90, 2.53]4.11 [3.31, 5.05]11% [0%, 17%]36%50%+0.51+0.532026-01-09 → 2026-08-30
tmin00Znearestall28 1 QC3.43 [2.83, 4.32]3.26+0.77 [-0.92, 2.43]4.11 [3.29, 5.20]11% [0%, 18%]36%50%+0.51+0.532026-01-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC2.70 [2.21, 3.29]2.39+1.11 [-0.55, 2.39]3.05 [2.51, 3.54]18% [0%, 31%]32%59%+0.53+0.592026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC2.70 [2.19, 3.47]2.39+1.11 [-0.91, 2.52]3.05 [2.52, 3.68]18% [0%, 31%]32%59%+0.53+0.592026-08-09 → 2026-08-30
tmin12Zbilinear365d27 1 QC3.16 [2.36, 4.36]2.96+1.02 [-1.01, 2.66]3.66 [2.73, 4.84]15% [0%, 29%]30%52%+0.55+0.572026-01-09 → 2026-08-30
tmin12Zbilinearall27 1 QC3.16 [2.41, 4.52]2.96+1.02 [-1.01, 2.61]3.66 [2.76, 5.00]15% [0%, 28%]30%52%+0.55+0.572026-01-09 → 2026-08-30
tmin12Znearest30d22 1 QC2.56 [1.99, 3.28]2.37+0.84 [-0.67, 2.05]2.93 [2.31, 3.56]18% [0%, 31%]36%68%+0.56+0.592026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC2.56 [2.00, 3.55]2.37+0.84 [-0.98, 2.18]2.93 [2.26, 3.79]18% [0%, 31%]36%68%+0.56+0.592026-08-09 → 2026-08-30
tmin12Znearest365d27 1 QC3.08 [2.15, 4.42]2.97+0.75 [-1.15, 2.38]3.60 [2.50, 4.88]15% [0%, 29%]30%59%+0.56+0.572026-01-09 → 2026-08-30
tmin12Znearestall27 1 QC3.08 [2.19, 4.67]2.97+0.75 [-1.18, 2.27]3.60 [2.51, 5.05]15% [0%, 28%]30%59%+0.56+0.572026-01-09 → 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 KDEN, lead day 8, 00Z bilinear tmax+25+12.50-12.5-252026-08-09: -13.06 °F2026-08-10: -2.33 °F2026-08-11: -16.19 °F2026-08-12: -17.28 °F2026-08-13: -7.85 °F2026-08-14: -10.63 °F2026-08-15: -5.41 °F2026-08-16: -2.31 °F2026-08-17: -11.86 °F2026-08-18: -0.97 °F2026-08-19: -11.2 °F2026-08-20: -14.42 °F2026-08-21: -20.31 °F2026-08-22: -6.36 °F2026-08-23: -9.92 °F2026-08-24: -8.44 °F2026-08-25: -4.36 °F2026-08-26: -6.75 °F2026-08-27: -6.82 °F2026-08-28: -18.75 °F2026-08-29: -9.67 °F2026-08-30: +3.56 °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+3.56
2026-08-29-9.67
2026-08-28-18.75
2026-08-27-6.82
2026-08-26-6.75
2026-08-25-4.36
2026-08-24-8.44
2026-08-23-9.92
2026-08-22-6.36
2026-08-21-20.31
2026-08-20-14.42
2026-08-19-11.20
2026-08-18-0.97
2026-08-17-11.86
2026-08-16-2.31
2026-08-15-5.41
2026-08-14-10.63
2026-08-13-7.85
2026-08-12-17.28
2026-08-11-16.19
2026-08-10-2.33
2026-08-09-13.06

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KDEN, lead day 8-25 to -22.5 °F: 0 days-22.5 to -20 °F: 1 day-20 to -17.5 °F: 2 days-17.5 to -15 °F: 2 days-15 to -12.5 °F: 2 days-12.5 to -10 °F: 5 days-10 to -7.5 °F: 4 days-7.5 to -5 °F: 5 days-5 to -2.5 °F: 1 day-2.5 to 0 °F: 3 days0 to 2.5 °F: 1 day2.5 to 5 °F: 2 days5 to 7.5 °F: 0 days7.5 to 10 °F: 0 days10 to 12.5 °F: 0 days12.5 to 15 °F: 0 days15 to 17.5 °F: 0 days17.5 to 20 °F: 0 days20 to 22.5 °F: 0 days22.5 to 25 °F: 0 daysdashed: P50 |e| 9.05 · P90 |e| 17.4 °F-250+25 °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
-25.00-22.500
-22.50-20.001
-20.00-17.502
-17.50-15.002
-15.00-12.502
-12.50-10.005
-10.00-7.504
-7.50-5.005
-5.00-2.501
-2.50+0.003
+0.00+2.501
+2.50+5.002
+5.00+7.500
+7.50+10.000
+10.00+12.500
+12.50+15.000
+15.00+17.500
+17.50+20.000
+20.00+22.500
+22.50+25.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08229.47 -9.15
2026-0168.57 -7.31

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 +4.54 [2.04, 6.72] yes
NCEP GFS 22 +4.15 [2.97, 5.69] yes
ECMWF IFS HRES 17 +3.04 [-0.73, 6.17] no
Persistence (baseline) 22 +1.79 [-0.61, 4.62] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDEN (Denver Intl), 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/KDEN/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