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 4

KPHL · gfs · lead 4

Target day = initialization date + 4 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
tmax00Zbilinear30d26 1 QC3.65 [2.10, 5.11]3.37-2.07 [-3.68, -0.42]4.64 [2.66, 5.99]23% [10%, 38%]35%54%-0.02+0.022026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.65 [1.80, 5.12]3.37-2.07 [-3.63, -0.20]4.64 [2.12, 5.99]23% [7%, 44%]35%54%-0.02+0.022026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC3.65 [1.83, 5.27]3.37-2.07 [-3.88, -0.20]4.64 [2.12, 6.12]23% [7%, 46%]35%54%-0.02+0.022026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC3.65 [1.75, 5.28]3.37-2.07 [-3.79, -0.21]4.64 [1.99, 6.11]23% [6%, 44%]35%54%-0.02+0.022026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC3.57 [2.01, 5.15]3.20-2.18 [-3.66, -0.75]4.56 [2.68, 5.99]15% [0%, 36%]46%54%+0.00+0.072026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC3.57 [1.66, 5.13]3.20-2.18 [-3.66, -0.51]4.56 [2.13, 5.97]15% [0%, 38%]46%54%+0.00+0.072026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC3.57 [1.73, 5.21]3.20-2.18 [-3.82, -0.48]4.56 [2.12, 6.04]15% [0%, 39%]46%54%+0.00+0.072026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC3.57 [1.57, 5.24]3.20-2.18 [-3.73, -0.51]4.56 [2.01, 6.09]15% [0%, 41%]46%54%+0.00+0.072026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.53 [1.81, 4.80]3.25-2.68 [-4.40, -0.57]4.79 [2.46, 6.10]27% [7%, 53%]50%58%+0.01+0.062026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.53 [1.36, 4.85]3.25-2.68 [-4.51, -0.26]4.79 [1.72, 6.19]27% [8%, 58%]50%58%+0.01+0.062026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC3.53 [1.37, 5.01]3.25-2.68 [-4.71, -0.25]4.79 [1.71, 6.29]27% [6%, 57%]50%58%+0.01+0.062026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC3.53 [1.28, 5.05]3.25-2.68 [-4.61, -0.16]4.79 [1.54, 6.32]27% [7%, 61%]50%58%+0.01+0.062026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC3.66 [1.81, 5.10]3.27-3.03 [-4.80, -0.90]5.04 [2.50, 6.59]23% [11%, 44%]46%58%-0.02+0.052026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC3.66 [1.35, 5.18]3.27-3.03 [-4.94, -0.58]5.04 [1.72, 6.72]23% [13%, 50%]46%58%-0.02+0.052026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC3.66 [1.32, 5.31]3.27-3.03 [-5.12, -0.51]5.04 [1.70, 6.81]23% [12%, 48%]46%58%-0.02+0.052026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC3.66 [1.24, 5.31]3.27-3.03 [-5.03, -0.48]5.04 [1.60, 6.81]23% [12%, 50%]46%58%-0.02+0.052026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC2.31 [1.69, 2.99]2.31+0.14 [-0.86, 1.00]2.74 [2.06, 3.34]27% [13%, 43%]38%65%+0.19+0.212026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC2.31 [1.63, 3.00]2.31+0.14 [-0.93, 1.05]2.74 [1.92, 3.37]27% [14%, 46%]38%65%+0.19+0.212026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC2.31 [1.58, 3.06]2.31+0.14 [-0.98, 1.12]2.74 [1.88, 3.43]27% [12%, 46%]38%65%+0.19+0.212026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC2.31 [1.61, 3.04]2.31+0.14 [-0.98, 1.16]2.74 [1.92, 3.40]27% [12%, 45%]38%65%+0.19+0.212026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC2.21 [1.41, 3.00]2.12-0.62 [-1.50, 0.14]2.72 [1.85, 3.38]27% [7%, 55%]54%77%+0.22+0.272026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC2.21 [1.21, 3.00]2.12-0.62 [-1.56, 0.15]2.72 [1.54, 3.36]27% [7%, 60%]54%77%+0.22+0.272026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC2.21 [1.12, 3.09]2.12-0.62 [-1.57, 0.23]2.72 [1.37, 3.42]27% [0%, 67%]54%77%+0.22+0.272026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC2.21 [1.17, 3.09]2.12-0.62 [-1.66, 0.23]2.72 [1.49, 3.43]27% [4%, 67%]54%77%+0.22+0.272026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC2.48 [1.87, 3.09]2.48+0.20 [-0.68, 0.97]2.83 [2.18, 3.38]15% [0%, 30%]50%62%+0.13+0.152026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC2.48 [1.89, 3.13]2.48+0.20 [-0.79, 1.19]2.83 [2.18, 3.43]15% [0%, 30%]50%62%+0.13+0.152026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC2.48 [1.84, 3.17]2.48+0.20 [-0.89, 1.19]2.83 [2.14, 3.46]15% [0%, 30%]50%62%+0.13+0.152026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC2.48 [1.80, 3.18]2.48+0.20 [-0.84, 1.21]2.83 [2.13, 3.45]15% [0%, 31%]50%62%+0.13+0.152026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC2.44 [1.74, 3.13]2.41-0.45 [-1.20, 0.33]2.83 [2.17, 3.36]19% [0%, 37%]50%54%+0.14+0.172026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC2.44 [1.72, 3.16]2.41-0.45 [-1.36, 0.47]2.83 [2.08, 3.38]19% [0%, 38%]50%54%+0.14+0.172026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC2.44 [1.68, 3.23]2.41-0.45 [-1.45, 0.52]2.83 [2.02, 3.42]19% [0%, 38%]50%54%+0.14+0.172026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC2.44 [1.72, 3.31]2.41-0.45 [-1.46, 0.44]2.83 [2.10, 3.44]19% [0%, 38%]50%54%+0.14+0.172026-08-05 → 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 4, 00Z bilinear tmax+10+50-5-102026-08-05: -1.68 °F2026-08-06: -2.81 °F2026-08-07: +1.1 °F2026-08-08: -0.62 °F2026-08-09: +0.38 °F2026-08-10: +2.41 °F2026-08-11: -3.27 °F2026-08-12: -6.35 °F2026-08-13: -4.04 °F2026-08-14: -8.29 °F2026-08-15: -9.76 °F2026-08-16: +5.75 °F2026-08-17: -8.57 °F2026-08-18: -0.62 °F2026-08-19: -1.3 °F2026-08-20: -4.92 °F2026-08-21: -8.77 °F2026-08-22: +2.09 °F2026-08-23: -2.06 °F2026-08-24: -6.24 °F2026-08-25: +2.37 °F2026-08-26: -0.93 °F2026-08-27: +5.66 °F2026-08-28: +0.8 °F2026-08-29: -3.55 °F2026-08-30: -0.59 °F2026-08-052026-08-30°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 (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.59
2026-08-29-3.55
2026-08-28+0.80
2026-08-27+5.66
2026-08-26-0.93
2026-08-25+2.37
2026-08-24-6.24
2026-08-23-2.06
2026-08-22+2.09
2026-08-21-8.77
2026-08-20-4.92
2026-08-19-1.30
2026-08-18-0.62
2026-08-17-8.57
2026-08-16+5.75
2026-08-15-9.76
2026-08-14-8.29
2026-08-13-4.04
2026-08-12-6.35
2026-08-11-3.27
2026-08-10+2.41
2026-08-09+0.38
2026-08-08-0.62
2026-08-07+1.10
2026-08-06-2.81
2026-08-05-1.68

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 4-10 to -9 °F: 1 day-9 to -8 °F: 3 days-8 to -7 °F: 0 days-7 to -6 °F: 2 days-6 to -5 °F: 0 days-5 to -4 °F: 2 days-4 to -3 °F: 2 days-3 to -2 °F: 2 days-2 to -1 °F: 2 days-1 to 0 °F: 4 days0 to 1 °F: 2 days1 to 2 °F: 1 day2 to 3 °F: 3 days3 to 4 °F: 0 days4 to 5 °F: 0 days5 to 6 °F: 2 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 2.61 · P90 |e| 8.43 °F-100+10 °Fn = 26 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
-10.00-9.001
-9.00-8.003
-8.00-7.000
-7.00-6.002
-6.00-5.000
-5.00-4.002
-4.00-3.002
-3.00-2.002
-2.00-1.002
-1.00+0.004
+0.00+1.002
+1.00+2.001
+2.00+3.003
+3.00+4.000
+4.00+5.000
+5.00+6.002
+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
2026-08263.65 -2.07

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26

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 26 +0.75 [-0.82, 1.77] no
GraphCast (IFS init) 25 -0.72 [-2.44, 0.65] no
ECMWF IFS HRES 20 +0.41 [-0.83, 1.80] no
Persistence (baseline) 26 +0.07 [-1.83, 1.84] no

Cite this page

ShortCastCheck, KPHL gfs lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHL/model/gfs/lead/4/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHL (Philadelphia Intl), model gfs, lead day 4. 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/4/

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