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 1

KTTN · gfs · lead 1

Target day = initialization date + 1 day. 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
tmax00Zbilinear30d29 1 QC2.94 [2.43, 3.45]2.74+0.58 [-1.01, 2.21]3.74 [3.04, 4.35]17% [10%, 28%]45%66%-0.25-0.172026-08-02 → 2026-08-30
tmax00Zbilinear90d29 1 QC2.94 [2.45, 3.52]2.74+0.58 [-1.25, 2.66]3.74 [3.07, 4.34]17% [6%, 31%]45%66%-0.25-0.172026-08-02 → 2026-08-30
tmax00Zbilinear365d29 1 QC2.94 [2.39, 3.60]2.74+0.58 [-1.49, 2.78]3.74 [2.97, 4.40]17% [0%, 30%]45%66%-0.25-0.172026-08-02 → 2026-08-30
tmax00Zbilinearall29 1 QC2.94 [2.39, 3.52]2.74+0.58 [-1.32, 2.58]3.74 [2.98, 4.41]17% [6%, 33%]45%66%-0.25-0.172026-08-02 → 2026-08-30
tmax00Znearest30d29 1 QC3.23 [2.63, 3.81]2.83+1.18 [-0.45, 2.87]3.91 [3.22, 4.49]17% [10%, 28%]24%52%-0.38-0.212026-08-02 → 2026-08-30
tmax00Znearest90d29 1 QC3.23 [2.63, 3.96]2.83+1.18 [-0.66, 3.32]3.91 [3.26, 4.62]17% [6%, 31%]24%52%-0.38-0.212026-08-02 → 2026-08-30
tmax00Znearest365d29 1 QC3.23 [2.58, 4.03]2.83+1.18 [-0.90, 3.43]3.91 [3.18, 4.71]17% [0%, 30%]24%52%-0.38-0.212026-08-02 → 2026-08-30
tmax00Znearestall29 1 QC3.23 [2.59, 3.97]2.83+1.18 [-0.77, 3.23]3.91 [3.19, 4.65]17% [6%, 33%]24%52%-0.38-0.212026-08-02 → 2026-08-30
tmax12Zbilinear30d29 1 QC2.73 [2.25, 3.16]2.52+0.71 [-0.63, 1.97]3.37 [2.85, 3.86]24% [14%, 34%]41%62%-0.16-0.082026-08-02 → 2026-08-30
tmax12Zbilinear90d29 1 QC2.73 [2.22, 3.17]2.52+0.71 [-0.93, 2.33]3.37 [2.77, 3.86]24% [11%, 38%]41%62%-0.16-0.082026-08-02 → 2026-08-30
tmax12Zbilinear365d29 1 QC2.73 [2.22, 3.15]2.52+0.71 [-1.07, 2.37]3.37 [2.77, 3.84]24% [10%, 38%]41%62%-0.16-0.082026-08-02 → 2026-08-30
tmax12Zbilinearall29 1 QC2.73 [2.14, 3.19]2.52+0.71 [-0.90, 2.43]3.37 [2.75, 3.86]24% [12%, 40%]41%62%-0.16-0.082026-08-02 → 2026-08-30
tmax12Znearest30d29 1 QC3.23 [2.67, 3.73]2.76+1.37 [-0.09, 2.79]3.82 [3.22, 4.26]17% [7%, 28%]31%45%-0.38-0.182026-08-02 → 2026-08-30
tmax12Znearest90d29 1 QC3.23 [2.63, 3.75]2.76+1.37 [-0.41, 3.23]3.82 [3.15, 4.26]17% [3%, 29%]31%45%-0.38-0.182026-08-02 → 2026-08-30
tmax12Znearest365d29 1 QC3.23 [2.61, 3.79]2.76+1.37 [-0.53, 3.25]3.82 [3.10, 4.23]17% [0%, 29%]31%45%-0.38-0.182026-08-02 → 2026-08-30
tmax12Znearestall29 1 QC3.23 [2.55, 3.75]2.76+1.37 [-0.37, 3.18]3.82 [3.00, 4.23]17% [3%, 29%]31%45%-0.38-0.182026-08-02 → 2026-08-30
tmin00Zbilinear30d29 1 QC3.63 [2.69, 4.50]2.02+3.39 [2.09, 4.46]4.24 [3.25, 5.04]14% [3%, 27%]24%45%-0.21+0.322026-08-02 → 2026-08-30
tmin00Zbilinear90d29 1 QC3.63 [2.61, 4.73]2.02+3.39 [2.13, 4.71]4.24 [3.25, 5.17]14% [0%, 29%]24%45%-0.21+0.322026-08-02 → 2026-08-30
tmin00Zbilinear365d29 1 QC3.63 [2.55, 4.84]2.02+3.39 [1.98, 4.84]4.24 [3.11, 5.20]14% [0%, 29%]24%45%-0.21+0.322026-08-02 → 2026-08-30
tmin00Zbilinearall29 1 QC3.63 [2.48, 4.76]2.02+3.39 [2.00, 4.76]4.24 [3.07, 5.25]14% [0%, 29%]24%45%-0.21+0.322026-08-02 → 2026-08-30
tmin00Znearest30d29 1 QC3.81 [2.79, 4.77]2.13+3.59 [2.26, 4.70]4.46 [3.41, 5.30]14% [3%, 27%]21%41%-0.27+0.282026-08-02 → 2026-08-30
tmin00Znearest90d29 1 QC3.81 [2.71, 4.98]2.13+3.59 [2.26, 4.97]4.46 [3.39, 5.46]14% [0%, 29%]21%41%-0.27+0.282026-08-02 → 2026-08-30
tmin00Znearest365d29 1 QC3.81 [2.65, 5.13]2.13+3.59 [2.13, 5.13]4.46 [3.26, 5.49]14% [0%, 29%]21%41%-0.27+0.282026-08-02 → 2026-08-30
tmin00Znearestall29 1 QC3.81 [2.58, 5.06]2.13+3.59 [2.16, 5.06]4.46 [3.21, 5.50]14% [0%, 29%]21%41%-0.27+0.282026-08-02 → 2026-08-30
tmin12Zbilinear30d29 1 QC3.13 [2.21, 4.08]1.85+3.12 [2.18, 4.08]3.85 [2.84, 4.72]21% [10%, 32%]31%59%-0.04+0.382026-08-02 → 2026-08-30
tmin12Zbilinear90d29 1 QC3.13 [2.20, 4.32]1.85+3.12 [2.18, 4.32]3.85 [2.87, 4.87]21% [5%, 33%]31%59%-0.04+0.382026-08-02 → 2026-08-30
tmin12Zbilinear365d29 1 QC3.13 [2.10, 4.57]1.85+3.12 [2.07, 4.56]3.85 [2.69, 5.03]21% [0%, 35%]31%59%-0.04+0.382026-08-02 → 2026-08-30
tmin12Zbilinearall29 1 QC3.13 [2.17, 4.40]1.85+3.12 [2.14, 4.38]3.85 [2.77, 4.94]21% [6%, 35%]31%59%-0.04+0.382026-08-02 → 2026-08-30
tmin12Znearest30d29 1 QC3.30 [2.31, 4.33]1.89+3.30 [2.31, 4.33]4.03 [2.92, 4.99]21% [10%, 32%]28%52%-0.10+0.362026-08-02 → 2026-08-30
tmin12Znearest90d29 1 QC3.30 [2.32, 4.61]1.89+3.30 [2.32, 4.61]4.03 [2.94, 5.14]21% [5%, 33%]28%52%-0.10+0.362026-08-02 → 2026-08-30
tmin12Znearest365d29 1 QC3.30 [2.19, 4.84]1.89+3.30 [2.19, 4.84]4.03 [2.77, 5.31]21% [0%, 35%]28%52%-0.10+0.362026-08-02 → 2026-08-30
tmin12Znearestall29 1 QC3.30 [2.23, 4.66]1.89+3.30 [2.23, 4.66]4.03 [2.84, 5.23]21% [6%, 35%]28%52%-0.10+0.362026-08-02 → 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 1, 00Z bilinear tmax+10+50-5-102026-08-02: +0.61 °F2026-08-03: -4.76 °F2026-08-04: +0.1 °F2026-08-05: -9.27 °F2026-08-06: +2.12 °F2026-08-07: +1.24 °F2026-08-08: +1.56 °F2026-08-09: +2.67 °F2026-08-10: +4.33 °F2026-08-11: +5.1 °F2026-08-12: -0.38 °F2026-08-13: +1.7 °F2026-08-14: +2.45 °F2026-08-15: -0.1 °F2026-08-16: -3.96 °F2026-08-17: -1.87 °F2026-08-18: +2.53 °F2026-08-19: +1.34 °F2026-08-20: -7.98 °F2026-08-21: +1.02 °F2026-08-22: -5.99 °F2026-08-23: +1.87 °F2026-08-24: +0.27 °F2026-08-25: +2.8 °F2026-08-26: +1.61 °F2026-08-27: +6.36 °F2026-08-28: +4.46 °F2026-08-29: +2.37 °F2026-08-30: +4.47 °F2026-08-022026-08-30°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 (29 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+4.47
2026-08-29+2.37
2026-08-28+4.46
2026-08-27+6.36
2026-08-26+1.61
2026-08-25+2.80
2026-08-24+0.27
2026-08-23+1.87
2026-08-22-5.99
2026-08-21+1.02
2026-08-20-7.98
2026-08-19+1.34
2026-08-18+2.53
2026-08-17-1.87
2026-08-16-3.96
2026-08-15-0.10
2026-08-14+2.45
2026-08-13+1.70
2026-08-12-0.38
2026-08-11+5.10
2026-08-10+4.33
2026-08-09+2.67
2026-08-08+1.56
2026-08-07+1.24
2026-08-06+2.12
2026-08-05-9.27
2026-08-04+0.10
2026-08-03-4.76
2026-08-02+0.61

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 1-10 to -9 °F: 1 day-9 to -8 °F: 0 days-8 to -7 °F: 1 day-7 to -6 °F: 0 days-6 to -5 °F: 1 day-5 to -4 °F: 1 day-4 to -3 °F: 1 day-3 to -2 °F: 0 days-2 to -1 °F: 1 day-1 to 0 °F: 2 days0 to 1 °F: 3 days1 to 2 °F: 7 days2 to 3 °F: 6 days3 to 4 °F: 0 days4 to 5 °F: 3 days5 to 6 °F: 1 day6 to 7 °F: 1 day7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 2.37 · P90 |e| 6.06 °F-100+10 °Fn = 29 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
-10.00-9.001
-9.00-8.000
-8.00-7.001
-7.00-6.000
-6.00-5.001
-5.00-4.001
-4.00-3.001
-3.00-2.000
-2.00-1.001
-1.00+0.002
+0.00+1.003
+1.00+2.007
+2.00+3.006
+3.00+4.000
+4.00+5.003
+5.00+6.001
+6.00+7.001
+7.00+8.000
+8.00+9.000
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08292.94 +0.58

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29

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 29 +1.20 [0.28, 2.16] yes
Aurora (GFS init) 1 +2.04 [2.04, 2.04] yes
Aurora (IFS init) 2 +2.88 [2.26, 3.49] yes
FourCastNet v2 (GFS init) 1 +3.27 [3.27, 3.27] yes
FourCastNet v2 (IFS init) 2 +0.76 [-0.95, 2.48] no
GraphCast (GFS init) 1 +1.03 [1.03, 1.03] yes
GraphCast (IFS init) 27 +0.35 [-0.72, 1.15] no
ECMWF IFS HRES 23 +0.22 [-0.50, 1.06] no
Pangu-Weather (GFS init) 1 +2.01 [2.01, 2.01] yes
Pangu-Weather (IFS init) 2 +0.61 [-1.70, 2.93] no
Persistence (baseline) 29 +0.60 [-0.02, 1.28] no

Cite this page

ShortCastCheck, KTTN gfs lead 1, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/1/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model gfs, lead day 1. 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/1/

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