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 1

KPHX · gfs · lead 1

Target day = initialization date + 1 day. 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
tmax00Zbilinear30d29 1 QC2.91 [2.07, 3.78]1.98-2.59 [-3.55, -1.61]3.59 [2.67, 4.41]21% [7%, 34%]38%66%+0.08+0.372026-08-02 → 2026-08-30
tmax00Zbilinear90d29 1 QC2.91 [2.04, 3.86]1.98-2.59 [-3.71, -1.53]3.59 [2.60, 4.51]21% [5%, 35%]38%66%+0.08+0.372026-08-02 → 2026-08-30
tmax00Zbilinear365d29 1 QC2.91 [2.07, 3.96]1.98-2.59 [-3.81, -1.57]3.59 [2.66, 4.61]21% [0%, 35%]38%66%+0.08+0.372026-08-02 → 2026-08-30
tmax00Zbilinearall29 1 QC2.91 [2.02, 3.87]1.98-2.59 [-3.69, -1.62]3.59 [2.48, 4.55]21% [0%, 35%]38%66%+0.08+0.372026-08-02 → 2026-08-30
tmax00Znearest30d29 1 QC2.89 [2.07, 3.78]1.99-2.52 [-3.50, -1.57]3.56 [2.66, 4.36]21% [7%, 34%]38%66%+0.09+0.372026-08-02 → 2026-08-30
tmax00Znearest90d29 1 QC2.89 [2.05, 3.84]1.99-2.52 [-3.63, -1.46]3.56 [2.59, 4.46]21% [5%, 35%]38%66%+0.09+0.372026-08-02 → 2026-08-30
tmax00Znearest365d29 1 QC2.89 [2.09, 3.95]1.99-2.52 [-3.74, -1.50]3.56 [2.64, 4.56]21% [0%, 35%]38%66%+0.09+0.372026-08-02 → 2026-08-30
tmax00Znearestall29 1 QC2.89 [2.02, 3.85]1.99-2.52 [-3.63, -1.52]3.56 [2.50, 4.50]21% [0%, 35%]38%66%+0.09+0.372026-08-02 → 2026-08-30
tmax12Zbilinear30d29 1 QC2.76 [2.06, 3.54]1.48-2.58 [-3.45, -1.77]3.25 [2.38, 4.03]17% [10%, 24%]31%55%+0.13+0.532026-08-02 → 2026-08-30
tmax12Zbilinear90d29 1 QC2.76 [2.05, 3.63]1.48-2.58 [-3.54, -1.69]3.25 [2.38, 4.11]17% [8%, 25%]31%55%+0.13+0.532026-08-02 → 2026-08-30
tmax12Zbilinear365d29 1 QC2.76 [2.04, 3.72]1.48-2.58 [-3.68, -1.71]3.25 [2.31, 4.14]17% [7%, 25%]31%55%+0.13+0.532026-08-02 → 2026-08-30
tmax12Zbilinearall29 1 QC2.76 [1.97, 3.69]1.48-2.58 [-3.66, -1.70]3.25 [2.23, 4.09]17% [7%, 27%]31%55%+0.13+0.532026-08-02 → 2026-08-30
tmax12Znearest30d29 1 QC2.67 [1.98, 3.45]1.54-2.45 [-3.29, -1.68]3.17 [2.33, 3.94]17% [10%, 24%]41%59%+0.16+0.512026-08-02 → 2026-08-30
tmax12Znearest90d29 1 QC2.67 [1.98, 3.50]1.54-2.45 [-3.35, -1.62]3.17 [2.33, 4.00]17% [8%, 25%]41%59%+0.16+0.512026-08-02 → 2026-08-30
tmax12Znearest365d29 1 QC2.67 [1.98, 3.55]1.54-2.45 [-3.41, -1.62]3.17 [2.27, 4.03]17% [7%, 25%]41%59%+0.16+0.512026-08-02 → 2026-08-30
tmax12Znearestall29 1 QC2.67 [1.90, 3.52]1.54-2.45 [-3.39, -1.63]3.17 [2.19, 3.99]17% [7%, 27%]41%59%+0.16+0.512026-08-02 → 2026-08-30
tmin00Zbilinear30d29 1 QC4.07 [2.61, 5.62]2.94+3.12 [0.67, 5.40]4.97 [3.04, 6.54]3% [0%, 10%]28%45%-0.26+0.092026-08-02 → 2026-08-30
tmin00Zbilinear90d29 1 QC4.07 [2.32, 5.64]2.94+3.12 [0.10, 5.37]4.97 [2.64, 6.55]3% [0%, 10%]28%45%-0.26+0.092026-08-02 → 2026-08-30
tmin00Zbilinear365d29 1 QC4.07 [2.40, 5.60]2.94+3.12 [0.03, 5.32]4.97 [2.77, 6.59]3% [0%, 11%]28%45%-0.26+0.092026-08-02 → 2026-08-30
tmin00Zbilinearall29 1 QC4.07 [2.22, 5.80]2.94+3.12 [-0.07, 5.46]4.97 [2.52, 6.74]3% [0%, 11%]28%45%-0.26+0.092026-08-02 → 2026-08-30
tmin00Znearest30d29 1 QC4.93 [2.95, 6.77]2.99+4.37 [1.84, 6.65]5.85 [3.53, 7.56]7% [0%, 21%]10%31%-0.52+0.072026-08-02 → 2026-08-30
tmin00Znearest90d29 1 QC4.93 [2.53, 6.71]2.99+4.37 [1.23, 6.62]5.85 [2.88, 7.59]7% [0%, 23%]10%31%-0.52+0.072026-08-02 → 2026-08-30
tmin00Znearest365d29 1 QC4.93 [2.59, 6.75]2.99+4.37 [1.15, 6.59]5.85 [2.88, 7.58]7% [0%, 22%]10%31%-0.52+0.072026-08-02 → 2026-08-30
tmin00Znearestall29 1 QC4.93 [2.34, 6.95]2.99+4.37 [0.95, 6.73]5.85 [2.71, 7.75]7% [0%, 23%]10%31%-0.52+0.072026-08-02 → 2026-08-30
tmin12Zbilinear30d29 1 QC4.25 [3.36, 5.15]3.10+2.64 [0.02, 4.73]4.89 [3.86, 5.81]3% [0%, 11%]17%31%-0.31+0.042026-08-02 → 2026-08-30
tmin12Zbilinear90d29 1 QC4.25 [3.08, 5.28]3.10+2.64 [-0.61, 4.69]4.89 [3.49, 5.96]3% [0%, 12%]17%31%-0.31+0.042026-08-02 → 2026-08-30
tmin12Zbilinear365d29 1 QC4.25 [3.22, 5.33]3.10+2.64 [-0.76, 4.86]4.89 [3.61, 6.00]3% [0%, 12%]17%31%-0.31+0.042026-08-02 → 2026-08-30
tmin12Zbilinearall29 1 QC4.25 [3.13, 5.39]3.10+2.64 [-0.99, 4.87]4.89 [3.54, 6.02]3% [0%, 11%]17%31%-0.31+0.042026-08-02 → 2026-08-30
tmin12Znearest30d29 1 QC5.12 [3.77, 6.34]3.17+3.99 [1.33, 6.13]5.76 [4.43, 6.85]7% [0%, 18%]14%14%-0.58+0.022026-08-02 → 2026-08-30
tmin12Znearest90d29 1 QC5.12 [3.41, 6.38]3.17+3.99 [0.68, 6.07]5.76 [4.01, 6.90]7% [0%, 20%]14%14%-0.58+0.022026-08-02 → 2026-08-30
tmin12Znearest365d29 1 QC5.12 [3.50, 6.41]3.17+3.99 [0.56, 6.27]5.76 [4.14, 6.91]7% [0%, 20%]14%14%-0.58+0.022026-08-02 → 2026-08-30
tmin12Znearestall29 1 QC5.12 [3.42, 6.56]3.17+3.99 [0.28, 6.23]5.76 [4.11, 7.02]7% [0%, 20%]14%14%-0.58+0.022026-08-02 → 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 1, 00Z bilinear tmax+10+50-5-102026-08-02: -4.45 °F2026-08-03: -6.31 °F2026-08-04: +2.02 °F2026-08-05: +0.73 °F2026-08-06: +0.5 °F2026-08-07: -1.46 °F2026-08-08: -2.06 °F2026-08-09: -1.45 °F2026-08-10: -1.65 °F2026-08-11: -0.98 °F2026-08-12: -5.17 °F2026-08-13: +0.01 °F2026-08-14: -0.39 °F2026-08-15: -2.99 °F2026-08-16: -6.14 °F2026-08-17: -4.29 °F2026-08-18: -6.31 °F2026-08-19: -2.62 °F2026-08-20: +1.33 °F2026-08-21: -2.03 °F2026-08-22: -3.57 °F2026-08-23: -1.72 °F2026-08-24: -0.9 °F2026-08-25: -3.57 °F2026-08-26: -5.02 °F2026-08-27: -2.89 °F2026-08-28: -2.87 °F2026-08-29: -8.73 °F2026-08-30: -2.2 °F2026-08-022026-08-30°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 (29 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-2.20
2026-08-29-8.73
2026-08-28-2.87
2026-08-27-2.89
2026-08-26-5.02
2026-08-25-3.57
2026-08-24-0.90
2026-08-23-1.72
2026-08-22-3.57
2026-08-21-2.03
2026-08-20+1.33
2026-08-19-2.62
2026-08-18-6.31
2026-08-17-4.29
2026-08-16-6.14
2026-08-15-2.99
2026-08-14-0.39
2026-08-13+0.01
2026-08-12-5.17
2026-08-11-0.98
2026-08-10-1.65
2026-08-09-1.45
2026-08-08-2.06
2026-08-07-1.46
2026-08-06+0.50
2026-08-05+0.73
2026-08-04+2.02
2026-08-03-6.31
2026-08-02-4.45

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHX, lead day 1-10 to -9 °F: 0 days-9 to -8 °F: 1 day-8 to -7 °F: 0 days-7 to -6 °F: 3 days-6 to -5 °F: 2 days-5 to -4 °F: 2 days-4 to -3 °F: 2 days-3 to -2 °F: 7 days-2 to -1 °F: 4 days-1 to 0 °F: 3 days0 to 1 °F: 3 days1 to 2 °F: 1 day2 to 3 °F: 1 day3 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| 2.2 · P90 |e| 6.18 °F-100+10 °Fn = 29 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
-10.00-9.000
-9.00-8.001
-8.00-7.000
-7.00-6.003
-6.00-5.002
-5.00-4.002
-4.00-3.002
-3.00-2.007
-2.00-1.004
-1.00+0.003
+0.00+1.003
+1.00+2.001
+2.00+3.001
+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
2026-08292.91 -2.59

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29

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 29 -0.24 [-1.30, 0.98] no
Aurora (GFS init) 1 -12.38 [-12.38, -12.38] yes
Aurora (IFS init) 2 -2.89 [-6.00, 0.22] no
FourCastNet v2 (GFS init) 1 -10.44 [-10.44, -10.44] yes
FourCastNet v2 (IFS init) 2 -4.87 [-6.89, -2.84] yes
GraphCast (GFS init) 1 -11.70 [-11.70, -11.70] yes
GraphCast (IFS init) 27 -0.41 [-1.34, 0.54] no
ECMWF IFS HRES 22 +0.79 [-0.34, 2.07] no
Pangu-Weather (GFS init) 1 -5.22 [-5.22, -5.22] yes
Pangu-Weather (IFS init) 2 -1.98 [-3.65, -0.32] yes
Persistence (baseline) 29 -0.26 [-1.19, 0.76] no

Cite this page

ShortCastCheck, KPHX gfs lead 1, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHX/model/gfs/lead/1/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHX (Phoenix Sky Harbor), model gfs, lead day 1. 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/1/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

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