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

All stations (mean of daily station errors) · GraphCast (IFS init) · lead day 8

ALL · graphcast_ifs · lead 8

Target day = initialization date + 8 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, 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, 3 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
tmax00Zbilinear30d22 2 QC6.41 [5.78, 7.02]1.25-5.66 [-6.25, -5.19]7.60 [6.88, 8.24]6% [4%, 8%]12%22%-0.49-0.012026-08-09 → 2026-08-30
tmax00Zbilinear90d22 2 QC6.41 [5.73, 7.07]1.25-5.66 [-6.36, -5.18]7.60 [6.83, 8.29]6% [4%, 8%]12%22%-0.49-0.012026-08-09 → 2026-08-30
tmax00Zbilinear365d28 3 QC6.14 [5.39, 6.81]1.32-5.32 [-6.02, -4.55]7.36 [6.56, 8.03]8% [5%, 12%]14%25%-0.10+0.142026-01-09 → 2026-08-30
tmax00Zbilinearall28 3 QC6.14 [5.36, 6.87]1.32-5.32 [-6.04, -4.47]7.36 [6.55, 8.08]8% [5%, 12%]14%25%-0.10+0.142026-01-09 → 2026-08-30
tmax00Znearest30d22 2 QC6.49 [5.79, 7.14]1.25-5.62 [-6.20, -5.15]7.75 [6.90, 8.46]6% [4%, 7%]13%23%-0.51-0.012026-08-09 → 2026-08-30
tmax00Znearest90d22 2 QC6.49 [5.69, 7.21]1.25-5.62 [-6.33, -5.14]7.75 [6.83, 8.53]6% [4%, 7%]13%23%-0.51-0.012026-08-09 → 2026-08-30
tmax00Znearest365d28 3 QC6.22 [5.44, 6.95]1.32-5.30 [-6.00, -4.56]7.49 [6.59, 8.26]7% [5%, 11%]15%25%-0.12+0.132026-01-09 → 2026-08-30
tmax00Znearestall28 3 QC6.22 [5.42, 6.97]1.32-5.30 [-6.00, -4.48]7.49 [6.58, 8.27]7% [5%, 11%]15%25%-0.12+0.132026-01-09 → 2026-08-30
tmax12Zbilinear30d22 2 QC6.43 [6.09, 6.76]0.98-5.99 [-6.30, -5.62]7.53 [7.18, 7.87]5% [3%, 7%]12%21%-0.50+0.202026-08-09 → 2026-08-30
tmax12Zbilinear90d22 2 QC6.43 [6.06, 6.78]0.98-5.99 [-6.32, -5.56]7.53 [7.11, 7.86]5% [2%, 7%]12%21%-0.50+0.202026-08-09 → 2026-08-30
tmax12Zbilinear365d27 3 QC6.26 [5.78, 6.65]1.22-5.61 [-6.18, -4.61]7.44 [7.03, 7.78]7% [3%, 12%]14%23%-0.16+0.232026-01-09 → 2026-08-30
tmax12Zbilinearall27 3 QC6.26 [5.73, 6.66]1.22-5.61 [-6.18, -4.49]7.44 [7.04, 7.78]7% [4%, 12%]14%23%-0.16+0.232026-01-09 → 2026-08-30
tmax12Znearest30d22 2 QC6.55 [6.13, 6.91]1.00-5.94 [-6.26, -5.55]7.69 [7.23, 8.06]6% [4%, 8%]13%20%-0.52+0.192026-08-09 → 2026-08-30
tmax12Znearest90d22 2 QC6.55 [6.05, 6.93]1.00-5.94 [-6.26, -5.45]7.69 [7.12, 8.09]6% [4%, 8%]13%20%-0.52+0.192026-08-09 → 2026-08-30
tmax12Znearest365d27 3 QC6.37 [5.82, 6.81]1.23-5.56 [-6.13, -4.55]7.57 [7.08, 7.97]7% [4%, 11%]14%23%-0.18+0.222026-01-09 → 2026-08-30
tmax12Znearestall27 3 QC6.37 [5.80, 6.80]1.23-5.56 [-6.13, -4.46]7.57 [7.07, 7.96]7% [5%, 11%]14%23%-0.18+0.222026-01-09 → 2026-08-30
tmin00Zbilinear30d22 2 QC3.18 [2.89, 3.45]1.01+0.29 [-0.29, 0.85]4.14 [3.79, 4.48]23% [20%, 26%]42%58%+0.16+0.142026-08-09 → 2026-08-30
tmin00Zbilinear90d22 2 QC3.18 [2.87, 3.46]1.01+0.29 [-0.37, 0.92]4.14 [3.76, 4.51]23% [20%, 26%]42%58%+0.16+0.142026-08-09 → 2026-08-30
tmin00Zbilinear365d28 2 QC3.54 [2.99, 4.30]1.20+0.50 [-0.15, 1.27]4.68 [3.91, 5.59]21% [15%, 25%]39%54%+0.33+0.182026-01-09 → 2026-08-30
tmin00Zbilinearall28 2 QC3.54 [2.99, 4.41]1.20+0.50 [-0.15, 1.17]4.68 [3.92, 5.73]21% [14%, 25%]39%54%+0.33+0.182026-01-09 → 2026-08-30
tmin00Znearest30d22 2 QC3.20 [2.90, 3.50]1.01+0.32 [-0.28, 0.88]4.20 [3.85, 4.55]19% [16%, 23%]42%59%+0.15+0.152026-08-09 → 2026-08-30
tmin00Znearest90d22 2 QC3.20 [2.88, 3.52]1.01+0.32 [-0.36, 0.94]4.20 [3.82, 4.59]19% [16%, 22%]42%59%+0.15+0.152026-08-09 → 2026-08-30
tmin00Znearest365d28 2 QC3.58 [3.00, 4.36]1.21+0.53 [-0.12, 1.28]4.82 [3.94, 5.87]19% [15%, 22%]39%55%+0.32+0.172026-01-09 → 2026-08-30
tmin00Znearestall28 2 QC3.58 [3.01, 4.48]1.21+0.53 [-0.13, 1.18]4.82 [3.98, 6.03]19% [16%, 22%]39%55%+0.32+0.172026-01-09 → 2026-08-30
tmin12Zbilinear30d22 2 QC2.94 [2.63, 3.21]0.97+0.27 [-0.35, 0.82]3.75 [3.44, 4.02]22% [18%, 25%]41%58%+0.22+0.182026-08-09 → 2026-08-30
tmin12Zbilinear90d22 2 QC2.94 [2.63, 3.22]0.97+0.27 [-0.49, 0.89]3.75 [3.43, 4.02]22% [18%, 25%]41%58%+0.22+0.182026-08-09 → 2026-08-30
tmin12Zbilinear365d27 2 QC3.33 [2.75, 4.25]1.20+0.65 [-0.14, 1.76]4.33 [3.58, 5.45]20% [13%, 24%]38%54%+0.35+0.192026-01-09 → 2026-08-30
tmin12Zbilinearall27 2 QC3.33 [2.74, 4.41]1.20+0.65 [-0.17, 1.72]4.33 [3.54, 5.63]20% [12%, 24%]38%54%+0.35+0.192026-01-09 → 2026-08-30
tmin12Znearest30d22 2 QC3.00 [2.68, 3.27]0.97+0.31 [-0.32, 0.85]3.82 [3.48, 4.11]20% [16%, 23%]41%61%+0.21+0.182026-08-09 → 2026-08-30
tmin12Znearest90d22 2 QC3.00 [2.68, 3.27]0.97+0.31 [-0.47, 0.93]3.82 [3.47, 4.12]20% [15%, 23%]41%61%+0.21+0.182026-08-09 → 2026-08-30
tmin12Znearest365d27 2 QC3.41 [2.81, 4.38]1.20+0.69 [-0.10, 1.79]4.51 [3.63, 5.81]18% [12%, 22%]39%57%+0.33+0.192026-01-09 → 2026-08-30
tmin12Znearestall27 2 QC3.41 [2.79, 4.55]1.20+0.69 [-0.12, 1.73]4.51 [3.61, 5.99]18% [11%, 22%]39%57%+0.33+0.192026-01-09 → 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 ALL, lead day 8, 00Z bilinear tmax+10+50-5-102026-08-09: -6.34 °F2026-08-10: -5.57 °F2026-08-11: -3.99 °F2026-08-12: -7.84 °F2026-08-13: -4.25 °F2026-08-14: -4.92 °F2026-08-15: -5.1 °F2026-08-16: -4.65 °F2026-08-17: -5.47 °F2026-08-18: -6.34 °F2026-08-19: -7.2 °F2026-08-20: -3.74 °F2026-08-21: -4.11 °F2026-08-22: -3.29 °F2026-08-23: -4.97 °F2026-08-24: -8.77 °F2026-08-25: -7.73 °F2026-08-26: -6.04 °F2026-08-27: -4.95 °F2026-08-28: -8.61 °F2026-08-29: -5.78 °F2026-08-30: -4.81 °F2026-08-092026-08-30°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 (22 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.81
2026-08-29-5.78
2026-08-28-8.61
2026-08-27-4.95
2026-08-26-6.04
2026-08-25-7.73
2026-08-24-8.77
2026-08-23-4.97
2026-08-22-3.29
2026-08-21-4.11
2026-08-20-3.74
2026-08-19-7.20
2026-08-18-6.34
2026-08-17-5.47
2026-08-16-4.65
2026-08-15-5.10
2026-08-14-4.92
2026-08-13-4.25
2026-08-12-7.84
2026-08-11-3.99
2026-08-10-5.57
2026-08-09-6.34

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at ALL, lead day 8-10 to -9 °F: 0 days-9 to -8 °F: 2 days-8 to -7 °F: 3 days-7 to -6 °F: 4 days-6 to -5 °F: 5 days-5 to -4 °F: 8 days-4 to -3 °F: 4 days-3 to -2 °F: 2 days-2 to -1 °F: 0 days-1 to 0 °F: 0 days0 to 1 °F: 0 days1 to 2 °F: 0 days2 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| 5.03 · P90 |e| 7.76 °F-100+10 °Fn = 28 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
-9.00-8.002
-8.00-7.003
-7.00-6.004
-6.00-5.005
-5.00-4.008
-4.00-3.004
-3.00-2.002
-2.00-1.000
-1.00+0.000
+0.00+1.000
+1.00+2.000
+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
2026-08225.66 -5.66
2026-0164.10 -4.10

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 28
GraphCast (IFS init)2026-01-09 → 2026-08-30 27
GraphCast (IFS init)2026-01-09 → 2026-08-30 27

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 22 +1.62 [0.89, 2.26] yes
NCEP GFS 22 +2.07 [1.60, 2.70] yes
ECMWF IFS HRES 17 +2.31 [1.40, 3.05] yes
Persistence (baseline) 22 +2.11 [1.30, 2.87] yes

Cite this page

ShortCastCheck, ALL graphcast_ifs lead 8, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/ALL/model/graphcast_ifs/lead/8/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: ALL (All stations (mean of daily station errors)), model graphcast_ifs, lead day 8. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/ALL/model/graphcast_ifs/lead/8/

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