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 (IFS init) · lead day 1

KPHX · graphcast_ifs · 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 2026-01-01 — 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 QC3.32 [2.47, 4.31]1.94-3.13 [-4.22, -2.19]3.99 [2.92, 5.07]7% [0%, 16%]30%59%-0.03+0.402026-08-02 → 2026-08-30
tmax00Zbilinear90d27 1 QC3.32 [2.24, 4.74]1.94-3.13 [-4.69, -1.97]3.99 [2.58, 5.56]7% [0%, 17%]30%59%-0.03+0.402026-08-02 → 2026-08-30
tmax00Zbilinear365d33 1 QC3.71 [2.68, 5.24]2.00-3.55 [-5.23, -2.39]4.34 [3.15, 5.81]6% [0%, 14%]24%48%-0.06+0.432026-01-02 → 2026-08-30
tmax00Zbilinearall33 1 QC3.71 [2.65, 5.09]2.00-3.55 [-5.06, -2.40]4.34 [3.12, 5.67]6% [0%, 15%]24%48%-0.06+0.432026-01-02 → 2026-08-30
tmax00Znearest30d27 1 QC3.21 [2.37, 4.19]1.94-3.01 [-4.10, -2.07]3.90 [2.80, 4.97]19% [7%, 29%]33%59%+0.00+0.402026-08-02 → 2026-08-30
tmax00Znearest90d27 1 QC3.21 [2.13, 4.57]1.94-3.01 [-4.54, -1.86]3.90 [2.47, 5.43]19% [5%, 30%]33%59%+0.00+0.402026-08-02 → 2026-08-30
tmax00Znearest365d33 1 QC3.62 [2.57, 5.17]2.05-3.46 [-5.17, -2.28]4.28 [3.04, 5.76]15% [0%, 26%]27%48%-0.04+0.412026-01-02 → 2026-08-30
tmax00Znearestall33 1 QC3.62 [2.53, 4.99]2.05-3.46 [-4.99, -2.26]4.28 [3.00, 5.60]15% [0%, 26%]27%48%-0.04+0.412026-01-02 → 2026-08-30
tmax12Zbilinear30d27 1 QC3.66 [2.70, 4.66]1.83-3.56 [-4.61, -2.58]4.23 [3.22, 5.09]11% [0%, 25%]22%44%-0.14+0.432026-08-02 → 2026-08-30
tmax12Zbilinear90d27 1 QC3.66 [2.46, 4.89]1.83-3.56 [-4.87, -2.33]4.23 [2.86, 5.37]11% [0%, 26%]22%44%-0.14+0.432026-08-02 → 2026-08-30
tmax12Zbilinear365d32 1 QC4.08 [2.93, 5.66]1.98-3.99 [-5.65, -2.78]4.65 [3.47, 6.00]9% [0%, 22%]19%38%-0.24+0.402026-01-02 → 2026-08-30
tmax12Zbilinearall32 1 QC4.08 [2.82, 5.42]1.98-3.99 [-5.41, -2.70]4.65 [3.42, 5.83]9% [0%, 24%]19%38%-0.24+0.402026-01-02 → 2026-08-30
tmax12Znearest30d27 1 QC3.51 [2.58, 4.48]1.81-3.40 [-4.46, -2.46]4.07 [3.10, 4.92]11% [0%, 25%]22%48%-0.09+0.442026-08-02 → 2026-08-30
tmax12Znearest90d27 1 QC3.51 [2.34, 4.71]1.81-3.40 [-4.69, -2.22]4.07 [2.76, 5.19]11% [0%, 26%]22%48%-0.09+0.442026-08-02 → 2026-08-30
tmax12Znearest365d32 1 QC3.96 [2.82, 5.53]1.99-3.86 [-5.49, -2.68]4.54 [3.35, 5.92]9% [0%, 22%]19%41%-0.21+0.392026-01-02 → 2026-08-30
tmax12Znearestall32 1 QC3.96 [2.68, 5.33]1.99-3.86 [-5.29, -2.56]4.54 [3.29, 5.72]9% [0%, 24%]19%41%-0.21+0.392026-01-02 → 2026-08-30
tmin00Zbilinear30d27 1 QC2.83 [1.66, 4.25]2.82-0.08 [-1.30, 1.35]3.86 [2.15, 5.42]26% [11%, 40%]44%56%+0.14+0.142026-08-02 → 2026-08-30
tmin00Zbilinear90d27 1 QC2.83 [1.45, 4.21]2.82-0.08 [-1.35, 1.34]3.86 [1.83, 5.48]26% [12%, 42%]44%56%+0.14+0.142026-08-02 → 2026-08-30
tmin00Zbilinear365d33 1 QC2.64 [1.54, 3.89]2.58-0.35 [-1.48, 0.99]3.60 [1.83, 5.12]27% [14%, 40%]45%61%+0.17+0.192026-01-02 → 2026-08-30
tmin00Zbilinearall33 1 QC2.64 [1.54, 3.88]2.58-0.35 [-1.59, 0.97]3.60 [1.87, 5.07]27% [14%, 41%]45%61%+0.17+0.192026-01-02 → 2026-08-30
tmin00Znearest30d27 1 QC2.91 [1.69, 4.36]2.90-0.10 [-1.35, 1.32]3.92 [2.20, 5.49]19% [4%, 35%]44%56%+0.12+0.122026-08-02 → 2026-08-30
tmin00Znearest90d27 1 QC2.91 [1.54, 4.31]2.90-0.10 [-1.34, 1.34]3.92 [1.91, 5.54]19% [5%, 39%]44%56%+0.12+0.122026-08-02 → 2026-08-30
tmin00Znearest365d33 1 QC2.70 [1.59, 3.99]2.65-0.37 [-1.53, 0.96]3.65 [1.87, 5.18]21% [7%, 37%]48%61%+0.15+0.162026-01-02 → 2026-08-30
tmin00Znearestall33 1 QC2.70 [1.56, 3.94]2.65-0.37 [-1.64, 1.00]3.65 [1.89, 5.11]21% [8%, 38%]48%61%+0.15+0.162026-01-02 → 2026-08-30
tmin12Zbilinear30d27 1 QC3.17 [1.96, 4.70]3.00-0.92 [-1.91, 0.27]4.05 [2.47, 5.51]22% [7%, 39%]41%56%+0.04+0.092026-08-02 → 2026-08-30
tmin12Zbilinear90d27 1 QC3.17 [1.86, 4.81]3.00-0.92 [-1.98, 0.21]4.05 [2.36, 5.59]22% [5%, 44%]41%56%+0.04+0.092026-08-02 → 2026-08-30
tmin12Zbilinear365d32 1 QC2.89 [1.72, 4.38]2.66-0.98 [-1.89, 0.07]3.77 [2.09, 5.23]25% [8%, 43%]47%62%+0.07+0.142026-01-02 → 2026-08-30
tmin12Zbilinearall32 1 QC2.89 [1.62, 4.32]2.66-0.98 [-2.09, 0.05]3.77 [2.05, 5.22]25% [7%, 44%]47%62%+0.07+0.142026-01-02 → 2026-08-30
tmin12Znearest30d27 1 QC3.18 [1.94, 4.75]3.05-0.84 [-1.85, 0.34]4.07 [2.45, 5.57]22% [7%, 39%]41%56%+0.04+0.072026-08-02 → 2026-08-30
tmin12Znearest90d27 1 QC3.18 [1.80, 4.86]3.05-0.84 [-1.89, 0.29]4.07 [2.33, 5.66]22% [5%, 44%]41%56%+0.04+0.072026-08-02 → 2026-08-30
tmin12Znearest365d32 1 QC2.89 [1.69, 4.42]2.70-0.92 [-1.84, 0.13]3.79 [2.09, 5.27]22% [6%, 39%]47%62%+0.07+0.132026-01-02 → 2026-08-30
tmin12Znearestall32 1 QC2.89 [1.57, 4.35]2.70-0.92 [-2.05, 0.13]3.79 [1.98, 5.28]22% [6%, 40%]47%62%+0.07+0.132026-01-02 → 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 GraphCast (IFS init) at KPHX, lead day 1, 00Z bilinear tmax+10+50-5-102026-08-02: -1.8 °F2026-08-03: -4.35 °F2026-08-04: +0.97 °F2026-08-05: -1.02 °F2026-08-06: -2.46 °F2026-08-07: -2.07 °F2026-08-08: -2.24 °F2026-08-09: -2.07 °F2026-08-10: -1.17 °F2026-08-11: -1.04 °F2026-08-12: -7.65 °F2026-08-13: -4.31 °F2026-08-14: -5.68 °F2026-08-15: -4.93 °F2026-08-16: -2.9 °F2026-08-17: -2.72 °F2026-08-18: -4.23 °F2026-08-19: -2.42 °F2026-08-20: +1.62 °F2026-08-21: -1.2 °F2026-08-22: -4.01 °F2026-08-23: -5.37 °F2026-08-24: -0.99 °F2026-08-25: -3.28 °F2026-08-26: -2.46 °F2026-08-29: -9.63 °F2026-08-30: -7.13 °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
2026-08-30-7.13
2026-08-29-9.63
2026-08-28—
2026-08-27—
2026-08-26-2.46
2026-08-25-3.28
2026-08-24-0.99
2026-08-23-5.37
2026-08-22-4.01
2026-08-21-1.20
2026-08-20+1.62
2026-08-19-2.42
2026-08-18-4.23
2026-08-17-2.72
2026-08-16-2.90
2026-08-15-4.93
2026-08-14-5.68
2026-08-13-4.31
2026-08-12-7.65
2026-08-11-1.04
2026-08-10-1.17
2026-08-09-2.07
2026-08-08-2.24
2026-08-07-2.07
2026-08-06-2.46
2026-08-05-1.02
2026-08-04+0.97
2026-08-03-4.35
2026-08-02-1.80

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KPHX, lead day 1-10 to -9 °F: 1 day-9 to -8 °F: 1 day-8 to -7 °F: 2 days-7 to -6 °F: 0 days-6 to -5 °F: 4 days-5 to -4 °F: 7 days-4 to -3 °F: 2 days-3 to -2 °F: 8 days-2 to -1 °F: 5 days-1 to 0 °F: 1 day0 to 1 °F: 1 day1 to 2 °F: 1 day2 to 3 °F: 0 days3 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| 3.28 · P90 |e| 6.84 °F-100+10 °Fn = 33 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
-10.00-9.001
-9.00-8.001
-8.00-7.002
-7.00-6.000
-6.00-5.004
-5.00-4.007
-4.00-3.002
-3.00-2.008
-2.00-1.005
-1.00+0.001
+0.00+1.001
+1.00+2.001
+2.00+3.000
+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
2026-08273.32 -3.13
2026-0165.43 -5.43

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 33
GraphCast (IFS init)2026-01-02 → 2026-08-30 32
GraphCast (IFS init)2026-01-02 → 2026-08-30 32

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 27 +0.09 [-0.56, 0.87] no
Aurora (GFS init) 1 -7.45 [-7.45, -7.45] yes
Aurora (IFS init) 2 +0.02 [-1.07, 1.12] no
FourCastNet v2 (GFS init) 1 -5.51 [-5.51, -5.51] yes
FourCastNet v2 (IFS init) 2 -1.95 [-1.96, -1.94] yes
NCEP GFS 27 +0.41 [-0.54, 1.34] no
GraphCast (GFS init) 1 -6.77 [-6.77, -6.77] yes
ECMWF IFS HRES 20 +1.28 [0.68, 2.02] yes
Pangu-Weather (GFS init) 1 -0.29 [-0.29, -0.29] yes
Pangu-Weather (IFS init) 2 +0.93 [0.59, 1.28] yes
Persistence (baseline) 27 +0.10 [-1.11, 1.51] no

Cite this page

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

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