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

Boston Logan · GraphCast (IFS init) · lead day 8

KBOS · graphcast_ifs · 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, GRAP_v100, starting 2026-01-01 — 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
tmax00Zbilinear30d21 1 QC5.38 [3.24, 7.50]5.11-1.11 [-4.50, 1.62]6.56 [4.09, 8.45]5% [0%, 14%]19%33%+0.19+0.222026-08-09 → 2026-08-30
tmax00Zbilinear90d21 1 QC5.38 [2.90, 7.56]5.11-1.11 [-5.54, 1.64]6.56 [3.33, 8.68]5% [0%, 15%]19%33%+0.19+0.222026-08-09 → 2026-08-30
tmax00Zbilinear365d27 1 QC5.05 [3.19, 6.89]4.68-1.60 [-4.50, 1.08]6.19 [3.76, 7.90]7% [0%, 20%]22%33%+0.42+0.462026-01-09 → 2026-08-30
tmax00Zbilinearall27 1 QC5.05 [3.22, 7.02]4.68-1.60 [-4.62, 1.13]6.19 [3.91, 8.07]7% [0%, 20%]22%33%+0.42+0.462026-01-09 → 2026-08-30
tmax00Znearest30d21 1 QC5.35 [3.23, 7.50]5.11-1.09 [-4.50, 1.60]6.52 [4.02, 8.43]10% [0%, 18%]19%33%+0.20+0.222026-08-09 → 2026-08-30
tmax00Znearest90d21 1 QC5.35 [2.84, 7.54]5.11-1.09 [-5.56, 1.63]6.52 [3.20, 8.66]10% [0%, 17%]19%33%+0.20+0.222026-08-09 → 2026-08-30
tmax00Znearest365d27 1 QC5.01 [3.10, 6.86]4.66-1.54 [-4.44, 1.08]6.13 [3.65, 7.87]11% [0%, 20%]22%33%+0.42+0.462026-01-09 → 2026-08-30
tmax00Znearestall27 1 QC5.01 [3.16, 7.01]4.66-1.54 [-4.56, 1.13]6.13 [3.78, 8.06]11% [0%, 21%]22%33%+0.42+0.462026-01-09 → 2026-08-30
tmax12Zbilinear30d21 1 QC5.09 [4.06, 6.47]4.13-3.47 [-5.38, -2.15]6.14 [4.93, 7.78]14% [0%, 29%]24%29%+0.24+0.372026-08-09 → 2026-08-30
tmax12Zbilinear90d21 1 QC5.09 [4.12, 6.58]4.13-3.47 [-6.30, -1.93]6.14 [4.84, 8.29]14% [0%, 31%]24%29%+0.24+0.372026-08-09 → 2026-08-30
tmax12Zbilinear365d26 1 QC4.52 [3.09, 5.90]3.95-2.79 [-4.82, -0.80]5.62 [3.86, 7.17]15% [0%, 31%]23%38%+0.47+0.532026-01-09 → 2026-08-30
tmax12Zbilinearall26 1 QC4.52 [2.92, 6.00]3.95-2.79 [-4.96, -0.84]5.62 [3.56, 7.51]15% [0%, 29%]23%38%+0.47+0.532026-01-09 → 2026-08-30
tmax12Znearest30d21 1 QC5.06 [4.06, 6.43]4.13-3.45 [-5.34, -2.18]6.14 [4.93, 7.81]14% [0%, 29%]24%29%+0.24+0.372026-08-09 → 2026-08-30
tmax12Znearest90d21 1 QC5.06 [4.11, 6.52]4.13-3.45 [-6.17, -1.95]6.14 [4.88, 8.33]14% [0%, 31%]24%29%+0.24+0.372026-08-09 → 2026-08-30
tmax12Znearest365d26 1 QC4.51 [3.17, 5.80]4.01-2.72 [-4.72, -0.69]5.62 [3.94, 7.17]15% [0%, 31%]23%38%+0.47+0.532026-01-09 → 2026-08-30
tmax12Znearestall26 1 QC4.51 [2.96, 5.92]4.01-2.72 [-4.89, -0.65]5.62 [3.66, 7.52]15% [0%, 29%]23%38%+0.47+0.532026-01-09 → 2026-08-30
tmin00Zbilinear30d21 1 QC2.77 [2.07, 3.77]2.73-0.27 [-2.46, 1.06]3.55 [2.48, 4.71]19% [0%, 30%]43%67%+0.31+0.252026-08-09 → 2026-08-30
tmin00Zbilinear90d21 1 QC2.77 [1.97, 4.12]2.73-0.27 [-3.63, 1.29]3.55 [2.32, 4.82]19% [0%, 31%]43%67%+0.31+0.252026-08-09 → 2026-08-30
tmin00Zbilinear365d27 1 QC2.76 [2.04, 3.70]2.67-0.65 [-2.77, 0.82]3.64 [2.58, 4.65]22% [6%, 38%]44%70%+0.56+0.582026-01-09 → 2026-08-30
tmin00Zbilinearall27 1 QC2.76 [2.08, 3.69]2.67-0.65 [-2.98, 0.73]3.64 [2.58, 4.66]22% [6%, 37%]44%70%+0.56+0.582026-01-09 → 2026-08-30
tmin00Znearest30d21 1 QC2.69 [1.99, 3.60]2.69-0.04 [-2.25, 1.27]3.49 [2.48, 4.54]24% [4%, 39%]48%62%+0.33+0.262026-08-09 → 2026-08-30
tmin00Znearest90d21 1 QC2.69 [1.93, 3.88]2.69-0.04 [-3.40, 1.47]3.49 [2.35, 4.67]24% [0%, 40%]48%62%+0.33+0.262026-08-09 → 2026-08-30
tmin00Znearest365d27 1 QC2.62 [1.91, 3.47]2.63-0.37 [-2.47, 1.06]3.54 [2.57, 4.46]26% [7%, 43%]52%67%+0.58+0.592026-01-09 → 2026-08-30
tmin00Znearestall27 1 QC2.62 [1.95, 3.42]2.63-0.37 [-2.61, 0.99]3.54 [2.59, 4.48]26% [6%, 43%]52%67%+0.58+0.592026-01-09 → 2026-08-30
tmin12Zbilinear30d21 1 QC2.50 [1.95, 3.12]2.41-0.55 [-1.77, 0.62]2.90 [2.31, 3.49]19% [4%, 33%]43%67%+0.37+0.342026-08-09 → 2026-08-30
tmin12Zbilinear90d21 1 QC2.50 [1.93, 3.17]2.41-0.55 [-2.24, 0.87]2.90 [2.32, 3.55]19% [0%, 36%]43%67%+0.37+0.342026-08-09 → 2026-08-30
tmin12Zbilinear365d26 1 QC2.93 [2.10, 4.23]2.93+0.46 [-1.21, 3.07]3.52 [2.49, 4.95]15% [0%, 29%]38%58%+0.50+0.512026-01-09 → 2026-08-30
tmin12Zbilinearall26 1 QC2.93 [2.07, 4.33]2.93+0.46 [-1.37, 3.48]3.52 [2.41, 5.02]15% [0%, 29%]38%58%+0.50+0.512026-01-09 → 2026-08-30
tmin12Znearest30d21 1 QC2.39 [1.77, 3.05]2.35-0.27 [-1.43, 0.82]2.78 [2.19, 3.34]14% [0%, 30%]38%71%+0.40+0.362026-08-09 → 2026-08-30
tmin12Znearest90d21 1 QC2.39 [1.75, 3.10]2.35-0.27 [-1.72, 1.03]2.78 [2.20, 3.46]14% [0%, 29%]38%71%+0.40+0.362026-08-09 → 2026-08-30
tmin12Znearest365d26 1 QC2.91 [1.96, 4.48]2.90+0.76 [-0.91, 3.38]3.55 [2.40, 5.17]12% [0%, 25%]35%62%+0.51+0.522026-01-09 → 2026-08-30
tmin12Znearestall26 1 QC2.91 [1.92, 4.62]2.90+0.76 [-1.07, 3.80]3.55 [2.30, 5.27]12% [0%, 25%]35%62%+0.51+0.522026-01-09 → 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 GraphCast (IFS init) at KBOS, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: -1.46 °F2026-08-10: +1.67 °F2026-08-11: -2.32 °F2026-08-12: -5.69 °F2026-08-13: -3.98 °F2026-08-14: -2.06 °F2026-08-15: -1.13 °F2026-08-16: -3.97 °F2026-08-17: +7.52 °F2026-08-18: +3.17 °F2026-08-19: -10.28 °F2026-08-20: +3.17 °F2026-08-21: +5.99 °F2026-08-22: +11.31 °F2026-08-23: +11.89 °F2026-08-24: -9.95 °F2026-08-25: -7.79 °F2026-08-26: +0.1 °F2026-08-27: -4.99 °F2026-08-29: -2.4 °F2026-08-30: -12.04 °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
2026-08-30-12.04
2026-08-29-2.40
2026-08-28—
2026-08-27-4.99
2026-08-26+0.10
2026-08-25-7.79
2026-08-24-9.95
2026-08-23+11.89
2026-08-22+11.31
2026-08-21+5.99
2026-08-20+3.17
2026-08-19-10.28
2026-08-18+3.17
2026-08-17+7.52
2026-08-16-3.97
2026-08-15-1.13
2026-08-14-2.06
2026-08-13-3.98
2026-08-12-5.69
2026-08-11-2.32
2026-08-10+1.67
2026-08-09-1.46

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KBOS, 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: 1 day-12 to -10 °F: 1 day-10 to -8 °F: 2 days-8 to -6 °F: 1 day-6 to -4 °F: 4 days-4 to -2 °F: 6 days-2 to 0 °F: 2 days0 to 2 °F: 4 days2 to 4 °F: 2 days4 to 6 °F: 1 day6 to 8 °F: 1 day8 to 10 °F: 0 days10 to 12 °F: 2 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.98 · P90 |e| 10.69 °F-200+20 °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
-20.00-18.000
-18.00-16.000
-16.00-14.000
-14.00-12.001
-12.00-10.001
-10.00-8.002
-8.00-6.001
-6.00-4.004
-4.00-2.006
-2.00+0.002
+0.00+2.004
+2.00+4.002
+4.00+6.001
+6.00+8.001
+8.00+10.000
+10.00+12.002
+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
2026-08215.38 -1.11
2026-0163.91 -3.32

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-09 → 2026-08-30 27
GraphCast (IFS init)2026-01-09 → 2026-08-30 27
GraphCast (IFS init)2026-01-09 → 2026-08-30 26
GraphCast (IFS init)2026-01-09 → 2026-08-30 26

Compared with other models

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

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 21 -0.06 [-2.36, 1.65] no
NCEP GFS 21 -1.07 [-2.74, 0.59] no
ECMWF IFS HRES 16 -0.46 [-7.02, 2.57] no
Persistence (baseline) 21 -1.29 [-3.79, 1.31] no

Cite this page

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

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KBOS (Boston Logan), model graphcast_ifs, 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/KBOS/model/graphcast_ifs/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