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 8

KPHL · gfs · lead 8

Target day = initialization date + 8 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
tmax00Zbilinear30d22 1 QC4.89 [3.74, 5.81]4.98-2.02 [-4.81, 1.19]6.24 [5.04, 7.11]23% [6%, 41%]36%36%-0.13-0.292026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC4.89 [3.49, 5.78]4.98-2.02 [-4.93, 1.42]6.24 [4.74, 7.01]23% [0%, 43%]36%36%-0.13-0.292026-08-09 → 2026-08-30
tmax00Zbilinear365d22 1 QC4.89 [3.43, 5.80]4.98-2.02 [-5.00, 1.68]6.24 [4.71, 7.06]23% [0%, 44%]36%36%-0.13-0.292026-08-09 → 2026-08-30
tmax00Zbilinearall22 1 QC4.89 [3.45, 5.88]4.98-2.02 [-5.11, 2.04]6.24 [4.72, 7.14]23% [0%, 44%]36%36%-0.13-0.292026-08-09 → 2026-08-30
tmax00Znearest30d22 1 QC5.19 [3.78, 6.31]5.00-2.61 [-5.35, 0.59]6.59 [5.08, 7.64]18% [3%, 40%]27%36%-0.20-0.292026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC5.19 [3.42, 6.37]5.00-2.61 [-5.38, 0.78]6.59 [4.76, 7.66]18% [0%, 44%]27%36%-0.20-0.292026-08-09 → 2026-08-30
tmax00Znearest365d22 1 QC5.19 [3.48, 6.38]5.00-2.61 [-5.62, 0.93]6.59 [4.67, 7.71]18% [0%, 45%]27%36%-0.20-0.292026-08-09 → 2026-08-30
tmax00Znearestall22 1 QC5.19 [3.43, 6.39]5.00-2.61 [-5.90, 1.48]6.59 [4.58, 7.72]18% [0%, 44%]27%36%-0.20-0.292026-08-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC4.64 [3.18, 5.44]4.64-1.07 [-3.37, 1.61]5.53 [4.48, 6.15]9% [0%, 33%]23%32%-0.07-0.202026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC4.64 [2.93, 5.54]4.64-1.07 [-3.34, 1.75]5.53 [4.32, 6.16]9% [0%, 41%]23%32%-0.07-0.202026-08-09 → 2026-08-30
tmax12Zbilinear365d22 1 QC4.64 [3.12, 5.46]4.64-1.07 [-3.63, 1.91]5.53 [4.32, 6.22]9% [0%, 39%]23%32%-0.07-0.202026-08-09 → 2026-08-30
tmax12Zbilinearall22 1 QC4.64 [3.11, 5.44]4.64-1.07 [-3.50, 2.48]5.53 [4.37, 6.25]9% [0%, 40%]23%32%-0.07-0.202026-08-09 → 2026-08-30
tmax12Znearest30d22 1 QC4.69 [3.32, 5.45]4.57-1.24 [-3.63, 1.39]5.49 [4.44, 6.13]9% [0%, 33%]18%36%-0.08-0.182026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC4.69 [3.03, 5.62]4.57-1.24 [-3.67, 1.63]5.49 [4.29, 6.14]9% [0%, 41%]18%36%-0.08-0.182026-08-09 → 2026-08-30
tmax12Znearest365d22 1 QC4.69 [3.29, 5.62]4.57-1.24 [-3.95, 1.67]5.49 [4.26, 6.22]9% [0%, 39%]18%36%-0.08-0.182026-08-09 → 2026-08-30
tmax12Znearestall22 1 QC4.69 [3.32, 5.62]4.57-1.24 [-3.93, 2.44]5.49 [4.40, 6.28]9% [0%, 40%]18%36%-0.08-0.182026-08-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC3.57 [2.33, 4.49]3.57+0.38 [-1.92, 2.66]4.16 [2.93, 5.02]14% [0%, 36%]23%50%+0.12+0.012026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC3.57 [2.08, 4.49]3.57+0.38 [-1.98, 2.92]4.16 [2.69, 5.07]14% [0%, 41%]23%50%+0.12+0.012026-08-09 → 2026-08-30
tmin00Zbilinear365d22 1 QC3.57 [2.08, 4.66]3.57+0.38 [-2.15, 2.91]4.16 [2.65, 5.16]14% [0%, 40%]23%50%+0.12+0.012026-08-09 → 2026-08-30
tmin00Zbilinearall22 1 QC3.57 [2.05, 4.59]3.57+0.38 [-2.16, 3.20]4.16 [2.61, 5.10]14% [0%, 40%]23%50%+0.12+0.012026-08-09 → 2026-08-30
tmin00Znearest30d22 1 QC3.86 [2.58, 4.72]3.89-0.54 [-2.86, 1.79]4.43 [3.19, 5.21]9% [0%, 33%]18%36%+0.05-0.082026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC3.86 [2.26, 4.74]3.89-0.54 [-2.97, 2.03]4.43 [2.95, 5.23]9% [0%, 41%]18%36%+0.05-0.082026-08-09 → 2026-08-30
tmin00Znearest365d22 1 QC3.86 [2.40, 4.88]3.89-0.54 [-3.16, 2.05]4.43 [2.96, 5.42]9% [0%, 39%]18%36%+0.05-0.082026-08-09 → 2026-08-30
tmin00Znearestall22 1 QC3.86 [2.34, 4.81]3.89-0.54 [-3.16, 2.27]4.43 [2.91, 5.33]9% [0%, 40%]18%36%+0.05-0.082026-08-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC3.93 [3.02, 4.76]3.92+0.16 [-2.65, 2.72]4.75 [3.71, 5.57]9% [0%, 20%]27%45%+0.03-0.082026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC3.93 [2.86, 4.84]3.92+0.16 [-2.70, 2.97]4.75 [3.41, 5.63]9% [0%, 20%]27%45%+0.03-0.082026-08-09 → 2026-08-30
tmin12Zbilinear365d22 1 QC3.93 [2.77, 4.88]3.92+0.16 [-2.87, 3.09]4.75 [3.41, 5.65]9% [0%, 21%]27%45%+0.03-0.082026-08-09 → 2026-08-30
tmin12Zbilinearall22 1 QC3.93 [2.83, 5.02]3.92+0.16 [-2.82, 3.47]4.75 [3.40, 5.74]9% [0%, 21%]27%45%+0.03-0.082026-08-09 → 2026-08-30
tmin12Znearest30d22 1 QC3.76 [2.92, 4.61]3.77-0.52 [-3.29, 2.06]4.61 [3.56, 5.50]14% [5%, 22%]27%41%+0.07-0.042026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC3.76 [2.67, 4.70]3.77-0.52 [-3.34, 2.39]4.61 [3.24, 5.67]14% [0%, 21%]27%41%+0.07-0.042026-08-09 → 2026-08-30
tmin12Znearest365d22 1 QC3.76 [2.55, 4.71]3.77-0.52 [-3.52, 2.41]4.61 [3.24, 5.64]14% [0%, 21%]27%41%+0.07-0.042026-08-09 → 2026-08-30
tmin12Znearestall22 1 QC3.76 [2.67, 4.72]3.77-0.52 [-3.48, 2.63]4.61 [3.24, 5.71]14% [0%, 22%]27%41%+0.07-0.042026-08-09 → 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 8, 00Z bilinear tmax+20+100-10-202026-08-09: +1.04 °F2026-08-10: -1.47 °F2026-08-11: +3.18 °F2026-08-12: -11.52 °F2026-08-13: -9.95 °F2026-08-14: -1.59 °F2026-08-15: -6.73 °F2026-08-16: +0.99 °F2026-08-17: -9.39 °F2026-08-18: -4 °F2026-08-19: -5.14 °F2026-08-20: +4.64 °F2026-08-21: +3.21 °F2026-08-22: +11.2 °F2026-08-23: +0.49 °F2026-08-24: +5.47 °F2026-08-25: +0.5 °F2026-08-26: +0.23 °F2026-08-27: -11.68 °F2026-08-28: -8.45 °F2026-08-29: +0.68 °F2026-08-30: -6.09 °F2026-08-092026-08-30°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 (22 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.09
2026-08-29+0.68
2026-08-28-8.45
2026-08-27-11.68
2026-08-26+0.23
2026-08-25+0.50
2026-08-24+5.47
2026-08-23+0.49
2026-08-22+11.20
2026-08-21+3.21
2026-08-20+4.64
2026-08-19-5.14
2026-08-18-4.00
2026-08-17-9.39
2026-08-16+0.99
2026-08-15-6.73
2026-08-14-1.59
2026-08-13-9.95
2026-08-12-11.52
2026-08-11+3.18
2026-08-10-1.47
2026-08-09+1.04

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 8-20 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: 2 days-10 to -8 °F: 3 days-8 to -6 °F: 2 days-6 to -4 °F: 1 day-4 to -2 °F: 1 day-2 to 0 °F: 2 days0 to 2 °F: 6 days2 to 4 °F: 2 days4 to 6 °F: 2 days6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 4.32 · P90 |e| 11.07 °F-200+20 °Fn = 22 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
-12.00-10.002
-10.00-8.003
-8.00-6.002
-6.00-4.001
-4.00-2.001
-2.00+0.002
+0.00+2.006
+2.00+4.002
+4.00+6.002
+6.00+8.000
+8.00+10.000
+10.00+12.001
+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
2026-08224.89 -2.02

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22

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 22 +0.25 [-1.15, 1.24] no
GraphCast (IFS init) 22 -0.39 [-2.66, 0.67] no
ECMWF IFS HRES 17 +1.13 [-3.02, 2.29] no
Persistence (baseline) 22 +0.57 [-1.11, 2.39] no

Cite this page

ShortCastCheck, KPHL gfs lead 8, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHL/model/gfs/lead/8/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHL (Philadelphia Intl), model gfs, lead day 8. 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/8/

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