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

Philadelphia Intl · NCEP GFS · lead day 1

KPHL · 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 QC2.88 [1.90, 3.74]2.34-2.49 [-3.61, -1.33]3.78 [2.79, 4.55]31% [13%, 52%]41%62%+0.10+0.272026-08-02 → 2026-08-30
tmax00Zbilinear90d29 1 QC2.88 [1.53, 4.09]2.34-2.49 [-3.99, -0.84]3.78 [2.35, 4.79]31% [11%, 60%]41%62%+0.10+0.272026-08-02 → 2026-08-30
tmax00Zbilinear365d29 1 QC2.88 [1.34, 4.13]2.34-2.49 [-4.06, -0.65]3.78 [2.10, 4.90]31% [9%, 64%]41%62%+0.10+0.272026-08-02 → 2026-08-30
tmax00Zbilinearall29 1 QC2.88 [1.56, 4.20]2.34-2.49 [-4.09, -0.81]3.78 [2.36, 4.91]31% [9%, 61%]41%62%+0.10+0.272026-08-02 → 2026-08-30
tmax00Znearest30d29 1 QC2.77 [1.90, 3.54]2.20-2.44 [-3.40, -1.41]3.65 [2.70, 4.37]28% [13%, 50%]48%66%+0.14+0.322026-08-02 → 2026-08-30
tmax00Znearest90d29 1 QC2.77 [1.57, 3.96]2.20-2.44 [-3.77, -1.01]3.65 [2.29, 4.78]28% [10%, 57%]48%66%+0.14+0.322026-08-02 → 2026-08-30
tmax00Znearest365d29 1 QC2.77 [1.41, 3.96]2.20-2.44 [-3.78, -0.77]3.65 [2.04, 4.70]28% [9%, 64%]48%66%+0.14+0.322026-08-02 → 2026-08-30
tmax00Znearestall29 1 QC2.77 [1.63, 4.13]2.20-2.44 [-4.07, -0.97]3.65 [2.33, 4.89]28% [10%, 59%]48%66%+0.14+0.322026-08-02 → 2026-08-30
tmax12Zbilinear30d29 1 QC2.60 [1.90, 3.27]2.35-1.73 [-2.82, -0.54]3.55 [2.60, 4.30]34% [24%, 45%]59%62%+0.19+0.272026-08-02 → 2026-08-30
tmax12Zbilinear90d29 1 QC2.60 [1.64, 3.69]2.35-1.73 [-3.26, -0.24]3.55 [2.19, 4.75]34% [24%, 47%]59%62%+0.19+0.272026-08-02 → 2026-08-30
tmax12Zbilinear365d29 1 QC2.60 [1.46, 3.62]2.35-1.73 [-3.24, -0.16]3.55 [1.93, 4.70]34% [23%, 50%]59%62%+0.19+0.272026-08-02 → 2026-08-30
tmax12Zbilinearall29 1 QC2.60 [1.68, 3.91]2.35-1.73 [-3.53, -0.22]3.55 [2.22, 4.86]34% [22%, 47%]59%62%+0.19+0.272026-08-02 → 2026-08-30
tmax12Znearest30d29 1 QC2.45 [1.84, 3.05]2.37-1.64 [-2.63, -0.62]3.44 [2.56, 4.16]38% [29%, 48%]52%66%+0.24+0.262026-08-02 → 2026-08-30
tmax12Znearest90d29 1 QC2.45 [1.57, 3.41]2.37-1.64 [-2.96, -0.26]3.44 [2.15, 4.39]38% [26%, 52%]52%66%+0.24+0.262026-08-02 → 2026-08-30
tmax12Znearest365d29 1 QC2.45 [1.45, 3.37]2.37-1.64 [-3.04, -0.23]3.44 [1.91, 4.47]38% [26%, 50%]52%66%+0.24+0.262026-08-02 → 2026-08-30
tmax12Znearestall29 1 QC2.45 [1.63, 3.58]2.37-1.64 [-3.24, -0.29]3.44 [2.17, 4.57]38% [25%, 50%]52%66%+0.24+0.262026-08-02 → 2026-08-30
tmin00Zbilinear30d29 1 QC1.85 [1.50, 2.28]1.85+0.08 [-1.14, 1.16]2.45 [1.92, 3.07]38% [28%, 47%]59%86%+0.33+0.332026-08-02 → 2026-08-30
tmin00Zbilinear90d29 1 QC1.85 [1.40, 2.29]1.85+0.08 [-1.16, 1.40]2.45 [1.83, 3.04]38% [27%, 47%]59%86%+0.33+0.332026-08-02 → 2026-08-30
tmin00Zbilinear365d29 1 QC1.85 [1.40, 2.43]1.85+0.08 [-1.29, 1.54]2.45 [1.84, 3.16]38% [25%, 48%]59%86%+0.33+0.332026-08-02 → 2026-08-30
tmin00Zbilinearall29 1 QC1.85 [1.42, 2.32]1.85+0.08 [-1.23, 1.50]2.45 [1.86, 3.06]38% [27%, 47%]59%86%+0.33+0.332026-08-02 → 2026-08-30
tmin00Znearest30d29 1 QC1.95 [1.56, 2.43]1.94-0.47 [-1.66, 0.70]2.52 [1.90, 3.15]31% [17%, 45%]69%76%+0.29+0.302026-08-02 → 2026-08-30
tmin00Znearest90d29 1 QC1.95 [1.49, 2.40]1.94-0.47 [-1.72, 0.85]2.52 [1.81, 3.14]31% [16%, 46%]69%76%+0.29+0.302026-08-02 → 2026-08-30
tmin00Znearest365d29 1 QC1.95 [1.49, 2.51]1.94-0.47 [-1.84, 0.90]2.52 [1.78, 3.23]31% [14%, 46%]69%76%+0.29+0.302026-08-02 → 2026-08-30
tmin00Znearestall29 1 QC1.95 [1.48, 2.41]1.94-0.47 [-1.77, 0.90]2.52 [1.77, 3.15]31% [16%, 44%]69%76%+0.29+0.302026-08-02 → 2026-08-30
tmin12Zbilinear30d29 1 QC1.82 [1.48, 2.19]1.81+0.03 [-0.70, 0.78]2.20 [1.80, 2.63]31% [17%, 46%]59%86%+0.34+0.342026-08-02 → 2026-08-30
tmin12Zbilinear90d29 1 QC1.82 [1.42, 2.21]1.81+0.03 [-0.82, 1.05]2.20 [1.76, 2.64]31% [15%, 50%]59%86%+0.34+0.342026-08-02 → 2026-08-30
tmin12Zbilinear365d29 1 QC1.82 [1.38, 2.28]1.81+0.03 [-0.88, 1.31]2.20 [1.74, 2.71]31% [14%, 50%]59%86%+0.34+0.342026-08-02 → 2026-08-30
tmin12Zbilinearall29 1 QC1.82 [1.44, 2.21]1.81+0.03 [-0.87, 1.07]2.20 [1.75, 2.65]31% [14%, 50%]59%86%+0.34+0.342026-08-02 → 2026-08-30
tmin12Znearest30d29 1 QC1.91 [1.47, 2.40]1.88-0.51 [-1.21, 0.18]2.33 [1.78, 2.88]28% [17%, 39%]59%83%+0.31+0.322026-08-02 → 2026-08-30
tmin12Znearest90d29 1 QC1.91 [1.41, 2.41]1.88-0.51 [-1.33, 0.36]2.33 [1.69, 2.89]28% [12%, 42%]59%83%+0.31+0.322026-08-02 → 2026-08-30
tmin12Znearest365d29 1 QC1.91 [1.33, 2.45]1.88-0.51 [-1.38, 0.55]2.33 [1.61, 2.95]28% [11%, 43%]59%83%+0.31+0.322026-08-02 → 2026-08-30
tmin12Znearestall29 1 QC1.91 [1.41, 2.41]1.88-0.51 [-1.40, 0.40]2.33 [1.68, 2.90]28% [12%, 43%]59%83%+0.31+0.322026-08-02 → 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 KPHL, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-02: -6.49 °F2026-08-03: -7.36 °F2026-08-04: -2.47 °F2026-08-05: -6.66 °F2026-08-06: -1.14 °F2026-08-07: -0.41 °F2026-08-08: +0.85 °F2026-08-09: -0.6 °F2026-08-10: +2.72 °F2026-08-11: +1.1 °F2026-08-12: -5.06 °F2026-08-13: -2.38 °F2026-08-14: -3.82 °F2026-08-15: -3.03 °F2026-08-16: -5.82 °F2026-08-17: -4.6 °F2026-08-18: +0.45 °F2026-08-19: -2.82 °F2026-08-20: -5.4 °F2026-08-21: -3.19 °F2026-08-22: -8.99 °F2026-08-23: -1.39 °F2026-08-24: -2.92 °F2026-08-25: -0.13 °F2026-08-26: -2.57 °F2026-08-27: -0.44 °F2026-08-28: +0.58 °F2026-08-29: -0.09 °F2026-08-30: -0.08 °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
2026-08-30-0.08
2026-08-29-0.09
2026-08-28+0.58
2026-08-27-0.44
2026-08-26-2.57
2026-08-25-0.13
2026-08-24-2.92
2026-08-23-1.39
2026-08-22-8.99
2026-08-21-3.19
2026-08-20-5.40
2026-08-19-2.82
2026-08-18+0.45
2026-08-17-4.60
2026-08-16-5.82
2026-08-15-3.03
2026-08-14-3.82
2026-08-13-2.38
2026-08-12-5.06
2026-08-11+1.10
2026-08-10+2.72
2026-08-09-0.60
2026-08-08+0.85
2026-08-07-0.41
2026-08-06-1.14
2026-08-05-6.66
2026-08-04-2.47
2026-08-03-7.36
2026-08-02-6.49

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 1-10 to -9 °F: 0 days-9 to -8 °F: 1 day-8 to -7 °F: 1 day-7 to -6 °F: 2 days-6 to -5 °F: 3 days-5 to -4 °F: 1 day-4 to -3 °F: 3 days-3 to -2 °F: 5 days-2 to -1 °F: 2 days-1 to 0 °F: 6 days0 to 1 °F: 3 days1 to 2 °F: 1 day2 to 3 °F: 1 day3 to 4 °F: 0 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 2.57 · P90 |e| 6.52 °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
-10.00-9.000
-9.00-8.001
-8.00-7.001
-7.00-6.002
-6.00-5.003
-5.00-4.001
-4.00-3.003
-3.00-2.005
-2.00-1.002
-1.00+0.006
+0.00+1.003
+1.00+2.001
+2.00+3.001
+3.00+4.000
+4.00+5.000
+5.00+6.000
+6.00+7.000
+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
2026-08292.88 -2.49

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 +0.47 [-0.79, 1.44] no
Aurora (GFS init) 1 -6.44 [-6.44, -6.44] yes
Aurora (IFS init) 2 -4.10 [-4.76, -3.45] yes
FourCastNet v2 (GFS init) 1 -4.64 [-4.64, -4.64] yes
FourCastNet v2 (IFS init) 2 -2.62 [-5.17, -0.07] yes
GraphCast (GFS init) 1 -6.27 [-6.27, -6.27] yes
GraphCast (IFS init) 27 -2.10 [-3.26, -1.33] yes
ECMWF IFS HRES 23 -1.36 [-3.36, 0.48] no
Pangu-Weather (GFS init) 1 -2.46 [-2.46, -2.46] yes
Pangu-Weather (IFS init) 2 -1.57 [-3.23, 0.09] no
Persistence (baseline) 29 -0.33 [-2.14, 1.25] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHL (Philadelphia Intl), 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/KPHL/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