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CastCheck methodology v0.2 · data through 2026-08-30

Philadelphia Intl · GraphCast (IFS init) · lead day 8

KPHL · graphcast_ifs · 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, GRAP_v100, starting 2026-01-01 — 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 QC5.29 [4.56, 6.44]3.78-3.96 [-6.21, -1.83]6.10 [5.27, 7.11]9% [0%, 16%]18%27%-0.22+0.022026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC5.29 [4.49, 6.67]3.78-3.96 [-6.62, -1.63]6.10 [5.24, 7.27]9% [0%, 14%]18%27%-0.22+0.022026-08-09 → 2026-08-30
tmax00Zbilinear365d28 1 QC5.44 [4.71, 6.58]3.97-3.99 [-6.12, -2.03]6.21 [5.48, 7.07]11% [0%, 17%]18%25%+0.14+0.392026-01-09 → 2026-08-30
tmax00Zbilinearall28 1 QC5.44 [4.66, 6.50]3.97-3.99 [-6.06, -1.93]6.21 [5.39, 7.05]11% [0%, 18%]18%25%+0.14+0.392026-01-09 → 2026-08-30
tmax00Znearest30d22 1 QC5.09 [4.43, 6.17]3.77-3.67 [-5.89, -1.57]5.89 [5.17, 6.79]9% [0%, 16%]14%32%-0.18+0.022026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC5.09 [4.38, 6.34]3.77-3.67 [-6.28, -1.36]5.89 [5.13, 6.94]9% [0%, 14%]14%32%-0.18+0.022026-08-09 → 2026-08-30
tmax00Znearest365d28 1 QC5.27 [4.57, 6.29]3.97-3.63 [-5.72, -1.64]6.00 [5.34, 6.75]11% [0%, 17%]14%29%+0.17+0.392026-01-09 → 2026-08-30
tmax00Znearestall28 1 QC5.27 [4.52, 6.29]3.97-3.63 [-5.72, -1.61]6.00 [5.24, 6.75]11% [0%, 18%]14%29%+0.17+0.392026-01-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC5.75 [4.56, 7.11]3.53-5.20 [-6.95, -3.68]6.90 [5.51, 8.24]9% [0%, 20%]27%27%-0.33+0.092026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC5.75 [4.21, 7.13]3.53-5.20 [-6.97, -3.42]6.90 [5.10, 8.35]9% [0%, 22%]27%27%-0.33+0.092026-08-09 → 2026-08-30
tmax12Zbilinear365d27 1 QC5.66 [4.52, 6.90]4.05-4.18 [-6.50, -1.01]6.81 [5.46, 8.08]7% [0%, 16%]22%33%+0.07+0.352026-01-09 → 2026-08-30
tmax12Zbilinearall27 1 QC5.66 [4.41, 6.97]4.05-4.18 [-6.55, -1.14]6.81 [5.30, 8.07]7% [0%, 17%]22%33%+0.07+0.352026-01-09 → 2026-08-30
tmax12Znearest30d22 1 QC5.43 [4.21, 6.79]3.42-4.80 [-6.56, -3.26]6.59 [5.11, 7.94]14% [0%, 26%]23%27%-0.26+0.122026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC5.43 [3.90, 6.83]3.42-4.80 [-6.58, -2.99]6.59 [4.75, 8.06]14% [0%, 29%]23%27%-0.26+0.122026-08-09 → 2026-08-30
tmax12Znearest365d27 1 QC5.39 [4.25, 6.63]4.01-3.77 [-6.10, -0.57]6.55 [5.09, 7.86]11% [0%, 24%]22%30%+0.12+0.362026-01-09 → 2026-08-30
tmax12Znearestall27 1 QC5.39 [4.13, 6.69]4.01-3.77 [-6.13, -0.70]6.55 [4.88, 7.83]11% [0%, 25%]22%30%+0.12+0.362026-01-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC3.47 [1.91, 4.93]3.41-0.68 [-2.13, 0.76]4.34 [2.37, 5.66]23% [9%, 45%]36%55%+0.14+0.062026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC3.47 [1.66, 5.08]3.41-0.68 [-2.02, 0.98]4.34 [2.05, 5.86]23% [7%, 50%]36%55%+0.14+0.062026-08-09 → 2026-08-30
tmin00Zbilinear365d28 1 QC3.12 [1.77, 4.61]3.07-0.54 [-1.88, 0.87]3.99 [2.17, 5.42]21% [8%, 40%]43%57%+0.41+0.422026-01-09 → 2026-08-30
tmin00Zbilinearall28 1 QC3.12 [1.72, 4.50]3.07-0.54 [-1.96, 0.89]3.99 [2.13, 5.35]21% [9%, 40%]43%57%+0.41+0.422026-01-09 → 2026-08-30
tmin00Znearest30d22 1 QC3.36 [1.72, 4.90]3.39-0.28 [-1.72, 1.15]4.28 [2.24, 5.65]14% [0%, 29%]45%50%+0.17+0.062026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC3.36 [1.52, 5.09]3.39-0.28 [-1.60, 1.36]4.28 [1.97, 5.84]14% [0%, 33%]45%50%+0.17+0.062026-08-09 → 2026-08-30
tmin00Znearest365d28 1 QC3.03 [1.68, 4.59]3.04-0.15 [-1.48, 1.23]3.94 [2.10, 5.42]18% [5%, 33%]46%57%+0.42+0.422026-01-09 → 2026-08-30
tmin00Znearestall28 1 QC3.03 [1.68, 4.47]3.04-0.15 [-1.54, 1.24]3.94 [2.08, 5.34]18% [5%, 35%]46%57%+0.42+0.422026-01-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC2.76 [2.30, 3.12]2.76-0.04 [-1.05, 0.92]3.03 [2.53, 3.40]9% [0%, 20%]27%55%+0.32+0.242026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC2.76 [2.29, 3.16]2.76-0.04 [-1.02, 1.08]3.03 [2.48, 3.43]9% [0%, 21%]27%55%+0.32+0.242026-08-09 → 2026-08-30
tmin12Zbilinear365d27 1 QC3.29 [2.47, 4.78]3.18+1.01 [-0.67, 3.81]4.00 [2.70, 5.93]7% [0%, 17%]26%52%+0.34+0.362026-01-09 → 2026-08-30
tmin12Zbilinearall27 1 QC3.29 [2.47, 4.90]3.18+1.01 [-0.62, 4.05]4.00 [2.69, 6.09]7% [0%, 16%]26%52%+0.34+0.362026-01-09 → 2026-08-30
tmin12Znearest30d22 1 QC2.71 [2.30, 3.07]2.71+0.41 [-0.61, 1.40]3.03 [2.54, 3.43]9% [0%, 20%]41%68%+0.33+0.252026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC2.71 [2.30, 3.10]2.71+0.41 [-0.56, 1.54]3.03 [2.51, 3.46]9% [0%, 21%]41%68%+0.33+0.252026-08-09 → 2026-08-30
tmin12Znearest365d27 1 QC3.35 [2.43, 5.01]3.15+1.47 [-0.22, 4.27]4.14 [2.68, 6.23]7% [0%, 17%]33%59%+0.33+0.362026-01-09 → 2026-08-30
tmin12Znearestall27 1 QC3.35 [2.44, 5.22]3.15+1.47 [-0.17, 4.52]4.14 [2.69, 6.41]7% [0%, 16%]33%59%+0.33+0.362026-01-09 → 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 GraphCast (IFS init) at KPHL, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: -7.2 °F2026-08-10: -4.67 °F2026-08-11: +1.63 °F2026-08-12: -9.24 °F2026-08-13: -3.07 °F2026-08-14: -4.2 °F2026-08-15: -9.89 °F2026-08-16: -0.37 °F2026-08-17: -2.8 °F2026-08-18: -9.31 °F2026-08-19: -7.32 °F2026-08-20: +3.94 °F2026-08-21: +2.24 °F2026-08-22: +6.73 °F2026-08-23: -0.43 °F2026-08-24: -5.57 °F2026-08-25: -4.77 °F2026-08-26: -5.17 °F2026-08-27: -1.92 °F2026-08-28: -11.01 °F2026-08-29: -6.18 °F2026-08-30: -8.6 °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
2026-08-30-8.60
2026-08-29-6.18
2026-08-28-11.01
2026-08-27-1.92
2026-08-26-5.17
2026-08-25-4.77
2026-08-24-5.57
2026-08-23-0.43
2026-08-22+6.73
2026-08-21+2.24
2026-08-20+3.94
2026-08-19-7.32
2026-08-18-9.31
2026-08-17-2.80
2026-08-16-0.37
2026-08-15-9.89
2026-08-14-4.20
2026-08-13-3.07
2026-08-12-9.24
2026-08-11+1.63
2026-08-10-4.67
2026-08-09-7.20

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) 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: 1 day-10 to -8 °F: 5 days-8 to -6 °F: 6 days-6 to -4 °F: 5 days-4 to -2 °F: 2 days-2 to 0 °F: 3 days0 to 2 °F: 2 days2 to 4 °F: 2 days4 to 6 °F: 1 day6 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| 5.5 · P90 |e| 9.26 °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
-14.00-12.000
-12.00-10.001
-10.00-8.005
-8.00-6.006
-6.00-4.005
-4.00-2.002
-2.00+0.003
+0.00+2.002
+2.00+4.002
+4.00+6.001
+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
2026-08225.29 -3.96
2026-0166.02 -4.09

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 27
GraphCast (IFS init)2026-01-09 → 2026-08-30 27

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means GraphCast (IFS init) has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 22 +0.64 [-0.48, 2.30] no
NCEP GFS 22 +0.39 [-0.67, 2.66] no
ECMWF IFS HRES 17 +1.92 [1.25, 2.87] yes
Persistence (baseline) 22 +0.97 [-0.90, 3.77] no

Cite this page

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

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