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

Phoenix Sky Harbor · NCEP GFS · lead day 6

KPHX · gfs · 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, 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
tmax00Zbilinear30d24 1 QC4.38 [3.42, 5.58]2.77-3.83 [-5.38, -2.47]5.14 [4.16, 6.28]8% [0%, 17%]25%38%+0.12+0.452026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC4.38 [3.33, 5.91]2.77-3.83 [-5.82, -2.38]5.14 [4.04, 6.59]8% [0%, 18%]25%38%+0.12+0.452026-08-07 → 2026-08-30
tmax00Zbilinear365d24 1 QC4.38 [3.17, 5.79]2.77-3.83 [-5.63, -2.26]5.14 [3.90, 6.40]8% [0%, 18%]25%38%+0.12+0.452026-08-07 → 2026-08-30
tmax00Zbilinearall24 1 QC4.38 [3.26, 5.86]2.77-3.83 [-5.78, -2.32]5.14 [4.02, 6.46]8% [0%, 17%]25%38%+0.12+0.452026-08-07 → 2026-08-30
tmax00Znearest30d24 1 QC4.36 [3.42, 5.58]2.79-3.77 [-5.38, -2.40]5.12 [4.09, 6.31]8% [0%, 17%]21%38%+0.13+0.452026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC4.36 [3.30, 5.94]2.79-3.77 [-5.81, -2.30]5.12 [3.98, 6.69]8% [0%, 18%]21%38%+0.13+0.452026-08-07 → 2026-08-30
tmax00Znearest365d24 1 QC4.36 [3.19, 5.85]2.79-3.77 [-5.62, -2.19]5.12 [3.92, 6.47]8% [0%, 18%]21%38%+0.13+0.452026-08-07 → 2026-08-30
tmax00Znearestall24 1 QC4.36 [3.27, 5.87]2.79-3.77 [-5.84, -2.21]5.12 [3.97, 6.55]8% [0%, 17%]21%38%+0.13+0.452026-08-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC4.87 [3.84, 5.84]2.67-4.58 [-5.69, -3.45]5.70 [4.40, 6.78]8% [0%, 17%]8%38%+0.03+0.472026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC4.87 [3.64, 5.95]2.67-4.58 [-5.75, -3.32]5.70 [4.19, 6.86]8% [0%, 18%]8%38%+0.03+0.472026-08-07 → 2026-08-30
tmax12Zbilinear365d24 1 QC4.87 [3.61, 6.05]2.67-4.58 [-5.97, -3.17]5.70 [4.12, 6.99]8% [0%, 17%]8%38%+0.03+0.472026-08-07 → 2026-08-30
tmax12Zbilinearall24 1 QC4.87 [3.70, 6.08]2.67-4.58 [-5.99, -3.27]5.70 [4.20, 7.02]8% [0%, 17%]8%38%+0.03+0.472026-08-07 → 2026-08-30
tmax12Znearest30d24 1 QC4.81 [3.83, 5.71]2.58-4.47 [-5.52, -3.40]5.58 [4.31, 6.61]8% [0%, 17%]8%33%+0.04+0.492026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC4.81 [3.65, 5.81]2.58-4.47 [-5.59, -3.25]5.58 [4.05, 6.66]8% [0%, 18%]8%33%+0.04+0.492026-08-07 → 2026-08-30
tmax12Znearest365d24 1 QC4.81 [3.60, 5.91]2.58-4.47 [-5.75, -3.14]5.58 [4.01, 6.78]8% [0%, 17%]8%33%+0.04+0.492026-08-07 → 2026-08-30
tmax12Znearestall24 1 QC4.81 [3.68, 5.94]2.58-4.47 [-5.84, -3.20]5.58 [4.08, 6.82]8% [0%, 17%]8%33%+0.04+0.492026-08-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC4.51 [2.94, 5.71]3.55+3.47 [0.81, 5.21]5.68 [3.47, 6.82]12% [4%, 24%]29%46%+0.21+0.382026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC4.51 [2.76, 5.79]3.55+3.47 [-0.20, 5.19]5.68 [3.13, 6.88]12% [0%, 25%]29%46%+0.21+0.382026-08-07 → 2026-08-30
tmin00Zbilinear365d24 1 QC4.51 [2.76, 5.81]3.55+3.47 [0.01, 5.47]5.68 [3.14, 6.90]12% [0%, 25%]29%46%+0.21+0.382026-08-07 → 2026-08-30
tmin00Zbilinearall24 1 QC4.51 [2.59, 5.80]3.55+3.47 [-0.36, 5.53]5.68 [2.84, 6.88]12% [0%, 25%]29%46%+0.21+0.382026-08-07 → 2026-08-30
tmin00Znearest30d24 1 QC5.28 [3.30, 6.71]3.56+4.74 [1.97, 6.53]6.55 [4.13, 7.87]21% [9%, 40%]21%29%+0.07+0.382026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC5.28 [2.74, 6.71]3.56+4.74 [1.01, 6.51]6.55 [3.44, 7.94]21% [9%, 46%]21%29%+0.07+0.382026-08-07 → 2026-08-30
tmin00Znearest365d24 1 QC5.28 [2.85, 6.84]3.56+4.74 [1.16, 6.80]6.55 [3.45, 7.97]21% [7%, 43%]21%29%+0.07+0.382026-08-07 → 2026-08-30
tmin00Znearestall24 1 QC5.28 [2.66, 6.85]3.56+4.74 [0.76, 6.81]6.55 [3.36, 7.95]21% [7%, 50%]21%29%+0.07+0.382026-08-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC4.19 [2.78, 5.39]3.60+2.94 [0.56, 4.73]5.51 [3.32, 7.03]17% [4%, 31%]29%54%+0.27+0.372026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC4.19 [2.42, 5.42]3.60+2.94 [0.05, 4.84]5.51 [2.89, 7.10]17% [0%, 33%]29%54%+0.27+0.372026-08-07 → 2026-08-30
tmin12Zbilinear365d24 1 QC4.19 [2.40, 5.57]3.60+2.94 [-0.20, 5.18]5.51 [2.90, 7.30]17% [0%, 33%]29%54%+0.27+0.372026-08-07 → 2026-08-30
tmin12Zbilinearall24 1 QC4.19 [2.31, 5.51]3.60+2.94 [-0.20, 4.85]5.51 [2.78, 7.19]17% [0%, 33%]29%54%+0.27+0.372026-08-07 → 2026-08-30
tmin12Znearest30d24 1 QC4.91 [3.17, 6.33]3.62+4.17 [1.58, 6.05]6.31 [3.92, 8.03]12% [4%, 24%]33%33%+0.14+0.372026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC4.91 [2.68, 6.44]3.62+4.17 [1.05, 6.21]6.31 [3.17, 8.10]12% [4%, 25%]33%33%+0.14+0.372026-08-07 → 2026-08-30
tmin12Znearest365d24 1 QC4.91 [2.73, 6.66]3.62+4.17 [0.84, 6.57]6.31 [3.16, 8.34]12% [0%, 25%]33%33%+0.14+0.372026-08-07 → 2026-08-30
tmin12Znearestall24 1 QC4.91 [2.58, 6.44]3.62+4.17 [0.78, 6.25]6.31 [3.04, 8.19]12% [0%, 25%]33%33%+0.14+0.372026-08-07 → 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 NCEP GFS at KPHX, lead day 6, 00Z bilinear tmax+20+100-10-202026-08-07: -10.29 °F2026-08-08: -6.66 °F2026-08-09: -4.7 °F2026-08-10: -5.04 °F2026-08-11: -0.43 °F2026-08-12: +1.5 °F2026-08-13: +1.89 °F2026-08-14: +1.29 °F2026-08-15: -2.6 °F2026-08-16: -6.55 °F2026-08-17: -7.53 °F2026-08-18: -4.31 °F2026-08-19: -3.51 °F2026-08-20: +1.68 °F2026-08-21: -3.59 °F2026-08-22: -8.28 °F2026-08-23: -4.55 °F2026-08-24: -4.29 °F2026-08-25: -5.79 °F2026-08-26: -9.56 °F2026-08-27: -2.88 °F2026-08-28: +0.26 °F2026-08-29: -2.5 °F2026-08-30: -5.43 °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
2026-08-30-5.43
2026-08-29-2.50
2026-08-28+0.26
2026-08-27-2.88
2026-08-26-9.56
2026-08-25-5.79
2026-08-24-4.29
2026-08-23-4.55
2026-08-22-8.28
2026-08-21-3.59
2026-08-20+1.68
2026-08-19-3.51
2026-08-18-4.31
2026-08-17-7.53
2026-08-16-6.55
2026-08-15-2.60
2026-08-14+1.29
2026-08-13+1.89
2026-08-12+1.50
2026-08-11-0.43
2026-08-10-5.04
2026-08-09-4.70
2026-08-08-6.66
2026-08-07-10.29

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHX, lead day 6-20 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: 2 days-8 to -6 °F: 3 days-6 to -4 °F: 7 days-4 to -2 °F: 5 days-2 to 0 °F: 1 day0 to 2 °F: 5 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| 4.3 · P90 |e| 8.06 °F-200+20 °Fn = 24 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
-10.00-8.002
-8.00-6.003
-6.00-4.007
-4.00-2.005
-2.00+0.001
+0.00+2.005
+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
2026-08244.38 -3.83

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24

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 24 -0.54 [-2.20, 1.36] no
GraphCast (IFS init) 24 -1.62 [-3.88, 0.43] no
ECMWF IFS HRES 19 +1.51 [0.27, 2.85] yes
Persistence (baseline) 24 -0.62 [-2.55, 2.59] no

Cite this page

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

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