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 6

KSFO · gfs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC4.65 [3.65, 5.58]2.70-4.40 [-5.25, -3.45]5.54 [4.32, 6.49]8% [0%, 18%]21%33%-0.24+0.252026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC4.65 [3.39, 5.67]2.70-4.40 [-5.20, -3.21]5.54 [3.98, 6.50]8% [0%, 20%]21%33%-0.24+0.252026-08-07 → 2026-08-30
tmax00Zbilinear365d24 1 QC4.65 [3.36, 5.77]2.70-4.40 [-5.29, -3.18]5.54 [3.78, 6.60]8% [0%, 20%]21%33%-0.24+0.252026-08-07 → 2026-08-30
tmax00Zbilinearall24 1 QC4.65 [3.38, 5.68]2.70-4.40 [-5.24, -3.19]5.54 [3.92, 6.54]8% [0%, 19%]21%33%-0.24+0.252026-08-07 → 2026-08-30
tmax00Znearest30d24 1 QC2.75 [1.77, 3.62]2.81+0.56 [-0.21, 1.55]3.64 [2.55, 4.45]29% [19%, 39%]46%58%+0.27+0.222026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC2.75 [1.85, 3.76]2.81+0.56 [-0.23, 1.94]3.64 [2.60, 4.56]29% [17%, 40%]46%58%+0.27+0.222026-08-07 → 2026-08-30
tmax00Znearest365d24 1 QC2.75 [1.67, 3.74]2.81+0.56 [-0.24, 1.97]3.64 [2.43, 4.56]29% [16%, 41%]46%58%+0.27+0.222026-08-07 → 2026-08-30
tmax00Znearestall24 1 QC2.75 [1.73, 3.76]2.81+0.56 [-0.25, 1.81]3.64 [2.45, 4.51]29% [14%, 41%]46%58%+0.27+0.222026-08-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC5.00 [4.19, 5.76]2.50-4.60 [-5.36, -3.69]5.64 [4.55, 6.65]0% [0%, 0%]12%25%-0.33+0.302026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC5.00 [4.01, 5.83]2.50-4.60 [-5.30, -3.31]5.64 [4.38, 6.72]0% [0%, 0%]12%25%-0.33+0.302026-08-07 → 2026-08-30
tmax12Zbilinear365d24 1 QC5.00 [3.94, 5.90]2.50-4.60 [-5.36, -3.33]5.64 [4.28, 6.82]0% [0%, 0%]12%25%-0.33+0.302026-08-07 → 2026-08-30
tmax12Zbilinearall24 1 QC5.00 [4.04, 5.85]2.50-4.60 [-5.40, -3.40]5.64 [4.31, 6.76]0% [0%, 0%]12%25%-0.33+0.302026-08-07 → 2026-08-30
tmax12Znearest30d24 1 QC2.69 [1.49, 4.18]2.72+0.38 [-0.52, 1.56]3.71 [1.97, 5.14]21% [0%, 46%]46%75%+0.28+0.242026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC2.69 [1.48, 4.41]2.72+0.38 [-0.49, 2.11]3.71 [1.84, 5.33]21% [0%, 45%]46%75%+0.28+0.242026-08-07 → 2026-08-30
tmax12Znearest365d24 1 QC2.69 [1.31, 4.37]2.72+0.38 [-0.55, 2.06]3.71 [1.65, 5.40]21% [0%, 50%]46%75%+0.28+0.242026-08-07 → 2026-08-30
tmax12Znearestall24 1 QC2.69 [1.31, 4.37]2.72+0.38 [-0.59, 1.99]3.71 [1.70, 5.36]21% [0%, 50%]46%75%+0.28+0.242026-08-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC1.06 [0.85, 1.30]0.81-0.74 [-1.03, -0.42]1.23 [1.00, 1.44]54% [35%, 73%]92%100%-0.11+0.172026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC1.06 [0.86, 1.33]0.81-0.74 [-1.05, -0.38]1.23 [0.98, 1.46]54% [33%, 74%]92%100%-0.11+0.172026-08-07 → 2026-08-30
tmin00Zbilinear365d24 1 QC1.06 [0.84, 1.34]0.81-0.74 [-1.07, -0.34]1.23 [0.96, 1.47]54% [31%, 75%]92%100%-0.11+0.172026-08-07 → 2026-08-30
tmin00Zbilinearall24 1 QC1.06 [0.83, 1.33]0.81-0.74 [-1.07, -0.38]1.23 [0.96, 1.46]54% [31%, 76%]92%100%-0.11+0.172026-08-07 → 2026-08-30
tmin00Znearest30d24 1 QC2.31 [2.01, 2.63]1.00-2.28 [-2.60, -1.98]2.55 [2.29, 2.79]12% [0%, 26%]38%62%-1.41-0.022026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC2.31 [2.02, 2.64]1.00-2.28 [-2.63, -1.99]2.55 [2.28, 2.82]12% [0%, 27%]38%62%-1.41-0.022026-08-07 → 2026-08-30
tmin00Znearest365d24 1 QC2.31 [1.98, 2.63]1.00-2.28 [-2.62, -1.94]2.55 [2.25, 2.82]12% [0%, 29%]38%62%-1.41-0.022026-08-07 → 2026-08-30
tmin00Znearestall24 1 QC2.31 [1.99, 2.67]1.00-2.28 [-2.67, -1.97]2.55 [2.26, 2.83]12% [0%, 29%]38%62%-1.41-0.022026-08-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC0.82 [0.59, 1.04]0.66-0.48 [-0.89, -0.06]1.00 [0.74, 1.21]67% [50%, 86%]100%100%+0.14+0.322026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC0.82 [0.50, 1.08]0.66-0.48 [-0.96, -0.05]1.00 [0.57, 1.23]67% [45%, 92%]100%100%+0.14+0.322026-08-07 → 2026-08-30
tmin12Zbilinear365d24 1 QC0.82 [0.49, 1.09]0.66-0.48 [-0.97, -0.01]1.00 [0.52, 1.24]67% [45%, 100%]100%100%+0.14+0.322026-08-07 → 2026-08-30
tmin12Zbilinearall24 1 QC0.82 [0.48, 1.06]0.66-0.48 [-0.96, -0.03]1.00 [0.51, 1.24]67% [48%, 100%]100%100%+0.14+0.322026-08-07 → 2026-08-30
tmin12Znearest30d24 1 QC2.10 [1.78, 2.39]0.85-1.89 [-2.37, -1.36]2.24 [1.96, 2.47]8% [0%, 17%]42%88%-1.19+0.122026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC2.10 [1.78, 2.38]0.85-1.89 [-2.38, -1.30]2.24 [1.94, 2.48]8% [0%, 17%]42%88%-1.19+0.122026-08-07 → 2026-08-30
tmin12Znearest365d24 1 QC2.10 [1.75, 2.41]0.85-1.89 [-2.41, -1.25]2.24 [1.92, 2.49]8% [0%, 17%]42%88%-1.19+0.122026-08-07 → 2026-08-30
tmin12Znearestall24 1 QC2.10 [1.76, 2.41]0.85-1.89 [-2.41, -1.22]2.24 [1.91, 2.49]8% [0%, 17%]42%88%-1.19+0.122026-08-07 → 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 6, 00Z bilinear tmax+20+100-10-202026-08-07: -1.44 °F2026-08-08: +0.19 °F2026-08-09: -4.99 °F2026-08-10: -7.89 °F2026-08-11: -10.14 °F2026-08-12: -5.93 °F2026-08-13: -1.84 °F2026-08-14: -2.39 °F2026-08-15: -3.06 °F2026-08-16: -3.97 °F2026-08-17: -6.03 °F2026-08-18: -3.21 °F2026-08-19: -3.01 °F2026-08-20: -4.68 °F2026-08-21: +0.17 °F2026-08-22: -1.61 °F2026-08-23: -10.66 °F2026-08-24: -6.94 °F2026-08-25: -2.8 °F2026-08-26: -11.05 °F2026-08-27: -5.36 °F2026-08-28: +2.65 °F2026-08-29: -5.22 °F2026-08-30: -6.31 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.31
2026-08-29-5.22
2026-08-28+2.65
2026-08-27-5.36
2026-08-26-11.05
2026-08-25-2.80
2026-08-24-6.94
2026-08-23-10.66
2026-08-22-1.61
2026-08-21+0.17
2026-08-20-4.68
2026-08-19-3.01
2026-08-18-3.21
2026-08-17-6.03
2026-08-16-3.97
2026-08-15-3.06
2026-08-14-2.39
2026-08-13-1.84
2026-08-12-5.93
2026-08-11-10.14
2026-08-10-7.89
2026-08-09-4.99
2026-08-08+0.19
2026-08-07-1.44

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSFO, lead day 6-20 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: 3 days-10 to -8 °F: 0 days-8 to -6 °F: 4 days-6 to -4 °F: 5 days-4 to -2 °F: 6 days-2 to 0 °F: 3 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| 4.32 · P90 |e| 9.46 °F-200+20 °Fn = 24 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
-12.00-10.003
-10.00-8.000
-8.00-6.004
-6.00-4.005
-4.00-2.006
-2.00+0.003
+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
2026-08244.65 -4.40

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24

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 24 -0.21 [-1.06, 0.84] no
GraphCast (IFS init) 24 -0.95 [-2.09, 0.56] no
ECMWF IFS HRES 19 -1.65 [-2.57, -0.77] yes
Persistence (baseline) 24 +0.90 [-1.82, 2.23] no

Cite this page

ShortCastCheck, KSFO gfs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSFO/model/gfs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSFO (San Francisco Intl), model gfs, lead day 6. 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/6/

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