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

Phoenix Sky Harbor · NCEP GFS · lead day 0

KPHX · gfs · lead 0

Target day = initialization date + 0 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
tmax00Zbilinear30d30 1 QC2.96 [2.20, 3.77]1.74-2.69 [-3.60, -1.86]3.58 [2.59, 4.47]7% [0%, 20%]37%63%——2026-08-01 → 2026-08-30
tmax00Zbilinear90d30 1 QC2.96 [2.16, 3.97]1.74-2.69 [-3.80, -1.80]3.58 [2.56, 4.76]7% [0%, 19%]37%63%——2026-08-01 → 2026-08-30
tmax00Zbilinear365d30 1 QC2.96 [2.18, 4.22]1.74-2.69 [-4.18, -1.82]3.58 [2.57, 4.99]7% [0%, 21%]37%63%——2026-08-01 → 2026-08-30
tmax00Zbilinearall30 1 QC2.96 [2.16, 4.06]1.74-2.69 [-3.90, -1.77]3.58 [2.49, 4.79]7% [0%, 19%]37%63%——2026-08-01 → 2026-08-30
tmax00Znearest30d30 1 QC2.64 [2.09, 3.21]1.66-2.31 [-3.01, -1.67]3.14 [2.53, 3.72]13% [3%, 27%]43%67%——2026-08-01 → 2026-08-30
tmax00Znearest90d30 1 QC2.64 [2.07, 3.27]1.66-2.31 [-3.04, -1.64]3.14 [2.47, 3.79]13% [0%, 31%]43%67%——2026-08-01 → 2026-08-30
tmax00Znearest365d30 1 QC2.64 [2.06, 3.29]1.66-2.31 [-3.09, -1.62]3.14 [2.47, 3.88]13% [0%, 33%]43%67%——2026-08-01 → 2026-08-30
tmax00Znearestall30 1 QC2.64 [2.03, 3.19]1.66-2.31 [-3.07, -1.63]3.14 [2.38, 3.82]13% [0%, 32%]43%67%——2026-08-01 → 2026-08-30
tmin00Zbilinear30d30 1 QC4.44 [3.15, 5.85]3.26+3.22 [0.87, 5.60]5.27 [3.71, 6.67]7% [0%, 20%]17%43%——2026-08-01 → 2026-08-30
tmin00Zbilinear90d30 1 QC4.44 [2.96, 5.90]3.26+3.22 [0.35, 5.51]5.27 [3.42, 6.74]7% [0%, 24%]17%43%——2026-08-01 → 2026-08-30
tmin00Zbilinear365d30 1 QC4.44 [3.02, 5.92]3.26+3.22 [0.23, 5.68]5.27 [3.53, 6.77]7% [0%, 27%]17%43%——2026-08-01 → 2026-08-30
tmin00Zbilinearall30 1 QC4.44 [2.95, 5.95]3.26+3.22 [0.20, 5.59]5.27 [3.45, 6.88]7% [0%, 22%]17%43%——2026-08-01 → 2026-08-30
tmin00Znearest30d30 1 QC5.29 [3.66, 7.06]3.28+4.57 [2.20, 6.97]6.17 [4.27, 7.74]7% [0%, 13%]17%27%——2026-08-01 → 2026-08-30
tmin00Znearest90d30 1 QC5.29 [3.34, 7.05]3.28+4.57 [1.60, 6.87]6.17 [3.81, 7.80]7% [0%, 17%]17%27%——2026-08-01 → 2026-08-30
tmin00Znearest365d30 1 QC5.29 [3.38, 7.17]3.28+4.57 [1.57, 7.06]6.17 [3.84, 7.89]7% [0%, 17%]17%27%——2026-08-01 → 2026-08-30
tmin00Znearestall30 1 QC5.29 [3.28, 7.19]3.28+4.57 [1.55, 6.96]6.17 [3.69, 7.92]7% [0%, 16%]17%27%——2026-08-01 → 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 0, 00Z bilinear tmax+20+100-10-202026-08-01: -3.37 °F2026-08-02: -2.38 °F2026-08-03: -4.76 °F2026-08-04: +1.05 °F2026-08-05: +1.31 °F2026-08-06: -2.84 °F2026-08-07: -1.14 °F2026-08-08: -4.71 °F2026-08-09: -1.4 °F2026-08-10: -1.2 °F2026-08-11: -2.23 °F2026-08-12: +0.12 °F2026-08-13: -0.93 °F2026-08-14: -1.63 °F2026-08-15: -3.51 °F2026-08-16: -6.83 °F2026-08-17: -3.8 °F2026-08-18: -5.18 °F2026-08-19: -2.78 °F2026-08-20: +1.56 °F2026-08-21: -2.01 °F2026-08-22: -2.99 °F2026-08-23: -1.46 °F2026-08-24: -2.24 °F2026-08-25: -2.77 °F2026-08-26: -4.17 °F2026-08-27: -3.22 °F2026-08-28: -1.61 °F2026-08-29: -10.02 °F2026-08-30: -5.5 °F2026-08-012026-08-30°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 (30 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-5.50
2026-08-29-10.02
2026-08-28-1.61
2026-08-27-3.22
2026-08-26-4.17
2026-08-25-2.77
2026-08-24-2.24
2026-08-23-1.46
2026-08-22-2.99
2026-08-21-2.01
2026-08-20+1.56
2026-08-19-2.78
2026-08-18-5.18
2026-08-17-3.80
2026-08-16-6.83
2026-08-15-3.51
2026-08-14-1.63
2026-08-13-0.93
2026-08-12+0.12
2026-08-11-2.23
2026-08-10-1.20
2026-08-09-1.40
2026-08-08-4.71
2026-08-07-1.14
2026-08-06-2.84
2026-08-05+1.31
2026-08-04+1.05
2026-08-03-4.76
2026-08-02-2.38
2026-08-01-3.37

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KPHX, lead day 0-20 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: 1 day-6 to -4 °F: 5 days-4 to -2 °F: 12 days-2 to 0 °F: 7 days0 to 2 °F: 4 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| 2.58 · P90 |e| 5.21 °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
-16.00-14.000
-14.00-12.000
-12.00-10.001
-10.00-8.000
-8.00-6.001
-6.00-4.005
-4.00-2.0012
-2.00+0.007
+0.00+2.004
+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
2026-08302.96 -2.69

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-01 → 2026-08-30 30
NCEP GFS2026-08-01 → 2026-08-30 30

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 30 -0.13 [-1.01, 0.77] no
Aurora (GFS init) 2 -5.68 [-7.20, -4.16] yes
Aurora (IFS init) 3 -0.00 [-2.10, 1.05] no
FourCastNet v2 (GFS init) 2 -2.81 [-4.86, -0.76] yes
FourCastNet v2 (IFS init) 3 -2.23 [-4.81, -0.95] yes
GraphCast (GFS init) 2 -7.13 [-9.78, -4.48] yes
GraphCast (IFS init) 28 +0.02 [-0.83, 0.73] no
ECMWF IFS HRES 25 +1.04 [0.23, 1.83] yes
Pangu-Weather (GFS init) 2 -0.99 [-3.31, 1.33] no
Pangu-Weather (IFS init) 3 -0.39 [-2.69, 0.76] no

Cite this page

ShortCastCheck, KPHX gfs lead 0, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KPHX/model/gfs/lead/0/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KPHX (Phoenix Sky Harbor), model gfs, lead day 0. 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/0/

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

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