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

Trenton Mercer · NCEP GFS · lead day 9

KTTN · gfs · lead 9

Target day = initialization date + 9 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
tmax00Zbilinear30d21 1 QC5.33 [3.81, 6.64]5.23+1.40 [-1.02, 4.06]6.37 [4.64, 7.63]10% [0%, 23%]19%29%-0.38-1.092026-08-10 → 2026-08-30
tmax00Zbilinear90d21 1 QC5.33 [3.58, 6.72]5.23+1.40 [-1.20, 4.12]6.37 [4.30, 7.66]10% [0%, 27%]19%29%-0.38-1.092026-08-10 → 2026-08-30
tmax00Zbilinear365d21 1 QC5.33 [3.44, 6.77]5.23+1.40 [-1.27, 4.09]6.37 [4.04, 7.72]10% [0%, 27%]19%29%-0.38-1.092026-08-10 → 2026-08-30
tmax00Zbilinearall21 1 QC5.33 [3.51, 6.87]5.23+1.40 [-1.25, 4.31]6.37 [4.23, 7.89]10% [0%, 30%]19%29%-0.38-1.092026-08-10 → 2026-08-30
tmax00Znearest30d21 1 QC5.65 [4.02, 7.12]5.43+1.85 [-0.59, 4.55]6.63 [4.66, 8.06]5% [0%, 20%]10%29%-0.46-1.172026-08-10 → 2026-08-30
tmax00Znearest90d21 1 QC5.65 [3.77, 7.27]5.43+1.85 [-0.85, 4.75]6.63 [4.45, 8.11]5% [0%, 24%]10%29%-0.46-1.172026-08-10 → 2026-08-30
tmax00Znearest365d21 1 QC5.65 [3.59, 7.38]5.43+1.85 [-0.84, 4.73]6.63 [4.19, 8.19]5% [0%, 22%]10%29%-0.46-1.172026-08-10 → 2026-08-30
tmax00Znearestall21 1 QC5.65 [3.69, 7.41]5.43+1.85 [-0.86, 4.85]6.63 [4.27, 8.40]5% [0%, 30%]10%29%-0.46-1.172026-08-10 → 2026-08-30
tmax12Zbilinear30d21 1 QC5.83 [3.85, 7.61]5.75+1.68 [-0.85, 4.72]7.18 [4.44, 9.21]5% [0%, 12%]14%33%-0.51-1.302026-08-10 → 2026-08-30
tmax12Zbilinear90d21 1 QC5.83 [3.81, 7.87]5.75+1.68 [-0.92, 5.17]7.18 [4.37, 9.33]5% [0%, 13%]14%33%-0.51-1.302026-08-10 → 2026-08-30
tmax12Zbilinear365d21 1 QC5.83 [3.52, 7.88]5.75+1.68 [-0.91, 5.47]7.18 [4.10, 9.56]5% [0%, 14%]14%33%-0.51-1.302026-08-10 → 2026-08-30
tmax12Zbilinearall21 1 QC5.83 [3.65, 7.91]5.75+1.68 [-0.87, 5.87]7.18 [4.21, 9.61]5% [0%, 14%]14%33%-0.51-1.302026-08-10 → 2026-08-30
tmax12Znearest30d21 1 QC6.18 [4.01, 8.11]6.06+2.26 [-0.39, 5.47]7.65 [4.65, 9.78]5% [0%, 12%]14%29%-0.60-1.422026-08-10 → 2026-08-30
tmax12Znearest90d21 1 QC6.18 [3.93, 8.45]6.06+2.26 [-0.51, 5.91]7.65 [4.53, 9.93]5% [0%, 13%]14%29%-0.60-1.422026-08-10 → 2026-08-30
tmax12Znearest365d21 1 QC6.18 [3.63, 8.50]6.06+2.26 [-0.45, 6.08]7.65 [4.24, 10.11]5% [0%, 14%]14%29%-0.60-1.422026-08-10 → 2026-08-30
tmax12Znearestall21 1 QC6.18 [3.73, 8.58]6.06+2.26 [-0.45, 6.61]7.65 [4.35, 10.14]5% [0%, 14%]14%29%-0.60-1.422026-08-10 → 2026-08-30
tmin00Zbilinear30d21 1 QC5.67 [4.37, 7.17]4.59+3.29 [0.38, 6.56]6.46 [4.73, 8.10]5% [0%, 14%]10%14%-0.23-0.352026-08-10 → 2026-08-30
tmin00Zbilinear90d21 1 QC5.67 [4.33, 7.41]4.59+3.29 [0.28, 6.83]6.46 [4.65, 8.36]5% [0%, 15%]10%14%-0.23-0.352026-08-10 → 2026-08-30
tmin00Zbilinear365d21 1 QC5.67 [4.31, 7.43]4.59+3.29 [0.04, 7.07]6.46 [4.65, 8.39]5% [0%, 14%]10%14%-0.23-0.352026-08-10 → 2026-08-30
tmin00Zbilinearall21 1 QC5.67 [4.32, 7.55]4.59+3.29 [0.05, 7.45]6.46 [4.61, 8.59]5% [0%, 15%]10%14%-0.23-0.352026-08-10 → 2026-08-30
tmin00Znearest30d21 1 QC5.70 [4.34, 7.25]4.64+3.43 [0.49, 6.69]6.54 [4.71, 8.18]5% [0%, 14%]14%19%-0.23-0.372026-08-10 → 2026-08-30
tmin00Znearest90d21 1 QC5.70 [4.31, 7.49]4.64+3.43 [0.43, 7.07]6.54 [4.63, 8.45]5% [0%, 15%]14%19%-0.23-0.372026-08-10 → 2026-08-30
tmin00Znearest365d21 1 QC5.70 [4.29, 7.53]4.64+3.43 [0.19, 7.23]6.54 [4.65, 8.49]5% [0%, 14%]14%19%-0.23-0.372026-08-10 → 2026-08-30
tmin00Znearestall21 1 QC5.70 [4.27, 7.64]4.64+3.43 [0.19, 7.53]6.54 [4.60, 8.70]5% [0%, 15%]14%19%-0.23-0.372026-08-10 → 2026-08-30
tmin12Zbilinear30d21 1 QC5.31 [3.65, 7.18]5.31+3.05 [-0.22, 6.46]6.82 [4.15, 8.77]10% [0%, 28%]29%38%-0.15-0.572026-08-10 → 2026-08-30
tmin12Zbilinear90d21 1 QC5.31 [3.55, 7.39]5.31+3.05 [-0.36, 6.72]6.82 [3.96, 8.95]10% [0%, 31%]29%38%-0.15-0.572026-08-10 → 2026-08-30
tmin12Zbilinear365d21 1 QC5.31 [3.47, 7.57]5.31+3.05 [-0.66, 6.93]6.82 [3.81, 9.12]10% [0%, 32%]29%38%-0.15-0.572026-08-10 → 2026-08-30
tmin12Zbilinearall21 1 QC5.31 [3.51, 7.96]5.31+3.05 [-0.61, 6.94]6.82 [3.91, 9.43]10% [0%, 31%]29%38%-0.15-0.572026-08-10 → 2026-08-30
tmin12Znearest30d21 1 QC5.35 [3.70, 7.22]5.31+3.10 [-0.18, 6.49]6.85 [4.21, 8.82]10% [0%, 28%]24%43%-0.16-0.572026-08-10 → 2026-08-30
tmin12Znearest90d21 1 QC5.35 [3.62, 7.46]5.31+3.10 [-0.31, 6.74]6.85 [4.07, 8.99]10% [0%, 31%]24%43%-0.16-0.572026-08-10 → 2026-08-30
tmin12Znearest365d21 1 QC5.35 [3.49, 7.59]5.31+3.10 [-0.60, 6.95]6.85 [3.86, 9.13]10% [0%, 32%]24%43%-0.16-0.572026-08-10 → 2026-08-30
tmin12Znearestall21 1 QC5.35 [3.58, 7.98]5.31+3.10 [-0.56, 6.97]6.85 [3.91, 9.48]10% [0%, 31%]24%43%-0.16-0.572026-08-10 → 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 9, 00Z bilinear tmax+20+100-10-202026-08-10: +3.7 °F2026-08-11: +7.86 °F2026-08-12: +9.89 °F2026-08-13: -6.74 °F2026-08-14: -4.65 °F2026-08-15: +0.28 °F2026-08-16: +2.32 °F2026-08-17: -6.95 °F2026-08-18: +2.33 °F2026-08-19: -4.77 °F2026-08-20: +2 °F2026-08-21: -5.57 °F2026-08-22: +11.56 °F2026-08-23: +6.82 °F2026-08-24: +4.87 °F2026-08-25: +13.96 °F2026-08-26: -3.29 °F2026-08-27: -1.21 °F2026-08-28: -7.61 °F2026-08-29: +5.04 °F2026-08-30: -0.46 °F2026-08-102026-08-30°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 (21 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.46
2026-08-29+5.04
2026-08-28-7.61
2026-08-27-1.21
2026-08-26-3.29
2026-08-25+13.96
2026-08-24+4.87
2026-08-23+6.82
2026-08-22+11.56
2026-08-21-5.57
2026-08-20+2.00
2026-08-19-4.77
2026-08-18+2.33
2026-08-17-6.95
2026-08-16+2.32
2026-08-15+0.28
2026-08-14-4.65
2026-08-13-6.74
2026-08-12+9.89
2026-08-11+7.86
2026-08-10+3.70

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 9-20 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: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 3 days-6 to -4 °F: 3 days-4 to -2 °F: 1 day-2 to 0 °F: 2 days0 to 2 °F: 2 days2 to 4 °F: 3 days4 to 6 °F: 2 days6 to 8 °F: 2 days8 to 10 °F: 1 day10 to 12 °F: 1 day12 to 14 °F: 1 day14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 4.87 · P90 |e| 9.89 °F-200+20 °Fn = 21 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
-12.00-10.000
-10.00-8.000
-8.00-6.003
-6.00-4.003
-4.00-2.001
-2.00+0.002
+0.00+2.002
+2.00+4.003
+4.00+6.002
+6.00+8.002
+8.00+10.001
+10.00+12.001
+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
2026-08215.33 +1.40

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21
NCEP GFS2026-08-10 → 2026-08-30 21

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 21 +1.42 [-0.96, 3.67] no
GraphCast (IFS init) 21 +1.18 [-1.04, 3.48] no
ECMWF IFS HRES 16 +0.64 [-3.62, 3.69] no
Persistence (baseline) 21 +1.47 [-0.86, 3.91] no

Cite this page

ShortCastCheck, KTTN gfs lead 9, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/9/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model gfs, lead day 9. 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/9/

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