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

Boston Logan · GraphCast (IFS init) · lead day 6

KBOS · graphcast_ifs · 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, 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
tmax00Zbilinear30d23 1 QC4.34 [3.35, 5.43]3.99-1.71 [-3.42, -0.26]4.97 [4.04, 5.81]13% [0%, 32%]26%35%+0.33+0.372026-08-07 → 2026-08-30
tmax00Zbilinear90d23 1 QC4.34 [3.33, 5.59]3.99-1.71 [-3.55, -0.26]4.97 [4.02, 5.95]13% [0%, 33%]26%35%+0.33+0.372026-08-07 → 2026-08-30
tmax00Zbilinear365d29 1 QC4.64 [3.45, 5.79]4.25-1.54 [-3.31, 0.18]5.51 [4.22, 6.80]10% [0%, 28%]21%38%+0.43+0.482026-01-07 → 2026-08-30
tmax00Zbilinearall29 1 QC4.64 [3.56, 5.87]4.25-1.54 [-3.17, -0.03]5.51 [4.22, 6.90]10% [0%, 28%]21%38%+0.43+0.482026-01-07 → 2026-08-30
tmax00Znearest30d23 1 QC4.29 [3.26, 5.41]3.95-1.72 [-3.48, -0.25]4.94 [3.99, 5.81]9% [0%, 21%]26%35%+0.34+0.372026-08-07 → 2026-08-30
tmax00Znearest90d23 1 QC4.29 [3.27, 5.62]3.95-1.72 [-3.62, -0.27]4.94 [3.97, 5.95]9% [0%, 22%]26%35%+0.34+0.372026-08-07 → 2026-08-30
tmax00Znearest365d29 1 QC4.53 [3.32, 5.68]4.17-1.48 [-3.25, 0.25]5.43 [4.15, 6.65]7% [0%, 19%]28%38%+0.44+0.492026-01-07 → 2026-08-30
tmax00Znearestall29 1 QC4.53 [3.45, 5.72]4.17-1.48 [-3.16, 0.02]5.43 [4.16, 6.75]7% [0%, 18%]28%38%+0.44+0.492026-01-07 → 2026-08-30
tmax12Zbilinear30d23 1 QC4.12 [3.24, 5.00]3.62-2.20 [-3.18, -1.43]4.66 [3.76, 5.44]4% [0%, 14%]26%35%+0.37+0.432026-08-07 → 2026-08-30
tmax12Zbilinear90d23 1 QC4.12 [3.21, 5.28]3.62-2.20 [-3.33, -1.42]4.66 [3.73, 5.61]4% [0%, 15%]26%35%+0.37+0.432026-08-07 → 2026-08-30
tmax12Zbilinear365d28 1 QC3.91 [3.07, 4.80]3.45-1.97 [-3.10, -0.98]4.46 [3.52, 5.23]7% [0%, 20%]29%36%+0.53+0.592026-01-07 → 2026-08-30
tmax12Zbilinearall28 1 QC3.91 [3.01, 4.81]3.45-1.97 [-2.97, -1.05]4.46 [3.43, 5.28]7% [0%, 20%]29%36%+0.53+0.592026-01-07 → 2026-08-30
tmax12Znearest30d23 1 QC4.10 [3.17, 5.00]3.60-2.18 [-3.19, -1.39]4.65 [3.71, 5.44]4% [0%, 14%]26%35%+0.37+0.432026-08-07 → 2026-08-30
tmax12Znearest90d23 1 QC4.10 [3.14, 5.26]3.60-2.18 [-3.35, -1.39]4.65 [3.65, 5.60]4% [0%, 15%]26%35%+0.37+0.432026-08-07 → 2026-08-30
tmax12Znearest365d28 1 QC3.90 [3.03, 4.79]3.43-1.94 [-3.12, -0.94]4.43 [3.44, 5.23]7% [0%, 20%]25%36%+0.53+0.592026-01-07 → 2026-08-30
tmax12Znearestall28 1 QC3.90 [2.98, 4.80]3.43-1.94 [-2.98, -0.99]4.43 [3.33, 5.25]7% [0%, 20%]25%36%+0.53+0.592026-01-07 → 2026-08-30
tmin00Zbilinear30d23 1 QC1.82 [1.37, 2.31]1.86+0.19 [-0.39, 0.82]2.12 [1.61, 2.58]26% [15%, 35%]48%91%+0.50+0.472026-08-07 → 2026-08-30
tmin00Zbilinear90d23 1 QC1.82 [1.31, 2.37]1.86+0.19 [-0.47, 0.95]2.12 [1.53, 2.66]26% [14%, 35%]48%91%+0.50+0.472026-08-07 → 2026-08-30
tmin00Zbilinear365d29 1 QC2.38 [1.47, 3.81]2.46+0.58 [-0.26, 1.85]3.31 [1.78, 5.15]28% [17%, 38%]45%79%+0.57+0.582026-01-07 → 2026-08-30
tmin00Zbilinearall29 1 QC2.38 [1.50, 3.91]2.46+0.58 [-0.39, 1.83]3.31 [1.74, 5.31]28% [15%, 38%]45%79%+0.57+0.582026-01-07 → 2026-08-30
tmin00Znearest30d23 1 QC1.71 [1.25, 2.20]1.79+0.45 [-0.10, 1.08]2.10 [1.53, 2.57]30% [18%, 42%]57%83%+0.53+0.492026-08-07 → 2026-08-30
tmin00Znearest90d23 1 QC1.71 [1.17, 2.25]1.79+0.45 [-0.17, 1.19]2.10 [1.42, 2.63]30% [14%, 43%]57%83%+0.53+0.492026-08-07 → 2026-08-30
tmin00Znearest365d29 1 QC2.33 [1.38, 3.88]2.41+0.86 [0.00, 2.17]3.35 [1.73, 5.29]28% [14%, 39%]52%72%+0.58+0.592026-01-07 → 2026-08-30
tmin00Znearestall29 1 QC2.33 [1.39, 4.03]2.41+0.86 [-0.09, 2.14]3.35 [1.72, 5.42]28% [12%, 39%]52%72%+0.58+0.592026-01-07 → 2026-08-30
tmin12Zbilinear30d23 1 QC1.92 [1.14, 2.68]1.90-0.10 [-0.78, 0.72]2.35 [1.60, 2.90]30% [4%, 60%]52%74%+0.48+0.462026-08-07 → 2026-08-30
tmin12Zbilinear90d23 1 QC1.92 [0.82, 2.77]1.90-0.10 [-0.80, 0.83]2.35 [1.19, 2.95]30% [0%, 69%]52%74%+0.48+0.462026-08-07 → 2026-08-30
tmin12Zbilinear365d28 1 QC2.50 [1.24, 4.01]2.55+0.33 [-0.78, 2.08]3.50 [1.73, 5.46]25% [0%, 54%]46%64%+0.56+0.572026-01-07 → 2026-08-30
tmin12Zbilinearall28 1 QC2.50 [1.37, 4.20]2.55+0.33 [-0.81, 2.08]3.50 [1.86, 5.64]25% [0%, 53%]46%64%+0.56+0.572026-01-07 → 2026-08-30
tmin12Znearest30d23 1 QC1.86 [1.02, 2.68]1.88+0.12 [-0.57, 0.94]2.33 [1.51, 2.93]39% [6%, 71%]52%74%+0.49+0.472026-08-07 → 2026-08-30
tmin12Znearest90d23 1 QC1.86 [0.68, 2.80]1.88+0.12 [-0.59, 1.06]2.33 [1.12, 2.97]39% [0%, 83%]52%74%+0.49+0.472026-08-07 → 2026-08-30
tmin12Znearest365d28 1 QC2.46 [1.11, 4.11]2.56+0.58 [-0.56, 2.36]3.53 [1.63, 5.57]32% [0%, 67%]46%68%+0.57+0.572026-01-07 → 2026-08-30
tmin12Znearestall28 1 QC2.46 [1.26, 4.28]2.56+0.58 [-0.57, 2.40]3.53 [1.76, 5.70]32% [0%, 66%]46%68%+0.57+0.572026-01-07 → 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 GraphCast (IFS init) at KBOS, lead day 6, 00Z bilinear tmax+10+50-5-102026-08-07: -3.61 °F2026-08-08: -6.87 °F2026-08-09: -0.97 °F2026-08-10: +0.6 °F2026-08-11: -6.73 °F2026-08-12: -2.4 °F2026-08-13: -1 °F2026-08-14: -6.15 °F2026-08-15: +2.62 °F2026-08-16: -1.45 °F2026-08-17: +4.03 °F2026-08-18: +1.99 °F2026-08-19: -7.9 °F2026-08-20: -4.31 °F2026-08-21: +3.53 °F2026-08-22: +8.49 °F2026-08-23: +4.74 °F2026-08-24: -6.62 °F2026-08-25: -6.37 °F2026-08-26: -1.45 °F2026-08-27: -6.17 °F2026-08-29: +4.18 °F2026-08-30: -7.63 °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
2026-08-30-7.63
2026-08-29+4.18
2026-08-28—
2026-08-27-6.17
2026-08-26-1.45
2026-08-25-6.37
2026-08-24-6.62
2026-08-23+4.74
2026-08-22+8.49
2026-08-21+3.53
2026-08-20-4.31
2026-08-19-7.90
2026-08-18+1.99
2026-08-17+4.03
2026-08-16-1.45
2026-08-15+2.62
2026-08-14-6.15
2026-08-13-1.00
2026-08-12-2.40
2026-08-11-6.73
2026-08-10+0.60
2026-08-09-0.97
2026-08-08-6.87
2026-08-07-3.61

Error distribution

Distribution of the signed daily error in °F for GraphCast (IFS init) at KBOS, 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: 1 day-10 to -8 °F: 0 days-8 to -6 °F: 8 days-6 to -4 °F: 2 days-4 to -2 °F: 4 days-2 to 0 °F: 4 days0 to 2 °F: 2 days2 to 4 °F: 3 days4 to 6 °F: 3 days6 to 8 °F: 0 days8 to 10 °F: 1 day10 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| 4.09 · P90 |e| 8.02 °F-200+20 °Fn = 29 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
-10.00-8.000
-8.00-6.008
-6.00-4.002
-4.00-2.004
-2.00+0.004
+0.00+2.002
+2.00+4.003
+4.00+6.003
+6.00+8.000
+8.00+10.001
+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
2026-08234.34 -1.71
2026-0165.80 -0.85

Availability

ModelScored period DaysCoverage
GraphCast (IFS init)2026-01-07 → 2026-08-30 29
GraphCast (IFS init)2026-01-07 → 2026-08-30 29
GraphCast (IFS init)2026-01-07 → 2026-08-30 28
GraphCast (IFS init)2026-01-07 → 2026-08-30 28

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 23 -0.34 [-1.50, 0.50] no
NCEP GFS 23 -0.21 [-1.72, 1.59] no
ECMWF IFS HRES 18 -0.19 [-3.51, 1.64] no
Persistence (baseline) 23 -2.18 [-3.74, 0.11] no

Cite this page

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

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