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

San Francisco Intl · NCEP GFS · lead day 1

KSFO · 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, gfs-0p25, starting 2026-08-01 — 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
tmax00Zbilinear30d29 1 QC4.75 [3.66, 5.97]2.82-4.49 [-5.87, -3.22]5.65 [4.47, 6.73]17% [7%, 27%]21%31%-0.55+0.082026-08-02 → 2026-08-30
tmax00Zbilinear90d29 1 QC4.75 [3.60, 6.24]2.82-4.49 [-6.16, -3.21]5.65 [4.41, 7.02]17% [7%, 28%]21%31%-0.55+0.082026-08-02 → 2026-08-30
tmax00Zbilinear365d29 1 QC4.75 [3.56, 6.27]2.82-4.49 [-6.11, -3.14]5.65 [4.35, 6.98]17% [6%, 29%]21%31%-0.55+0.082026-08-02 → 2026-08-30
tmax00Zbilinearall29 1 QC4.75 [3.62, 6.43]2.82-4.49 [-6.35, -3.05]5.65 [4.41, 7.12]17% [5%, 27%]21%31%-0.55+0.082026-08-02 → 2026-08-30
tmax00Znearest30d29 1 QC3.48 [2.72, 4.45]3.35+1.10 [-0.75, 2.85]4.25 [3.21, 5.44]10% [3%, 18%]34%55%-0.13-0.102026-08-02 → 2026-08-30
tmax00Znearest90d29 1 QC3.48 [2.71, 4.50]3.35+1.10 [-0.88, 2.91]4.25 [3.20, 5.49]10% [0%, 18%]34%55%-0.13-0.102026-08-02 → 2026-08-30
tmax00Znearest365d29 1 QC3.48 [2.65, 4.62]3.35+1.10 [-1.09, 2.98]4.25 [3.12, 5.50]10% [0%, 19%]34%55%-0.13-0.102026-08-02 → 2026-08-30
tmax00Znearestall29 1 QC3.48 [2.70, 4.57]3.35+1.10 [-1.19, 3.14]4.25 [3.19, 5.53]10% [0%, 19%]34%55%-0.13-0.102026-08-02 → 2026-08-30
tmax12Zbilinear30d29 1 QC4.80 [3.74, 6.03]2.80-4.57 [-5.85, -3.46]5.72 [4.50, 6.85]14% [4%, 23%]28%28%-0.56+0.092026-08-02 → 2026-08-30
tmax12Zbilinear90d29 1 QC4.80 [3.69, 6.36]2.80-4.57 [-6.21, -3.37]5.72 [4.43, 7.11]14% [4%, 23%]28%28%-0.56+0.092026-08-02 → 2026-08-30
tmax12Zbilinear365d29 1 QC4.80 [3.67, 6.33]2.80-4.57 [-6.17, -3.36]5.72 [4.39, 7.11]14% [3%, 23%]28%28%-0.56+0.092026-08-02 → 2026-08-30
tmax12Zbilinearall29 1 QC4.80 [3.68, 6.56]2.80-4.57 [-6.39, -3.34]5.72 [4.43, 7.28]14% [0%, 24%]28%28%-0.56+0.092026-08-02 → 2026-08-30
tmax12Znearest30d29 1 QC3.12 [2.31, 3.99]3.10+0.75 [-0.81, 2.21]3.95 [2.97, 4.90]21% [10%, 33%]41%59%-0.02-0.012026-08-02 → 2026-08-30
tmax12Znearest90d29 1 QC3.12 [2.29, 4.09]3.10+0.75 [-0.91, 2.27]3.95 [2.93, 4.97]21% [9%, 33%]41%59%-0.02-0.012026-08-02 → 2026-08-30
tmax12Znearest365d29 1 QC3.12 [2.16, 4.20]3.10+0.75 [-1.10, 2.32]3.95 [2.79, 5.05]21% [8%, 36%]41%59%-0.02-0.012026-08-02 → 2026-08-30
tmax12Znearestall29 1 QC3.12 [2.23, 4.14]3.10+0.75 [-1.26, 2.33]3.95 [2.90, 5.02]21% [8%, 36%]41%59%-0.02-0.012026-08-02 → 2026-08-30
tmin00Zbilinear30d29 1 QC0.91 [0.61, 1.21]0.88-0.19 [-0.79, 0.39]1.23 [0.82, 1.58]69% [52%, 83%]86%97%+0.05+0.092026-08-02 → 2026-08-30
tmin00Zbilinear90d29 1 QC0.91 [0.55, 1.21]0.88-0.19 [-0.80, 0.51]1.23 [0.74, 1.55]69% [53%, 86%]86%97%+0.05+0.092026-08-02 → 2026-08-30
tmin00Zbilinear365d29 1 QC0.91 [0.58, 1.21]0.88-0.19 [-0.85, 0.58]1.23 [0.78, 1.57]69% [52%, 86%]86%97%+0.05+0.092026-08-02 → 2026-08-30
tmin00Zbilinearall29 1 QC0.91 [0.57, 1.21]0.88-0.19 [-0.84, 0.49]1.23 [0.75, 1.57]69% [51%, 86%]86%97%+0.05+0.092026-08-02 → 2026-08-30
tmin00Znearest30d29 1 QC1.61 [1.06, 2.17]1.30-1.18 [-2.04, -0.37]2.03 [1.43, 2.53]45% [23%, 68%]66%83%-0.66-0.352026-08-02 → 2026-08-30
tmin00Znearest90d29 1 QC1.61 [0.98, 2.18]1.30-1.18 [-2.10, -0.28]2.03 [1.31, 2.53]45% [22%, 71%]66%83%-0.66-0.352026-08-02 → 2026-08-30
tmin00Znearest365d29 1 QC1.61 [0.98, 2.20]1.30-1.18 [-2.13, -0.26]2.03 [1.31, 2.53]45% [21%, 70%]66%83%-0.66-0.352026-08-02 → 2026-08-30
tmin00Znearestall29 1 QC1.61 [0.98, 2.20]1.30-1.18 [-2.11, -0.35]2.03 [1.30, 2.53]45% [20%, 71%]66%83%-0.66-0.352026-08-02 → 2026-08-30
tmin12Zbilinear30d29 1 QC1.01 [0.79, 1.23]0.93-0.31 [-0.91, 0.34]1.30 [0.95, 1.64]62% [45%, 79%]90%97%-0.04+0.042026-08-02 → 2026-08-30
tmin12Zbilinear90d29 1 QC1.01 [0.75, 1.24]0.93-0.31 [-0.94, 0.41]1.30 [0.90, 1.62]62% [44%, 81%]90%97%-0.04+0.042026-08-02 → 2026-08-30
tmin12Zbilinear365d29 1 QC1.01 [0.74, 1.21]0.93-0.31 [-0.96, 0.53]1.30 [0.88, 1.63]62% [44%, 82%]90%97%-0.04+0.042026-08-02 → 2026-08-30
tmin12Zbilinearall29 1 QC1.01 [0.75, 1.24]0.93-0.31 [-0.98, 0.45]1.30 [0.90, 1.64]62% [43%, 81%]90%97%-0.04+0.042026-08-02 → 2026-08-30
tmin12Znearest30d29 1 QC1.86 [1.45, 2.32]1.23-1.47 [-2.22, -0.69]2.25 [1.79, 2.69]31% [17%, 45%]62%83%-0.92-0.272026-08-02 → 2026-08-30
tmin12Znearest90d29 1 QC1.86 [1.44, 2.36]1.23-1.47 [-2.27, -0.59]2.25 [1.77, 2.69]31% [17%, 44%]62%83%-0.92-0.272026-08-02 → 2026-08-30
tmin12Znearest365d29 1 QC1.86 [1.44, 2.40]1.23-1.47 [-2.32, -0.52]2.25 [1.77, 2.75]31% [14%, 44%]62%83%-0.92-0.272026-08-02 → 2026-08-30
tmin12Znearestall29 1 QC1.86 [1.37, 2.38]1.23-1.47 [-2.30, -0.60]2.25 [1.70, 2.73]31% [16%, 46%]62%83%-0.92-0.272026-08-02 → 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 NCEP GFS at KSFO, lead day 1, 00Z bilinear tmax+20+100-10-202026-08-02: -11.99 °F2026-08-03: -8.27 °F2026-08-04: -3.67 °F2026-08-05: -3.49 °F2026-08-06: -3.37 °F2026-08-07: +0.85 °F2026-08-08: +2.74 °F2026-08-09: -0.24 °F2026-08-10: -5.49 °F2026-08-11: -8.71 °F2026-08-12: -8.89 °F2026-08-13: -9.13 °F2026-08-14: -6.14 °F2026-08-15: -5.03 °F2026-08-16: -3.69 °F2026-08-17: -6.96 °F2026-08-18: -4.64 °F2026-08-19: -0.28 °F2026-08-20: -2.66 °F2026-08-21: -3.56 °F2026-08-22: -1.57 °F2026-08-23: -8.6 °F2026-08-24: -4.76 °F2026-08-25: +0.17 °F2026-08-26: -6.48 °F2026-08-27: -2.3 °F2026-08-28: -0.81 °F2026-08-29: -5.97 °F2026-08-30: -7.2 °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
2026-08-30-7.20
2026-08-29-5.97
2026-08-28-0.81
2026-08-27-2.30
2026-08-26-6.48
2026-08-25+0.17
2026-08-24-4.76
2026-08-23-8.60
2026-08-22-1.57
2026-08-21-3.56
2026-08-20-2.66
2026-08-19-0.28
2026-08-18-4.64
2026-08-17-6.96
2026-08-16-3.69
2026-08-15-5.03
2026-08-14-6.14
2026-08-13-9.13
2026-08-12-8.89
2026-08-11-8.71
2026-08-10-5.49
2026-08-09-0.24
2026-08-08+2.74
2026-08-07+0.85
2026-08-06-3.37
2026-08-05-3.49
2026-08-04-3.67
2026-08-03-8.27
2026-08-02-11.99

Error distribution

Distribution of the signed daily error in °F for NCEP GFS 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: 1 day-10 to -8 °F: 5 days-8 to -6 °F: 4 days-6 to -4 °F: 5 days-4 to -2 °F: 7 days-2 to 0 °F: 4 days0 to 2 °F: 2 days2 to 4 °F: 1 day4 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| 4.64 · P90 |e| 8.75 °F-200+20 °Fn = 29 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
-12.00-10.001
-10.00-8.005
-8.00-6.004
-6.00-4.005
-4.00-2.007
-2.00+0.004
+0.00+2.002
+2.00+4.001
+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
2026-08294.75 -4.49

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29
NCEP GFS2026-08-02 → 2026-08-30 29

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 29 +0.10 [-0.23, 0.53] no
Aurora (GFS init) 1 +0.56 [0.56, 0.56] yes
Aurora (IFS init) 2 -1.74 [-2.37, -1.11] yes
FourCastNet v2 (GFS init) 1 +5.79 [5.79, 5.79] yes
FourCastNet v2 (IFS init) 2 +4.14 [3.40, 4.87] yes
GraphCast (GFS init) 1 +2.56 [2.56, 2.56] yes
GraphCast (IFS init) 27 -0.08 [-0.62, 0.72] no
ECMWF IFS HRES 22 -1.48 [-2.19, -0.35] yes
Pangu-Weather (GFS init) 1 +0.56 [0.56, 0.56] yes
Pangu-Weather (IFS init) 2 -0.12 [-0.62, 0.38] no
Persistence (baseline) 29 +1.68 [-0.36, 3.69] no

Cite this page

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

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