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

San Francisco Intl · GraphCast (IFS init) · lead day 2

KSFO · graphcast_ifs · lead 2

Target day = initialization date + 2 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, 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
tmax00Zbilinear30d26 1 QC5.16 [4.09, 6.40]2.78-5.07 [-6.36, -4.01]6.03 [4.79, 7.14]12% [4%, 19%]23%27%-0.37+0.262026-08-03 → 2026-08-30
tmax00Zbilinear90d26 1 QC5.16 [3.99, 6.48]2.78-5.07 [-6.45, -3.92]6.03 [4.71, 7.18]12% [0%, 19%]23%27%-0.37+0.262026-08-03 → 2026-08-30
tmax00Zbilinear365d32 1 QC4.83 [3.76, 6.17]2.57-4.75 [-6.08, -3.73]5.65 [4.27, 6.90]9% [0%, 17%]22%25%-0.32+0.302026-01-03 → 2026-08-30
tmax00Zbilinearall32 1 QC4.83 [3.81, 6.15]2.57-4.75 [-6.14, -3.78]5.65 [4.39, 6.85]9% [0%, 17%]22%25%-0.32+0.302026-01-03 → 2026-08-30
tmax00Znearest30d26 1 QC3.44 [2.47, 4.66]3.08+2.15 [0.41, 3.97]4.54 [3.20, 5.86]23% [8%, 41%]42%58%+0.09+0.182026-08-03 → 2026-08-30
tmax00Znearest90d26 1 QC3.44 [2.34, 4.69]3.08+2.15 [0.22, 4.13]4.54 [3.12, 5.91]23% [0%, 44%]42%58%+0.09+0.182026-08-03 → 2026-08-30
tmax00Znearest365d32 1 QC3.45 [2.53, 4.54]3.37+1.09 [-1.43, 3.32]4.42 [3.30, 5.63]22% [7%, 39%]38%50%+0.06+0.082026-01-03 → 2026-08-30
tmax00Znearestall32 1 QC3.45 [2.58, 4.55]3.37+1.09 [-1.27, 3.34]4.42 [3.31, 5.70]22% [7%, 39%]38%50%+0.06+0.082026-01-03 → 2026-08-30
tmax12Zbilinear30d26 1 QC5.02 [3.88, 6.31]2.78-4.92 [-6.26, -3.78]5.89 [4.58, 7.12]12% [0%, 23%]23%31%-0.33+0.262026-08-03 → 2026-08-30
tmax12Zbilinear90d26 1 QC5.02 [3.78, 6.41]2.78-4.92 [-6.36, -3.69]5.89 [4.51, 7.13]12% [0%, 23%]23%31%-0.33+0.262026-08-03 → 2026-08-30
tmax12Zbilinear365d31 1 QC4.74 [3.61, 6.16]2.62-4.65 [-6.13, -3.56]5.58 [4.17, 6.94]10% [0%, 20%]23%32%-0.28+0.302026-01-03 → 2026-08-30
tmax12Zbilinearall31 1 QC4.74 [3.66, 6.12]2.62-4.65 [-6.07, -3.62]5.58 [4.26, 6.87]10% [0%, 20%]23%32%-0.28+0.302026-01-03 → 2026-08-30
tmax12Znearest30d26 1 QC3.69 [2.65, 4.86]3.00+2.39 [0.56, 4.06]4.65 [3.28, 5.95]19% [7%, 35%]27%58%+0.02+0.212026-08-03 → 2026-08-30
tmax12Znearest90d26 1 QC3.69 [2.54, 4.93]3.00+2.39 [0.41, 4.15]4.65 [3.17, 5.99]19% [6%, 34%]27%58%+0.02+0.212026-08-03 → 2026-08-30
tmax12Znearest365d31 1 QC3.62 [2.66, 4.74]3.39+1.47 [-1.01, 3.55]4.51 [3.28, 5.75]19% [7%, 34%]26%55%+0.02+0.092026-01-03 → 2026-08-30
tmax12Znearestall31 1 QC3.62 [2.66, 4.75]3.39+1.47 [-0.96, 3.58]4.51 [3.25, 5.79]19% [7%, 33%]26%55%+0.02+0.092026-01-03 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.00 [0.81, 1.25]0.95-0.17 [-0.76, 0.55]1.26 [0.98, 1.61]54% [43%, 63%]85%100%+0.04+0.092026-08-03 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.00 [0.78, 1.27]0.95-0.17 [-0.89, 0.68]1.26 [0.91, 1.62]54% [42%, 67%]85%100%+0.04+0.092026-08-03 → 2026-08-30
tmin00Zbilinear365d32 1 QC0.93 [0.70, 1.18]0.92-0.03 [-0.63, 0.69]1.18 [0.82, 1.53]59% [47%, 75%]88%100%+0.34+0.352026-01-03 → 2026-08-30
tmin00Zbilinearall32 1 QC0.93 [0.71, 1.19]0.92-0.03 [-0.63, 0.64]1.18 [0.84, 1.54]59% [46%, 74%]88%100%+0.34+0.352026-01-03 → 2026-08-30
tmin00Znearest30d26 1 QC1.02 [0.82, 1.37]0.91-0.39 [-0.76, 0.07]1.27 [0.98, 1.66]54% [35%, 67%]88%96%+0.02+0.132026-08-03 → 2026-08-30
tmin00Znearest90d26 1 QC1.02 [0.81, 1.48]0.91-0.39 [-0.83, 0.05]1.27 [0.98, 1.74]54% [33%, 68%]88%96%+0.02+0.132026-08-03 → 2026-08-30
tmin00Znearest365d32 1 QC1.08 [0.83, 1.46]0.93-0.56 [-1.05, -0.12]1.33 [1.02, 1.71]50% [29%, 67%]84%97%+0.23+0.352026-01-03 → 2026-08-30
tmin00Znearestall32 1 QC1.08 [0.84, 1.46]0.93-0.56 [-1.12, -0.08]1.33 [1.03, 1.69]50% [30%, 64%]84%97%+0.23+0.352026-01-03 → 2026-08-30
tmin12Zbilinear30d26 1 QC1.01 [0.79, 1.31]0.95-0.27 [-0.78, 0.35]1.24 [0.99, 1.58]54% [36%, 68%]85%100%+0.03+0.092026-08-03 → 2026-08-30
tmin12Zbilinear90d26 1 QC1.01 [0.75, 1.34]0.95-0.27 [-0.86, 0.43]1.24 [0.95, 1.60]54% [35%, 70%]85%100%+0.03+0.092026-08-03 → 2026-08-30
tmin12Zbilinear365d31 1 QC0.97 [0.73, 1.25]0.95-0.13 [-0.66, 0.58]1.19 [0.90, 1.50]55% [40%, 71%]87%100%+0.25+0.272026-01-03 → 2026-08-30
tmin12Zbilinearall31 1 QC0.97 [0.75, 1.25]0.95-0.13 [-0.70, 0.48]1.19 [0.91, 1.50]55% [37%, 70%]87%100%+0.25+0.272026-01-03 → 2026-08-30
tmin12Znearest30d26 1 QC1.04 [0.79, 1.38]0.90-0.60 [-0.95, -0.24]1.34 [1.02, 1.68]62% [40%, 77%]81%100%-0.00+0.142026-08-03 → 2026-08-30
tmin12Znearest90d26 1 QC1.04 [0.78, 1.52]0.90-0.60 [-1.00, -0.22]1.34 [0.99, 1.82]62% [33%, 77%]81%100%-0.00+0.142026-08-03 → 2026-08-30
tmin12Znearest365d31 1 QC1.04 [0.80, 1.44]0.86-0.68 [-1.02, -0.35]1.32 [1.00, 1.70]58% [33%, 75%]84%100%+0.19+0.342026-01-03 → 2026-08-30
tmin12Znearestall31 1 QC1.04 [0.81, 1.42]0.86-0.68 [-1.04, -0.33]1.32 [1.03, 1.69]58% [35%, 74%]84%100%+0.19+0.342026-01-03 → 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 KSFO, lead day 2, 00Z bilinear tmax+20+100-10-202026-08-03: -6.79 °F2026-08-04: -5.66 °F2026-08-05: -6.09 °F2026-08-06: -6.25 °F2026-08-07: -0.58 °F2026-08-08: +1.21 °F2026-08-09: -1.03 °F2026-08-10: -7.65 °F2026-08-11: -9.56 °F2026-08-12: -10.15 °F2026-08-13: -10.54 °F2026-08-14: -7.39 °F2026-08-15: -4.82 °F2026-08-16: -3.43 °F2026-08-17: -6.22 °F2026-08-18: -1.98 °F2026-08-19: -0.18 °F2026-08-20: -4.35 °F2026-08-21: -3.03 °F2026-08-22: -3.47 °F2026-08-23: -9.68 °F2026-08-24: -7.31 °F2026-08-25: -0.41 °F2026-08-26: -7.82 °F2026-08-27: -2.54 °F2026-08-30: -6 °F2026-08-032026-08-30°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 (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.00
2026-08-29—
2026-08-28—
2026-08-27-2.54
2026-08-26-7.82
2026-08-25-0.41
2026-08-24-7.31
2026-08-23-9.68
2026-08-22-3.47
2026-08-21-3.03
2026-08-20-4.35
2026-08-19-0.18
2026-08-18-1.98
2026-08-17-6.22
2026-08-16-3.43
2026-08-15-4.82
2026-08-14-7.39
2026-08-13-10.54
2026-08-12-10.15
2026-08-11-9.56
2026-08-10-7.65
2026-08-09-1.03
2026-08-08+1.21
2026-08-07-0.58
2026-08-06-6.25
2026-08-05-6.09
2026-08-04-5.66
2026-08-03-6.79

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSFO, lead day 2-20 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: 2 days-10 to -8 °F: 2 days-8 to -6 °F: 9 days-6 to -4 °F: 4 days-4 to -2 °F: 8 days-2 to 0 °F: 6 days0 to 2 °F: 1 day2 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| 4.59 · P90 |e| 9.38 °F-200+20 °Fn = 32 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
-12.00-10.002
-10.00-8.002
-8.00-6.009
-6.00-4.004
-4.00-2.008
-2.00+0.006
+0.00+2.001
+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
2026-08265.16 -5.07
2026-0163.39 -3.39

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 32
GraphCast (IFS init)2026-01-03 → 2026-08-30 31
GraphCast (IFS init)2026-01-03 → 2026-08-30 31

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 26 +0.52 [0.19, 0.78] yes
Aurora (IFS init) 1 -2.33 [-2.33, -2.33] yes
FourCastNet v2 (IFS init) 1 +4.39 [4.39, 4.39] yes
NCEP GFS 26 +0.54 [-0.03, 0.98] no
ECMWF IFS HRES 21 -1.11 [-2.35, -0.12] yes
Pangu-Weather (IFS init) 1 -0.38 [-0.38, -0.38] yes
Persistence (baseline) 26 +1.39 [-0.32, 2.88] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSFO (San Francisco Intl), model graphcast_ifs, lead day 2. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KSFO/model/graphcast_ifs/lead/2/

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