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

Trenton Mercer · NCEP GFS · lead day 0

KTTN · gfs · lead 0

Target day = initialization date + 0 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
tmax00Zbilinear30d30 1 QC1.88 [1.37, 2.35]1.64+0.73 [-0.04, 1.52]2.35 [1.73, 2.88]30% [13%, 50%]63%83%——2026-08-01 → 2026-08-30
tmax00Zbilinear90d30 1 QC1.88 [1.33, 2.39]1.64+0.73 [-0.28, 1.67]2.35 [1.66, 2.89]30% [10%, 50%]63%83%——2026-08-01 → 2026-08-30
tmax00Zbilinear365d30 1 QC1.88 [1.33, 2.39]1.64+0.73 [-0.25, 1.74]2.35 [1.58, 2.94]30% [11%, 50%]63%83%——2026-08-01 → 2026-08-30
tmax00Zbilinearall30 1 QC1.88 [1.31, 2.36]1.64+0.73 [-0.31, 1.70]2.35 [1.55, 2.90]30% [11%, 50%]63%83%——2026-08-01 → 2026-08-30
tmax00Znearest30d30 1 QC2.29 [1.88, 2.72]1.75+1.36 [0.62, 2.15]2.72 [2.25, 3.21]20% [7%, 33%]50%73%——2026-08-01 → 2026-08-30
tmax00Znearest90d30 1 QC2.29 [1.86, 2.74]1.75+1.36 [0.40, 2.31]2.72 [2.21, 3.20]20% [4%, 33%]50%73%——2026-08-01 → 2026-08-30
tmax00Znearest365d30 1 QC2.29 [1.85, 2.77]1.75+1.36 [0.46, 2.37]2.72 [2.17, 3.29]20% [0%, 33%]50%73%——2026-08-01 → 2026-08-30
tmax00Znearestall30 1 QC2.29 [1.88, 2.78]1.75+1.36 [0.39, 2.31]2.72 [2.20, 3.22]20% [4%, 33%]50%73%——2026-08-01 → 2026-08-30
tmin00Zbilinear30d30 1 QC3.35 [2.63, 3.95]1.57+3.34 [2.61, 3.95]3.91 [3.11, 4.51]13% [3%, 23%]23%43%——2026-08-01 → 2026-08-30
tmin00Zbilinear90d30 1 QC3.35 [2.72, 4.08]1.57+3.34 [2.70, 4.08]3.91 [3.18, 4.55]13% [0%, 23%]23%43%——2026-08-01 → 2026-08-30
tmin00Zbilinear365d30 1 QC3.35 [2.57, 4.13]1.57+3.34 [2.55, 4.13]3.91 [3.05, 4.61]13% [0%, 24%]23%43%——2026-08-01 → 2026-08-30
tmin00Zbilinearall30 1 QC3.35 [2.66, 4.09]1.57+3.34 [2.63, 4.09]3.91 [3.11, 4.61]13% [0%, 23%]23%43%——2026-08-01 → 2026-08-30
tmin00Znearest30d30 1 QC3.50 [2.74, 4.13]1.64+3.50 [2.74, 4.13]4.11 [3.22, 4.75]17% [7%, 30%]23%43%——2026-08-01 → 2026-08-30
tmin00Znearest90d30 1 QC3.50 [2.81, 4.19]1.64+3.50 [2.81, 4.19]4.11 [3.26, 4.76]17% [0%, 28%]23%43%——2026-08-01 → 2026-08-30
tmin00Znearest365d30 1 QC3.50 [2.69, 4.28]1.64+3.50 [2.69, 4.28]4.11 [3.19, 4.83]17% [0%, 29%]23%43%——2026-08-01 → 2026-08-30
tmin00Znearestall30 1 QC3.50 [2.74, 4.24]1.64+3.50 [2.74, 4.24]4.11 [3.19, 4.84]17% [0%, 29%]23%43%——2026-08-01 → 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 0, 00Z bilinear tmax+10+50-5-102026-08-01: +1.33 °F2026-08-02: -2.68 °F2026-08-03: -4.55 °F2026-08-04: +1.38 °F2026-08-05: -1.47 °F2026-08-06: +1.48 °F2026-08-07: +0.12 °F2026-08-08: +2.47 °F2026-08-09: +2.22 °F2026-08-10: -1.56 °F2026-08-11: -4.16 °F2026-08-12: +3.07 °F2026-08-13: +2.05 °F2026-08-14: +3.69 °F2026-08-15: -0.68 °F2026-08-16: +0.08 °F2026-08-17: +0.77 °F2026-08-18: +1.63 °F2026-08-19: +0.78 °F2026-08-20: +1.51 °F2026-08-21: +0.52 °F2026-08-22: -1.95 °F2026-08-23: +0.76 °F2026-08-24: +1.62 °F2026-08-25: +0.78 °F2026-08-26: +1.24 °F2026-08-27: +6.54 °F2026-08-28: +2.94 °F2026-08-29: +2.19 °F2026-08-30: -0.24 °F2026-08-012026-08-30°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 (30 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.24
2026-08-29+2.19
2026-08-28+2.94
2026-08-27+6.54
2026-08-26+1.24
2026-08-25+0.78
2026-08-24+1.62
2026-08-23+0.76
2026-08-22-1.95
2026-08-21+0.52
2026-08-20+1.51
2026-08-19+0.78
2026-08-18+1.63
2026-08-17+0.77
2026-08-16+0.08
2026-08-15-0.68
2026-08-14+3.69
2026-08-13+2.05
2026-08-12+3.07
2026-08-11-4.16
2026-08-10-1.56
2026-08-09+2.22
2026-08-08+2.47
2026-08-07+0.12
2026-08-06+1.48
2026-08-05-1.47
2026-08-04+1.38
2026-08-03-4.55
2026-08-02-2.68
2026-08-01+1.33

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 0-10 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: 0 days-5 to -4 °F: 2 days-4 to -3 °F: 0 days-3 to -2 °F: 1 day-2 to -1 °F: 3 days-1 to 0 °F: 2 days0 to 1 °F: 7 days1 to 2 °F: 7 days2 to 3 °F: 5 days3 to 4 °F: 2 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 1 day7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 1.53 · P90 |e| 3.74 °F-100+10 °Fn = 30 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
-6.00-5.000
-5.00-4.002
-4.00-3.000
-3.00-2.001
-2.00-1.003
-1.00+0.002
+0.00+1.007
+1.00+2.007
+2.00+3.005
+3.00+4.002
+4.00+5.000
+5.00+6.000
+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
2026-08301.88 +0.73

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-01 → 2026-08-30 30
NCEP GFS2026-08-01 → 2026-08-30 30

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 30 +0.05 [-0.45, 0.62] no
Aurora (GFS init) 2 -0.40 [-2.31, 1.50] no
Aurora (IFS init) 3 +0.83 [0.14, 1.18] yes
FourCastNet v2 (GFS init) 2 -1.38 [-3.52, 0.76] no
FourCastNet v2 (IFS init) 3 -0.93 [-2.87, 0.04] no
GraphCast (GFS init) 2 -0.54 [-2.38, 1.29] no
GraphCast (IFS init) 28 -0.33 [-1.41, 0.85] no
ECMWF IFS HRES 24 +0.32 [-0.25, 0.93] no
Pangu-Weather (GFS init) 2 -1.04 [-1.43, -0.64] yes
Pangu-Weather (IFS init) 3 +0.20 [-1.67, 2.85] no

Cite this page

ShortCastCheck, KTTN gfs lead 0, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/0/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model gfs, lead day 0. 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/0/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

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