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 3

KTTN · gfs · lead 3

Target day = initialization date + 3 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
tmax00Zbilinear30d27 1 QC2.53 [2.09, 2.96]2.47+0.71 [-0.22, 1.53]3.23 [2.73, 3.67]30% [17%, 44%]48%63%+0.25+0.252026-08-04 → 2026-08-30
tmax00Zbilinear90d27 1 QC2.53 [2.14, 3.00]2.47+0.71 [-0.43, 1.67]3.23 [2.72, 3.69]30% [15%, 43%]48%63%+0.25+0.252026-08-04 → 2026-08-30
tmax00Zbilinear365d27 1 QC2.53 [2.05, 3.00]2.47+0.71 [-0.41, 1.71]3.23 [2.63, 3.69]30% [14%, 47%]48%63%+0.25+0.252026-08-04 → 2026-08-30
tmax00Zbilinearall27 1 QC2.53 [2.06, 3.07]2.47+0.71 [-0.64, 1.78]3.23 [2.62, 3.75]30% [14%, 45%]48%63%+0.25+0.252026-08-04 → 2026-08-30
tmax00Znearest30d27 1 QC2.85 [2.31, 3.37]2.64+1.14 [0.14, 2.02]3.57 [2.96, 4.06]26% [12%, 40%]41%59%+0.15+0.202026-08-04 → 2026-08-30
tmax00Znearest90d27 1 QC2.85 [2.36, 3.41]2.64+1.14 [-0.07, 2.18]3.57 [3.00, 4.11]26% [11%, 40%]41%59%+0.15+0.202026-08-04 → 2026-08-30
tmax00Znearest365d27 1 QC2.85 [2.26, 3.38]2.64+1.14 [-0.05, 2.21]3.57 [2.90, 4.10]26% [11%, 43%]41%59%+0.15+0.202026-08-04 → 2026-08-30
tmax00Znearestall27 1 QC2.85 [2.26, 3.48]2.64+1.14 [-0.21, 2.34]3.57 [2.83, 4.19]26% [7%, 43%]41%59%+0.15+0.202026-08-04 → 2026-08-30
tmax12Zbilinear30d27 1 QC2.85 [2.29, 3.47]2.78+0.40 [-0.60, 1.27]3.64 [2.94, 4.30]33% [23%, 44%]44%52%+0.16+0.152026-08-04 → 2026-08-30
tmax12Zbilinear90d27 1 QC2.85 [2.26, 3.65]2.78+0.40 [-0.89, 1.50]3.64 [2.92, 4.37]33% [21%, 45%]44%52%+0.16+0.152026-08-04 → 2026-08-30
tmax12Zbilinear365d27 1 QC2.85 [2.20, 3.68]2.78+0.40 [-0.86, 1.66]3.64 [2.87, 4.43]33% [20%, 46%]44%52%+0.16+0.152026-08-04 → 2026-08-30
tmax12Zbilinearall27 1 QC2.85 [2.19, 3.62]2.78+0.40 [-1.02, 1.57]3.64 [2.87, 4.38]33% [20%, 46%]44%52%+0.16+0.152026-08-04 → 2026-08-30
tmax12Znearest30d27 1 QC3.10 [2.56, 3.69]2.93+0.92 [-0.16, 1.85]3.88 [3.22, 4.50]22% [11%, 36%]41%52%+0.08+0.112026-08-04 → 2026-08-30
tmax12Znearest90d27 1 QC3.10 [2.52, 3.83]2.93+0.92 [-0.46, 2.07]3.88 [3.19, 4.56]22% [8%, 38%]41%52%+0.08+0.112026-08-04 → 2026-08-30
tmax12Znearest365d27 1 QC3.10 [2.43, 3.90]2.93+0.92 [-0.42, 2.26]3.88 [3.09, 4.64]22% [8%, 38%]41%52%+0.08+0.112026-08-04 → 2026-08-30
tmax12Znearestall27 1 QC3.10 [2.37, 3.81]2.93+0.92 [-0.58, 2.17]3.88 [3.11, 4.60]22% [7%, 38%]41%52%+0.08+0.112026-08-04 → 2026-08-30
tmin00Zbilinear30d27 1 QC4.42 [3.46, 5.69]2.51+4.24 [3.15, 5.62]5.28 [4.13, 6.51]15% [4%, 30%]22%37%-0.08+0.362026-08-04 → 2026-08-30
tmin00Zbilinear90d27 1 QC4.42 [3.55, 5.94]2.51+4.24 [3.23, 5.92]5.28 [4.19, 6.71]15% [0%, 29%]22%37%-0.08+0.362026-08-04 → 2026-08-30
tmin00Zbilinear365d27 1 QC4.42 [3.43, 5.93]2.51+4.24 [3.07, 5.89]5.28 [4.02, 6.83]15% [0%, 31%]22%37%-0.08+0.362026-08-04 → 2026-08-30
tmin00Zbilinearall27 1 QC4.42 [3.48, 6.12]2.51+4.24 [3.15, 6.04]5.28 [4.08, 6.96]15% [0%, 29%]22%37%-0.08+0.362026-08-04 → 2026-08-30
tmin00Znearest30d27 1 QC4.73 [3.80, 5.96]2.62+4.55 [3.43, 5.89]5.59 [4.45, 6.72]11% [0%, 23%]22%30%-0.15+0.342026-08-04 → 2026-08-30
tmin00Znearest90d27 1 QC4.73 [3.88, 6.18]2.62+4.55 [3.55, 6.16]5.59 [4.51, 7.00]11% [0%, 23%]22%30%-0.15+0.342026-08-04 → 2026-08-30
tmin00Znearest365d27 1 QC4.73 [3.77, 6.20]2.62+4.55 [3.40, 6.16]5.59 [4.37, 7.06]11% [0%, 25%]22%30%-0.15+0.342026-08-04 → 2026-08-30
tmin00Znearestall27 1 QC4.73 [3.80, 6.41]2.62+4.55 [3.47, 6.31]5.59 [4.42, 7.14]11% [0%, 25%]22%30%-0.15+0.342026-08-04 → 2026-08-30
tmin12Zbilinear30d27 1 QC3.86 [3.17, 4.59]1.99+3.65 [2.63, 4.55]4.48 [3.72, 5.18]7% [0%, 19%]22%41%+0.06+0.492026-08-04 → 2026-08-30
tmin12Zbilinear90d27 1 QC3.86 [3.23, 4.76]1.99+3.65 [2.70, 4.76]4.48 [3.79, 5.36]7% [0%, 18%]22%41%+0.06+0.492026-08-04 → 2026-08-30
tmin12Zbilinear365d27 1 QC3.86 [3.08, 4.78]1.99+3.65 [2.58, 4.76]4.48 [3.64, 5.46]7% [0%, 19%]22%41%+0.06+0.492026-08-04 → 2026-08-30
tmin12Zbilinearall27 1 QC3.86 [3.16, 4.85]1.99+3.65 [2.60, 4.85]4.48 [3.69, 5.42]7% [0%, 18%]22%41%+0.06+0.492026-08-04 → 2026-08-30
tmin12Znearest30d27 1 QC4.11 [3.38, 4.85]2.03+3.85 [2.74, 4.82]4.69 [3.89, 5.40]7% [0%, 19%]7%37%-0.00+0.482026-08-04 → 2026-08-30
tmin12Znearest90d27 1 QC4.11 [3.44, 5.01]2.03+3.85 [2.82, 5.01]4.69 [3.96, 5.57]7% [0%, 18%]7%37%-0.00+0.482026-08-04 → 2026-08-30
tmin12Znearest365d27 1 QC4.11 [3.29, 4.98]2.03+3.85 [2.68, 4.97]4.69 [3.81, 5.60]7% [0%, 19%]7%37%-0.00+0.482026-08-04 → 2026-08-30
tmin12Znearestall27 1 QC4.11 [3.35, 5.06]2.03+3.85 [2.72, 5.06]4.69 [3.84, 5.59]7% [0%, 18%]7%37%-0.00+0.482026-08-04 → 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 3, 00Z bilinear tmax+10+50-5-102026-08-04: -2.12 °F2026-08-05: -5.02 °F2026-08-06: +2.42 °F2026-08-07: -0.25 °F2026-08-08: +1.61 °F2026-08-09: +1.85 °F2026-08-10: +3.74 °F2026-08-11: +7.13 °F2026-08-12: -0.15 °F2026-08-13: +3.3 °F2026-08-14: -2.77 °F2026-08-15: -1.09 °F2026-08-16: -3.28 °F2026-08-17: -0.14 °F2026-08-18: +0.36 °F2026-08-19: +2.78 °F2026-08-20: +7.18 °F2026-08-21: +1.24 °F2026-08-22: -5.15 °F2026-08-23: +0.97 °F2026-08-24: +1.65 °F2026-08-25: +3.8 °F2026-08-26: +0.81 °F2026-08-27: -0.64 °F2026-08-28: -4 °F2026-08-29: +0.07 °F2026-08-30: +4.79 °F2026-08-042026-08-30°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 (27 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+4.79
2026-08-29+0.07
2026-08-28-4.00
2026-08-27-0.64
2026-08-26+0.81
2026-08-25+3.80
2026-08-24+1.65
2026-08-23+0.97
2026-08-22-5.15
2026-08-21+1.24
2026-08-20+7.18
2026-08-19+2.78
2026-08-18+0.36
2026-08-17-0.14
2026-08-16-3.28
2026-08-15-1.09
2026-08-14-2.77
2026-08-13+3.30
2026-08-12-0.15
2026-08-11+7.13
2026-08-10+3.74
2026-08-09+1.85
2026-08-08+1.61
2026-08-07-0.25
2026-08-06+2.42
2026-08-05-5.02
2026-08-04-2.12

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 3-10 to -9 °F: 0 days-9 to -8 °F: 0 days-8 to -7 °F: 0 days-7 to -6 °F: 0 days-6 to -5 °F: 2 days-5 to -4 °F: 0 days-4 to -3 °F: 2 days-3 to -2 °F: 2 days-2 to -1 °F: 1 day-1 to 0 °F: 4 days0 to 1 °F: 4 days1 to 2 °F: 4 days2 to 3 °F: 2 days3 to 4 °F: 3 days4 to 5 °F: 1 day5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 2 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 2.12 · P90 |e| 5.07 °F-100+10 °Fn = 27 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
-10.00-9.000
-9.00-8.000
-8.00-7.000
-7.00-6.000
-6.00-5.002
-5.00-4.000
-4.00-3.002
-3.00-2.002
-2.00-1.001
-1.00+0.004
+0.00+1.004
+1.00+2.004
+2.00+3.002
+3.00+4.003
+4.00+5.001
+5.00+6.000
+6.00+7.000
+7.00+8.002
+8.00+9.000
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08272.53 +0.71

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27

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 27 +0.90 [0.25, 1.61] yes
GraphCast (IFS init) 25 +0.07 [-1.35, 1.10] no
ECMWF IFS HRES 22 +0.25 [-0.30, 0.93] no
Persistence (baseline) 27 -0.84 [-1.67, -0.14] yes

Cite this page

ShortCastCheck, KTTN gfs lead 3, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/3/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model gfs, lead day 3. 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/3/

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