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 6

KPHL · gfs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC4.09 [2.57, 5.12]3.98-1.31 [-3.06, 0.49]5.07 [3.30, 6.07]12% [0%, 33%]21%42%-0.18-0.172026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC4.09 [2.10, 5.14]3.98-1.31 [-3.05, 0.71]5.07 [2.66, 6.08]12% [0%, 40%]21%42%-0.18-0.172026-08-07 → 2026-08-30
tmax00Zbilinear365d24 1 QC4.09 [1.98, 5.20]3.98-1.31 [-3.10, 0.78]5.07 [2.61, 6.14]12% [0%, 43%]21%42%-0.18-0.172026-08-07 → 2026-08-30
tmax00Zbilinearall24 1 QC4.09 [1.80, 5.28]3.98-1.31 [-3.17, 0.65]5.07 [2.40, 6.16]12% [0%, 43%]21%42%-0.18-0.172026-08-07 → 2026-08-30
tmax00Znearest30d24 1 QC4.16 [2.55, 5.38]3.96-1.39 [-3.23, 0.33]5.15 [3.18, 6.37]8% [0%, 21%]25%42%-0.20-0.162026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC4.16 [1.96, 5.38]3.96-1.39 [-3.31, 0.49]5.15 [2.24, 6.29]8% [0%, 23%]25%42%-0.20-0.162026-08-07 → 2026-08-30
tmax00Znearest365d24 1 QC4.16 [1.90, 5.48]3.96-1.39 [-3.41, 0.52]5.15 [2.10, 6.41]8% [0%, 25%]25%42%-0.20-0.162026-08-07 → 2026-08-30
tmax00Znearestall24 1 QC4.16 [1.75, 5.54]3.96-1.39 [-3.45, 0.43]5.15 [2.02, 6.43]8% [0%, 23%]25%42%-0.20-0.162026-08-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC4.47 [3.04, 5.46]4.00-2.51 [-4.13, -0.25]5.72 [3.80, 6.87]12% [0%, 27%]21%46%-0.29-0.182026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC4.47 [2.60, 5.52]4.00-2.51 [-4.19, 0.60]5.72 [3.39, 6.94]12% [0%, 33%]21%46%-0.29-0.182026-08-07 → 2026-08-30
tmax12Zbilinear365d24 1 QC4.47 [2.69, 5.77]4.00-2.51 [-4.52, 0.68]5.72 [3.44, 7.02]12% [0%, 29%]21%46%-0.29-0.182026-08-07 → 2026-08-30
tmax12Zbilinearall24 1 QC4.47 [2.53, 5.74]4.00-2.51 [-4.49, 0.70]5.72 [3.32, 7.06]12% [0%, 33%]21%46%-0.29-0.182026-08-07 → 2026-08-30
tmax12Znearest30d24 1 QC4.68 [3.38, 5.78]4.21-2.92 [-4.49, -0.75]6.07 [4.53, 7.16]12% [0%, 23%]33%50%-0.35-0.242026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC4.68 [2.93, 5.79]4.21-2.92 [-4.46, 0.07]6.07 [3.76, 7.19]12% [0%, 25%]33%50%-0.35-0.242026-08-07 → 2026-08-30
tmax12Znearest365d24 1 QC4.68 [2.94, 6.09]4.21-2.92 [-4.63, 0.07]6.07 [3.86, 7.35]12% [0%, 25%]33%50%-0.35-0.242026-08-07 → 2026-08-30
tmax12Znearestall24 1 QC4.68 [2.77, 6.11]4.21-2.92 [-4.64, 0.26]6.07 [3.56, 7.39]12% [0%, 24%]33%50%-0.35-0.242026-08-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC3.08 [2.19, 3.82]3.04+0.32 [-1.51, 2.08]3.79 [2.79, 4.53]21% [9%, 36%]33%58%+0.10+0.072026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC3.08 [2.16, 3.92]3.04+0.32 [-1.54, 2.32]3.79 [2.73, 4.59]21% [7%, 40%]33%58%+0.10+0.072026-08-07 → 2026-08-30
tmin00Zbilinear365d24 1 QC3.08 [2.19, 4.09]3.04+0.32 [-1.72, 2.36]3.79 [2.76, 4.70]21% [7%, 38%]33%58%+0.10+0.072026-08-07 → 2026-08-30
tmin00Zbilinearall24 1 QC3.08 [2.19, 3.97]3.04+0.32 [-1.75, 2.42]3.79 [2.70, 4.64]21% [7%, 40%]33%58%+0.10+0.072026-08-07 → 2026-08-30
tmin00Znearest30d24 1 QC3.01 [1.85, 4.03]3.01-0.46 [-2.27, 1.35]3.67 [2.34, 4.62]17% [4%, 31%]42%58%+0.12+0.072026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC3.01 [1.67, 4.06]3.01-0.46 [-2.30, 1.62]3.67 [2.15, 4.64]17% [5%, 36%]42%58%+0.12+0.072026-08-07 → 2026-08-30
tmin00Znearest365d24 1 QC3.01 [1.69, 4.32]3.01-0.46 [-2.49, 1.67]3.67 [2.12, 4.75]17% [0%, 33%]42%58%+0.12+0.072026-08-07 → 2026-08-30
tmin00Znearestall24 1 QC3.01 [1.64, 4.23]3.01-0.46 [-2.48, 1.71]3.67 [2.14, 4.72]17% [0%, 33%]42%58%+0.12+0.072026-08-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC3.06 [2.18, 3.89]3.04+0.14 [-1.86, 2.49]4.21 [3.10, 5.02]33% [19%, 45%]54%58%+0.10+0.072026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC3.06 [1.98, 4.01]3.04+0.14 [-1.84, 3.12]4.21 [2.72, 5.12]33% [17%, 44%]54%58%+0.10+0.072026-08-07 → 2026-08-30
tmin12Zbilinear365d24 1 QC3.06 [1.97, 4.14]3.04+0.14 [-2.12, 3.08]4.21 [2.61, 5.27]33% [15%, 46%]54%58%+0.10+0.072026-08-07 → 2026-08-30
tmin12Zbilinearall24 1 QC3.06 [1.97, 4.17]3.04+0.14 [-2.09, 3.38]4.21 [2.66, 5.21]33% [17%, 45%]54%58%+0.10+0.072026-08-07 → 2026-08-30
tmin12Znearest30d24 1 QC3.14 [1.99, 4.10]3.17-0.59 [-2.63, 1.68]4.31 [3.04, 5.20]33% [19%, 47%]54%54%+0.08+0.022026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC3.14 [1.73, 4.17]3.17-0.59 [-2.62, 2.30]4.31 [2.66, 5.29]33% [18%, 48%]54%54%+0.08+0.022026-08-07 → 2026-08-30
tmin12Znearest365d24 1 QC3.14 [1.76, 4.27]3.17-0.59 [-2.90, 2.26]4.31 [2.43, 5.35]33% [17%, 47%]54%54%+0.08+0.022026-08-07 → 2026-08-30
tmin12Znearestall24 1 QC3.14 [1.73, 4.25]3.17-0.59 [-2.86, 2.48]4.31 [2.52, 5.27]33% [14%, 47%]54%54%+0.08+0.022026-08-07 → 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 6, 00Z bilinear tmax+20+100-10-202026-08-07: -1.06 °F2026-08-08: +3.47 °F2026-08-09: +0.47 °F2026-08-10: +4.44 °F2026-08-11: +4.27 °F2026-08-12: -7.73 °F2026-08-13: -4.42 °F2026-08-14: -4.71 °F2026-08-15: -12.63 °F2026-08-16: +2.96 °F2026-08-17: -4.13 °F2026-08-18: -2.8 °F2026-08-19: -2.86 °F2026-08-20: +5.71 °F2026-08-21: +1.05 °F2026-08-22: -10.74 °F2026-08-23: +3.56 °F2026-08-24: -3.32 °F2026-08-25: +6.91 °F2026-08-26: -2.14 °F2026-08-27: -5.45 °F2026-08-28: -2.61 °F2026-08-29: +0.46 °F2026-08-30: -0.25 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.25
2026-08-29+0.46
2026-08-28-2.61
2026-08-27-5.45
2026-08-26-2.14
2026-08-25+6.91
2026-08-24-3.32
2026-08-23+3.56
2026-08-22-10.74
2026-08-21+1.05
2026-08-20+5.71
2026-08-19-2.86
2026-08-18-2.80
2026-08-17-4.13
2026-08-16+2.96
2026-08-15-12.63
2026-08-14-4.71
2026-08-13-4.42
2026-08-12-7.73
2026-08-11+4.27
2026-08-10+4.44
2026-08-09+0.47
2026-08-08+3.47
2026-08-07-1.06

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 6-20 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: 1 day-10 to -8 °F: 0 days-8 to -6 °F: 1 day-6 to -4 °F: 4 days-4 to -2 °F: 5 days-2 to 0 °F: 2 days0 to 2 °F: 3 days2 to 4 °F: 3 days4 to 6 °F: 3 days6 to 8 °F: 1 day8 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| 3.51 · P90 |e| 7.49 °F-200+20 °Fn = 24 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
-12.00-10.001
-10.00-8.000
-8.00-6.001
-6.00-4.004
-4.00-2.005
-2.00+0.002
+0.00+2.003
+2.00+4.003
+4.00+6.003
+6.00+8.001
+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
2026-08244.09 -1.31

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24

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 24 +0.84 [-0.95, 1.86] no
GraphCast (IFS init) 24 -0.38 [-2.45, 0.70] no
ECMWF IFS HRES 19 -0.45 [-3.97, 1.05] no
Persistence (baseline) 24 +0.63 [-1.37, 1.88] no

Cite this page

ShortCastCheck, KPHL gfs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHL/model/gfs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHL (Philadelphia Intl), model gfs, lead day 6. 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/6/

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