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

Phoenix Sky Harbor · GraphCast (IFS init) · lead day 6

KPHX · graphcast_ifs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC6.00 [3.72, 8.30]3.32-5.79 [-8.27, -3.21]7.16 [4.48, 9.25]8% [0%, 14%]21%25%-0.20+0.342026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC6.00 [3.74, 8.56]3.32-5.79 [-8.53, -3.17]7.16 [4.41, 9.50]8% [0%, 14%]21%25%-0.20+0.342026-08-07 → 2026-08-30
tmax00Zbilinear365d30 1 QC5.49 [3.48, 7.74]3.08-5.33 [-7.71, -3.12]6.64 [4.10, 8.84]10% [0%, 17%]23%27%-0.04+0.422026-01-07 → 2026-08-30
tmax00Zbilinearall30 1 QC5.49 [3.50, 7.89]3.08-5.33 [-7.85, -3.12]6.64 [4.03, 8.93]10% [0%, 17%]23%27%-0.04+0.422026-01-07 → 2026-08-30
tmax00Znearest30d24 1 QC5.85 [3.58, 8.13]3.33-5.61 [-8.07, -3.05]7.01 [4.38, 9.09]8% [0%, 14%]21%25%-0.17+0.342026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC5.85 [3.57, 8.41]3.33-5.61 [-8.36, -3.04]7.01 [4.26, 9.32]8% [0%, 14%]21%25%-0.17+0.342026-08-07 → 2026-08-30
tmax00Znearest365d30 1 QC5.37 [3.38, 7.60]3.07-5.18 [-7.58, -3.03]6.51 [4.00, 8.68]10% [0%, 17%]23%27%-0.02+0.422026-01-07 → 2026-08-30
tmax00Znearestall30 1 QC5.37 [3.41, 7.76]3.07-5.18 [-7.68, -3.03]6.51 [3.97, 8.76]10% [0%, 17%]23%27%-0.02+0.422026-01-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC6.23 [4.21, 8.43]2.80-6.09 [-8.43, -3.90]7.07 [4.75, 9.07]0% [0%, 0%]8%21%-0.25+0.442026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC6.23 [4.06, 8.52]2.80-6.09 [-8.52, -3.77]7.07 [4.51, 9.16]0% [0%, 0%]8%21%-0.25+0.442026-08-07 → 2026-08-30
tmax12Zbilinear365d29 1 QC5.63 [3.58, 8.03]2.84-5.50 [-8.03, -3.30]6.56 [4.08, 8.74]3% [0%, 12%]10%24%-0.05+0.472026-01-07 → 2026-08-30
tmax12Zbilinearall29 1 QC5.63 [3.48, 8.07]2.84-5.50 [-8.07, -3.20]6.56 [3.94, 8.80]3% [0%, 14%]10%24%-0.05+0.472026-01-07 → 2026-08-30
tmax12Znearest30d24 1 QC6.07 [4.09, 8.24]2.77-5.94 [-8.24, -3.76]6.93 [4.60, 8.93]0% [0%, 0%]8%21%-0.21+0.452026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC6.07 [3.91, 8.37]2.77-5.94 [-8.37, -3.60]6.93 [4.39, 9.01]0% [0%, 0%]8%21%-0.21+0.452026-08-07 → 2026-08-30
tmax12Znearest365d29 1 QC5.51 [3.49, 7.86]2.80-5.37 [-7.86, -3.21]6.43 [3.96, 8.60]3% [0%, 12%]10%24%-0.02+0.482026-01-07 → 2026-08-30
tmax12Znearestall29 1 QC5.51 [3.40, 7.91]2.80-5.37 [-7.91, -3.11]6.43 [3.88, 8.65]3% [0%, 14%]10%24%-0.02+0.482026-01-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC3.81 [2.86, 4.92]3.60-0.94 [-3.38, 0.86]4.55 [3.36, 5.68]8% [0%, 17%]21%50%+0.33+0.372026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC3.81 [2.71, 5.05]3.60-0.94 [-4.05, 0.98]4.55 [3.20, 5.84]8% [0%, 17%]21%50%+0.33+0.372026-08-07 → 2026-08-30
tmin00Zbilinear365d30 1 QC4.11 [3.05, 5.42]3.88-1.43 [-3.99, 0.50]5.02 [3.60, 6.48]10% [0%, 19%]23%47%+0.32+0.352026-01-07 → 2026-08-30
tmin00Zbilinearall30 1 QC4.11 [3.06, 5.43]3.88-1.43 [-4.04, 0.43]5.02 [3.60, 6.52]10% [0%, 19%]23%47%+0.32+0.352026-01-07 → 2026-08-30
tmin00Znearest30d24 1 QC3.84 [2.90, 4.96]3.65-0.88 [-3.34, 0.91]4.57 [3.41, 5.70]8% [0%, 17%]21%50%+0.33+0.362026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC3.84 [2.71, 5.08]3.65-0.88 [-3.98, 1.00]4.57 [3.20, 5.86]8% [0%, 17%]21%50%+0.33+0.362026-08-07 → 2026-08-30
tmin00Znearest365d30 1 QC4.12 [3.08, 5.40]3.92-1.35 [-3.86, 0.53]5.00 [3.64, 6.39]10% [0%, 19%]23%47%+0.32+0.342026-01-07 → 2026-08-30
tmin00Znearestall30 1 QC4.12 [3.11, 5.39]3.92-1.35 [-3.95, 0.52]5.00 [3.65, 6.43]10% [0%, 19%]23%47%+0.32+0.342026-01-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC4.03 [3.00, 5.33]3.73-1.46 [-3.68, 0.17]4.74 [3.58, 5.91]12% [0%, 21%]25%38%+0.29+0.352026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC4.03 [2.89, 5.42]3.73-1.46 [-4.40, 0.29]4.74 [3.45, 6.00]12% [0%, 22%]25%38%+0.29+0.352026-08-07 → 2026-08-30
tmin12Zbilinear365d29 1 QC3.97 [2.95, 5.25]3.69-1.40 [-3.66, 0.15]4.73 [3.54, 5.89]10% [0%, 20%]28%41%+0.35+0.382026-01-07 → 2026-08-30
tmin12Zbilinearall29 1 QC3.97 [3.00, 5.25]3.69-1.40 [-3.87, 0.15]4.73 [3.60, 5.96]10% [0%, 19%]28%41%+0.35+0.382026-01-07 → 2026-08-30
tmin12Znearest30d24 1 QC4.10 [3.04, 5.40]3.80-1.45 [-3.74, 0.26]4.82 [3.59, 6.00]12% [0%, 21%]25%33%+0.28+0.332026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC4.10 [2.91, 5.46]3.80-1.45 [-4.43, 0.38]4.82 [3.45, 6.09]12% [0%, 22%]25%33%+0.28+0.332026-08-07 → 2026-08-30
tmin12Znearest365d29 1 QC4.00 [2.97, 5.30]3.72-1.40 [-3.72, 0.18]4.76 [3.52, 5.96]10% [0%, 20%]28%38%+0.34+0.372026-01-07 → 2026-08-30
tmin12Znearestall29 1 QC4.00 [2.98, 5.23]3.72-1.40 [-3.88, 0.18]4.76 [3.59, 6.00]10% [0%, 19%]28%38%+0.34+0.372026-01-07 → 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 6, 00Z bilinear tmax+20+100-10-202026-08-07: -8.5 °F2026-08-08: -5.87 °F2026-08-09: -4.86 °F2026-08-10: -1.87 °F2026-08-11: -1.98 °F2026-08-12: -3.98 °F2026-08-13: +0.42 °F2026-08-14: +1.89 °F2026-08-15: -2.5 °F2026-08-16: -5.05 °F2026-08-17: -6.02 °F2026-08-18: -6.98 °F2026-08-19: -3.98 °F2026-08-20: +0.19 °F2026-08-21: -8.47 °F2026-08-22: -14.8 °F2026-08-23: -14.37 °F2026-08-24: -8.95 °F2026-08-25: -6.31 °F2026-08-26: -9.33 °F2026-08-27: -4.57 °F2026-08-28: -3.32 °F2026-08-29: -7.76 °F2026-08-30: -11.99 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-11.99
2026-08-29-7.76
2026-08-28-3.32
2026-08-27-4.57
2026-08-26-9.33
2026-08-25-6.31
2026-08-24-8.95
2026-08-23-14.37
2026-08-22-14.80
2026-08-21-8.47
2026-08-20+0.19
2026-08-19-3.98
2026-08-18-6.98
2026-08-17-6.02
2026-08-16-5.05
2026-08-15-2.50
2026-08-14+1.89
2026-08-13+0.42
2026-08-12-3.98
2026-08-11-1.98
2026-08-10-1.87
2026-08-09-4.86
2026-08-08-5.87
2026-08-07-8.50

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KPHX, lead day 6-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 2 days-14 to -12 °F: 0 days-12 to -10 °F: 1 day-10 to -8 °F: 4 days-8 to -6 °F: 5 days-6 to -4 °F: 6 days-4 to -2 °F: 5 days-2 to 0 °F: 4 days0 to 2 °F: 3 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| 4.76 · P90 |e| 9.6 °F-200+20 °Fn = 30 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
-16.00-14.002
-14.00-12.000
-12.00-10.001
-10.00-8.004
-8.00-6.005
-6.00-4.006
-4.00-2.005
-2.00+0.004
+0.00+2.003
+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
2026-08246.00 -5.79
2026-0163.48 -3.48

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-07 → 2026-08-30 30
GraphCast (IFS init)2026-01-07 → 2026-08-30 30
GraphCast (IFS init)2026-01-07 → 2026-08-30 29
GraphCast (IFS init)2026-01-07 → 2026-08-30 29

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 24 +1.07 [-0.20, 2.23] no
NCEP GFS 24 +1.62 [-0.43, 3.88] no
ECMWF IFS HRES 19 +3.54 [1.59, 4.91] yes
Persistence (baseline) 24 +1.00 [-2.24, 4.83] no

Cite this page

ShortCastCheck, KPHX graphcast_ifs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHX/model/graphcast_ifs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHX (Phoenix Sky Harbor), model graphcast_ifs, lead day 6. 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/6/

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