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

San Francisco Intl · ECMWF AIFS Single · lead day 8

KSFO · aifs_single · lead 8

Target day = initialization date + 8 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, aifs-single-gpid5, 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
tmax00Zbilinear30d22 1 QC5.35 [3.88, 6.88]3.17-4.31 [-6.40, -2.39]6.20 [4.77, 7.46]9% [0%, 24%]18%27%-0.53+0.082026-08-09 → 2026-08-30
tmax00Zbilinear90d22 1 QC5.35 [3.78, 7.14]3.17-4.31 [-6.83, -2.10]6.20 [4.54, 7.62]9% [0%, 25%]18%27%-0.53+0.082026-08-09 → 2026-08-30
tmax00Zbilinear365d22 1 QC5.35 [3.65, 7.13]3.17-4.31 [-6.77, -2.14]6.20 [4.44, 7.59]9% [0%, 29%]18%27%-0.53+0.082026-08-09 → 2026-08-30
tmax00Zbilinearall22 1 QC5.35 [3.90, 7.05]3.17-4.31 [-6.93, -2.04]6.20 [4.72, 7.59]9% [0%, 25%]18%27%-0.53+0.082026-08-09 → 2026-08-30
tmax00Znearest30d22 1 QC3.35 [2.43, 4.66]3.20-0.87 [-2.71, 0.94]4.66 [2.95, 6.70]18% [8%, 29%]41%55%+0.04+0.082026-08-09 → 2026-08-30
tmax00Znearest90d22 1 QC3.35 [2.28, 4.96]3.20-0.87 [-3.15, 1.21]4.66 [2.81, 7.32]18% [7%, 30%]41%55%+0.04+0.082026-08-09 → 2026-08-30
tmax00Znearest365d22 1 QC3.35 [2.27, 4.76]3.20-0.87 [-3.12, 1.18]4.66 [2.73, 7.01]18% [0%, 29%]41%55%+0.04+0.082026-08-09 → 2026-08-30
tmax00Znearestall22 1 QC3.35 [2.33, 4.73]3.20-0.87 [-3.15, 1.33]4.66 [2.88, 6.99]18% [6%, 29%]41%55%+0.04+0.082026-08-09 → 2026-08-30
tmax12Zbilinear30d22 1 QC6.01 [4.99, 7.05]3.19-5.27 [-6.78, -3.56]6.79 [5.66, 7.75]5% [0%, 12%]9%18%-0.72+0.082026-08-09 → 2026-08-30
tmax12Zbilinear90d22 1 QC6.01 [4.85, 7.15]3.19-5.27 [-7.04, -3.39]6.79 [5.37, 7.88]5% [0%, 13%]9%18%-0.72+0.082026-08-09 → 2026-08-30
tmax12Zbilinear365d22 1 QC6.01 [4.77, 7.14]3.19-5.27 [-7.04, -3.30]6.79 [5.32, 7.75]5% [0%, 14%]9%18%-0.72+0.082026-08-09 → 2026-08-30
tmax12Zbilinearall22 1 QC6.01 [4.95, 7.15]3.19-5.27 [-7.10, -3.16]6.79 [5.41, 7.78]5% [0%, 14%]9%18%-0.72+0.082026-08-09 → 2026-08-30
tmax12Znearest30d22 1 QC3.85 [2.81, 5.11]3.47-1.75 [-3.26, 0.05]4.99 [3.64, 6.30]23% [6%, 39%]41%55%-0.10-0.002026-08-09 → 2026-08-30
tmax12Znearest90d22 1 QC3.85 [2.59, 5.20]3.47-1.75 [-3.30, 0.52]4.99 [3.19, 6.42]23% [0%, 40%]41%55%-0.10-0.002026-08-09 → 2026-08-30
tmax12Znearest365d22 1 QC3.85 [2.46, 5.17]3.47-1.75 [-3.37, 0.75]4.99 [3.19, 6.39]23% [0%, 43%]41%55%-0.10-0.002026-08-09 → 2026-08-30
tmax12Znearestall22 1 QC3.85 [2.52, 5.18]3.47-1.75 [-3.30, 1.04]4.99 [3.17, 6.31]23% [0%, 43%]41%55%-0.10-0.002026-08-09 → 2026-08-30
tmin00Zbilinear30d22 1 QC1.65 [1.03, 2.34]1.59-0.17 [-1.07, 1.24]2.08 [1.25, 2.88]41% [24%, 67%]68%91%-0.91-0.792026-08-09 → 2026-08-30
tmin00Zbilinear90d22 1 QC1.65 [0.90, 2.50]1.59-0.17 [-1.11, 1.72]2.08 [1.14, 3.09]41% [23%, 75%]68%91%-0.91-0.792026-08-09 → 2026-08-30
tmin00Zbilinear365d22 1 QC1.65 [0.87, 2.51]1.59-0.17 [-1.13, 1.75]2.08 [1.12, 3.01]41% [21%, 76%]68%91%-0.91-0.792026-08-09 → 2026-08-30
tmin00Zbilinearall22 1 QC1.65 [0.87, 2.44]1.59-0.17 [-1.11, 1.68]2.08 [1.12, 3.00]41% [22%, 75%]68%91%-0.91-0.792026-08-09 → 2026-08-30
tmin00Znearest30d22 1 QC1.79 [0.99, 2.78]1.82+0.23 [-0.84, 1.82]2.37 [1.18, 3.48]36% [20%, 65%]73%86%-1.07-1.062026-08-09 → 2026-08-30
tmin00Znearest90d22 1 QC1.79 [0.81, 3.09]1.82+0.23 [-0.91, 2.30]2.37 [1.03, 3.85]36% [20%, 75%]73%86%-1.07-1.062026-08-09 → 2026-08-30
tmin00Znearest365d22 1 QC1.79 [0.79, 3.09]1.82+0.23 [-0.94, 2.32]2.37 [0.98, 3.78]36% [18%, 76%]73%86%-1.07-1.062026-08-09 → 2026-08-30
tmin00Znearestall22 1 QC1.79 [0.82, 3.05]1.82+0.23 [-0.92, 2.27]2.37 [0.98, 3.72]36% [17%, 75%]73%86%-1.07-1.062026-08-09 → 2026-08-30
tmin12Zbilinear30d22 1 QC1.49 [1.06, 1.76]1.25-0.71 [-1.53, 0.57]1.76 [1.37, 2.01]36% [18%, 65%]64%91%-0.72-0.412026-08-09 → 2026-08-30
tmin12Zbilinear90d22 1 QC1.49 [0.92, 1.79]1.25-0.71 [-1.54, 1.01]1.76 [1.29, 2.03]36% [18%, 75%]64%91%-0.72-0.412026-08-09 → 2026-08-30
tmin12Zbilinear365d22 1 QC1.49 [0.91, 1.78]1.25-0.71 [-1.59, 1.09]1.76 [1.29, 2.01]36% [14%, 78%]64%91%-0.72-0.412026-08-09 → 2026-08-30
tmin12Zbilinearall22 1 QC1.49 [0.89, 1.77]1.25-0.71 [-1.56, 0.99]1.76 [1.25, 2.02]36% [15%, 79%]64%91%-0.72-0.412026-08-09 → 2026-08-30
tmin12Znearest30d22 1 QC1.54 [0.97, 2.11]1.51-0.24 [-1.25, 1.27]1.88 [1.26, 2.44]41% [20%, 73%]64%91%-0.78-0.712026-08-09 → 2026-08-30
tmin12Znearest90d22 1 QC1.54 [0.80, 2.27]1.51-0.24 [-1.28, 1.67]1.88 [1.12, 2.61]41% [19%, 86%]64%91%-0.78-0.712026-08-09 → 2026-08-30
tmin12Znearest365d22 1 QC1.54 [0.80, 2.28]1.51-0.24 [-1.34, 1.66]1.88 [1.14, 2.61]41% [15%, 88%]64%91%-0.78-0.712026-08-09 → 2026-08-30
tmin12Znearestall22 1 QC1.54 [0.78, 2.21]1.51-0.24 [-1.35, 1.66]1.88 [1.10, 2.59]41% [17%, 86%]64%91%-0.78-0.712026-08-09 → 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 ECMWF AIFS Single at KSFO, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: -5.42 °F2026-08-10: -7.64 °F2026-08-11: -10.76 °F2026-08-12: -8.26 °F2026-08-13: -5.97 °F2026-08-14: -5.01 °F2026-08-15: -2.15 °F2026-08-16: -5.29 °F2026-08-17: -6.94 °F2026-08-18: -0.26 °F2026-08-19: -0.94 °F2026-08-20: -3.19 °F2026-08-21: -2.28 °F2026-08-22: -4.19 °F2026-08-23: -8.93 °F2026-08-24: -6.56 °F2026-08-25: -2 °F2026-08-26: -8.9 °F2026-08-27: -1.69 °F2026-08-28: +11.48 °F2026-08-29: -3 °F2026-08-30: -6.95 °F2026-08-092026-08-30°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 (22 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-6.95
2026-08-29-3.00
2026-08-28+11.48
2026-08-27-1.69
2026-08-26-8.90
2026-08-25-2.00
2026-08-24-6.56
2026-08-23-8.93
2026-08-22-4.19
2026-08-21-2.28
2026-08-20-3.19
2026-08-19-0.94
2026-08-18-0.26
2026-08-17-6.94
2026-08-16-5.29
2026-08-15-2.15
2026-08-14-5.01
2026-08-13-5.97
2026-08-12-8.26
2026-08-11-10.76
2026-08-10-7.64
2026-08-09-5.42

Error distribution

Distribution of the signed daily error in °F for ECMWF AIFS Single at KSFO, lead day 8-20 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: 3 days-8 to -6 °F: 4 days-6 to -4 °F: 5 days-4 to -2 °F: 4 days-2 to 0 °F: 4 days0 to 2 °F: 0 days2 to 4 °F: 0 days4 to 6 °F: 0 days6 to 8 °F: 0 days8 to 10 °F: 0 days10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 5.35 · P90 |e| 8.93 °F-200+20 °Fn = 22 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
-10.00-8.003
-8.00-6.004
-6.00-4.005
-4.00-2.004
-2.00+0.004
+0.00+2.000
+2.00+4.000
+4.00+6.000
+6.00+8.000
+8.00+10.000
+10.00+12.001
+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
2026-08225.35 -4.31

Availability

ModelScored period DaysCoverage
ECMWF AIFS Single2026-08-09 → 2026-08-30 22
ECMWF AIFS Single2026-08-09 → 2026-08-30 22
ECMWF AIFS Single2026-08-09 → 2026-08-30 22
ECMWF AIFS Single2026-08-09 → 2026-08-30 22

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
NCEP GFS 22 +0.47 [-0.46, 1.62] no
GraphCast (IFS init) 22 -1.40 [-2.30, 0.08] no
ECMWF IFS HRES 17 -0.66 [-1.43, 1.47] no
Persistence (baseline) 22 +1.85 [-0.06, 4.22] no

Cite this page

ShortCastCheck, KSFO aifs_single lead 8, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSFO/model/aifs_single/lead/8/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSFO (San Francisco Intl), model aifs_single, lead day 8. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KSFO/model/aifs_single/lead/8/

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