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

San Francisco Intl · GraphCast (IFS init) · lead day 1

KSFO · 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 QC5.07 [3.92, 6.24]2.65-4.91 [-6.17, -3.75]5.85 [4.58, 6.97]7% [0%, 15%]26%33%-0.78+0.092026-08-02 → 2026-08-30
tmax00Zbilinear90d27 1 QC5.07 [3.85, 6.42]2.65-4.91 [-6.34, -3.69]5.85 [4.49, 7.04]7% [0%, 17%]26%33%-0.78+0.092026-08-02 → 2026-08-30
tmax00Zbilinear365d33 1 QC4.75 [3.64, 6.01]2.49-4.62 [-5.89, -3.51]5.51 [4.14, 6.76]6% [0%, 13%]24%36%-0.72+0.112026-01-02 → 2026-08-30
tmax00Zbilinearall33 1 QC4.75 [3.71, 6.05]2.49-4.62 [-5.99, -3.61]5.51 [4.24, 6.71]6% [0%, 14%]24%36%-0.72+0.112026-01-02 → 2026-08-30
tmax00Znearest30d27 1 QC3.63 [2.59, 4.94]2.92+2.38 [0.62, 4.04]4.58 [3.14, 6.03]11% [0%, 24%]33%56%-0.27-0.002026-08-02 → 2026-08-30
tmax00Znearest90d27 1 QC3.63 [2.45, 4.96]2.92+2.38 [0.53, 4.06]4.58 [3.01, 6.03]11% [0%, 25%]33%56%-0.27-0.002026-08-02 → 2026-08-30
tmax00Znearest365d33 1 QC3.55 [2.62, 4.69]3.34+1.36 [-1.14, 3.45]4.43 [3.18, 5.74]12% [0%, 24%]33%55%-0.29-0.202026-01-02 → 2026-08-30
tmax00Znearestall33 1 QC3.55 [2.64, 4.75]3.34+1.36 [-0.95, 3.52]4.43 [3.19, 5.80]12% [0%, 25%]33%55%-0.29-0.202026-01-02 → 2026-08-30
tmax12Zbilinear30d27 1 QC5.04 [3.85, 6.28]2.56-5.00 [-6.26, -3.81]5.89 [4.59, 7.05]15% [4%, 25%]26%30%-0.77+0.122026-08-02 → 2026-08-30
tmax12Zbilinear90d27 1 QC5.04 [3.77, 6.42]2.56-5.00 [-6.41, -3.75]5.89 [4.47, 7.10]15% [4%, 25%]26%30%-0.77+0.122026-08-02 → 2026-08-30
tmax12Zbilinear365d32 1 QC4.77 [3.60, 6.05]2.48-4.74 [-6.01, -3.57]5.59 [4.18, 6.87]12% [0%, 22%]25%34%-0.69+0.132026-01-02 → 2026-08-30
tmax12Zbilinearall32 1 QC4.77 [3.66, 6.15]2.48-4.74 [-6.13, -3.64]5.59 [4.27, 6.83]12% [0%, 23%]25%34%-0.69+0.132026-01-02 → 2026-08-30
tmax12Znearest30d27 1 QC3.41 [2.48, 4.53]2.86+2.17 [0.55, 3.65]4.35 [3.06, 5.53]15% [0%, 27%]44%52%-0.19+0.022026-08-02 → 2026-08-30
tmax12Znearest90d27 1 QC3.41 [2.33, 4.53]2.86+2.17 [0.30, 3.72]4.35 [2.95, 5.56]15% [0%, 29%]44%52%-0.19+0.022026-08-02 → 2026-08-30
tmax12Znearest365d32 1 QC3.38 [2.49, 4.42]3.12+1.32 [-1.21, 3.21]4.27 [3.09, 5.38]16% [3%, 28%]41%50%-0.20-0.102026-01-02 → 2026-08-30
tmax12Znearestall32 1 QC3.38 [2.46, 4.39]3.12+1.32 [-0.86, 3.21]4.27 [3.12, 5.41]16% [0%, 29%]41%50%-0.20-0.102026-01-02 → 2026-08-30
tmin00Zbilinear30d27 1 QC0.83 [0.63, 1.16]0.84+0.12 [-0.28, 0.62]1.11 [0.75, 1.61]67% [52%, 81%]96%96%+0.07+0.082026-08-02 → 2026-08-30
tmin00Zbilinear90d27 1 QC0.83 [0.62, 1.19]0.84+0.12 [-0.36, 0.69]1.11 [0.74, 1.64]67% [50%, 82%]96%96%+0.07+0.082026-08-02 → 2026-08-30
tmin00Zbilinear365d33 1 QC0.78 [0.59, 1.06]0.76+0.20 [-0.20, 0.76]1.04 [0.72, 1.50]70% [55%, 83%]97%97%+0.28+0.322026-01-02 → 2026-08-30
tmin00Zbilinearall33 1 QC0.78 [0.60, 1.08]0.76+0.20 [-0.26, 0.70]1.04 [0.71, 1.52]70% [55%, 83%]97%97%+0.28+0.322026-01-02 → 2026-08-30
tmin00Znearest30d27 1 QC0.83 [0.61, 1.13]0.80-0.29 [-0.59, -0.01]1.09 [0.77, 1.44]74% [55%, 87%]89%100%+0.07+0.122026-08-02 → 2026-08-30
tmin00Znearest90d27 1 QC0.83 [0.59, 1.23]0.80-0.29 [-0.65, -0.01]1.09 [0.71, 1.52]74% [50%, 86%]89%100%+0.07+0.122026-08-02 → 2026-08-30
tmin00Znearest365d33 1 QC0.83 [0.64, 1.13]0.75-0.39 [-0.74, -0.11]1.07 [0.78, 1.42]73% [53%, 85%]91%100%+0.24+0.332026-01-02 → 2026-08-30
tmin00Znearestall33 1 QC0.83 [0.63, 1.13]0.75-0.39 [-0.77, -0.10]1.07 [0.77, 1.41]73% [55%, 85%]91%100%+0.24+0.332026-01-02 → 2026-08-30
tmin12Zbilinear30d27 1 QC0.80 [0.63, 1.11]0.76-0.17 [-0.50, 0.26]1.04 [0.74, 1.47]63% [48%, 75%]96%96%+0.09+0.172026-08-02 → 2026-08-30
tmin12Zbilinear90d27 1 QC0.80 [0.62, 1.13]0.76-0.17 [-0.57, 0.31]1.04 [0.74, 1.49]63% [46%, 76%]96%96%+0.09+0.172026-08-02 → 2026-08-30
tmin12Zbilinear365d32 1 QC0.76 [0.59, 1.04]0.75-0.06 [-0.47, 0.47]1.00 [0.73, 1.40]62% [50%, 75%]97%97%+0.28+0.302026-01-02 → 2026-08-30
tmin12Zbilinearall32 1 QC0.76 [0.59, 1.03]0.75-0.06 [-0.47, 0.40]1.00 [0.73, 1.39]62% [47%, 73%]97%97%+0.28+0.302026-01-02 → 2026-08-30
tmin12Znearest30d27 1 QC0.93 [0.69, 1.25]0.76-0.64 [-0.92, -0.39]1.21 [0.85, 1.57]63% [46%, 77%]85%100%-0.04+0.172026-08-02 → 2026-08-30
tmin12Znearest90d27 1 QC0.93 [0.69, 1.36]0.76-0.64 [-1.00, -0.39]1.21 [0.85, 1.68]63% [44%, 78%]85%100%-0.04+0.172026-08-02 → 2026-08-30
tmin12Znearest365d32 1 QC0.93 [0.70, 1.28]0.76-0.69 [-0.98, -0.45]1.21 [0.89, 1.59]62% [45%, 76%]88%100%+0.13+0.302026-01-02 → 2026-08-30
tmin12Znearestall32 1 QC0.93 [0.70, 1.26]0.76-0.69 [-0.99, -0.46]1.21 [0.90, 1.57]62% [46%, 76%]88%100%+0.13+0.302026-01-02 → 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 KSFO, lead day 1, 00Z bilinear tmax+20+100-10-202026-08-02: -9.02 °F2026-08-03: -6.9 °F2026-08-04: -5.89 °F2026-08-05: -5.28 °F2026-08-06: -5.61 °F2026-08-07: +0.62 °F2026-08-08: +1.51 °F2026-08-09: -1.53 °F2026-08-10: -6.34 °F2026-08-11: -10.45 °F2026-08-12: -10.41 °F2026-08-13: -9.67 °F2026-08-14: -6.59 °F2026-08-15: -3.8 °F2026-08-16: -2.54 °F2026-08-17: -5.78 °F2026-08-18: -1.63 °F2026-08-19: -1.23 °F2026-08-20: -4.09 °F2026-08-21: -2.86 °F2026-08-22: -1.9 °F2026-08-23: -8.48 °F2026-08-24: -7.04 °F2026-08-25: -0.98 °F2026-08-26: -5.8 °F2026-08-29: -6.11 °F2026-08-30: -4.74 °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
2026-08-30-4.74
2026-08-29-6.11
2026-08-28—
2026-08-27—
2026-08-26-5.80
2026-08-25-0.98
2026-08-24-7.04
2026-08-23-8.48
2026-08-22-1.90
2026-08-21-2.86
2026-08-20-4.09
2026-08-19-1.23
2026-08-18-1.63
2026-08-17-5.78
2026-08-16-2.54
2026-08-15-3.80
2026-08-14-6.59
2026-08-13-9.67
2026-08-12-10.41
2026-08-11-10.45
2026-08-10-6.34
2026-08-09-1.53
2026-08-08+1.51
2026-08-07+0.62
2026-08-06-5.61
2026-08-05-5.28
2026-08-04-5.89
2026-08-03-6.90
2026-08-02-9.02

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KSFO, 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: 0 days-12 to -10 °F: 2 days-10 to -8 °F: 3 days-8 to -6 °F: 5 days-6 to -4 °F: 10 days-4 to -2 °F: 5 days-2 to 0 °F: 6 days0 to 2 °F: 2 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| 4.74 · P90 |e| 8.91 °F-200+20 °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
-20.00-18.000
-18.00-16.000
-16.00-14.000
-14.00-12.000
-12.00-10.002
-10.00-8.003
-8.00-6.005
-6.00-4.0010
-4.00-2.005
-2.00+0.006
+0.00+2.002
+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
2026-08275.07 -4.91
2026-0163.32 -3.32

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 +0.25 [-0.00, 0.45] no
Aurora (GFS init) 1 -1.89 [-1.89, -1.89] yes
Aurora (IFS init) 2 -2.90 [-3.56, -2.23] yes
FourCastNet v2 (GFS init) 1 +3.33 [3.33, 3.33] yes
FourCastNet v2 (IFS init) 2 +2.98 [2.42, 3.54] yes
NCEP GFS 27 +0.08 [-0.72, 0.62] no
GraphCast (GFS init) 1 +0.11 [0.11, 0.11] yes
ECMWF IFS HRES 20 -1.58 [-2.67, -0.40] yes
Pangu-Weather (GFS init) 1 -1.90 [-1.90, -1.90] yes
Pangu-Weather (IFS init) 2 -1.28 [-2.07, -0.48] yes
Persistence (baseline) 27 +2.21 [0.55, 3.86] yes

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSFO (San Francisco Intl), 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/KSFO/model/graphcast_ifs/lead/1/

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

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