Raw model output on the native 0.25° grid — no MOS, no bias correction, no post-processing. Scores understate operational forecast quality. Read the fairness statement →

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

Denver Intl · NCEP GFS · lead day 4

KDEN · gfs · lead 4

Target day = initialization date + 4 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, gfs-0p25, starting 2026-08-01 — 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 QC4.48 [3.38, 5.52]3.86-2.88 [-4.48, -0.31]5.36 [4.22, 6.29]15% [5%, 27%]23%42%+0.42+0.502026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC4.48 [3.19, 5.60]3.86-2.88 [-4.49, 0.41]5.36 [4.01, 6.34]15% [0%, 30%]23%42%+0.42+0.502026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC4.48 [3.18, 5.68]3.86-2.88 [-4.62, 0.18]5.36 [3.98, 6.36]15% [0%, 29%]23%42%+0.42+0.502026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC4.48 [3.15, 5.71]3.86-2.88 [-4.51, 0.44]5.36 [3.95, 6.38]15% [0%, 29%]23%42%+0.42+0.502026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC4.52 [3.20, 5.79]3.85-3.05 [-4.70, -0.62]5.40 [4.12, 6.45]15% [0%, 30%]27%42%+0.41+0.502026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC4.52 [3.01, 5.93]3.85-3.05 [-4.76, -0.00]5.40 [3.88, 6.52]15% [0%, 33%]27%42%+0.41+0.502026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC4.52 [2.97, 5.99]3.85-3.05 [-4.91, -0.21]5.40 [3.87, 6.56]15% [0%, 33%]27%42%+0.41+0.502026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC4.52 [2.92, 6.00]3.85-3.05 [-4.81, -0.11]5.40 [3.77, 6.57]15% [0%, 32%]27%42%+0.41+0.502026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.55 [2.47, 4.56]2.98-2.72 [-4.29, -0.90]4.43 [3.12, 5.34]23% [13%, 33%]38%46%+0.54+0.612026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.55 [2.12, 4.60]2.98-2.72 [-4.43, -0.36]4.43 [2.55, 5.39]23% [12%, 35%]38%46%+0.54+0.612026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC3.55 [2.11, 4.69]2.98-2.72 [-4.56, -0.49]4.43 [2.47, 5.47]23% [11%, 36%]38%46%+0.54+0.612026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC3.55 [2.11, 4.65]2.98-2.72 [-4.39, -0.38]4.43 [2.50, 5.41]23% [12%, 36%]38%46%+0.54+0.612026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC3.35 [2.27, 4.34]2.78-2.73 [-4.07, -1.11]4.30 [3.01, 5.20]31% [17%, 44%]38%50%+0.56+0.642026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC3.35 [2.02, 4.41]2.78-2.73 [-4.17, -0.65]4.30 [2.57, 5.22]31% [15%, 45%]38%50%+0.56+0.642026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC3.35 [1.96, 4.46]2.78-2.73 [-4.33, -0.66]4.30 [2.43, 5.28]31% [12%, 46%]38%50%+0.56+0.642026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC3.35 [2.02, 4.44]2.78-2.73 [-4.23, -0.60]4.30 [2.50, 5.27]31% [14%, 46%]38%50%+0.56+0.642026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC5.25 [3.87, 6.77]3.13+4.75 [3.14, 6.60]6.18 [4.71, 7.78]4% [0%, 11%]15%35%+0.11+0.472026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC5.25 [3.84, 6.91]3.13+4.75 [3.11, 6.84]6.18 [4.72, 7.93]4% [0%, 11%]15%35%+0.11+0.472026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC5.25 [3.67, 6.91]3.13+4.75 [2.93, 6.73]6.18 [4.46, 7.90]4% [0%, 12%]15%35%+0.11+0.472026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC5.25 [3.81, 7.10]3.13+4.75 [3.03, 7.08]6.18 [4.62, 8.19]4% [0%, 12%]15%35%+0.11+0.472026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC5.51 [4.00, 7.26]3.05+5.22 [3.65, 7.09]6.50 [4.90, 8.38]4% [0%, 11%]19%31%+0.06+0.482026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC5.51 [3.99, 7.38]3.05+5.22 [3.66, 7.32]6.50 [4.91, 8.66]4% [0%, 11%]19%31%+0.06+0.482026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC5.51 [3.79, 7.42]3.05+5.22 [3.50, 7.18]6.50 [4.63, 8.51]4% [0%, 12%]19%31%+0.06+0.482026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC5.51 [3.95, 7.75]3.05+5.22 [3.55, 7.68]6.50 [4.81, 8.82]4% [0%, 12%]19%31%+0.06+0.482026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC4.88 [3.62, 6.14]2.89+4.72 [3.26, 6.10]5.90 [4.49, 7.13]8% [0%, 14%]31%38%+0.17+0.512026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC4.88 [3.60, 6.22]2.89+4.72 [3.21, 6.19]5.90 [4.47, 7.24]8% [0%, 14%]31%38%+0.17+0.512026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC4.88 [3.38, 6.29]2.89+4.72 [2.99, 6.27]5.90 [4.26, 7.28]8% [0%, 14%]31%38%+0.17+0.512026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC4.88 [3.49, 6.30]2.89+4.72 [3.03, 6.28]5.90 [4.34, 7.28]8% [0%, 14%]31%38%+0.17+0.512026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC5.20 [4.01, 6.36]2.77+5.12 [3.85, 6.36]6.19 [4.75, 7.49]4% [0%, 11%]19%35%+0.12+0.532026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC5.20 [3.95, 6.54]2.77+5.12 [3.73, 6.53]6.19 [4.72, 7.67]4% [0%, 11%]19%35%+0.12+0.532026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC5.20 [3.71, 6.63]2.77+5.12 [3.51, 6.63]6.19 [4.43, 7.92]4% [0%, 12%]19%35%+0.12+0.532026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC5.20 [3.80, 6.57]2.77+5.12 [3.62, 6.57]6.19 [4.49, 7.90]4% [0%, 12%]19%35%+0.12+0.532026-08-05 → 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 NCEP GFS at KDEN, lead day 4, 00Z bilinear tmax+20+100-10-202026-08-05: +6.45 °F2026-08-06: -0.19 °F2026-08-07: +2.82 °F2026-08-08: +0.51 °F2026-08-09: +2.54 °F2026-08-10: -6.25 °F2026-08-11: -2.37 °F2026-08-12: -7.23 °F2026-08-13: -1.26 °F2026-08-14: -7.14 °F2026-08-15: -1.12 °F2026-08-16: +0.89 °F2026-08-17: -6.11 °F2026-08-18: +2.64 °F2026-08-19: -7.38 °F2026-08-20: -9.23 °F2026-08-21: -6.95 °F2026-08-22: -0.97 °F2026-08-23: -4.84 °F2026-08-24: -3.55 °F2026-08-25: +5 °F2026-08-26: -9.21 °F2026-08-27: -10.76 °F2026-08-28: -4.59 °F2026-08-29: -4.4 °F2026-08-30: -2.15 °F2026-08-052026-08-30°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 (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.15
2026-08-29-4.40
2026-08-28-4.59
2026-08-27-10.76
2026-08-26-9.21
2026-08-25+5.00
2026-08-24-3.55
2026-08-23-4.84
2026-08-22-0.97
2026-08-21-6.95
2026-08-20-9.23
2026-08-19-7.38
2026-08-18+2.64
2026-08-17-6.11
2026-08-16+0.89
2026-08-15-1.12
2026-08-14-7.14
2026-08-13-1.26
2026-08-12-7.23
2026-08-11-2.37
2026-08-10-6.25
2026-08-09+2.54
2026-08-08+0.51
2026-08-07+2.82
2026-08-06-0.19
2026-08-05+6.45

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KDEN, lead day 4-20 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: 1 day-10 to -8 °F: 2 days-8 to -6 °F: 6 days-6 to -4 °F: 3 days-4 to -2 °F: 3 days-2 to 0 °F: 4 days0 to 2 °F: 2 days2 to 4 °F: 3 days4 to 6 °F: 1 day6 to 8 °F: 1 day8 to 10 °F: 0 days10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 4.49 · P90 |e| 8.29 °F-200+20 °Fn = 26 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
-12.00-10.001
-10.00-8.002
-8.00-6.006
-6.00-4.003
-4.00-2.003
-2.00+0.004
+0.00+2.002
+2.00+4.003
+4.00+6.001
+6.00+8.001
+8.00+10.000
+10.00+12.000
+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
2026-08264.48 -2.88

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means NCEP GFS has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 26 +0.22 [-1.18, 2.10] no
GraphCast (IFS init) 25 -2.73 [-3.70, -1.31] yes
ECMWF IFS HRES 20 +0.65 [-1.19, 3.10] no
Persistence (baseline) 26 -3.21 [-6.55, 0.37] no

Cite this page

ShortCastCheck, KDEN gfs lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDEN/model/gfs/lead/4/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDEN (Denver Intl), model gfs, lead day 4. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KDEN/model/gfs/lead/4/

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