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 3

KSFO · gfs · lead 3

Target day = initialization date + 3 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, 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
tmax00Zbilinear30d27 1 QC4.70 [3.81, 5.53]2.57-4.31 [-5.35, -3.11]5.33 [4.45, 6.01]4% [0%, 11%]19%30%-0.36+0.202026-08-04 → 2026-08-30
tmax00Zbilinear90d27 1 QC4.70 [3.69, 5.70]2.57-4.31 [-5.50, -2.90]5.33 [4.22, 6.13]4% [0%, 11%]19%30%-0.36+0.202026-08-04 → 2026-08-30
tmax00Zbilinear365d27 1 QC4.70 [3.63, 5.78]2.57-4.31 [-5.60, -2.90]5.33 [4.20, 6.18]4% [0%, 12%]19%30%-0.36+0.202026-08-04 → 2026-08-30
tmax00Zbilinearall27 1 QC4.70 [3.63, 5.74]2.57-4.31 [-5.60, -2.92]5.33 [4.24, 6.16]4% [0%, 12%]19%30%-0.36+0.202026-08-04 → 2026-08-30
tmax00Znearest30d27 1 QC3.67 [2.84, 4.75]3.56+1.28 [-0.46, 3.32]4.52 [3.16, 5.96]7% [0%, 15%]30%52%-0.07-0.112026-08-04 → 2026-08-30
tmax00Znearest90d27 1 QC3.67 [2.71, 4.91]3.56+1.28 [-0.68, 3.70]4.52 [3.03, 6.15]7% [0%, 15%]30%52%-0.07-0.112026-08-04 → 2026-08-30
tmax00Znearest365d27 1 QC3.67 [2.74, 4.87]3.56+1.28 [-0.88, 3.65]4.52 [3.01, 6.10]7% [0%, 15%]30%52%-0.07-0.112026-08-04 → 2026-08-30
tmax00Znearestall27 1 QC3.67 [2.67, 5.00]3.56+1.28 [-0.94, 3.65]4.52 [2.98, 6.26]7% [0%, 15%]30%52%-0.07-0.112026-08-04 → 2026-08-30
tmax12Zbilinear30d27 1 QC4.69 [3.76, 5.63]2.71-4.22 [-5.38, -3.02]5.36 [4.31, 6.17]7% [0%, 15%]19%33%-0.36+0.152026-08-04 → 2026-08-30
tmax12Zbilinear90d27 1 QC4.69 [3.55, 5.81]2.71-4.22 [-5.51, -2.76]5.36 [4.05, 6.29]7% [0%, 16%]19%33%-0.36+0.152026-08-04 → 2026-08-30
tmax12Zbilinear365d27 1 QC4.69 [3.54, 5.93]2.71-4.22 [-5.62, -2.78]5.36 [3.98, 6.35]7% [0%, 15%]19%33%-0.36+0.152026-08-04 → 2026-08-30
tmax12Zbilinearall27 1 QC4.69 [3.62, 5.85]2.71-4.22 [-5.61, -2.80]5.36 [4.20, 6.28]7% [0%, 17%]19%33%-0.36+0.152026-08-04 → 2026-08-30
tmax12Znearest30d27 1 QC3.75 [2.55, 5.06]3.64+1.29 [-0.51, 3.37]4.71 [3.00, 6.23]7% [0%, 21%]26%56%-0.09-0.142026-08-04 → 2026-08-30
tmax12Znearest90d27 1 QC3.75 [2.50, 5.23]3.64+1.29 [-0.77, 3.81]4.71 [2.90, 6.43]7% [0%, 21%]26%56%-0.09-0.142026-08-04 → 2026-08-30
tmax12Znearest365d27 1 QC3.75 [2.38, 5.26]3.64+1.29 [-0.89, 3.84]4.71 [2.79, 6.37]7% [0%, 22%]26%56%-0.09-0.142026-08-04 → 2026-08-30
tmax12Znearestall27 1 QC3.75 [2.36, 5.29]3.64+1.29 [-0.86, 3.87]4.71 [2.76, 6.51]7% [0%, 21%]26%56%-0.09-0.142026-08-04 → 2026-08-30
tmin00Zbilinear30d27 1 QC0.82 [0.50, 1.16]0.75-0.35 [-0.96, 0.21]1.19 [0.70, 1.53]78% [59%, 96%]85%93%+0.15+0.222026-08-04 → 2026-08-30
tmin00Zbilinear90d27 1 QC0.82 [0.41, 1.16]0.75-0.35 [-0.93, 0.31]1.19 [0.43, 1.52]78% [59%, 100%]85%93%+0.15+0.222026-08-04 → 2026-08-30
tmin00Zbilinear365d27 1 QC0.82 [0.40, 1.18]0.75-0.35 [-1.02, 0.36]1.19 [0.41, 1.54]78% [57%, 100%]85%93%+0.15+0.222026-08-04 → 2026-08-30
tmin00Zbilinearall27 1 QC0.82 [0.40, 1.16]0.75-0.35 [-1.00, 0.30]1.19 [0.41, 1.52]78% [58%, 100%]85%93%+0.15+0.222026-08-04 → 2026-08-30
tmin00Znearest30d27 1 QC1.93 [1.41, 2.51]1.18-1.51 [-2.42, -0.67]2.23 [1.58, 2.79]19% [7%, 33%]56%81%-1.01-0.232026-08-04 → 2026-08-30
tmin00Znearest90d27 1 QC1.93 [1.36, 2.52]1.18-1.51 [-2.38, -0.54]2.23 [1.49, 2.80]19% [5%, 36%]56%81%-1.01-0.232026-08-04 → 2026-08-30
tmin00Znearest365d27 1 QC1.93 [1.34, 2.56]1.18-1.51 [-2.48, -0.58]2.23 [1.46, 2.83]19% [5%, 35%]56%81%-1.01-0.232026-08-04 → 2026-08-30
tmin00Znearestall27 1 QC1.93 [1.34, 2.52]1.18-1.51 [-2.42, -0.55]2.23 [1.46, 2.80]19% [5%, 36%]56%81%-1.01-0.232026-08-04 → 2026-08-30
tmin12Zbilinear30d27 1 QC0.98 [0.68, 1.27]0.91-0.27 [-0.93, 0.49]1.26 [0.85, 1.58]63% [43%, 81%]89%96%-0.02+0.062026-08-04 → 2026-08-30
tmin12Zbilinear90d27 1 QC0.98 [0.63, 1.27]0.91-0.27 [-0.91, 0.55]1.26 [0.76, 1.57]63% [44%, 83%]89%96%-0.02+0.062026-08-04 → 2026-08-30
tmin12Zbilinear365d27 1 QC0.98 [0.61, 1.27]0.91-0.27 [-0.96, 0.75]1.26 [0.74, 1.58]63% [43%, 86%]89%96%-0.02+0.062026-08-04 → 2026-08-30
tmin12Zbilinearall27 1 QC0.98 [0.62, 1.29]0.91-0.27 [-0.97, 0.61]1.26 [0.73, 1.60]63% [42%, 86%]89%96%-0.02+0.062026-08-04 → 2026-08-30
tmin12Znearest30d27 1 QC1.74 [1.10, 2.49]1.29-1.36 [-2.36, -0.52]2.16 [1.36, 2.85]37% [19%, 57%]67%78%-0.80-0.342026-08-04 → 2026-08-30
tmin12Znearest90d27 1 QC1.74 [1.01, 2.50]1.29-1.36 [-2.36, -0.47]2.16 [1.20, 2.85]37% [16%, 59%]67%78%-0.80-0.342026-08-04 → 2026-08-30
tmin12Znearest365d27 1 QC1.74 [1.01, 2.56]1.29-1.36 [-2.42, -0.42]2.16 [1.20, 2.90]37% [14%, 60%]67%78%-0.80-0.342026-08-04 → 2026-08-30
tmin12Znearestall27 1 QC1.74 [1.00, 2.52]1.29-1.36 [-2.41, -0.47]2.16 [1.19, 2.88]37% [14%, 58%]67%78%-0.80-0.342026-08-04 → 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 3, 00Z bilinear tmax+10+50-5-102026-08-04: -3.95 °F2026-08-05: -3.97 °F2026-08-06: -3.6 °F2026-08-07: +1.4 °F2026-08-08: +2.38 °F2026-08-09: -2.3 °F2026-08-10: -6.31 °F2026-08-11: -8.38 °F2026-08-12: -7.16 °F2026-08-13: -5.21 °F2026-08-14: -6.79 °F2026-08-15: -5.47 °F2026-08-16: -3.33 °F2026-08-17: -8.74 °F2026-08-18: -4.52 °F2026-08-19: -1 °F2026-08-20: -2.42 °F2026-08-21: -3.69 °F2026-08-22: -0.95 °F2026-08-23: -8.64 °F2026-08-24: -6.68 °F2026-08-25: -1.36 °F2026-08-26: -7.95 °F2026-08-27: -4.51 °F2026-08-28: +1.42 °F2026-08-29: -6.91 °F2026-08-30: -7.77 °F2026-08-042026-08-30°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 (27 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-7.77
2026-08-29-6.91
2026-08-28+1.42
2026-08-27-4.51
2026-08-26-7.95
2026-08-25-1.36
2026-08-24-6.68
2026-08-23-8.64
2026-08-22-0.95
2026-08-21-3.69
2026-08-20-2.42
2026-08-19-1.00
2026-08-18-4.52
2026-08-17-8.74
2026-08-16-3.33
2026-08-15-5.47
2026-08-14-6.79
2026-08-13-5.21
2026-08-12-7.16
2026-08-11-8.38
2026-08-10-6.31
2026-08-09-2.30
2026-08-08+2.38
2026-08-07+1.40
2026-08-06-3.60
2026-08-05-3.97
2026-08-04-3.95

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSFO, lead day 3-10 to -9 °F: 0 days-9 to -8 °F: 3 days-8 to -7 °F: 3 days-7 to -6 °F: 4 days-6 to -5 °F: 2 days-5 to -4 °F: 2 days-4 to -3 °F: 5 days-3 to -2 °F: 2 days-2 to -1 °F: 2 days-1 to 0 °F: 1 day0 to 1 °F: 0 days1 to 2 °F: 2 days2 to 3 °F: 1 day3 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| 4.51 · P90 |e| 8.12 °F-100+10 °Fn = 27 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
-9.00-8.003
-8.00-7.003
-7.00-6.004
-6.00-5.002
-5.00-4.002
-4.00-3.005
-3.00-2.002
-2.00-1.002
-1.00+0.001
+0.00+1.000
+1.00+2.002
+2.00+3.001
+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
2026-08274.70 -4.31

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27

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 27 +0.28 [-0.30, 0.85] no
GraphCast (IFS init) 25 -0.58 [-1.18, -0.08] yes
ECMWF IFS HRES 22 -1.18 [-2.43, -0.20] yes
Persistence (baseline) 27 +1.25 [-0.66, 2.52] no

Cite this page

ShortCastCheck, KSFO gfs lead 3, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSFO/model/gfs/lead/3/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSFO (San Francisco Intl), model gfs, lead day 3. 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/3/

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