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 3

KPHL · gfs · lead 3

Target day = initialization date + 3 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
tmax00Zbilinear30d27 1 QC3.12 [2.55, 3.87]2.53-1.93 [-3.17, -0.82]4.05 [3.15, 5.19]15% [3%, 28%]41%63%+0.08+0.252026-08-04 → 2026-08-30
tmax00Zbilinear90d27 1 QC3.12 [2.47, 3.95]2.53-1.93 [-3.39, -0.61]4.05 [3.02, 5.27]15% [0%, 29%]41%63%+0.08+0.252026-08-04 → 2026-08-30
tmax00Zbilinear365d27 1 QC3.12 [2.41, 4.01]2.53-1.93 [-3.30, -0.66]4.05 [2.94, 5.24]15% [0%, 29%]41%63%+0.08+0.252026-08-04 → 2026-08-30
tmax00Zbilinearall27 1 QC3.12 [2.42, 4.03]2.53-1.93 [-3.43, -0.54]4.05 [2.93, 5.30]15% [0%, 29%]41%63%+0.08+0.252026-08-04 → 2026-08-30
tmax00Znearest30d27 1 QC3.14 [2.50, 4.04]2.40-2.07 [-3.49, -0.95]4.10 [3.00, 5.46]19% [7%, 31%]33%63%+0.08+0.292026-08-04 → 2026-08-30
tmax00Znearest90d27 1 QC3.14 [2.40, 4.15]2.40-2.07 [-3.69, -0.74]4.10 [2.82, 5.63]19% [6%, 33%]33%63%+0.08+0.292026-08-04 → 2026-08-30
tmax00Znearest365d27 1 QC3.14 [2.34, 4.11]2.40-2.07 [-3.63, -0.73]4.10 [2.73, 5.50]19% [6%, 33%]33%63%+0.08+0.292026-08-04 → 2026-08-30
tmax00Znearestall27 1 QC3.14 [2.34, 4.20]2.40-2.07 [-3.76, -0.67]4.10 [2.70, 5.58]19% [5%, 33%]33%63%+0.08+0.292026-08-04 → 2026-08-30
tmax12Zbilinear30d27 1 QC3.02 [2.38, 3.59]2.63-1.69 [-2.82, -0.72]3.76 [3.18, 4.27]15% [0%, 37%]48%52%+0.12+0.222026-08-04 → 2026-08-30
tmax12Zbilinear90d27 1 QC3.02 [2.26, 3.70]2.63-1.69 [-3.00, -0.56]3.76 [3.04, 4.42]15% [0%, 40%]48%52%+0.12+0.222026-08-04 → 2026-08-30
tmax12Zbilinear365d27 1 QC3.02 [2.20, 3.72]2.63-1.69 [-3.00, -0.45]3.76 [2.99, 4.39]15% [0%, 38%]48%52%+0.12+0.222026-08-04 → 2026-08-30
tmax12Zbilinearall27 1 QC3.02 [2.26, 3.75]2.63-1.69 [-3.33, -0.45]3.76 [3.04, 4.44]15% [0%, 40%]48%52%+0.12+0.222026-08-04 → 2026-08-30
tmax12Znearest30d27 1 QC3.09 [2.46, 3.69]2.72-1.77 [-2.95, -0.71]3.86 [3.21, 4.39]15% [0%, 30%]48%59%+0.09+0.202026-08-04 → 2026-08-30
tmax12Znearest90d27 1 QC3.09 [2.34, 3.78]2.72-1.77 [-3.11, -0.52]3.86 [3.10, 4.51]15% [0%, 31%]48%59%+0.09+0.202026-08-04 → 2026-08-30
tmax12Znearest365d27 1 QC3.09 [2.33, 3.81]2.72-1.77 [-3.13, -0.40]3.86 [3.06, 4.49]15% [0%, 30%]48%59%+0.09+0.202026-08-04 → 2026-08-30
tmax12Znearestall27 1 QC3.09 [2.31, 3.82]2.72-1.77 [-3.41, -0.41]3.86 [3.03, 4.49]15% [0%, 31%]48%59%+0.09+0.202026-08-04 → 2026-08-30
tmin00Zbilinear30d27 1 QC1.83 [1.50, 2.23]1.80+0.67 [-0.28, 1.58]2.46 [1.90, 3.00]41% [21%, 54%]63%78%+0.48+0.482026-08-04 → 2026-08-30
tmin00Zbilinear90d27 1 QC1.83 [1.48, 2.35]1.80+0.67 [-0.31, 1.92]2.46 [1.77, 3.11]41% [17%, 55%]63%78%+0.48+0.482026-08-04 → 2026-08-30
tmin00Zbilinear365d27 1 QC1.83 [1.48, 2.45]1.80+0.67 [-0.45, 1.90]2.46 [1.69, 3.16]41% [17%, 57%]63%78%+0.48+0.482026-08-04 → 2026-08-30
tmin00Zbilinearall27 1 QC1.83 [1.49, 2.40]1.80+0.67 [-0.34, 1.94]2.46 [1.72, 3.10]41% [14%, 57%]63%78%+0.48+0.482026-08-04 → 2026-08-30
tmin00Znearest30d27 1 QC1.79 [1.49, 2.08]1.78-0.27 [-1.21, 0.68]2.30 [1.99, 2.55]41% [26%, 53%]67%74%+0.49+0.482026-08-04 → 2026-08-30
tmin00Znearest90d27 1 QC1.79 [1.48, 2.13]1.78-0.27 [-1.24, 0.92]2.30 [1.94, 2.62]41% [28%, 52%]67%74%+0.49+0.482026-08-04 → 2026-08-30
tmin00Znearest365d27 1 QC1.79 [1.51, 2.17]1.78-0.27 [-1.27, 0.97]2.30 [1.94, 2.65]41% [23%, 52%]67%74%+0.49+0.482026-08-04 → 2026-08-30
tmin00Znearestall27 1 QC1.79 [1.50, 2.17]1.78-0.27 [-1.25, 0.99]2.30 [1.95, 2.63]41% [23%, 50%]67%74%+0.49+0.482026-08-04 → 2026-08-30
tmin12Zbilinear30d27 1 QC1.75 [1.20, 2.34]1.82+0.51 [-0.48, 1.55]2.47 [1.66, 3.25]41% [23%, 56%]59%85%+0.50+0.472026-08-04 → 2026-08-30
tmin12Zbilinear90d27 1 QC1.75 [1.14, 2.48]1.82+0.51 [-0.55, 1.74]2.47 [1.55, 3.37]41% [22%, 57%]59%85%+0.50+0.472026-08-04 → 2026-08-30
tmin12Zbilinear365d27 1 QC1.75 [1.12, 2.51]1.82+0.51 [-0.59, 1.77]2.47 [1.56, 3.38]41% [20%, 59%]59%85%+0.50+0.472026-08-04 → 2026-08-30
tmin12Zbilinearall27 1 QC1.75 [1.13, 2.46]1.82+0.51 [-0.59, 1.82]2.47 [1.57, 3.36]41% [20%, 59%]59%85%+0.50+0.472026-08-04 → 2026-08-30
tmin12Znearest30d27 1 QC1.96 [1.54, 2.36]1.96-0.04 [-1.11, 1.10]2.45 [1.99, 2.88]30% [19%, 41%]63%81%+0.44+0.432026-08-04 → 2026-08-30
tmin12Znearest90d27 1 QC1.96 [1.49, 2.40]1.96-0.04 [-1.24, 1.32]2.45 [1.91, 2.93]30% [18%, 43%]63%81%+0.44+0.432026-08-04 → 2026-08-30
tmin12Znearest365d27 1 QC1.96 [1.49, 2.43]1.96-0.04 [-1.25, 1.35]2.45 [1.94, 2.92]30% [18%, 43%]63%81%+0.44+0.432026-08-04 → 2026-08-30
tmin12Znearestall27 1 QC1.96 [1.47, 2.41]1.96-0.04 [-1.23, 1.26]2.45 [1.92, 2.91]30% [18%, 43%]63%81%+0.44+0.432026-08-04 → 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 3, 00Z bilinear tmax+20+100-10-202026-08-04: -7.98 °F2026-08-05: -4.06 °F2026-08-06: -0.11 °F2026-08-07: -1.14 °F2026-08-08: +0.45 °F2026-08-09: -1.14 °F2026-08-10: +3.2 °F2026-08-11: +5.02 °F2026-08-12: -4.42 °F2026-08-13: -1.16 °F2026-08-14: -6.59 °F2026-08-15: -2.97 °F2026-08-16: -4.12 °F2026-08-17: -2.36 °F2026-08-18: -1.92 °F2026-08-19: -0.84 °F2026-08-20: +4.8 °F2026-08-21: -0.79 °F2026-08-22: -4.63 °F2026-08-23: -2.87 °F2026-08-24: -2.48 °F2026-08-25: +1.61 °F2026-08-26: -2.07 °F2026-08-27: -2.53 °F2026-08-28: -12.13 °F2026-08-29: -1.8 °F2026-08-30: +1.03 °F2026-08-042026-08-30°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 (27 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.03
2026-08-29-1.80
2026-08-28-12.13
2026-08-27-2.53
2026-08-26-2.07
2026-08-25+1.61
2026-08-24-2.48
2026-08-23-2.87
2026-08-22-4.63
2026-08-21-0.79
2026-08-20+4.80
2026-08-19-0.84
2026-08-18-1.92
2026-08-17-2.36
2026-08-16-4.12
2026-08-15-2.97
2026-08-14-6.59
2026-08-13-1.16
2026-08-12-4.42
2026-08-11+5.02
2026-08-10+3.20
2026-08-09-1.14
2026-08-08+0.45
2026-08-07-1.14
2026-08-06-0.11
2026-08-05-4.06
2026-08-04-7.98

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 3-20 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: 0 days-8 to -6 °F: 2 days-6 to -4 °F: 4 days-4 to -2 °F: 6 days-2 to 0 °F: 8 days0 to 2 °F: 3 days2 to 4 °F: 1 day4 to 6 °F: 2 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| 2.48 · P90 |e| 5.65 °F-200+20 °Fn = 27 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
-10.00-8.000
-8.00-6.002
-6.00-4.004
-4.00-2.006
-2.00+0.008
+0.00+2.003
+2.00+4.001
+4.00+6.002
+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
2026-08273.12 -1.93

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27

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 27 +0.68 [-0.29, 1.61] no
GraphCast (IFS init) 25 -1.33 [-2.35, -0.33] yes
ECMWF IFS HRES 22 +0.22 [-0.67, 1.36] no
Persistence (baseline) 27 -0.29 [-1.73, 1.09] no

Cite this page

ShortCastCheck, KPHL gfs lead 3, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHL/model/gfs/lead/3/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHL (Philadelphia Intl), model gfs, lead day 3. 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/3/

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