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 2

KTTN · gfs · lead 2

Target day = initialization date + 2 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
tmax00Zbilinear30d28 1 QC3.08 [2.26, 4.13]3.13-0.26 [-1.68, 1.17]4.26 [2.97, 5.52]29% [15%, 41%]46%54%-0.12-0.192026-08-03 → 2026-08-30
tmax00Zbilinear90d28 1 QC3.08 [2.30, 4.40]3.13-0.26 [-2.24, 1.85]4.26 [3.04, 5.87]29% [14%, 41%]46%54%-0.12-0.192026-08-03 → 2026-08-30
tmax00Zbilinear365d28 1 QC3.08 [2.24, 4.46]3.13-0.26 [-2.56, 2.03]4.26 [2.95, 5.86]29% [13%, 43%]46%54%-0.12-0.192026-08-03 → 2026-08-30
tmax00Zbilinearall28 1 QC3.08 [2.21, 4.66]3.13-0.26 [-2.70, 1.73]4.26 [2.95, 6.10]29% [12%, 43%]46%54%-0.12-0.192026-08-03 → 2026-08-30
tmax00Znearest30d28 1 QC3.34 [2.54, 4.39]3.23+0.37 [-1.21, 1.96]4.38 [3.22, 5.66]29% [18%, 39%]43%50%-0.22-0.222026-08-03 → 2026-08-30
tmax00Znearest90d28 1 QC3.34 [2.61, 4.62]3.23+0.37 [-1.78, 2.64]4.38 [3.33, 5.98]29% [16%, 38%]43%50%-0.22-0.222026-08-03 → 2026-08-30
tmax00Znearest365d28 1 QC3.34 [2.52, 4.56]3.23+0.37 [-2.12, 2.81]4.38 [3.22, 5.93]29% [14%, 42%]43%50%-0.22-0.222026-08-03 → 2026-08-30
tmax00Znearestall28 1 QC3.34 [2.54, 4.82]3.23+0.37 [-2.18, 2.53]4.38 [3.22, 6.20]29% [14%, 41%]43%50%-0.22-0.222026-08-03 → 2026-08-30
tmax12Zbilinear30d28 1 QC2.90 [2.07, 3.94]2.94-0.14 [-1.27, 0.86]4.16 [2.68, 5.43]29% [13%, 43%]57%68%-0.06-0.122026-08-03 → 2026-08-30
tmax12Zbilinear90d28 1 QC2.90 [2.04, 4.07]2.94-0.14 [-1.60, 1.20]4.16 [2.62, 5.64]29% [11%, 43%]57%68%-0.06-0.122026-08-03 → 2026-08-30
tmax12Zbilinear365d28 1 QC2.90 [2.01, 4.20]2.94-0.14 [-1.72, 1.35]4.16 [2.57, 5.74]29% [10%, 44%]57%68%-0.06-0.122026-08-03 → 2026-08-30
tmax12Zbilinearall28 1 QC2.90 [1.98, 4.27]2.94-0.14 [-1.79, 1.21]4.16 [2.55, 5.81]29% [11%, 44%]57%68%-0.06-0.122026-08-03 → 2026-08-30
tmax12Znearest30d28 1 QC3.21 [2.37, 4.26]3.12+0.32 [-0.82, 1.38]4.44 [2.94, 5.70]18% [7%, 29%]43%61%-0.17-0.182026-08-03 → 2026-08-30
tmax12Znearest90d28 1 QC3.21 [2.37, 4.37]3.12+0.32 [-1.19, 1.73]4.44 [2.92, 5.95]18% [7%, 30%]43%61%-0.17-0.182026-08-03 → 2026-08-30
tmax12Znearest365d28 1 QC3.21 [2.32, 4.48]3.12+0.32 [-1.26, 1.91]4.44 [2.90, 6.01]18% [7%, 29%]43%61%-0.17-0.182026-08-03 → 2026-08-30
tmax12Znearestall28 1 QC3.21 [2.30, 4.64]3.12+0.32 [-1.24, 1.74]4.44 [2.87, 6.26]18% [7%, 32%]43%61%-0.17-0.182026-08-03 → 2026-08-30
tmin00Zbilinear30d28 1 QC3.34 [2.19, 4.61]2.28+3.01 [1.64, 4.55]4.15 [2.82, 5.28]21% [4%, 37%]36%61%+0.14+0.412026-08-03 → 2026-08-30
tmin00Zbilinear90d28 1 QC3.34 [2.17, 4.91]2.28+3.01 [1.52, 4.91]4.15 [2.73, 5.63]21% [0%, 40%]36%61%+0.14+0.412026-08-03 → 2026-08-30
tmin00Zbilinear365d28 1 QC3.34 [2.10, 5.19]2.28+3.01 [1.47, 5.19]4.15 [2.64, 5.78]21% [0%, 41%]36%61%+0.14+0.412026-08-03 → 2026-08-30
tmin00Zbilinearall28 1 QC3.34 [2.15, 5.08]2.28+3.01 [1.53, 5.08]4.15 [2.66, 5.67]21% [0%, 40%]36%61%+0.14+0.412026-08-03 → 2026-08-30
tmin00Znearest30d28 1 QC3.50 [2.35, 4.80]2.25+3.21 [1.85, 4.75]4.31 [2.92, 5.50]21% [7%, 39%]29%54%+0.10+0.422026-08-03 → 2026-08-30
tmin00Znearest90d28 1 QC3.50 [2.29, 5.11]2.25+3.21 [1.71, 5.11]4.31 [2.82, 5.80]21% [0%, 40%]29%54%+0.10+0.422026-08-03 → 2026-08-30
tmin00Znearest365d28 1 QC3.50 [2.21, 5.41]2.25+3.21 [1.64, 5.41]4.31 [2.72, 6.02]21% [0%, 41%]29%54%+0.10+0.422026-08-03 → 2026-08-30
tmin00Znearestall28 1 QC3.50 [2.28, 5.27]2.25+3.21 [1.71, 5.27]4.31 [2.75, 5.85]21% [0%, 39%]29%54%+0.10+0.422026-08-03 → 2026-08-30
tmin12Zbilinear30d28 1 QC3.27 [2.52, 4.10]2.19+3.00 [2.11, 3.94]4.02 [3.16, 4.80]14% [3%, 27%]43%50%+0.16+0.442026-08-03 → 2026-08-30
tmin12Zbilinear90d28 1 QC3.27 [2.55, 4.23]2.19+3.00 [2.11, 4.10]4.02 [3.18, 4.97]14% [0%, 26%]43%50%+0.16+0.442026-08-03 → 2026-08-30
tmin12Zbilinear365d28 1 QC3.27 [2.43, 4.32]2.19+3.00 [2.02, 4.22]4.02 [3.01, 5.04]14% [0%, 29%]43%50%+0.16+0.442026-08-03 → 2026-08-30
tmin12Zbilinearall28 1 QC3.27 [2.53, 4.32]2.19+3.00 [2.10, 4.15]4.02 [3.11, 5.05]14% [0%, 27%]43%50%+0.16+0.442026-08-03 → 2026-08-30
tmin12Znearest30d28 1 QC3.48 [2.72, 4.29]2.21+3.19 [2.27, 4.15]4.21 [3.36, 5.02]14% [3%, 27%]39%43%+0.10+0.432026-08-03 → 2026-08-30
tmin12Znearest90d28 1 QC3.48 [2.75, 4.44]2.21+3.19 [2.28, 4.28]4.21 [3.35, 5.16]14% [0%, 26%]39%43%+0.10+0.432026-08-03 → 2026-08-30
tmin12Znearest365d28 1 QC3.48 [2.63, 4.53]2.21+3.19 [2.18, 4.43]4.21 [3.19, 5.22]14% [0%, 29%]39%43%+0.10+0.432026-08-03 → 2026-08-30
tmin12Znearestall28 1 QC3.48 [2.74, 4.53]2.21+3.19 [2.26, 4.36]4.21 [3.29, 5.28]14% [0%, 27%]39%43%+0.10+0.432026-08-03 → 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 2, 00Z bilinear tmax+20+100-10-202026-08-03: -12.21 °F2026-08-04: -1.01 °F2026-08-05: -5.34 °F2026-08-06: -0.55 °F2026-08-07: +1.45 °F2026-08-08: +1.43 °F2026-08-09: +1.06 °F2026-08-10: +4.63 °F2026-08-11: +4.51 °F2026-08-12: -0.17 °F2026-08-13: -3.87 °F2026-08-14: +0.8 °F2026-08-15: -2.07 °F2026-08-16: -3.83 °F2026-08-17: +0.63 °F2026-08-18: -0.05 °F2026-08-19: +4.48 °F2026-08-20: -9.3 °F2026-08-21: +3.03 °F2026-08-22: -7.22 °F2026-08-23: +0.13 °F2026-08-24: -1.04 °F2026-08-25: +3.52 °F2026-08-26: +0.13 °F2026-08-27: +0.1 °F2026-08-28: +2.75 °F2026-08-29: +5.64 °F2026-08-30: +5.19 °F2026-08-032026-08-30°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 (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+5.19
2026-08-29+5.64
2026-08-28+2.75
2026-08-27+0.10
2026-08-26+0.13
2026-08-25+3.52
2026-08-24-1.04
2026-08-23+0.13
2026-08-22-7.22
2026-08-21+3.03
2026-08-20-9.30
2026-08-19+4.48
2026-08-18-0.05
2026-08-17+0.63
2026-08-16-3.83
2026-08-15-2.07
2026-08-14+0.80
2026-08-13-3.87
2026-08-12-0.17
2026-08-11+4.51
2026-08-10+4.63
2026-08-09+1.06
2026-08-08+1.43
2026-08-07+1.45
2026-08-06-0.55
2026-08-05-5.34
2026-08-04-1.01
2026-08-03-12.21

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KTTN, lead day 2-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 1 day-12 to -10 °F: 0 days-10 to -8 °F: 1 day-8 to -6 °F: 1 day-6 to -4 °F: 1 day-4 to -2 °F: 3 days-2 to 0 °F: 5 days0 to 2 °F: 8 days2 to 4 °F: 3 days4 to 6 °F: 5 days6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 2.41 · P90 |e| 6.12 °F-200+20 °Fn = 28 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
-14.00-12.001
-12.00-10.000
-10.00-8.001
-8.00-6.001
-6.00-4.001
-4.00-2.003
-2.00+0.005
+0.00+2.008
+2.00+4.003
+4.00+6.005
+6.00+8.000
+8.00+10.000
+10.00+12.000
+12.00+14.000
+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
2026-08283.08 -0.26

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28

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 28 +0.74 [0.05, 1.82] yes
Aurora (IFS init) 1 +4.88 [4.88, 4.88] yes
FourCastNet v2 (IFS init) 1 +4.12 [4.12, 4.12] yes
GraphCast (IFS init) 26 +0.41 [-0.37, 1.47] no
ECMWF IFS HRES 22 +0.88 [-0.14, 3.25] no
Pangu-Weather (IFS init) 1 +3.08 [3.08, 3.08] yes
Persistence (baseline) 28 +0.33 [-0.71, 1.90] no

Cite this page

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

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

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