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

San Francisco Intl · ECMWF AIFS Single · lead day 4

KSFO · aifs_single · lead 4

Target day = initialization date + 4 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
tmax00Zbilinear30d26 1 QC4.69 [3.79, 5.61]2.55-4.44 [-5.44, -3.46]5.40 [4.54, 6.12]12% [0%, 25%]19%35%-0.14+0.362026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC4.69 [3.62, 5.70]2.55-4.44 [-5.56, -3.33]5.40 [4.36, 6.18]12% [0%, 28%]19%35%-0.14+0.362026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC4.69 [3.60, 5.75]2.55-4.44 [-5.58, -3.28]5.40 [4.33, 6.17]12% [0%, 28%]19%35%-0.14+0.362026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC4.69 [3.69, 5.75]2.55-4.44 [-5.66, -3.41]5.40 [4.41, 6.16]12% [0%, 29%]19%35%-0.14+0.362026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC2.98 [2.11, 3.72]2.79-0.80 [-2.06, 0.77]3.55 [2.79, 4.13]23% [4%, 46%]38%46%+0.28+0.302026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC2.98 [2.01, 3.77]2.79-0.80 [-2.16, 1.10]3.55 [2.71, 4.12]23% [0%, 50%]38%46%+0.28+0.302026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC2.98 [1.88, 3.85]2.79-0.80 [-2.25, 1.13]3.55 [2.64, 4.18]23% [0%, 55%]38%46%+0.28+0.302026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC2.98 [2.05, 3.81]2.79-0.80 [-2.27, 1.13]3.55 [2.78, 4.12]23% [0%, 50%]38%46%+0.28+0.302026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC4.71 [3.81, 5.80]2.55-4.59 [-5.71, -3.67]5.53 [4.55, 6.41]12% [4%, 19%]23%35%-0.14+0.362026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC4.71 [3.68, 5.90]2.55-4.59 [-5.82, -3.53]5.53 [4.46, 6.47]12% [0%, 19%]23%35%-0.14+0.362026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC4.71 [3.62, 5.96]2.55-4.59 [-5.90, -3.48]5.53 [4.36, 6.53]12% [0%, 19%]23%35%-0.14+0.362026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC4.71 [3.77, 5.93]2.55-4.59 [-5.91, -3.56]5.53 [4.50, 6.51]12% [0%, 20%]23%35%-0.14+0.362026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC2.99 [2.33, 3.57]2.79-0.96 [-2.27, 0.30]3.53 [2.96, 3.97]23% [8%, 41%]38%46%+0.27+0.302026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC2.99 [2.19, 3.62]2.79-0.96 [-2.36, 0.53]3.53 [2.84, 4.01]23% [6%, 44%]38%46%+0.27+0.302026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC2.99 [2.14, 3.66]2.79-0.96 [-2.51, 0.56]3.53 [2.80, 4.00]23% [5%, 47%]38%46%+0.27+0.302026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC2.99 [2.25, 3.64]2.79-0.96 [-2.51, 0.49]3.53 [2.94, 4.01]23% [6%, 44%]38%46%+0.27+0.302026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.30 [1.10, 1.51]1.12-0.72 [-1.24, -0.14]1.49 [1.31, 1.65]31% [14%, 46%]88%100%+0.04+0.172026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.30 [1.07, 1.53]1.12-0.72 [-1.30, -0.12]1.49 [1.28, 1.67]31% [12%, 48%]88%100%+0.04+0.172026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC1.30 [1.08, 1.53]1.12-0.72 [-1.27, -0.01]1.49 [1.30, 1.67]31% [12%, 50%]88%100%+0.04+0.172026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC1.30 [1.08, 1.56]1.12-0.72 [-1.38, -0.08]1.49 [1.30, 1.69]31% [11%, 48%]88%100%+0.04+0.172026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC1.26 [0.92, 1.57]1.19-0.38 [-0.95, 0.22]1.50 [1.17, 1.75]38% [19%, 65%]77%96%+0.06+0.122026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC1.26 [0.79, 1.61]1.19-0.38 [-0.97, 0.29]1.50 [1.02, 1.78]38% [17%, 72%]77%96%+0.06+0.122026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC1.26 [0.83, 1.60]1.19-0.38 [-0.98, 0.28]1.50 [1.05, 1.78]38% [15%, 71%]77%96%+0.06+0.122026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC1.26 [0.76, 1.62]1.19-0.38 [-1.02, 0.27]1.50 [1.05, 1.79]38% [15%, 75%]77%96%+0.06+0.122026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC1.30 [1.08, 1.54]0.97-0.90 [-1.39, -0.34]1.52 [1.33, 1.70]42% [25%, 56%]81%100%+0.03+0.282026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC1.30 [1.03, 1.55]0.97-0.90 [-1.45, -0.33]1.52 [1.30, 1.72]42% [22%, 57%]81%100%+0.03+0.282026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC1.30 [1.04, 1.57]0.97-0.90 [-1.43, -0.21]1.52 [1.32, 1.72]42% [24%, 57%]81%100%+0.03+0.282026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC1.30 [1.04, 1.59]0.97-0.90 [-1.55, -0.30]1.52 [1.32, 1.75]42% [19%, 57%]81%100%+0.03+0.282026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC1.23 [0.85, 1.59]1.08-0.55 [-1.11, 0.01]1.49 [1.09, 1.81]54% [32%, 80%]81%92%+0.08+0.202026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC1.23 [0.69, 1.63]1.08-0.55 [-1.15, 0.05]1.49 [0.90, 1.84]54% [30%, 90%]81%92%+0.08+0.202026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC1.23 [0.71, 1.63]1.08-0.55 [-1.16, 0.07]1.49 [0.91, 1.83]54% [29%, 88%]81%92%+0.08+0.202026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC1.23 [0.69, 1.64]1.08-0.55 [-1.19, 0.06]1.49 [0.89, 1.85]54% [29%, 90%]81%92%+0.08+0.202026-08-05 → 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 4, 00Z bilinear tmax+10+50-5-102026-08-05: -4.98 °F2026-08-06: -5.63 °F2026-08-07: -0.15 °F2026-08-08: +0.78 °F2026-08-09: -1.23 °F2026-08-10: -5.58 °F2026-08-11: -9.13 °F2026-08-12: -8.04 °F2026-08-13: -6.79 °F2026-08-14: -6.38 °F2026-08-15: -4.41 °F2026-08-16: -4.44 °F2026-08-17: -7.56 °F2026-08-18: -2.65 °F2026-08-19: -1.78 °F2026-08-20: -3.28 °F2026-08-21: -2.82 °F2026-08-22: -2.57 °F2026-08-23: -9.88 °F2026-08-24: -7.59 °F2026-08-25: +0.34 °F2026-08-26: -6.43 °F2026-08-27: -5.4 °F2026-08-28: +2.18 °F2026-08-29: -6.01 °F2026-08-30: -5.87 °F2026-08-052026-08-30°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 (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-5.87
2026-08-29-6.01
2026-08-28+2.18
2026-08-27-5.40
2026-08-26-6.43
2026-08-25+0.34
2026-08-24-7.59
2026-08-23-9.88
2026-08-22-2.57
2026-08-21-2.82
2026-08-20-3.28
2026-08-19-1.78
2026-08-18-2.65
2026-08-17-7.56
2026-08-16-4.44
2026-08-15-4.41
2026-08-14-6.38
2026-08-13-6.79
2026-08-12-8.04
2026-08-11-9.13
2026-08-10-5.58
2026-08-09-1.23
2026-08-08+0.78
2026-08-07-0.15
2026-08-06-5.63
2026-08-05-4.98

Error distribution

Distribution of the signed daily error in °F for ECMWF AIFS Single at KSFO, lead day 4-10 to -9 °F: 2 days-9 to -8 °F: 1 day-8 to -7 °F: 2 days-7 to -6 °F: 4 days-6 to -5 °F: 4 days-5 to -4 °F: 3 days-4 to -3 °F: 1 day-3 to -2 °F: 3 days-2 to -1 °F: 2 days-1 to 0 °F: 1 day0 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| 5.19 · P90 |e| 7.82 °F-100+10 °Fn = 26 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
-10.00-9.002
-9.00-8.001
-8.00-7.002
-7.00-6.004
-6.00-5.004
-5.00-4.003
-4.00-3.001
-3.00-2.003
-2.00-1.002
-1.00+0.001
+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
2026-08264.69 -4.44

Availability

ModelScored period DaysCoverage
ECMWF AIFS Single2026-08-05 → 2026-08-30 26
ECMWF AIFS Single2026-08-05 → 2026-08-30 26
ECMWF AIFS Single2026-08-05 → 2026-08-30 26
ECMWF AIFS Single2026-08-05 → 2026-08-30 26

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 26 +0.12 [-0.49, 0.63] no
GraphCast (IFS init) 25 -0.49 [-0.74, -0.17] yes
ECMWF IFS HRES 20 -1.12 [-2.11, 0.37] no
Persistence (baseline) 26 +0.57 [-1.47, 1.93] no

Cite this page

ShortCastCheck, KSFO aifs_single lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSFO/model/aifs_single/lead/4/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSFO (San Francisco Intl), model aifs_single, lead day 4. 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/4/

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