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 3

KPHX · gfs · lead 3

Target day = initialization date + 3 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
tmax00Zbilinear30d27 1 QC4.05 [3.39, 4.65]2.29-3.32 [-4.39, -1.73]4.52 [3.72, 5.25]0% [0%, 0%]11%37%+0.30+0.602026-08-04 → 2026-08-30
tmax00Zbilinear90d27 1 QC4.05 [3.26, 4.71]2.29-3.32 [-4.62, -1.27]4.52 [3.55, 5.44]0% [0%, 0%]11%37%+0.30+0.602026-08-04 → 2026-08-30
tmax00Zbilinear365d27 1 QC4.05 [3.22, 4.91]2.29-3.32 [-4.74, -1.25]4.52 [3.51, 5.57]0% [0%, 0%]11%37%+0.30+0.602026-08-04 → 2026-08-30
tmax00Zbilinearall27 1 QC4.05 [3.16, 4.77]2.29-3.32 [-4.69, -1.13]4.52 [3.40, 5.42]0% [0%, 0%]11%37%+0.30+0.602026-08-04 → 2026-08-30
tmax00Znearest30d27 1 QC4.05 [3.39, 4.63]2.37-3.28 [-4.34, -1.68]4.59 [3.79, 5.23]0% [0%, 0%]11%41%+0.30+0.592026-08-04 → 2026-08-30
tmax00Znearest90d27 1 QC4.05 [3.25, 4.71]2.37-3.28 [-4.42, -1.24]4.59 [3.56, 5.38]0% [0%, 0%]11%41%+0.30+0.592026-08-04 → 2026-08-30
tmax00Znearest365d27 1 QC4.05 [3.27, 4.77]2.37-3.28 [-4.60, -1.23]4.59 [3.55, 5.49]0% [0%, 0%]11%41%+0.30+0.592026-08-04 → 2026-08-30
tmax00Znearestall27 1 QC4.05 [3.22, 4.72]2.37-3.28 [-4.50, -1.04]4.59 [3.38, 5.38]0% [0%, 0%]11%41%+0.30+0.592026-08-04 → 2026-08-30
tmax12Zbilinear30d27 1 QC3.24 [2.54, 3.87]1.98-2.61 [-3.59, -1.13]3.68 [2.88, 4.33]4% [0%, 10%]30%56%+0.44+0.662026-08-04 → 2026-08-30
tmax12Zbilinear90d27 1 QC3.24 [2.38, 4.01]1.98-2.61 [-3.78, -0.83]3.68 [2.62, 4.49]4% [0%, 11%]30%56%+0.44+0.662026-08-04 → 2026-08-30
tmax12Zbilinear365d27 1 QC3.24 [2.36, 4.17]1.98-2.61 [-3.96, -0.87]3.68 [2.62, 4.65]4% [0%, 11%]30%56%+0.44+0.662026-08-04 → 2026-08-30
tmax12Zbilinearall27 1 QC3.24 [2.32, 4.07]1.98-2.61 [-3.86, -0.85]3.68 [2.58, 4.50]4% [0%, 11%]30%56%+0.44+0.662026-08-04 → 2026-08-30
tmax12Znearest30d27 1 QC3.23 [2.59, 3.83]2.00-2.55 [-3.52, -1.07]3.65 [2.92, 4.25]7% [0%, 20%]22%52%+0.44+0.652026-08-04 → 2026-08-30
tmax12Znearest90d27 1 QC3.23 [2.43, 3.93]2.00-2.55 [-3.68, -0.75]3.65 [2.76, 4.39]7% [0%, 21%]22%52%+0.44+0.652026-08-04 → 2026-08-30
tmax12Znearest365d27 1 QC3.23 [2.44, 4.09]2.00-2.55 [-3.84, -0.83]3.65 [2.71, 4.52]7% [0%, 21%]22%52%+0.44+0.652026-08-04 → 2026-08-30
tmax12Znearestall27 1 QC3.23 [2.37, 4.01]2.00-2.55 [-3.74, -0.76]3.65 [2.69, 4.43]7% [0%, 21%]22%52%+0.44+0.652026-08-04 → 2026-08-30
tmin00Zbilinear30d27 1 QC4.11 [2.93, 5.61]3.25+3.26 [0.88, 5.25]5.36 [3.75, 6.94]15% [3%, 29%]37%52%+0.27+0.422026-08-04 → 2026-08-30
tmin00Zbilinear90d27 1 QC4.11 [2.68, 5.67]3.25+3.26 [0.36, 5.41]5.36 [3.37, 6.99]15% [0%, 29%]37%52%+0.27+0.422026-08-04 → 2026-08-30
tmin00Zbilinear365d27 1 QC4.11 [2.69, 5.79]3.25+3.26 [0.36, 5.41]5.36 [3.52, 7.06]15% [0%, 29%]37%52%+0.27+0.422026-08-04 → 2026-08-30
tmin00Zbilinearall27 1 QC4.11 [2.67, 5.97]3.25+3.26 [0.07, 5.56]5.36 [3.42, 7.18]15% [0%, 29%]37%52%+0.27+0.422026-08-04 → 2026-08-30
tmin00Znearest30d27 1 QC5.05 [3.41, 6.84]3.30+4.52 [2.04, 6.62]6.32 [4.44, 8.06]15% [0%, 31%]26%30%+0.11+0.412026-08-04 → 2026-08-30
tmin00Znearest90d27 1 QC5.05 [3.01, 6.87]3.30+4.52 [1.52, 6.74]6.32 [3.96, 8.09]15% [0%, 36%]26%30%+0.11+0.412026-08-04 → 2026-08-30
tmin00Znearest365d27 1 QC5.05 [3.14, 6.90]3.30+4.52 [1.50, 6.78]6.32 [4.10, 8.19]15% [0%, 36%]26%30%+0.11+0.412026-08-04 → 2026-08-30
tmin00Znearestall27 1 QC5.05 [2.97, 7.11]3.30+4.52 [1.12, 6.92]6.32 [3.89, 8.29]15% [0%, 36%]26%30%+0.11+0.412026-08-04 → 2026-08-30
tmin12Zbilinear30d27 1 QC4.30 [2.88, 5.48]3.43+3.24 [0.98, 5.03]5.38 [3.79, 6.62]15% [3%, 33%]30%48%+0.24+0.392026-08-04 → 2026-08-30
tmin12Zbilinear90d27 1 QC4.30 [2.47, 5.44]3.43+3.24 [0.51, 5.12]5.38 [3.34, 6.63]15% [3%, 36%]30%48%+0.24+0.392026-08-04 → 2026-08-30
tmin12Zbilinear365d27 1 QC4.30 [2.64, 5.47]3.43+3.24 [0.47, 5.10]5.38 [3.41, 6.70]15% [0%, 35%]30%48%+0.24+0.392026-08-04 → 2026-08-30
tmin12Zbilinearall27 1 QC4.30 [2.35, 5.63]3.43+3.24 [0.27, 5.23]5.38 [3.07, 6.73]15% [0%, 38%]30%48%+0.24+0.392026-08-04 → 2026-08-30
tmin12Znearest30d27 1 QC5.15 [3.35, 6.62]3.42+4.47 [2.12, 6.35]6.23 [4.30, 7.65]15% [0%, 38%]19%26%+0.09+0.392026-08-04 → 2026-08-30
tmin12Znearest90d27 1 QC5.15 [2.81, 6.59]3.42+4.47 [1.59, 6.43]6.23 [3.82, 7.63]15% [0%, 46%]19%26%+0.09+0.392026-08-04 → 2026-08-30
tmin12Znearest365d27 1 QC5.15 [2.78, 6.62]3.42+4.47 [1.61, 6.46]6.23 [3.72, 7.71]15% [0%, 43%]19%26%+0.09+0.392026-08-04 → 2026-08-30
tmin12Znearestall27 1 QC5.15 [2.64, 6.79]3.42+4.47 [1.39, 6.58]6.23 [3.51, 7.79]15% [0%, 46%]19%26%+0.09+0.392026-08-04 → 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 3, 00Z bilinear tmax+20+100-10-202026-08-04: +2.58 °F2026-08-05: +2.76 °F2026-08-06: +1.5 °F2026-08-07: -3.45 °F2026-08-08: -5.75 °F2026-08-09: -2.82 °F2026-08-10: -2.26 °F2026-08-11: -1.58 °F2026-08-12: -7.27 °F2026-08-13: -5.87 °F2026-08-14: -4.4 °F2026-08-15: -3.92 °F2026-08-16: -2.25 °F2026-08-17: -5.63 °F2026-08-18: -4.16 °F2026-08-19: -6.37 °F2026-08-20: +3.01 °F2026-08-21: -4.57 °F2026-08-22: -5 °F2026-08-23: -2.58 °F2026-08-24: -1.87 °F2026-08-25: -4.6 °F2026-08-26: -4.86 °F2026-08-27: -2.29 °F2026-08-28: -3.14 °F2026-08-29: -10.76 °F2026-08-30: -4.04 °F2026-08-042026-08-30°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 (27 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.04
2026-08-29-10.76
2026-08-28-3.14
2026-08-27-2.29
2026-08-26-4.86
2026-08-25-4.60
2026-08-24-1.87
2026-08-23-2.58
2026-08-22-5.00
2026-08-21-4.57
2026-08-20+3.01
2026-08-19-6.37
2026-08-18-4.16
2026-08-17-5.63
2026-08-16-2.25
2026-08-15-3.92
2026-08-14-4.40
2026-08-13-5.87
2026-08-12-7.27
2026-08-11-1.58
2026-08-10-2.26
2026-08-09-2.82
2026-08-08-5.75
2026-08-07-3.45
2026-08-06+1.50
2026-08-05+2.76
2026-08-04+2.58

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHX, lead day 3-20 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: 0 days-8 to -6 °F: 2 days-6 to -4 °F: 10 days-4 to -2 °F: 8 days-2 to 0 °F: 2 days0 to 2 °F: 1 day2 to 4 °F: 3 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| 3.92 · P90 |e| 6.07 °F-200+20 °Fn = 27 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
-10.00-8.000
-8.00-6.002
-6.00-4.0010
-4.00-2.008
-2.00+0.002
+0.00+2.001
+2.00+4.003
+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
2026-08274.05 -3.32

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27

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 27 +0.41 [-0.93, 1.50] no
GraphCast (IFS init) 25 +0.34 [-0.47, 1.17] no
ECMWF IFS HRES 22 +1.25 [0.37, 1.65] yes
Persistence (baseline) 27 -1.73 [-3.84, -0.10] yes

Cite this page

ShortCastCheck, KPHX gfs lead 3, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHX/model/gfs/lead/3/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHX (Phoenix Sky Harbor), model gfs, lead day 3. 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/3/

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