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 · NCEP GFS · lead day 8

KBOS · gfs · 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, 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
tmax00Zbilinear30d21 1 QC6.45 [4.96, 8.10]6.39-1.15 [-3.70, 1.47]7.42 [6.03, 8.64]0% [0%, 0%]10%24%+0.03+0.032026-08-09 → 2026-08-30
tmax00Zbilinear90d21 1 QC6.45 [4.83, 8.29]6.39-1.15 [-3.67, 1.65]7.42 [5.82, 8.68]0% [0%, 0%]10%24%+0.03+0.032026-08-09 → 2026-08-30
tmax00Zbilinear365d21 1 QC6.45 [4.68, 8.29]6.39-1.15 [-3.87, 2.00]7.42 [5.66, 8.72]0% [0%, 0%]10%24%+0.03+0.032026-08-09 → 2026-08-30
tmax00Zbilinearall21 1 QC6.45 [4.77, 8.53]6.39-1.15 [-3.87, 1.61]7.42 [5.79, 8.84]0% [0%, 0%]10%24%+0.03+0.032026-08-09 → 2026-08-30
tmax00Znearest30d21 1 QC6.62 [4.68, 8.58]6.54-1.36 [-4.22, 1.58]7.64 [5.93, 9.00]5% [0%, 17%]19%19%+0.01+0.002026-08-09 → 2026-08-30
tmax00Znearest90d21 1 QC6.62 [4.64, 8.83]6.54-1.36 [-4.24, 1.79]7.64 [5.72, 9.15]5% [0%, 20%]19%19%+0.01+0.002026-08-09 → 2026-08-30
tmax00Znearest365d21 1 QC6.62 [4.28, 8.87]6.54-1.36 [-4.36, 2.02]7.64 [5.38, 9.17]5% [0%, 18%]19%19%+0.01+0.002026-08-09 → 2026-08-30
tmax00Znearestall21 1 QC6.62 [4.51, 9.07]6.54-1.36 [-4.56, 1.65]7.64 [5.61, 9.33]5% [0%, 19%]19%19%+0.01+0.002026-08-09 → 2026-08-30
tmax12Zbilinear30d21 1 QC6.86 [5.50, 8.35]6.54-0.99 [-5.23, 2.18]8.25 [6.68, 9.66]5% [0%, 13%]14%29%-0.03+0.002026-08-09 → 2026-08-30
tmax12Zbilinear90d21 1 QC6.86 [5.47, 8.41]6.54-0.99 [-6.21, 2.60]8.25 [6.56, 9.71]5% [0%, 14%]14%29%-0.03+0.002026-08-09 → 2026-08-30
tmax12Zbilinear365d21 1 QC6.86 [5.40, 8.43]6.54-0.99 [-6.33, 2.65]8.25 [6.46, 9.75]5% [0%, 15%]14%29%-0.03+0.002026-08-09 → 2026-08-30
tmax12Zbilinearall21 1 QC6.86 [5.43, 8.57]6.54-0.99 [-7.29, 2.51]8.25 [6.55, 9.84]5% [0%, 14%]14%29%-0.03+0.002026-08-09 → 2026-08-30
tmax12Znearest30d21 1 QC6.59 [5.26, 8.10]6.32-1.26 [-5.01, 1.72]8.03 [6.24, 9.58]14% [0%, 29%]14%24%+0.01+0.042026-08-09 → 2026-08-30
tmax12Znearest90d21 1 QC6.59 [5.00, 8.23]6.32-1.26 [-5.61, 2.03]8.03 [5.98, 9.63]14% [0%, 33%]14%24%+0.01+0.042026-08-09 → 2026-08-30
tmax12Znearest365d21 1 QC6.59 [4.87, 8.27]6.32-1.26 [-6.03, 2.19]8.03 [5.93, 9.82]14% [0%, 33%]14%24%+0.01+0.042026-08-09 → 2026-08-30
tmax12Znearestall21 1 QC6.59 [4.85, 8.42]6.32-1.26 [-6.54, 1.91]8.03 [5.98, 9.96]14% [0%, 33%]14%24%+0.01+0.042026-08-09 → 2026-08-30
tmin00Zbilinear30d21 1 QC2.55 [1.67, 3.85]2.56-0.52 [-1.77, 0.78]3.11 [2.15, 4.34]29% [10%, 48%]43%62%+0.36+0.302026-08-09 → 2026-08-30
tmin00Zbilinear90d21 1 QC2.55 [1.51, 4.57]2.56-0.52 [-1.96, 0.90]3.11 [1.88, 4.90]29% [0%, 50%]43%62%+0.36+0.302026-08-09 → 2026-08-30
tmin00Zbilinear365d21 1 QC2.55 [1.36, 4.74]2.56-0.52 [-1.90, 0.96]3.11 [1.79, 4.94]29% [0%, 50%]43%62%+0.36+0.302026-08-09 → 2026-08-30
tmin00Zbilinearall21 1 QC2.55 [1.52, 4.94]2.56-0.52 [-1.96, 0.93]3.11 [1.94, 5.13]29% [0%, 50%]43%62%+0.36+0.302026-08-09 → 2026-08-30
tmin00Znearest30d21 1 QC2.45 [1.60, 3.72]2.45-0.04 [-1.30, 1.30]2.98 [2.09, 4.15]33% [11%, 57%]38%62%+0.39+0.332026-08-09 → 2026-08-30
tmin00Znearest90d21 1 QC2.45 [1.44, 4.35]2.45-0.04 [-1.49, 1.42]2.98 [1.94, 4.65]33% [0%, 64%]38%62%+0.39+0.332026-08-09 → 2026-08-30
tmin00Znearest365d21 1 QC2.45 [1.40, 4.52]2.45-0.04 [-1.39, 1.49]2.98 [1.93, 4.69]33% [0%, 62%]38%62%+0.39+0.332026-08-09 → 2026-08-30
tmin00Znearestall21 1 QC2.45 [1.48, 4.70]2.45-0.04 [-1.47, 1.43]2.98 [1.97, 4.84]33% [0%, 60%]38%62%+0.39+0.332026-08-09 → 2026-08-30
tmin12Zbilinear30d21 1 QC2.66 [1.96, 3.58]2.63-0.21 [-1.55, 1.34]3.45 [2.29, 4.48]29% [0%, 42%]48%71%+0.33+0.282026-08-09 → 2026-08-30
tmin12Zbilinear90d21 1 QC2.66 [1.91, 3.80]2.63-0.21 [-1.67, 1.47]3.45 [2.22, 4.66]29% [0%, 43%]48%71%+0.33+0.282026-08-09 → 2026-08-30
tmin12Zbilinear365d21 1 QC2.66 [1.87, 3.74]2.63-0.21 [-1.67, 1.53]3.45 [2.12, 4.57]29% [0%, 43%]48%71%+0.33+0.282026-08-09 → 2026-08-30
tmin12Zbilinearall21 1 QC2.66 [1.91, 3.79]2.63-0.21 [-1.67, 1.70]3.45 [2.18, 4.63]29% [0%, 43%]48%71%+0.33+0.282026-08-09 → 2026-08-30
tmin12Znearest30d21 1 QC2.47 [1.75, 3.41]2.49+0.32 [-0.99, 1.73]3.32 [2.18, 4.26]29% [0%, 52%]57%76%+0.38+0.322026-08-09 → 2026-08-30
tmin12Znearest90d21 1 QC2.47 [1.72, 3.60]2.49+0.32 [-1.16, 1.92]3.32 [2.08, 4.47]29% [0%, 56%]57%76%+0.38+0.322026-08-09 → 2026-08-30
tmin12Znearest365d21 1 QC2.47 [1.70, 3.50]2.49+0.32 [-1.16, 2.00]3.32 [2.03, 4.32]29% [0%, 57%]57%76%+0.38+0.322026-08-09 → 2026-08-30
tmin12Znearestall21 1 QC2.47 [1.72, 3.54]2.49+0.32 [-1.14, 2.12]3.32 [2.03, 4.46]29% [0%, 55%]57%76%+0.38+0.322026-08-09 → 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 NCEP GFS at KBOS, lead day 8, 00Z bilinear tmax+20+100-10-202026-08-09: +5.91 °F2026-08-10: +1.43 °F2026-08-11: -3.09 °F2026-08-12: -9.28 °F2026-08-13: -13.1 °F2026-08-14: +2.22 °F2026-08-15: +1.38 °F2026-08-16: -3.65 °F2026-08-17: +6.67 °F2026-08-18: -3.61 °F2026-08-19: -7.51 °F2026-08-20: +2.1 °F2026-08-21: +11.23 °F2026-08-22: +2.51 °F2026-08-23: +13.63 °F2026-08-24: -8.81 °F2026-08-25: -6.54 °F2026-08-26: -7.62 °F2026-08-27: -6.28 °F2026-08-29: +8.53 °F2026-08-30: -10.24 °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
2026-08-30-10.24
2026-08-29+8.53
2026-08-28—
2026-08-27-6.28
2026-08-26-7.62
2026-08-25-6.54
2026-08-24-8.81
2026-08-23+13.63
2026-08-22+2.51
2026-08-21+11.23
2026-08-20+2.10
2026-08-19-7.51
2026-08-18-3.61
2026-08-17+6.67
2026-08-16-3.65
2026-08-15+1.38
2026-08-14+2.22
2026-08-13-13.10
2026-08-12-9.28
2026-08-11-3.09
2026-08-10+1.43
2026-08-09+5.91

Error distribution

Distribution of the signed daily error in °F for NCEP GFS 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: 4 days-6 to -4 °F: 0 days-4 to -2 °F: 3 days-2 to 0 °F: 0 days0 to 2 °F: 2 days2 to 4 °F: 3 days4 to 6 °F: 1 day6 to 8 °F: 1 day8 to 10 °F: 1 day10 to 12 °F: 1 day12 to 14 °F: 1 day14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 6.54 · P90 |e| 11.23 °F-200+20 °Fn = 21 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
-8.00-6.004
-6.00-4.000
-4.00-2.003
-2.00+0.000
+0.00+2.002
+2.00+4.003
+4.00+6.001
+6.00+8.001
+8.00+10.001
+10.00+12.001
+12.00+14.001
+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
2026-08216.45 -1.15

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-09 → 2026-08-30 21
NCEP GFS2026-08-09 → 2026-08-30 21
NCEP GFS2026-08-09 → 2026-08-30 21
NCEP GFS2026-08-09 → 2026-08-30 21

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 21 +1.01 [-0.37, 2.29] no
GraphCast (IFS init) 21 +1.07 [-0.59, 2.74] no
ECMWF IFS HRES 16 +0.11 [-5.05, 3.18] no
Persistence (baseline) 21 -0.22 [-3.00, 2.52] no

Cite this page

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

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