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

Phoenix Sky Harbor · GraphCast (IFS init) · lead day 8

KPHX · 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 QC9.18 [6.07, 12.10]5.47-9.04 [-12.02, -5.72]10.90 [7.47, 13.42]0% [0%, 0%]9%23%-0.67-0.002026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC9.18 [5.35, 12.42]5.47-9.04 [-12.36, -4.75]10.90 [6.44, 13.66]0% [0%, 0%]9%23%-0.67-0.002026-08-09 → 2026-08-30
tmax00Zbilinear365d28 1 QC7.95 [4.28, 11.33]5.53-7.77 [-11.21, -3.82]9.91 [5.56, 12.77]4% [0%, 14%]21%32%-0.43+0.002026-01-09 → 2026-08-30
tmax00Zbilinearall28 1 QC7.95 [3.91, 11.58]5.53-7.77 [-11.50, -3.31]9.91 [5.19, 13.05]4% [0%, 14%]21%32%-0.43+0.002026-01-09 → 2026-08-30
tmax00Znearest30d22 1 QC9.04 [5.95, 11.97]5.46-8.88 [-11.85, -5.52]10.75 [7.32, 13.27]0% [0%, 0%]9%23%-0.64+0.002026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC9.04 [5.26, 12.27]5.46-8.88 [-12.18, -4.58]10.75 [6.29, 13.51]0% [0%, 0%]9%23%-0.64+0.002026-08-09 → 2026-08-30
tmax00Znearest365d28 1 QC7.84 [4.25, 11.17]5.45-7.66 [-11.04, -3.77]9.77 [5.46, 12.61]4% [0%, 14%]18%32%-0.41+0.022026-01-09 → 2026-08-30
tmax00Znearestall28 1 QC7.84 [3.87, 11.43]5.45-7.66 [-11.37, -3.31]9.77 [5.06, 12.89]4% [0%, 14%]18%32%-0.41+0.022026-01-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC7.29 [4.90, 9.72]3.77-7.04 [-9.72, -4.47]8.34 [5.94, 10.47]5% [0%, 19%]9%18%-0.33+0.312026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC7.29 [4.49, 9.73]3.77-7.04 [-9.73, -4.14]8.34 [5.50, 10.50]5% [0%, 22%]9%18%-0.33+0.312026-08-09 → 2026-08-30
tmax12Zbilinear365d27 1 QC6.44 [3.51, 8.99]3.78-6.24 [-8.97, -3.42]7.68 [4.54, 9.85]11% [0%, 33%]15%26%-0.20+0.302026-01-09 → 2026-08-30
tmax12Zbilinearall27 1 QC6.44 [3.06, 9.20]3.78-6.24 [-9.20, -3.03]7.68 [4.00, 10.09]11% [0%, 38%]15%26%-0.20+0.302026-01-09 → 2026-08-30
tmax12Znearest30d22 1 QC7.19 [4.86, 9.62]3.77-6.92 [-9.60, -4.32]8.24 [5.84, 10.33]5% [0%, 19%]9%18%-0.31+0.312026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC7.19 [4.44, 9.60]3.77-6.92 [-9.57, -3.99]8.24 [5.37, 10.39]5% [0%, 22%]9%18%-0.31+0.312026-08-09 → 2026-08-30
tmax12Znearest365d27 1 QC6.37 [3.48, 8.88]3.75-6.15 [-8.83, -3.27]7.59 [4.45, 9.75]7% [0%, 24%]15%26%-0.19+0.302026-01-09 → 2026-08-30
tmax12Znearestall27 1 QC6.37 [3.08, 9.08]3.75-6.15 [-9.08, -2.87]7.59 [3.91, 10.01]7% [0%, 25%]15%26%-0.19+0.302026-01-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC3.97 [2.23, 5.48]3.82-1.75 [-4.50, 0.72]4.72 [2.60, 6.05]9% [0%, 22%]32%55%+0.36+0.372026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC3.97 [1.86, 5.64]3.82-1.75 [-4.86, 1.00]4.72 [2.02, 6.16]9% [0%, 22%]32%55%+0.36+0.372026-08-09 → 2026-08-30
tmin00Zbilinear365d28 1 QC4.12 [2.29, 5.51]3.99-1.33 [-3.85, 1.14]4.98 [2.70, 6.22]11% [0%, 23%]32%50%+0.35+0.342026-01-09 → 2026-08-30
tmin00Zbilinearall28 1 QC4.12 [2.34, 5.62]3.99-1.33 [-3.83, 0.88]4.98 [2.85, 6.28]11% [0%, 22%]32%50%+0.35+0.342026-01-09 → 2026-08-30
tmin00Znearest30d22 1 QC3.97 [2.30, 5.43]3.84-1.66 [-4.44, 0.83]4.70 [2.66, 5.98]9% [0%, 22%]27%45%+0.36+0.372026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC3.97 [1.89, 5.57]3.84-1.66 [-4.82, 1.13]4.70 [2.07, 6.12]9% [0%, 22%]27%45%+0.36+0.372026-08-09 → 2026-08-30
tmin00Znearest365d28 1 QC4.12 [2.32, 5.48]4.00-1.22 [-3.72, 1.24]4.96 [2.75, 6.17]14% [0%, 33%]29%43%+0.35+0.342026-01-09 → 2026-08-30
tmin00Znearestall28 1 QC4.12 [2.39, 5.58]4.00-1.22 [-3.74, 1.02]4.96 [2.88, 6.23]14% [0%, 33%]29%43%+0.35+0.342026-01-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC4.16 [2.41, 5.42]3.97-1.17 [-3.94, 1.22]4.89 [2.87, 5.99]9% [0%, 23%]27%32%+0.33+0.352026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC4.16 [1.99, 5.55]3.97-1.17 [-4.22, 1.50]4.89 [2.56, 6.03]9% [0%, 25%]27%32%+0.33+0.352026-08-09 → 2026-08-30
tmin12Zbilinear365d27 1 QC4.15 [2.51, 5.37]3.93-1.28 [-3.73, 1.02]4.88 [2.98, 5.85]11% [0%, 25%]30%33%+0.37+0.372026-01-09 → 2026-08-30
tmin12Zbilinearall27 1 QC4.15 [2.68, 5.39]3.93-1.28 [-3.73, 1.07]4.88 [3.24, 5.85]11% [0%, 25%]30%33%+0.37+0.372026-01-09 → 2026-08-30
tmin12Znearest30d22 1 QC4.22 [2.51, 5.44]4.02-1.12 [-3.93, 1.30]4.93 [2.96, 6.01]9% [0%, 23%]27%32%+0.32+0.342026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC4.22 [2.12, 5.56]4.02-1.12 [-4.20, 1.60]4.93 [2.66, 6.06]9% [0%, 25%]27%32%+0.32+0.342026-08-09 → 2026-08-30
tmin12Znearest365d27 1 QC4.17 [2.56, 5.39]3.96-1.21 [-3.66, 1.09]4.88 [3.04, 5.85]11% [0%, 25%]30%33%+0.36+0.372026-01-09 → 2026-08-30
tmin12Znearestall27 1 QC4.17 [2.70, 5.38]3.96-1.21 [-3.67, 1.15]4.88 [3.30, 5.86]11% [0%, 25%]30%33%+0.36+0.372026-01-09 → 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 KPHX, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: -13.66 °F2026-08-10: -4.71 °F2026-08-11: -3 °F2026-08-12: -11.98 °F2026-08-13: -3.17 °F2026-08-14: -8.92 °F2026-08-15: -2.57 °F2026-08-16: -3.55 °F2026-08-17: -6.42 °F2026-08-18: -14.63 °F2026-08-19: -17.84 °F2026-08-20: -1.62 °F2026-08-21: -13.16 °F2026-08-22: -12.1 °F2026-08-23: -15.21 °F2026-08-24: -18.37 °F2026-08-25: -18.42 °F2026-08-26: -15.28 °F2026-08-27: -8.67 °F2026-08-28: -2.68 °F2026-08-29: -4.52 °F2026-08-30: +1.53 °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+1.53
2026-08-29-4.52
2026-08-28-2.68
2026-08-27-8.67
2026-08-26-15.28
2026-08-25-18.42
2026-08-24-18.37
2026-08-23-15.21
2026-08-22-12.10
2026-08-21-13.16
2026-08-20-1.62
2026-08-19-17.84
2026-08-18-14.63
2026-08-17-6.42
2026-08-16-3.55
2026-08-15-2.57
2026-08-14-8.92
2026-08-13-3.17
2026-08-12-11.98
2026-08-11-3.00
2026-08-10-4.71
2026-08-09-13.66

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KPHX, lead day 8-20 to -18 °F: 2 days-18 to -16 °F: 1 day-16 to -14 °F: 3 days-14 to -12 °F: 3 days-12 to -10 °F: 2 days-10 to -8 °F: 2 days-8 to -6 °F: 1 day-6 to -4 °F: 3 days-4 to -2 °F: 5 days-2 to 0 °F: 4 days0 to 2 °F: 2 days2 to 4 °F: 0 days4 to 6 °F: 0 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| 5.75 · P90 |e| 16.05 °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
-20.00-18.002
-18.00-16.001
-16.00-14.003
-14.00-12.003
-12.00-10.002
-10.00-8.002
-8.00-6.001
-6.00-4.003
-4.00-2.005
-2.00+0.004
+0.00+2.002
+2.00+4.000
+4.00+6.000
+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
2026-08229.18 -9.04
2026-0163.41 -3.11

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 +2.27 [-1.08, 5.80] no
NCEP GFS 22 +4.28 [0.12, 7.46] yes
ECMWF IFS HRES 17 +4.93 [0.26, 8.65] yes
Persistence (baseline) 22 +3.68 [-0.45, 6.88] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHX (Phoenix Sky Harbor), 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/KPHX/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