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

Trenton Mercer · NCEP GFS · lead day 5

KTTN · gfs · lead 5

Target day = initialization date + 5 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
tmax00Zbilinear30d25 1 QC4.27 [2.83, 5.41]4.22+0.56 [-1.94, 3.67]5.68 [4.14, 6.81]24% [11%, 38%]40%44%-0.14-0.132026-08-06 → 2026-08-30
tmax00Zbilinear90d25 1 QC4.27 [2.69, 5.72]4.22+0.56 [-2.04, 4.27]5.68 [3.98, 7.14]24% [10%, 40%]40%44%-0.14-0.132026-08-06 → 2026-08-30
tmax00Zbilinear365d25 1 QC4.27 [2.47, 5.76]4.22+0.56 [-2.36, 4.83]5.68 [3.65, 7.21]24% [11%, 40%]40%44%-0.14-0.132026-08-06 → 2026-08-30
tmax00Zbilinearall25 1 QC4.27 [2.53, 5.67]4.22+0.56 [-2.19, 4.21]5.68 [3.71, 7.10]24% [9%, 43%]40%44%-0.14-0.132026-08-06 → 2026-08-30
tmax00Znearest30d25 1 QC4.49 [3.10, 5.75]4.23+1.20 [-1.31, 4.32]5.84 [4.28, 7.12]20% [4%, 39%]36%44%-0.19-0.142026-08-06 → 2026-08-30
tmax00Znearest90d25 1 QC4.49 [2.80, 6.12]4.23+1.20 [-1.42, 4.90]5.84 [4.06, 7.42]20% [0%, 42%]36%44%-0.19-0.142026-08-06 → 2026-08-30
tmax00Znearest365d25 1 QC4.49 [2.71, 6.24]4.23+1.20 [-1.72, 5.49]5.84 [3.84, 7.56]20% [0%, 44%]36%44%-0.19-0.142026-08-06 → 2026-08-30
tmax00Znearestall25 1 QC4.49 [2.76, 6.05]4.23+1.20 [-1.55, 4.86]5.84 [3.80, 7.38]20% [0%, 40%]36%44%-0.19-0.142026-08-06 → 2026-08-30
tmax12Zbilinear30d25 1 QC3.52 [2.94, 4.05]3.14+1.20 [-0.33, 3.11]4.18 [3.46, 4.72]12% [0%, 24%]32%52%+0.07+0.162026-08-06 → 2026-08-30
tmax12Zbilinear90d25 1 QC3.52 [2.91, 4.08]3.14+1.20 [-0.29, 3.43]4.18 [3.40, 4.76]12% [0%, 23%]32%52%+0.07+0.162026-08-06 → 2026-08-30
tmax12Zbilinear365d25 1 QC3.52 [2.84, 4.05]3.14+1.20 [-0.43, 3.50]4.18 [3.40, 4.78]12% [0%, 25%]32%52%+0.07+0.162026-08-06 → 2026-08-30
tmax12Zbilinearall25 1 QC3.52 [2.86, 4.03]3.14+1.20 [-0.44, 3.42]4.18 [3.37, 4.75]12% [0%, 26%]32%52%+0.07+0.162026-08-06 → 2026-08-30
tmax12Znearest30d25 1 QC3.88 [3.21, 4.48]3.28+1.71 [0.13, 3.70]4.49 [3.89, 5.00]8% [0%, 19%]20%40%-0.03+0.122026-08-06 → 2026-08-30
tmax12Znearest90d25 1 QC3.88 [3.19, 4.55]3.28+1.71 [0.17, 4.06]4.49 [3.87, 5.07]8% [0%, 20%]20%40%-0.03+0.122026-08-06 → 2026-08-30
tmax12Znearest365d25 1 QC3.88 [3.04, 4.47]3.28+1.71 [-0.02, 4.09]4.49 [3.82, 5.07]8% [0%, 21%]20%40%-0.03+0.122026-08-06 → 2026-08-30
tmax12Znearestall25 1 QC3.88 [3.16, 4.46]3.28+1.71 [-0.03, 4.07]4.49 [3.85, 5.07]8% [0%, 19%]20%40%-0.03+0.122026-08-06 → 2026-08-30
tmin00Zbilinear30d25 1 QC4.05 [3.14, 5.07]3.07+3.01 [1.03, 4.90]5.03 [3.81, 6.24]20% [4%, 36%]36%40%-0.33-0.112026-08-06 → 2026-08-30
tmin00Zbilinear90d25 1 QC4.05 [3.08, 5.33]3.07+3.01 [1.05, 5.19]5.03 [3.71, 6.55]20% [0%, 38%]36%40%-0.33-0.112026-08-06 → 2026-08-30
tmin00Zbilinear365d25 1 QC4.05 [2.98, 5.39]3.07+3.01 [0.81, 5.37]5.03 [3.48, 6.59]20% [0%, 40%]36%40%-0.33-0.112026-08-06 → 2026-08-30
tmin00Zbilinearall25 1 QC4.05 [3.00, 5.29]3.07+3.01 [0.89, 5.25]5.03 [3.61, 6.52]20% [0%, 43%]36%40%-0.33-0.112026-08-06 → 2026-08-30
tmin00Znearest30d25 1 QC4.11 [3.19, 5.20]3.12+3.14 [1.24, 4.99]5.18 [3.87, 6.43]16% [8%, 26%]28%40%-0.35-0.132026-08-06 → 2026-08-30
tmin00Znearest90d25 1 QC4.11 [3.13, 5.35]3.12+3.14 [1.18, 5.28]5.18 [3.78, 6.81]16% [6%, 29%]28%40%-0.35-0.132026-08-06 → 2026-08-30
tmin00Znearest365d25 1 QC4.11 [3.07, 5.42]3.12+3.14 [0.96, 5.42]5.18 [3.59, 6.78]16% [6%, 29%]28%40%-0.35-0.132026-08-06 → 2026-08-30
tmin00Znearestall25 1 QC4.11 [3.09, 5.37]3.12+3.14 [0.98, 5.30]5.18 [3.63, 6.72]16% [7%, 29%]28%40%-0.35-0.132026-08-06 → 2026-08-30
tmin12Zbilinear30d25 1 QC4.24 [3.57, 5.02]3.31+2.81 [0.94, 4.74]4.96 [4.29, 5.73]16% [0%, 33%]24%28%-0.39-0.192026-08-06 → 2026-08-30
tmin12Zbilinear90d25 1 QC4.24 [3.54, 5.24]3.31+2.81 [0.99, 5.09]4.96 [4.26, 5.94]16% [0%, 33%]24%28%-0.39-0.192026-08-06 → 2026-08-30
tmin12Zbilinear365d25 1 QC4.24 [3.56, 5.18]3.31+2.81 [0.72, 5.12]4.96 [4.23, 5.88]16% [0%, 36%]24%28%-0.39-0.192026-08-06 → 2026-08-30
tmin12Zbilinearall25 1 QC4.24 [3.45, 5.12]3.31+2.81 [0.80, 5.02]4.96 [4.18, 5.92]16% [0%, 38%]24%28%-0.39-0.192026-08-06 → 2026-08-30
tmin12Znearest30d25 1 QC4.45 [3.75, 5.31]3.42+3.02 [1.09, 5.06]5.19 [4.42, 6.11]12% [0%, 25%]24%28%-0.46-0.232026-08-06 → 2026-08-30
tmin12Znearest90d25 1 QC4.45 [3.72, 5.54]3.42+3.02 [1.13, 5.42]5.19 [4.39, 6.35]12% [0%, 27%]24%28%-0.46-0.232026-08-06 → 2026-08-30
tmin12Znearest365d25 1 QC4.45 [3.71, 5.46]3.42+3.02 [0.83, 5.43]5.19 [4.35, 6.27]12% [0%, 27%]24%28%-0.46-0.232026-08-06 → 2026-08-30
tmin12Znearestall25 1 QC4.45 [3.63, 5.47]3.42+3.02 [0.94, 5.44]5.19 [4.31, 6.24]12% [0%, 29%]24%28%-0.46-0.232026-08-06 → 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 KTTN, lead day 5, 00Z bilinear tmax+20+100-10-202026-08-06: -1.26 °F2026-08-07: +1.33 °F2026-08-08: -0.1 °F2026-08-09: +3.13 °F2026-08-10: +5.02 °F2026-08-11: +8.06 °F2026-08-12: -6.2 °F2026-08-13: +1.22 °F2026-08-14: -7.85 °F2026-08-15: -4.34 °F2026-08-16: +5.31 °F2026-08-17: -0.47 °F2026-08-18: +0.02 °F2026-08-19: +0.39 °F2026-08-20: -1.31 °F2026-08-21: -12.2 °F2026-08-22: -4.52 °F2026-08-23: -8.16 °F2026-08-24: +2.36 °F2026-08-25: +0.57 °F2026-08-26: +5.72 °F2026-08-27: +9.72 °F2026-08-28: +4.04 °F2026-08-29: +12.95 °F2026-08-30: +0.52 °F2026-08-062026-08-30°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 (25 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+0.52
2026-08-29+12.95
2026-08-28+4.04
2026-08-27+9.72
2026-08-26+5.72
2026-08-25+0.57
2026-08-24+2.36
2026-08-23-8.16
2026-08-22-4.52
2026-08-21-12.20
2026-08-20-1.31
2026-08-19+0.39
2026-08-18+0.02
2026-08-17-0.47
2026-08-16+5.31
2026-08-15-4.34
2026-08-14-7.85
2026-08-13+1.22
2026-08-12-6.20
2026-08-11+8.06
2026-08-10+5.02
2026-08-09+3.13
2026-08-08-0.10
2026-08-07+1.33
2026-08-06-1.26

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 5-20 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: 0 days-10 to -8 °F: 1 day-8 to -6 °F: 2 days-6 to -4 °F: 2 days-4 to -2 °F: 0 days-2 to 0 °F: 4 days0 to 2 °F: 6 days2 to 4 °F: 2 days4 to 6 °F: 4 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| 4.04 · P90 |e| 9.09 °F-200+20 °Fn = 25 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
-12.00-10.000
-10.00-8.001
-8.00-6.002
-6.00-4.002
-4.00-2.000
-2.00+0.004
+0.00+2.006
+2.00+4.002
+4.00+6.004
+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
2026-08254.27 +0.56

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25
NCEP GFS2026-08-06 → 2026-08-30 25

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 25 +2.59 [0.96, 4.06] yes
GraphCast (IFS init) 25 +1.94 [-0.20, 3.68] no
ECMWF IFS HRES 18 +1.67 [-1.58, 3.67] no
Persistence (baseline) 25 +0.51 [-1.52, 2.52] no

Cite this page

ShortCastCheck, KTTN gfs lead 5, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/5/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model gfs, lead day 5. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/5/

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