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 2

KSFO · gfs · 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, 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
tmax00Zbilinear30d28 1 QC4.58 [3.65, 5.61]2.77-4.30 [-5.47, -3.21]5.38 [4.45, 6.16]14% [7%, 23%]21%32%-0.14+0.312026-08-03 → 2026-08-30
tmax00Zbilinear90d28 1 QC4.58 [3.56, 5.70]2.77-4.30 [-5.62, -3.12]5.38 [4.38, 6.29]14% [4%, 25%]21%32%-0.14+0.312026-08-03 → 2026-08-30
tmax00Zbilinear365d28 1 QC4.58 [3.54, 5.83]2.77-4.30 [-5.68, -3.12]5.38 [4.33, 6.31]14% [3%, 24%]21%32%-0.14+0.312026-08-03 → 2026-08-30
tmax00Zbilinearall28 1 QC4.58 [3.67, 5.92]2.77-4.30 [-5.69, -3.12]5.38 [4.44, 6.35]14% [4%, 24%]21%32%-0.14+0.312026-08-03 → 2026-08-30
tmax00Znearest30d28 1 QC3.61 [2.87, 4.52]3.51+1.37 [-0.37, 3.15]4.41 [3.26, 5.66]7% [0%, 14%]29%46%+0.10+0.132026-08-03 → 2026-08-30
tmax00Znearest90d28 1 QC3.61 [2.78, 4.57]3.51+1.37 [-0.73, 3.33]4.41 [3.19, 5.69]7% [0%, 14%]29%46%+0.10+0.132026-08-03 → 2026-08-30
tmax00Znearest365d28 1 QC3.61 [2.77, 4.66]3.51+1.37 [-0.76, 3.41]4.41 [3.16, 5.71]7% [0%, 14%]29%46%+0.10+0.132026-08-03 → 2026-08-30
tmax00Znearestall28 1 QC3.61 [2.66, 4.61]3.51+1.37 [-0.86, 3.44]4.41 [3.07, 5.78]7% [0%, 14%]29%46%+0.10+0.132026-08-03 → 2026-08-30
tmax12Zbilinear30d28 1 QC4.54 [3.69, 5.53]2.70-4.14 [-5.33, -3.06]5.24 [4.36, 6.10]11% [4%, 18%]18%36%-0.14+0.332026-08-03 → 2026-08-30
tmax12Zbilinear90d28 1 QC4.54 [3.61, 5.60]2.70-4.14 [-5.40, -3.05]5.24 [4.26, 6.20]11% [0%, 18%]18%36%-0.14+0.332026-08-03 → 2026-08-30
tmax12Zbilinear365d28 1 QC4.54 [3.58, 5.79]2.70-4.14 [-5.52, -3.00]5.24 [4.20, 6.31]11% [0%, 18%]18%36%-0.14+0.332026-08-03 → 2026-08-30
tmax12Zbilinearall28 1 QC4.54 [3.68, 5.85]2.70-4.14 [-5.68, -3.04]5.24 [4.27, 6.28]11% [0%, 19%]18%36%-0.14+0.332026-08-03 → 2026-08-30
tmax12Znearest30d28 1 QC3.39 [2.66, 4.37]3.23+1.34 [-0.34, 2.98]4.21 [3.03, 5.43]11% [0%, 21%]29%57%+0.15+0.202026-08-03 → 2026-08-30
tmax12Znearest90d28 1 QC3.39 [2.60, 4.41]3.23+1.34 [-0.52, 3.14]4.21 [2.98, 5.49]11% [0%, 21%]29%57%+0.15+0.202026-08-03 → 2026-08-30
tmax12Znearest365d28 1 QC3.39 [2.55, 4.46]3.23+1.34 [-0.79, 3.14]4.21 [2.89, 5.51]11% [0%, 22%]29%57%+0.15+0.202026-08-03 → 2026-08-30
tmax12Znearestall28 1 QC3.39 [2.54, 4.48]3.23+1.34 [-0.67, 3.25]4.21 [2.85, 5.57]11% [0%, 22%]29%57%+0.15+0.202026-08-03 → 2026-08-30
tmin00Zbilinear30d28 1 QC0.93 [0.59, 1.26]0.91-0.24 [-0.90, 0.43]1.25 [0.80, 1.56]68% [45%, 91%]86%100%+0.16+0.182026-08-03 → 2026-08-30
tmin00Zbilinear90d28 1 QC0.93 [0.51, 1.25]0.91-0.24 [-0.90, 0.49]1.25 [0.61, 1.56]68% [45%, 96%]86%100%+0.16+0.182026-08-03 → 2026-08-30
tmin00Zbilinear365d28 1 QC0.93 [0.52, 1.26]0.91-0.24 [-0.95, 0.60]1.25 [0.62, 1.57]68% [43%, 96%]86%100%+0.16+0.182026-08-03 → 2026-08-30
tmin00Zbilinearall28 1 QC0.93 [0.51, 1.27]0.91-0.24 [-0.92, 0.54]1.25 [0.60, 1.58]68% [43%, 100%]86%100%+0.16+0.182026-08-03 → 2026-08-30
tmin00Znearest30d28 1 QC1.75 [1.15, 2.50]1.29-1.35 [-2.39, -0.45]2.17 [1.38, 2.88]32% [15%, 47%]64%82%-0.58-0.162026-08-03 → 2026-08-30
tmin00Znearest90d28 1 QC1.75 [1.10, 2.48]1.29-1.35 [-2.38, -0.39]2.17 [1.29, 2.87]32% [13%, 47%]64%82%-0.58-0.162026-08-03 → 2026-08-30
tmin00Znearest365d28 1 QC1.75 [1.10, 2.58]1.29-1.35 [-2.48, -0.36]2.17 [1.29, 2.93]32% [14%, 48%]64%82%-0.58-0.162026-08-03 → 2026-08-30
tmin00Znearestall28 1 QC1.75 [1.10, 2.52]1.29-1.35 [-2.46, -0.37]2.17 [1.30, 2.88]32% [11%, 50%]64%82%-0.58-0.162026-08-03 → 2026-08-30
tmin12Zbilinear30d28 1 QC0.88 [0.49, 1.23]0.85-0.16 [-0.82, 0.51]1.24 [0.73, 1.59]75% [57%, 93%]82%96%+0.21+0.232026-08-03 → 2026-08-30
tmin12Zbilinear90d28 1 QC0.88 [0.41, 1.22]0.85-0.16 [-0.83, 0.58]1.24 [0.53, 1.58]75% [56%, 100%]82%96%+0.21+0.232026-08-03 → 2026-08-30
tmin12Zbilinear365d28 1 QC0.88 [0.41, 1.24]0.85-0.16 [-0.88, 0.70]1.24 [0.55, 1.60]75% [55%, 100%]82%96%+0.21+0.232026-08-03 → 2026-08-30
tmin12Zbilinearall28 1 QC0.88 [0.40, 1.25]0.85-0.16 [-0.83, 0.60]1.24 [0.52, 1.61]75% [55%, 100%]82%96%+0.21+0.232026-08-03 → 2026-08-30
tmin12Znearest30d28 1 QC1.74 [1.21, 2.38]1.27-1.32 [-2.28, -0.47]2.12 [1.41, 2.75]36% [23%, 48%]64%79%-0.57-0.142026-08-03 → 2026-08-30
tmin12Znearest90d28 1 QC1.74 [1.14, 2.37]1.27-1.32 [-2.27, -0.41]2.12 [1.33, 2.76]36% [21%, 49%]64%79%-0.57-0.142026-08-03 → 2026-08-30
tmin12Znearest365d28 1 QC1.74 [1.15, 2.44]1.27-1.32 [-2.34, -0.40]2.12 [1.33, 2.80]36% [20%, 50%]64%79%-0.57-0.142026-08-03 → 2026-08-30
tmin12Znearestall28 1 QC1.74 [1.15, 2.38]1.27-1.32 [-2.33, -0.45]2.12 [1.32, 2.77]36% [20%, 50%]64%79%-0.57-0.142026-08-03 → 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 NCEP GFS at KSFO, lead day 2, 00Z bilinear tmax+10+50-5-102026-08-03: -8.49 °F2026-08-04: -4.24 °F2026-08-05: -3.34 °F2026-08-06: -3.36 °F2026-08-07: +0.42 °F2026-08-08: +2.9 °F2026-08-09: -1.17 °F2026-08-10: -5.7 °F2026-08-11: -7.71 °F2026-08-12: -7.85 °F2026-08-13: -8.68 °F2026-08-14: -6.3 °F2026-08-15: -5.32 °F2026-08-16: -3.68 °F2026-08-17: -6.61 °F2026-08-18: -3 °F2026-08-19: -0.34 °F2026-08-20: -2.4 °F2026-08-21: -1.91 °F2026-08-22: -2.81 °F2026-08-23: -9.65 °F2026-08-24: -6.21 °F2026-08-25: -0.24 °F2026-08-26: -7.55 °F2026-08-27: -3.09 °F2026-08-28: +0.51 °F2026-08-29: -7.5 °F2026-08-30: -7.2 °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
2026-08-30-7.20
2026-08-29-7.50
2026-08-28+0.51
2026-08-27-3.09
2026-08-26-7.55
2026-08-25-0.24
2026-08-24-6.21
2026-08-23-9.65
2026-08-22-2.81
2026-08-21-1.91
2026-08-20-2.40
2026-08-19-0.34
2026-08-18-3.00
2026-08-17-6.61
2026-08-16-3.68
2026-08-15-5.32
2026-08-14-6.30
2026-08-13-8.68
2026-08-12-7.85
2026-08-11-7.71
2026-08-10-5.70
2026-08-09-1.17
2026-08-08+2.90
2026-08-07+0.42
2026-08-06-3.36
2026-08-05-3.34
2026-08-04-4.24
2026-08-03-8.49

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSFO, lead day 2-10 to -9 °F: 1 day-9 to -8 °F: 2 days-8 to -7 °F: 5 days-7 to -6 °F: 3 days-6 to -5 °F: 2 days-5 to -4 °F: 1 day-4 to -3 °F: 5 days-3 to -2 °F: 2 days-2 to -1 °F: 2 days-1 to 0 °F: 2 days0 to 1 °F: 2 days1 to 2 °F: 0 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| 3.96 · P90 |e| 8.04 °F-100+10 °Fn = 28 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
-10.00-9.001
-9.00-8.002
-8.00-7.005
-7.00-6.003
-6.00-5.002
-5.00-4.001
-4.00-3.005
-3.00-2.002
-2.00-1.002
-1.00+0.002
+0.00+1.002
+1.00+2.000
+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
2026-08284.58 -4.30

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28
NCEP GFS2026-08-03 → 2026-08-30 28

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 28 -0.00 [-0.33, 0.37] no
Aurora (IFS init) 1 -1.14 [-1.14, -1.14] yes
FourCastNet v2 (IFS init) 1 +5.59 [5.59, 5.59] yes
GraphCast (IFS init) 26 -0.54 [-0.98, 0.03] no
ECMWF IFS HRES 23 -1.24 [-2.15, -0.41] yes
Pangu-Weather (IFS init) 1 +0.81 [0.81, 0.81] yes
Persistence (baseline) 28 +0.58 [-1.17, 2.23] no

Cite this page

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

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