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 · GraphCast (GFS init) · lead day 1

KPHX · graphcast_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, GRAP_v100, starting 2026-08-28 — 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
tmax00Zbilinear30d1 1 QC13.90 [13.90, 13.90]0.00-13.90 [-13.90, -13.90]13.90 [13.90, 13.90]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Zbilinear90d1 1 QC13.90 [13.90, 13.90]0.00-13.90 [-13.90, -13.90]13.90 [13.90, 13.90]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Zbilinear365d1 1 QC13.90 [13.90, 13.90]0.00-13.90 [-13.90, -13.90]13.90 [13.90, 13.90]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Zbilinearall1 1 QC13.90 [13.90, 13.90]0.00-13.90 [-13.90, -13.90]13.90 [13.90, 13.90]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Znearest30d1 1 QC13.95 [13.95, 13.95]0.00-13.95 [-13.95, -13.95]13.95 [13.95, 13.95]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Znearest90d1 1 QC13.95 [13.95, 13.95]0.00-13.95 [-13.95, -13.95]13.95 [13.95, 13.95]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Znearest365d1 1 QC13.95 [13.95, 13.95]0.00-13.95 [-13.95, -13.95]13.95 [13.95, 13.95]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax00Znearestall1 1 QC13.95 [13.95, 13.95]0.00-13.95 [-13.95, -13.95]13.95 [13.95, 13.95]0% [0%, 0%]0%0%-0.99—2026-08-30 → 2026-08-30
tmax12Zbilinear30d2 1 QC12.22 [12.11, 12.33]0.11-12.22 [-12.33, -12.11]12.22 [12.11, 12.33]0% [0%, 0%]0%0%-2.05+0.972026-08-29 → 2026-08-30
tmax12Zbilinear90d2 1 QC12.22 [12.11, 12.33]0.11-12.22 [-12.33, -12.11]12.22 [12.11, 12.33]0% [0%, 0%]0%0%-2.05+0.972026-08-29 → 2026-08-30
tmax12Zbilinear365d2 1 QC12.22 [12.11, 12.33]0.11-12.22 [-12.33, -12.11]12.22 [12.11, 12.33]0% [0%, 0%]0%0%-2.05+0.972026-08-29 → 2026-08-30
tmax12Zbilinearall2 1 QC12.22 [12.11, 12.33]0.11-12.22 [-12.33, -12.11]12.22 [12.11, 12.33]0% [0%, 0%]0%0%-2.05+0.972026-08-29 → 2026-08-30
tmax12Znearest30d2 1 QC12.18 [12.17, 12.19]0.01-12.18 [-12.19, -12.17]12.18 [12.17, 12.19]0% [0%, 0%]0%0%-2.04+1.002026-08-29 → 2026-08-30
tmax12Znearest90d2 1 QC12.18 [12.17, 12.19]0.01-12.18 [-12.19, -12.17]12.18 [12.17, 12.19]0% [0%, 0%]0%0%-2.04+1.002026-08-29 → 2026-08-30
tmax12Znearest365d2 1 QC12.18 [12.17, 12.19]0.01-12.18 [-12.19, -12.17]12.18 [12.17, 12.19]0% [0%, 0%]0%0%-2.04+1.002026-08-29 → 2026-08-30
tmax12Znearestall2 1 QC12.18 [12.17, 12.19]0.01-12.18 [-12.19, -12.17]12.18 [12.17, 12.19]0% [0%, 0%]0%0%-2.04+1.002026-08-29 → 2026-08-30
tmin00Zbilinear30d1 1 QC8.09 [8.09, 8.09]0.00-8.09 [-8.09, -8.09]8.09 [8.09, 8.09]0% [0%, 0%]0%0%-3.04—2026-08-30 → 2026-08-30
tmin00Zbilinear90d1 1 QC8.09 [8.09, 8.09]0.00-8.09 [-8.09, -8.09]8.09 [8.09, 8.09]0% [0%, 0%]0%0%-3.04—2026-08-30 → 2026-08-30
tmin00Zbilinear365d1 1 QC8.09 [8.09, 8.09]0.00-8.09 [-8.09, -8.09]8.09 [8.09, 8.09]0% [0%, 0%]0%0%-3.04—2026-08-30 → 2026-08-30
tmin00Zbilinearall1 1 QC8.09 [8.09, 8.09]0.00-8.09 [-8.09, -8.09]8.09 [8.09, 8.09]0% [0%, 0%]0%0%-3.04—2026-08-30 → 2026-08-30
tmin00Znearest30d1 1 QC8.14 [8.14, 8.14]0.00-8.14 [-8.14, -8.14]8.14 [8.14, 8.14]0% [0%, 0%]0%0%-3.07—2026-08-30 → 2026-08-30
tmin00Znearest90d1 1 QC8.14 [8.14, 8.14]0.00-8.14 [-8.14, -8.14]8.14 [8.14, 8.14]0% [0%, 0%]0%0%-3.07—2026-08-30 → 2026-08-30
tmin00Znearest365d1 1 QC8.14 [8.14, 8.14]0.00-8.14 [-8.14, -8.14]8.14 [8.14, 8.14]0% [0%, 0%]0%0%-3.07—2026-08-30 → 2026-08-30
tmin00Znearestall1 1 QC8.14 [8.14, 8.14]0.00-8.14 [-8.14, -8.14]8.14 [8.14, 8.14]0% [0%, 0%]0%0%-3.07—2026-08-30 → 2026-08-30
tmin12Zbilinear30d2 1 QC6.51 [4.69, 8.33]1.82-6.51 [-8.33, -4.69]6.76 [4.69, 8.33]0% [0%, 0%]0%0%-1.17-0.822026-08-29 → 2026-08-30
tmin12Zbilinear90d2 1 QC6.51 [4.69, 8.33]1.82-6.51 [-8.33, -4.69]6.76 [4.69, 8.33]0% [0%, 0%]0%0%-1.17-0.822026-08-29 → 2026-08-30
tmin12Zbilinear365d2 1 QC6.51 [4.69, 8.33]1.82-6.51 [-8.33, -4.69]6.76 [4.69, 8.33]0% [0%, 0%]0%0%-1.17-0.822026-08-29 → 2026-08-30
tmin12Zbilinearall2 1 QC6.51 [4.69, 8.33]1.82-6.51 [-8.33, -4.69]6.76 [4.69, 8.33]0% [0%, 0%]0%0%-1.17-0.822026-08-29 → 2026-08-30
tmin12Znearest30d2 1 QC6.53 [4.74, 8.31]1.78-6.53 [-8.31, -4.74]6.77 [4.74, 8.31]0% [0%, 0%]0%0%-1.18-0.782026-08-29 → 2026-08-30
tmin12Znearest90d2 1 QC6.53 [4.74, 8.31]1.78-6.53 [-8.31, -4.74]6.77 [4.74, 8.31]0% [0%, 0%]0%0%-1.18-0.782026-08-29 → 2026-08-30
tmin12Znearest365d2 1 QC6.53 [4.74, 8.31]1.78-6.53 [-8.31, -4.74]6.77 [4.74, 8.31]0% [0%, 0%]0%0%-1.18-0.782026-08-29 → 2026-08-30
tmin12Znearestall2 1 QC6.53 [4.74, 8.31]1.78-6.53 [-8.31, -4.74]6.77 [4.74, 8.31]0% [0%, 0%]0%0%-1.18-0.782026-08-29 → 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 GraphCast (GFS init) at KPHX, lead day 1, 00Z bilinear tmax+20+100-10-202026-08-30: -13.9 °F2026-08-30°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 (1 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-13.90

Error distribution

Distribution of the signed daily error in °F for GraphCast (GFS init) at KPHX, lead day 1-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 1 day-12 to -10 °F: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 0 days-6 to -4 °F: 0 days-4 to -2 °F: 0 days-2 to 0 °F: 0 days0 to 2 °F: 0 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| 13.9 · P90 |e| 13.9 °F-200+20 °Fn = 1 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
-14.00-12.001
-12.00-10.000
-10.00-8.000
-8.00-6.000
-6.00-4.000
-4.00-2.000
-2.00+0.000
+0.00+2.000
+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
2026-08113.90 -13.90

Availability

ModelScored period DaysCoverage
GraphCast (GFS init)2026-08-30 → 2026-08-30 1
GraphCast (GFS init)2026-08-30 → 2026-08-30 1
GraphCast (GFS init)2026-08-29 → 2026-08-30 2
GraphCast (GFS init)2026-08-29 → 2026-08-30 2

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means GraphCast (GFS init) has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 1 +5.05 [5.05, 5.05] yes
Aurora (GFS init) 1 -0.68 [-0.68, -0.68] yes
Aurora (IFS init) 1 +5.70 [5.70, 5.70] yes
FourCastNet v2 (GFS init) 1 +1.26 [1.26, 1.26] yes
FourCastNet v2 (IFS init) 1 +4.80 [4.80, 4.80] yes
NCEP GFS 1 +11.70 [11.70, 11.70] yes
GraphCast (IFS init) 1 +6.77 [6.77, 6.77] yes
ECMWF IFS HRES 1 +8.92 [8.92, 8.92] yes
Pangu-Weather (GFS init) 1 +6.48 [6.48, 6.48] yes
Pangu-Weather (IFS init) 1 +8.05 [8.05, 8.05] yes
Persistence (baseline) 1 +6.90 [6.90, 6.90] yes

Cite this page

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

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

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