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 2

KPHL · gfs · lead 2

Target day = initialization date + 2 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
tmax00Zbilinear30d28 1 QC3.60 [2.69, 4.47]3.02-2.68 [-3.93, -1.45]4.73 [3.50, 5.95]21% [7%, 39%]36%50%-0.29-0.082026-08-03 → 2026-08-30
tmax00Zbilinear90d28 1 QC3.60 [2.42, 4.89]3.02-2.68 [-4.42, -0.93]4.73 [3.00, 6.47]21% [6%, 42%]36%50%-0.29-0.082026-08-03 → 2026-08-30
tmax00Zbilinear365d28 1 QC3.60 [2.34, 4.86]3.02-2.68 [-4.42, -0.69]4.73 [2.85, 6.44]21% [5%, 42%]36%50%-0.29-0.082026-08-03 → 2026-08-30
tmax00Zbilinearall28 1 QC3.60 [2.46, 5.20]3.02-2.68 [-4.70, -1.05]4.73 [3.14, 6.76]21% [3%, 42%]36%50%-0.29-0.082026-08-03 → 2026-08-30
tmax00Znearest30d28 1 QC3.67 [2.84, 4.67]3.08-2.81 [-4.10, -1.66]4.86 [3.58, 6.27]21% [11%, 33%]36%50%-0.32-0.112026-08-03 → 2026-08-30
tmax00Znearest90d28 1 QC3.67 [2.56, 5.12]3.08-2.81 [-4.66, -1.12]4.86 [3.10, 6.81]21% [10%, 35%]36%50%-0.32-0.112026-08-03 → 2026-08-30
tmax00Znearest365d28 1 QC3.67 [2.46, 5.07]3.08-2.81 [-4.62, -0.84]4.86 [2.95, 6.72]21% [10%, 36%]36%50%-0.32-0.112026-08-03 → 2026-08-30
tmax00Znearestall28 1 QC3.67 [2.57, 5.46]3.08-2.81 [-4.92, -1.23]4.86 [3.25, 7.18]21% [8%, 36%]36%50%-0.32-0.112026-08-03 → 2026-08-30
tmax12Zbilinear30d28 1 QC2.85 [2.15, 3.55]2.26-2.58 [-3.43, -1.69]3.88 [2.89, 4.75]25% [10%, 37%]50%68%-0.02+0.192026-08-03 → 2026-08-30
tmax12Zbilinear90d28 1 QC2.85 [1.96, 3.80]2.26-2.58 [-3.72, -1.48]3.88 [2.51, 4.98]25% [11%, 40%]50%68%-0.02+0.192026-08-03 → 2026-08-30
tmax12Zbilinear365d28 1 QC2.85 [1.83, 3.77]2.26-2.58 [-3.69, -1.38]3.88 [2.34, 5.04]25% [10%, 41%]50%68%-0.02+0.192026-08-03 → 2026-08-30
tmax12Zbilinearall28 1 QC2.85 [2.00, 3.86]2.26-2.58 [-3.81, -1.50]3.88 [2.48, 5.11]25% [11%, 42%]50%68%-0.02+0.192026-08-03 → 2026-08-30
tmax12Znearest30d28 1 QC2.98 [2.24, 3.75]2.39-2.76 [-3.66, -1.81]4.07 [3.06, 4.96]29% [14%, 44%]50%64%-0.07+0.142026-08-03 → 2026-08-30
tmax12Znearest90d28 1 QC2.98 [1.94, 4.01]2.39-2.76 [-3.98, -1.54]4.07 [2.64, 5.21]29% [12%, 48%]50%64%-0.07+0.142026-08-03 → 2026-08-30
tmax12Znearest365d28 1 QC2.98 [1.83, 4.09]2.39-2.76 [-4.04, -1.45]4.07 [2.45, 5.30]29% [13%, 53%]50%64%-0.07+0.142026-08-03 → 2026-08-30
tmax12Znearestall28 1 QC2.98 [1.97, 4.15]2.39-2.76 [-4.11, -1.56]4.07 [2.56, 5.32]29% [12%, 50%]50%64%-0.07+0.142026-08-03 → 2026-08-30
tmin00Zbilinear30d28 1 QC1.94 [1.66, 2.20]1.91+0.17 [-1.00, 1.34]2.54 [2.17, 2.86]39% [27%, 54%]61%79%+0.45+0.472026-08-03 → 2026-08-30
tmin00Zbilinear90d28 1 QC1.94 [1.56, 2.36]1.91+0.17 [-1.15, 1.57]2.54 [2.06, 3.03]39% [26%, 57%]61%79%+0.45+0.472026-08-03 → 2026-08-30
tmin00Zbilinear365d28 1 QC1.94 [1.55, 2.46]1.91+0.17 [-1.24, 1.76]2.54 [2.07, 3.08]39% [24%, 57%]61%79%+0.45+0.472026-08-03 → 2026-08-30
tmin00Zbilinearall28 1 QC1.94 [1.61, 2.35]1.91+0.17 [-1.18, 1.74]2.54 [2.08, 3.02]39% [26%, 57%]61%79%+0.45+0.472026-08-03 → 2026-08-30
tmin00Znearest30d28 1 QC1.84 [1.42, 2.27]1.83-0.44 [-1.62, 0.74]2.57 [2.15, 3.00]50% [36%, 64%]64%71%+0.48+0.492026-08-03 → 2026-08-30
tmin00Znearest90d28 1 QC1.84 [1.35, 2.33]1.83-0.44 [-1.82, 0.94]2.57 [2.04, 3.15]50% [33%, 65%]64%71%+0.48+0.492026-08-03 → 2026-08-30
tmin00Znearest365d28 1 QC1.84 [1.40, 2.37]1.83-0.44 [-1.79, 1.16]2.57 [2.08, 3.14]50% [33%, 67%]64%71%+0.48+0.492026-08-03 → 2026-08-30
tmin00Znearestall28 1 QC1.84 [1.36, 2.31]1.83-0.44 [-1.82, 0.99]2.57 [2.10, 3.08]50% [33%, 67%]64%71%+0.48+0.492026-08-03 → 2026-08-30
tmin12Zbilinear30d28 1 QC2.05 [1.69, 2.43]1.95+0.35 [-0.41, 1.19]2.43 [2.02, 2.83]29% [14%, 46%]57%82%+0.42+0.462026-08-03 → 2026-08-30
tmin12Zbilinear90d28 1 QC2.05 [1.64, 2.46]1.95+0.35 [-0.48, 1.33]2.43 [1.95, 2.85]29% [13%, 50%]57%82%+0.42+0.462026-08-03 → 2026-08-30
tmin12Zbilinear365d28 1 QC2.05 [1.64, 2.46]1.95+0.35 [-0.56, 1.35]2.43 [1.94, 2.87]29% [14%, 50%]57%82%+0.42+0.462026-08-03 → 2026-08-30
tmin12Zbilinearall28 1 QC2.05 [1.59, 2.46]1.95+0.35 [-0.50, 1.44]2.43 [1.91, 2.84]29% [13%, 50%]57%82%+0.42+0.462026-08-03 → 2026-08-30
tmin12Znearest30d28 1 QC1.95 [1.41, 2.41]1.95-0.02 [-0.96, 0.96]2.42 [1.78, 2.89]32% [15%, 52%]61%79%+0.45+0.462026-08-03 → 2026-08-30
tmin12Znearest90d28 1 QC1.95 [1.29, 2.42]1.95-0.02 [-1.02, 1.02]2.42 [1.61, 2.91]32% [14%, 54%]61%79%+0.45+0.462026-08-03 → 2026-08-30
tmin12Znearest365d28 1 QC1.95 [1.17, 2.47]1.95-0.02 [-1.07, 1.03]2.42 [1.29, 2.93]32% [13%, 56%]61%79%+0.45+0.462026-08-03 → 2026-08-30
tmin12Znearestall28 1 QC1.95 [1.24, 2.42]1.95-0.02 [-1.04, 1.06]2.42 [1.49, 2.89]32% [12%, 54%]61%79%+0.45+0.462026-08-03 → 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 2, 00Z bilinear tmax+20+100-10-202026-08-03: -13.86 °F2026-08-04: -5.18 °F2026-08-05: -3.32 °F2026-08-06: -1.53 °F2026-08-07: -0.48 °F2026-08-08: +0.45 °F2026-08-09: -0.78 °F2026-08-10: +3.48 °F2026-08-11: +0.95 °F2026-08-12: -4.99 °F2026-08-13: -7.77 °F2026-08-14: -2.21 °F2026-08-15: -4.13 °F2026-08-16: -7.13 °F2026-08-17: -2.77 °F2026-08-18: -2.85 °F2026-08-19: +0.38 °F2026-08-20: -9.36 °F2026-08-21: +2.4 °F2026-08-22: -6.39 °F2026-08-23: -1.55 °F2026-08-24: -4.87 °F2026-08-25: +1.18 °F2026-08-26: -3.43 °F2026-08-27: -3.72 °F2026-08-28: -1.54 °F2026-08-29: +4.01 °F2026-08-30: -0.08 °F2026-08-032026-08-30°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 (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-0.08
2026-08-29+4.01
2026-08-28-1.54
2026-08-27-3.72
2026-08-26-3.43
2026-08-25+1.18
2026-08-24-4.87
2026-08-23-1.55
2026-08-22-6.39
2026-08-21+2.40
2026-08-20-9.36
2026-08-19+0.38
2026-08-18-2.85
2026-08-17-2.77
2026-08-16-7.13
2026-08-15-4.13
2026-08-14-2.21
2026-08-13-7.77
2026-08-12-4.99
2026-08-11+0.95
2026-08-10+3.48
2026-08-09-0.78
2026-08-08+0.45
2026-08-07-0.48
2026-08-06-1.53
2026-08-05-3.32
2026-08-04-5.18
2026-08-03-13.86

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHL, lead day 2-20 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: 1 day-8 to -6 °F: 3 days-6 to -4 °F: 4 days-4 to -2 °F: 6 days-2 to 0 °F: 6 days0 to 2 °F: 4 days2 to 4 °F: 2 days4 to 6 °F: 1 day6 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| 3.08 · P90 |e| 7.32 °F-200+20 °Fn = 28 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
-10.00-8.001
-8.00-6.003
-6.00-4.004
-4.00-2.006
-2.00+0.006
+0.00+2.004
+2.00+4.002
+4.00+6.001
+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
2026-08283.60 -2.68

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28

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 28 +0.85 [-0.01, 1.62] no
Aurora (IFS init) 1 -4.40 [-4.40, -4.40] yes
FourCastNet v2 (IFS init) 1 -4.51 [-4.51, -4.51] yes
GraphCast (IFS init) 26 -1.18 [-2.08, -0.24] yes
ECMWF IFS HRES 22 +0.35 [-0.79, 1.72] no
Pangu-Weather (IFS init) 1 -3.15 [-3.15, -3.15] yes
Persistence (baseline) 28 +0.81 [-0.33, 2.36] no

Cite this page

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

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

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