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 7

KTTN · gfs · lead 7

Target day = initialization date + 7 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
tmax00Zbilinear30d23 1 QC3.29 [2.30, 4.26]3.19+0.62 [-0.62, 2.13]4.11 [2.94, 5.05]22% [13%, 33%]35%52%+0.10+0.052026-08-08 → 2026-08-30
tmax00Zbilinear90d23 1 QC3.29 [2.11, 4.25]3.19+0.62 [-0.67, 2.59]4.11 [2.80, 5.06]22% [12%, 33%]35%52%+0.10+0.052026-08-08 → 2026-08-30
tmax00Zbilinear365d23 1 QC3.29 [2.03, 4.39]3.19+0.62 [-0.65, 2.38]4.11 [2.62, 5.18]22% [12%, 33%]35%52%+0.10+0.052026-08-08 → 2026-08-30
tmax00Zbilinearall23 1 QC3.29 [1.94, 4.43]3.19+0.62 [-0.58, 2.32]4.11 [2.37, 5.25]22% [13%, 36%]35%52%+0.10+0.052026-08-08 → 2026-08-30
tmax00Znearest30d23 1 QC3.49 [2.47, 4.40]3.27+1.05 [-0.25, 2.59]4.29 [3.03, 5.21]13% [4%, 25%]30%57%+0.05+0.032026-08-08 → 2026-08-30
tmax00Znearest90d23 1 QC3.49 [2.36, 4.44]3.27+1.05 [-0.26, 3.07]4.29 [2.96, 5.25]13% [0%, 27%]30%57%+0.05+0.032026-08-08 → 2026-08-30
tmax00Znearest365d23 1 QC3.49 [2.29, 4.54]3.27+1.05 [-0.26, 2.90]4.29 [2.74, 5.36]13% [0%, 29%]30%57%+0.05+0.032026-08-08 → 2026-08-30
tmax00Znearestall23 1 QC3.49 [2.09, 4.59]3.27+1.05 [-0.18, 2.78]4.29 [2.34, 5.41]13% [0%, 31%]30%57%+0.05+0.032026-08-08 → 2026-08-30
tmax12Zbilinear30d23 1 QC5.12 [4.17, 6.21]4.80+1.43 [-0.34, 3.80]5.77 [4.62, 6.85]0% [0%, 0%]4%43%-0.40-0.422026-08-08 → 2026-08-30
tmax12Zbilinear90d23 1 QC5.12 [4.13, 6.34]4.80+1.43 [-0.23, 4.84]5.77 [4.53, 6.99]0% [0%, 0%]4%43%-0.40-0.422026-08-08 → 2026-08-30
tmax12Zbilinear365d23 1 QC5.12 [4.04, 6.37]4.80+1.43 [-0.45, 4.55]5.77 [4.45, 7.04]0% [0%, 0%]4%43%-0.40-0.422026-08-08 → 2026-08-30
tmax12Zbilinearall23 1 QC5.12 [3.97, 6.38]4.80+1.43 [-0.46, 4.98]5.77 [4.29, 7.01]0% [0%, 0%]4%43%-0.40-0.422026-08-08 → 2026-08-30
tmax12Znearest30d23 1 QC5.38 [4.56, 6.47]4.96+1.94 [0.06, 4.41]6.04 [5.01, 7.17]0% [0%, 0%]4%22%-0.47-0.472026-08-08 → 2026-08-30
tmax12Znearest90d23 1 QC5.38 [4.55, 6.62]4.96+1.94 [0.21, 5.53]6.04 [4.96, 7.35]0% [0%, 0%]4%22%-0.47-0.472026-08-08 → 2026-08-30
tmax12Znearest365d23 1 QC5.38 [4.39, 6.62]4.96+1.94 [-0.06, 5.20]6.04 [4.74, 7.41]0% [0%, 0%]4%22%-0.47-0.472026-08-08 → 2026-08-30
tmax12Znearestall23 1 QC5.38 [4.30, 6.68]4.96+1.94 [-0.13, 5.68]6.04 [4.64, 7.38]0% [0%, 0%]4%22%-0.47-0.472026-08-08 → 2026-08-30
tmin00Zbilinear30d23 1 QC5.05 [4.24, 6.13]3.85+3.23 [0.57, 5.90]5.75 [4.78, 6.87]9% [0%, 20%]13%22%-0.21-0.022026-08-08 → 2026-08-30
tmin00Zbilinear90d23 1 QC5.05 [4.28, 6.28]3.85+3.23 [0.51, 6.19]5.75 [4.84, 7.03]9% [0%, 23%]13%22%-0.21-0.022026-08-08 → 2026-08-30
tmin00Zbilinear365d23 1 QC5.05 [4.24, 6.22]3.85+3.23 [0.21, 6.10]5.75 [4.74, 6.97]9% [0%, 22%]13%22%-0.21-0.022026-08-08 → 2026-08-30
tmin00Zbilinearall23 1 QC5.05 [4.20, 6.40]3.85+3.23 [0.18, 6.38]5.75 [4.67, 7.08]9% [0%, 22%]13%22%-0.21-0.022026-08-08 → 2026-08-30
tmin00Znearest30d23 1 QC5.18 [4.29, 6.38]4.01+3.39 [0.64, 6.14]5.92 [4.85, 7.16]9% [0%, 20%]17%26%-0.24-0.072026-08-08 → 2026-08-30
tmin00Znearest90d23 1 QC5.18 [4.36, 6.61]4.01+3.39 [0.62, 6.51]5.92 [4.90, 7.39]9% [0%, 23%]17%26%-0.24-0.072026-08-08 → 2026-08-30
tmin00Znearest365d23 1 QC5.18 [4.30, 6.63]4.01+3.39 [0.30, 6.56]5.92 [4.77, 7.22]9% [0%, 22%]17%26%-0.24-0.072026-08-08 → 2026-08-30
tmin00Znearestall23 1 QC5.18 [4.24, 6.88]4.01+3.39 [0.28, 6.88]5.92 [4.73, 7.32]9% [0%, 22%]17%26%-0.24-0.072026-08-08 → 2026-08-30
tmin12Zbilinear30d23 1 QC5.25 [4.24, 6.70]3.86+3.85 [1.97, 6.19]6.21 [5.14, 7.59]9% [0%, 17%]22%26%-0.26-0.032026-08-08 → 2026-08-30
tmin12Zbilinear90d23 1 QC5.25 [4.25, 7.00]3.86+3.85 [2.17, 6.79]6.21 [5.22, 8.01]9% [0%, 17%]22%26%-0.26-0.032026-08-08 → 2026-08-30
tmin12Zbilinear365d23 1 QC5.25 [4.20, 6.90]3.86+3.85 [1.84, 6.50]6.21 [4.98, 7.80]9% [0%, 16%]22%26%-0.26-0.032026-08-08 → 2026-08-30
tmin12Zbilinearall23 1 QC5.25 [4.18, 7.19]3.86+3.85 [1.79, 6.88]6.21 [5.00, 8.10]9% [0%, 17%]22%26%-0.26-0.032026-08-08 → 2026-08-30
tmin12Znearest30d23 1 QC5.40 [4.39, 6.84]3.85+4.03 [2.11, 6.41]6.34 [5.20, 7.75]9% [0%, 17%]17%26%-0.29-0.022026-08-08 → 2026-08-30
tmin12Znearest90d23 1 QC5.40 [4.43, 7.16]3.85+4.03 [2.26, 6.95]6.34 [5.30, 8.20]9% [0%, 17%]17%26%-0.29-0.022026-08-08 → 2026-08-30
tmin12Znearest365d23 1 QC5.40 [4.31, 7.04]3.85+4.03 [1.92, 6.71]6.34 [5.10, 7.94]9% [0%, 16%]17%26%-0.29-0.022026-08-08 → 2026-08-30
tmin12Znearestall23 1 QC5.40 [4.31, 7.32]3.85+4.03 [1.95, 7.16]6.34 [5.07, 8.24]9% [0%, 17%]17%26%-0.29-0.022026-08-08 → 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 7, 00Z bilinear tmax+10+50-5-102026-08-08: +1.79 °F2026-08-09: +0.87 °F2026-08-10: +5.94 °F2026-08-11: +7.05 °F2026-08-12: +2.21 °F2026-08-13: +0.4 °F2026-08-14: -3.33 °F2026-08-15: -2.61 °F2026-08-16: +2.47 °F2026-08-17: -0.14 °F2026-08-18: -3.42 °F2026-08-19: +1.25 °F2026-08-20: -4.59 °F2026-08-21: +6.55 °F2026-08-22: +0.44 °F2026-08-23: +2.8 °F2026-08-24: -4.46 °F2026-08-25: +7.47 °F2026-08-26: -8.81 °F2026-08-27: -3.16 °F2026-08-28: +4.66 °F2026-08-29: +1.04 °F2026-08-30: -0.27 °F2026-08-082026-08-30°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 (23 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.27
2026-08-29+1.04
2026-08-28+4.66
2026-08-27-3.16
2026-08-26-8.81
2026-08-25+7.47
2026-08-24-4.46
2026-08-23+2.80
2026-08-22+0.44
2026-08-21+6.55
2026-08-20-4.59
2026-08-19+1.25
2026-08-18-3.42
2026-08-17-0.14
2026-08-16+2.47
2026-08-15-2.61
2026-08-14-3.33
2026-08-13+0.40
2026-08-12+2.21
2026-08-11+7.05
2026-08-10+5.94
2026-08-09+0.87
2026-08-08+1.79

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 7-10 to -9 °F: 0 days-9 to -8 °F: 1 day-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: 3 days-3 to -2 °F: 1 day-2 to -1 °F: 0 days-1 to 0 °F: 2 days0 to 1 °F: 3 days1 to 2 °F: 3 days2 to 3 °F: 3 days3 to 4 °F: 0 days4 to 5 °F: 1 day5 to 6 °F: 1 day6 to 7 °F: 1 day7 to 8 °F: 2 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 2.8 · P90 |e| 6.95 °F-100+10 °Fn = 23 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
-9.00-8.001
-8.00-7.000
-7.00-6.000
-6.00-5.000
-5.00-4.002
-4.00-3.003
-3.00-2.001
-2.00-1.000
-1.00+0.002
+0.00+1.003
+1.00+2.003
+2.00+3.003
+3.00+4.000
+4.00+5.001
+5.00+6.001
+6.00+7.001
+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
2026-08233.29 +0.62

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23
NCEP GFS2026-08-08 → 2026-08-30 23

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 23 +1.70 [0.65, 2.81] yes
GraphCast (IFS init) 23 +0.92 [-0.44, 2.10] no
ECMWF IFS HRES 18 +0.55 [-2.74, 2.23] no
Persistence (baseline) 23 -0.36 [-1.80, 1.06] no

Cite this page

ShortCastCheck, KTTN gfs lead 7, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KTTN/model/gfs/lead/7/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KTTN (Trenton Mercer), model gfs, lead day 7. 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/7/

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