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 8

KPHX · gfs · 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, 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
tmax00Zbilinear30d22 1 QC4.90 [3.79, 6.14]3.63-4.11 [-5.51, -2.38]5.96 [4.73, 6.99]9% [0%, 15%]18%45%+0.11+0.342026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC4.90 [3.71, 6.40]3.63-4.11 [-5.92, -2.33]5.96 [4.53, 7.08]9% [0%, 15%]18%45%+0.11+0.342026-08-09 → 2026-08-30
tmax00Zbilinear365d22 1 QC4.90 [3.73, 6.27]3.63-4.11 [-5.88, -2.01]5.96 [4.56, 7.00]9% [0%, 14%]18%45%+0.11+0.342026-08-09 → 2026-08-30
tmax00Zbilinearall22 1 QC4.90 [3.64, 6.26]3.63-4.11 [-5.64, -1.96]5.96 [4.53, 7.05]9% [0%, 14%]18%45%+0.11+0.342026-08-09 → 2026-08-30
tmax00Znearest30d22 1 QC4.85 [3.77, 6.07]3.58-4.03 [-5.43, -2.34]5.86 [4.67, 6.88]9% [0%, 15%]23%45%+0.12+0.352026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC4.85 [3.72, 6.27]3.58-4.03 [-5.85, -2.27]5.86 [4.48, 7.00]9% [0%, 15%]23%45%+0.12+0.352026-08-09 → 2026-08-30
tmax00Znearest365d22 1 QC4.85 [3.73, 6.19]3.58-4.03 [-5.86, -1.97]5.86 [4.58, 6.96]9% [0%, 14%]23%45%+0.12+0.352026-08-09 → 2026-08-30
tmax00Znearestall22 1 QC4.85 [3.69, 6.20]3.58-4.03 [-5.59, -1.91]5.86 [4.47, 6.92]9% [0%, 14%]23%45%+0.12+0.352026-08-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC5.02 [4.26, 5.81]2.73-4.37 [-5.34, -2.82]5.63 [4.93, 6.27]5% [0%, 13%]18%23%+0.09+0.502026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC5.02 [4.20, 5.90]2.73-4.37 [-5.56, -2.55]5.63 [4.83, 6.34]5% [0%, 14%]18%23%+0.09+0.502026-08-09 → 2026-08-30
tmax12Zbilinear365d22 1 QC5.02 [4.19, 5.90]2.73-4.37 [-5.55, -2.55]5.63 [4.83, 6.39]5% [0%, 14%]18%23%+0.09+0.502026-08-09 → 2026-08-30
tmax12Zbilinearall22 1 QC5.02 [4.19, 5.87]2.73-4.37 [-5.52, -2.05]5.63 [4.83, 6.32]5% [0%, 14%]18%23%+0.09+0.502026-08-09 → 2026-08-30
tmax12Znearest30d22 1 QC4.99 [4.21, 5.78]2.65-4.30 [-5.31, -2.67]5.55 [4.83, 6.21]9% [0%, 26%]18%18%+0.09+0.522026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC4.99 [4.11, 5.88]2.65-4.30 [-5.54, -2.32]5.55 [4.65, 6.33]9% [0%, 29%]18%18%+0.09+0.522026-08-09 → 2026-08-30
tmax12Znearest365d22 1 QC4.99 [4.15, 5.96]2.65-4.30 [-5.55, -2.41]5.55 [4.65, 6.38]9% [0%, 29%]18%18%+0.09+0.522026-08-09 → 2026-08-30
tmax12Znearestall22 1 QC4.99 [4.14, 5.87]2.65-4.30 [-5.55, -1.83]5.55 [4.66, 6.30]9% [0%, 29%]18%18%+0.09+0.522026-08-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC5.10 [3.80, 6.49]3.82+3.88 [2.06, 5.48]6.05 [4.74, 7.35]5% [0%, 14%]23%36%+0.18+0.372026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC5.10 [3.57, 6.80]3.82+3.88 [1.55, 5.40]6.05 [4.50, 7.60]5% [0%, 14%]23%36%+0.18+0.372026-08-09 → 2026-08-30
tmin00Zbilinear365d22 1 QC5.10 [3.51, 6.77]3.82+3.88 [1.69, 5.45]6.05 [4.44, 7.61]5% [0%, 14%]23%36%+0.18+0.372026-08-09 → 2026-08-30
tmin00Zbilinearall22 1 QC5.10 [3.50, 6.85]3.82+3.88 [1.54, 5.60]6.05 [4.40, 7.66]5% [0%, 14%]23%36%+0.18+0.372026-08-09 → 2026-08-30
tmin00Znearest30d22 1 QC6.00 [4.64, 7.30]3.82+5.21 [3.39, 6.73]6.98 [5.63, 8.15]5% [0%, 18%]14%23%+0.04+0.372026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC6.00 [4.30, 7.45]3.82+5.21 [2.96, 6.70]6.98 [5.28, 8.33]5% [0%, 22%]14%23%+0.04+0.372026-08-09 → 2026-08-30
tmin00Znearest365d22 1 QC6.00 [4.30, 7.50]3.82+5.21 [3.16, 6.73]6.98 [5.22, 8.40]5% [0%, 20%]14%23%+0.04+0.372026-08-09 → 2026-08-30
tmin00Znearestall22 1 QC6.00 [4.30, 7.47]3.82+5.21 [2.95, 6.90]6.98 [5.23, 8.35]5% [0%, 22%]14%23%+0.04+0.372026-08-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC5.12 [3.22, 6.54]4.36+3.52 [1.95, 5.06]6.25 [4.30, 7.37]23% [5%, 44%]27%32%+0.18+0.282026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC5.12 [3.01, 6.63]4.36+3.52 [1.78, 5.03]6.25 [4.13, 7.40]23% [0%, 46%]27%32%+0.18+0.282026-08-09 → 2026-08-30
tmin12Zbilinear365d22 1 QC5.12 [2.77, 6.66]4.36+3.52 [1.79, 5.23]6.25 [3.88, 7.47]23% [0%, 49%]27%32%+0.18+0.282026-08-09 → 2026-08-30
tmin12Zbilinearall22 1 QC5.12 [2.81, 6.65]4.36+3.52 [1.80, 5.36]6.25 [3.95, 7.47]23% [0%, 46%]27%32%+0.18+0.282026-08-09 → 2026-08-30
tmin12Znearest30d22 1 QC5.82 [3.87, 7.28]4.33+4.81 [3.25, 6.36]7.04 [5.18, 8.24]9% [0%, 27%]23%32%+0.07+0.292026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC5.82 [3.68, 7.40]4.33+4.81 [3.09, 6.31]7.04 [4.79, 8.24]9% [0%, 29%]23%32%+0.07+0.292026-08-09 → 2026-08-30
tmin12Znearest365d22 1 QC5.82 [3.51, 7.43]4.33+4.81 [3.09, 6.58]7.04 [4.76, 8.29]9% [0%, 29%]23%32%+0.07+0.292026-08-09 → 2026-08-30
tmin12Znearestall22 1 QC5.82 [3.62, 7.43]4.33+4.81 [3.09, 6.78]7.04 [4.80, 8.40]9% [0%, 30%]23%32%+0.07+0.292026-08-09 → 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 NCEP GFS at KPHX, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: -7.8 °F2026-08-10: -10.24 °F2026-08-11: -2.35 °F2026-08-12: +2.3 °F2026-08-13: +1.06 °F2026-08-14: -0.48 °F2026-08-15: -2.54 °F2026-08-16: -4.23 °F2026-08-17: -7.49 °F2026-08-18: -11.95 °F2026-08-19: -7.28 °F2026-08-20: -1.38 °F2026-08-21: -4.59 °F2026-08-22: -6.57 °F2026-08-23: +0.55 °F2026-08-24: -2.07 °F2026-08-25: -2.41 °F2026-08-26: -10.68 °F2026-08-27: -8.71 °F2026-08-28: -5.63 °F2026-08-29: -2.72 °F2026-08-30: +4.75 °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+4.75
2026-08-29-2.72
2026-08-28-5.63
2026-08-27-8.71
2026-08-26-10.68
2026-08-25-2.41
2026-08-24-2.07
2026-08-23+0.55
2026-08-22-6.57
2026-08-21-4.59
2026-08-20-1.38
2026-08-19-7.28
2026-08-18-11.95
2026-08-17-7.49
2026-08-16-4.23
2026-08-15-2.54
2026-08-14-0.48
2026-08-13+1.06
2026-08-12+2.30
2026-08-11-2.35
2026-08-10-10.24
2026-08-09-7.80

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHX, 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: 3 days-10 to -8 °F: 1 day-8 to -6 °F: 4 days-6 to -4 °F: 3 days-4 to -2 °F: 5 days-2 to 0 °F: 2 days0 to 2 °F: 2 days2 to 4 °F: 1 day4 to 6 °F: 1 day6 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| 4.41 · P90 |e| 10.09 °F-200+20 °Fn = 22 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
-12.00-10.003
-10.00-8.001
-8.00-6.004
-6.00-4.003
-4.00-2.005
-2.00+0.002
+0.00+2.002
+2.00+4.001
+4.00+6.001
+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
2026-08224.90 -4.11

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22
NCEP GFS2026-08-09 → 2026-08-30 22

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 22 -2.01 [-4.93, 2.56] no
GraphCast (IFS init) 22 -4.28 [-7.46, -0.12] yes
ECMWF IFS HRES 17 +0.29 [-2.29, 2.57] no
Persistence (baseline) 22 -0.60 [-2.40, 1.47] no

Cite this page

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

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