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

Phoenix Sky Harbor · GraphCast (IFS init) · lead day 2

KPHX · graphcast_ifs · 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, 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
tmax00Zbilinear30d26 1 QC3.49 [2.49, 4.37]1.90-3.35 [-4.30, -2.36]4.16 [3.22, 4.96]12% [0%, 38%]31%50%+0.29+0.612026-08-03 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.49 [2.22, 4.55]1.90-3.35 [-4.51, -2.11]4.16 [2.92, 5.19]12% [0%, 40%]31%50%+0.29+0.612026-08-03 → 2026-08-30
tmax00Zbilinear365d32 1 QC3.94 [2.86, 5.30]2.03-3.83 [-5.28, -2.68]4.62 [3.60, 5.85]9% [0%, 30%]25%41%+0.17+0.572026-01-03 → 2026-08-30
tmax00Zbilinearall32 1 QC3.94 [2.77, 5.20]2.03-3.83 [-5.18, -2.61]4.62 [3.47, 5.70]9% [0%, 31%]25%41%+0.17+0.572026-01-03 → 2026-08-30
tmax00Znearest30d26 1 QC3.37 [2.37, 4.28]1.91-3.21 [-4.20, -2.21]4.06 [3.12, 4.88]12% [0%, 38%]31%50%+0.31+0.612026-08-03 → 2026-08-30
tmax00Znearest90d26 1 QC3.37 [2.11, 4.45]1.91-3.21 [-4.41, -1.97]4.06 [2.79, 5.09]12% [0%, 40%]31%50%+0.31+0.612026-08-03 → 2026-08-30
tmax00Znearest365d32 1 QC3.87 [2.74, 5.30]2.09-3.74 [-5.25, -2.56]4.58 [3.48, 5.89]9% [0%, 30%]25%44%+0.19+0.562026-01-03 → 2026-08-30
tmax00Znearestall32 1 QC3.87 [2.65, 5.18]2.09-3.74 [-5.15, -2.47]4.58 [3.38, 5.75]9% [0%, 31%]25%44%+0.19+0.562026-01-03 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.92 [3.02, 4.90]1.89-3.74 [-4.83, -2.71]4.48 [3.45, 5.43]0% [0%, 0%]23%35%+0.20+0.612026-08-03 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.92 [2.83, 4.92]1.89-3.74 [-4.88, -2.50]4.48 [3.19, 5.49]0% [0%, 0%]23%35%+0.20+0.612026-08-03 → 2026-08-30
tmax12Zbilinear365d31 1 QC4.20 [3.20, 5.49]1.90-4.05 [-5.43, -2.96]4.71 [3.62, 5.82]0% [0%, 0%]19%29%+0.10+0.602026-01-03 → 2026-08-30
tmax12Zbilinearall31 1 QC4.20 [3.10, 5.33]1.90-4.05 [-5.33, -2.78]4.71 [3.57, 5.70]0% [0%, 0%]19%29%+0.10+0.602026-01-03 → 2026-08-30
tmax12Znearest30d26 1 QC3.80 [2.91, 4.81]1.94-3.60 [-4.70, -2.58]4.38 [3.35, 5.35]0% [0%, 0%]27%42%+0.22+0.612026-08-03 → 2026-08-30
tmax12Znearest90d26 1 QC3.80 [2.71, 4.83]1.94-3.60 [-4.75, -2.37]4.38 [3.08, 5.39]0% [0%, 0%]27%42%+0.22+0.612026-08-03 → 2026-08-30
tmax12Znearest365d31 1 QC4.11 [3.10, 5.42]1.97-3.94 [-5.40, -2.82]4.64 [3.57, 5.80]0% [0%, 0%]23%35%+0.12+0.582026-01-03 → 2026-08-30
tmax12Znearestall31 1 QC4.11 [2.99, 5.25]1.97-3.94 [-5.24, -2.63]4.64 [3.47, 5.64]0% [0%, 0%]23%35%+0.12+0.582026-01-03 → 2026-08-30
tmin00Zbilinear30d26 1 QC2.81 [1.92, 4.11]2.72-0.53 [-1.93, 1.03]3.81 [2.54, 5.18]23% [10%, 35%]54%62%+0.45+0.472026-08-03 → 2026-08-30
tmin00Zbilinear90d26 1 QC2.81 [1.81, 4.21]2.72-0.53 [-2.07, 1.13]3.81 [2.40, 5.29]23% [6%, 36%]54%62%+0.45+0.472026-08-03 → 2026-08-30
tmin00Zbilinear365d32 1 QC2.59 [1.74, 3.79]2.48-0.72 [-2.01, 0.68]3.55 [2.24, 4.92]25% [11%, 36%]53%66%+0.45+0.462026-01-03 → 2026-08-30
tmin00Zbilinearall32 1 QC2.59 [1.71, 3.73]2.48-0.72 [-2.12, 0.78]3.55 [2.19, 4.86]25% [11%, 36%]53%66%+0.45+0.462026-01-03 → 2026-08-30
tmin00Znearest30d26 1 QC2.88 [1.95, 4.23]2.81-0.52 [-1.94, 1.04]3.89 [2.57, 5.28]23% [10%, 35%]50%62%+0.44+0.452026-08-03 → 2026-08-30
tmin00Znearest90d26 1 QC2.88 [1.84, 4.29]2.81-0.52 [-2.08, 1.14]3.89 [2.45, 5.39]23% [6%, 36%]50%62%+0.44+0.452026-08-03 → 2026-08-30
tmin00Znearest365d32 1 QC2.66 [1.79, 3.88]2.56-0.74 [-2.07, 0.72]3.62 [2.33, 5.00]25% [11%, 36%]50%66%+0.43+0.442026-01-03 → 2026-08-30
tmin00Znearestall32 1 QC2.66 [1.74, 3.83]2.56-0.74 [-2.22, 0.81]3.62 [2.26, 4.96]25% [11%, 36%]50%66%+0.43+0.442026-01-03 → 2026-08-30
tmin12Zbilinear30d26 1 QC3.21 [2.17, 4.71]3.09-1.09 [-2.49, 0.31]4.17 [2.79, 5.55]27% [14%, 38%]42%58%+0.38+0.392026-08-03 → 2026-08-30
tmin12Zbilinear90d26 1 QC3.21 [2.08, 4.81]3.09-1.09 [-2.52, 0.40]4.17 [2.68, 5.64]27% [12%, 40%]42%58%+0.38+0.392026-08-03 → 2026-08-30
tmin12Zbilinear365d31 1 QC2.99 [1.97, 4.36]2.77-1.20 [-2.49, 0.07]3.91 [2.46, 5.31]26% [12%, 37%]45%61%+0.37+0.412026-01-03 → 2026-08-30
tmin12Zbilinearall31 1 QC2.99 [1.91, 4.28]2.77-1.20 [-2.68, 0.14]3.91 [2.45, 5.22]26% [12%, 38%]45%61%+0.37+0.412026-01-03 → 2026-08-30
tmin12Znearest30d26 1 QC3.28 [2.22, 4.79]3.17-1.09 [-2.52, 0.31]4.22 [2.84, 5.64]23% [10%, 35%]42%54%+0.36+0.382026-08-03 → 2026-08-30
tmin12Znearest90d26 1 QC3.28 [2.10, 4.87]3.17-1.09 [-2.57, 0.40]4.22 [2.72, 5.72]23% [8%, 36%]42%54%+0.36+0.382026-08-03 → 2026-08-30
tmin12Znearest365d31 1 QC3.05 [2.05, 4.43]2.84-1.22 [-2.56, 0.07]3.97 [2.55, 5.40]23% [8%, 32%]45%58%+0.36+0.392026-01-03 → 2026-08-30
tmin12Znearestall31 1 QC3.05 [1.98, 4.36]2.84-1.22 [-2.75, 0.14]3.97 [2.51, 5.29]23% [10%, 33%]45%58%+0.36+0.392026-01-03 → 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 GraphCast (IFS init) at KPHX, lead day 2, 00Z bilinear tmax+10+50-5-102026-08-03: -4.42 °F2026-08-04: +0.38 °F2026-08-05: -0.31 °F2026-08-06: -0.26 °F2026-08-07: -2.94 °F2026-08-08: -2.96 °F2026-08-09: -2.24 °F2026-08-10: -2.41 °F2026-08-11: -1.95 °F2026-08-12: -9.06 °F2026-08-13: -3.66 °F2026-08-14: -4.36 °F2026-08-15: -6.52 °F2026-08-16: -4.19 °F2026-08-17: -2.64 °F2026-08-18: -5.21 °F2026-08-19: -1.77 °F2026-08-20: +1.41 °F2026-08-21: -3.57 °F2026-08-22: -4.81 °F2026-08-23: -6.41 °F2026-08-24: -1.36 °F2026-08-25: -3.64 °F2026-08-26: -3.76 °F2026-08-27: -1.75 °F2026-08-30: -8.61 °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
2026-08-30-8.61
2026-08-29—
2026-08-28—
2026-08-27-1.75
2026-08-26-3.76
2026-08-25-3.64
2026-08-24-1.36
2026-08-23-6.41
2026-08-22-4.81
2026-08-21-3.57
2026-08-20+1.41
2026-08-19-1.77
2026-08-18-5.21
2026-08-17-2.64
2026-08-16-4.19
2026-08-15-6.52
2026-08-14-4.36
2026-08-13-3.66
2026-08-12-9.06
2026-08-11-1.95
2026-08-10-2.41
2026-08-09-2.24
2026-08-08-2.96
2026-08-07-2.94
2026-08-06-0.26
2026-08-05-0.31
2026-08-04+0.38
2026-08-03-4.42

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KPHX, lead day 2-10 to -9 °F: 2 days-9 to -8 °F: 1 day-8 to -7 °F: 0 days-7 to -6 °F: 4 days-6 to -5 °F: 2 days-5 to -4 °F: 5 days-4 to -3 °F: 5 days-3 to -2 °F: 5 days-2 to -1 °F: 4 days-1 to 0 °F: 2 days0 to 1 °F: 1 day1 to 2 °F: 1 day2 to 3 °F: 0 days3 to 4 °F: 0 days4 to 5 °F: 0 days5 to 6 °F: 0 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 0 days9 to 10 °F: 0 daysdashed: P50 |e| 3.65 · P90 |e| 6.94 °F-100+10 °Fn = 32 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
-10.00-9.002
-9.00-8.001
-8.00-7.000
-7.00-6.004
-6.00-5.002
-5.00-4.005
-4.00-3.005
-3.00-2.005
-2.00-1.004
-1.00+0.002
+0.00+1.001
+1.00+2.001
+2.00+3.000
+3.00+4.000
+4.00+5.000
+5.00+6.000
+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
2026-08263.49 -3.35
2026-0165.94 -5.94

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 31
GraphCast (IFS init)2026-01-03 → 2026-08-30 31

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 26 +0.25 [-0.44, 0.95] no
Aurora (IFS init) 1 -1.81 [-1.81, -1.81] yes
FourCastNet v2 (IFS init) 1 -3.09 [-3.09, -3.09] yes
NCEP GFS 26 +0.86 [-0.19, 2.04] no
ECMWF IFS HRES 21 +0.95 [0.00, 1.97] yes
Pangu-Weather (IFS init) 1 +1.62 [1.62, 1.62] yes
Persistence (baseline) 26 -1.40 [-2.80, -0.17] yes

Cite this page

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

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