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 9

KBOS · gfs · lead 9

Target day = initialization date + 9 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
tmax00Zbilinear30d20 1 QC7.15 [5.93, 9.11]7.00-1.85 [-6.62, 1.64]8.81 [7.12, 11.18]5% [0%, 20%]10%25%+0.10+0.112026-08-10 → 2026-08-30
tmax00Zbilinear90d20 1 QC7.15 [5.85, 9.57]7.00-1.85 [-7.64, 2.25]8.81 [6.91, 11.79]5% [0%, 25%]10%25%+0.10+0.112026-08-10 → 2026-08-30
tmax00Zbilinear365d20 1 QC7.15 [5.71, 9.66]7.00-1.85 [-8.13, 2.44]8.81 [6.74, 11.79]5% [0%, 25%]10%25%+0.10+0.112026-08-10 → 2026-08-30
tmax00Zbilinearall20 1 QC7.15 [5.88, 9.62]7.00-1.85 [-8.13, 2.43]8.81 [6.98, 11.82]5% [0%, 25%]10%25%+0.10+0.112026-08-10 → 2026-08-30
tmax00Znearest30d20 1 QC7.29 [6.00, 9.30]7.13-2.09 [-6.90, 1.26]8.82 [7.10, 11.26]5% [0%, 13%]20%20%+0.08+0.092026-08-10 → 2026-08-30
tmax00Znearest90d20 1 QC7.29 [5.87, 9.78]7.13-2.09 [-8.15, 1.90]8.82 [6.92, 11.64]5% [0%, 13%]20%20%+0.08+0.092026-08-10 → 2026-08-30
tmax00Znearest365d20 1 QC7.29 [5.72, 9.81]7.13-2.09 [-8.87, 2.22]8.82 [6.72, 11.65]5% [0%, 14%]20%20%+0.08+0.092026-08-10 → 2026-08-30
tmax00Znearestall20 1 QC7.29 [5.97, 9.85]7.13-2.09 [-8.87, 2.22]8.82 [6.96, 11.81]5% [0%, 14%]20%20%+0.08+0.092026-08-10 → 2026-08-30
tmax12Zbilinear30d20 1 QC8.21 [5.44, 11.28]8.07+0.68 [-3.62, 5.32]10.43 [6.42, 13.72]5% [0%, 13%]10%15%-0.03-0.032026-08-10 → 2026-08-30
tmax12Zbilinear90d20 1 QC8.21 [5.12, 11.57]8.07+0.68 [-4.04, 5.13]10.43 [6.14, 13.89]5% [0%, 14%]10%15%-0.03-0.032026-08-10 → 2026-08-30
tmax12Zbilinear365d20 1 QC8.21 [5.22, 11.88]8.07+0.68 [-4.07, 5.89]10.43 [6.00, 14.27]5% [0%, 14%]10%15%-0.03-0.032026-08-10 → 2026-08-30
tmax12Zbilinearall20 1 QC8.21 [4.73, 11.81]8.07+0.68 [-4.02, 5.53]10.43 [5.22, 14.20]5% [0%, 14%]10%15%-0.03-0.032026-08-10 → 2026-08-30
tmax12Znearest30d20 1 QC8.37 [5.36, 11.43]8.35+0.11 [-4.27, 4.75]10.56 [6.68, 13.70]5% [0%, 13%]15%25%-0.05-0.062026-08-10 → 2026-08-30
tmax12Znearest90d20 1 QC8.37 [4.97, 11.71]8.35+0.11 [-4.69, 4.78]10.56 [6.32, 13.82]5% [0%, 14%]15%25%-0.05-0.062026-08-10 → 2026-08-30
tmax12Znearest365d20 1 QC8.37 [5.10, 12.11]8.35+0.11 [-4.79, 5.49]10.56 [6.41, 14.21]5% [0%, 14%]15%25%-0.05-0.062026-08-10 → 2026-08-30
tmax12Znearestall20 1 QC8.37 [4.67, 12.01]8.35+0.11 [-4.66, 5.28]10.56 [5.66, 14.12]5% [0%, 14%]15%25%-0.05-0.062026-08-10 → 2026-08-30
tmin00Zbilinear30d20 1 QC3.22 [2.37, 3.94]3.03-1.48 [-2.88, -0.00]3.92 [3.00, 4.50]10% [0%, 25%]40%65%+0.20+0.212026-08-10 → 2026-08-30
tmin00Zbilinear90d20 1 QC3.22 [2.16, 4.10]3.03-1.48 [-3.00, 0.23]3.92 [2.59, 4.61]10% [0%, 30%]40%65%+0.20+0.212026-08-10 → 2026-08-30
tmin00Zbilinear365d20 1 QC3.22 [2.15, 4.11]3.03-1.48 [-3.02, 0.22]3.92 [2.62, 4.59]10% [0%, 29%]40%65%+0.20+0.212026-08-10 → 2026-08-30
tmin00Zbilinearall20 1 QC3.22 [1.86, 4.14]3.03-1.48 [-2.97, 0.29]3.92 [2.28, 4.60]10% [0%, 33%]40%65%+0.20+0.212026-08-10 → 2026-08-30
tmin00Znearest30d20 1 QC2.89 [1.72, 3.67]2.85-1.04 [-2.33, 0.26]3.48 [2.37, 4.07]15% [0%, 41%]35%65%+0.28+0.262026-08-10 → 2026-08-30
tmin00Znearest90d20 1 QC2.89 [1.40, 3.80]2.85-1.04 [-2.44, 0.46]3.48 [1.89, 4.15]15% [0%, 50%]35%65%+0.28+0.262026-08-10 → 2026-08-30
tmin00Znearest365d20 1 QC2.89 [1.31, 3.79]2.85-1.04 [-2.44, 0.38]3.48 [1.73, 4.16]15% [0%, 51%]35%65%+0.28+0.262026-08-10 → 2026-08-30
tmin00Znearestall20 1 QC2.89 [1.07, 3.82]2.85-1.04 [-2.44, 0.42]3.48 [1.60, 4.16]15% [0%, 64%]35%65%+0.28+0.262026-08-10 → 2026-08-30
tmin12Zbilinear30d20 1 QC3.75 [2.83, 4.38]3.39-1.17 [-2.83, 0.69]4.45 [3.46, 5.11]10% [0%, 17%]35%45%+0.06+0.122026-08-10 → 2026-08-30
tmin12Zbilinear90d20 1 QC3.75 [2.58, 4.37]3.39-1.17 [-2.95, 0.92]4.45 [3.22, 5.14]10% [0%, 16%]35%45%+0.06+0.122026-08-10 → 2026-08-30
tmin12Zbilinear365d20 1 QC3.75 [2.70, 4.43]3.39-1.17 [-2.87, 0.99]4.45 [3.36, 5.23]10% [0%, 17%]35%45%+0.06+0.122026-08-10 → 2026-08-30
tmin12Zbilinearall20 1 QC3.75 [2.61, 4.39]3.39-1.17 [-2.95, 0.97]4.45 [3.19, 5.19]10% [0%, 16%]35%45%+0.06+0.122026-08-10 → 2026-08-30
tmin12Znearest30d20 1 QC3.15 [2.27, 3.76]2.92-0.60 [-2.17, 1.14]3.82 [2.72, 4.56]15% [0%, 24%]40%50%+0.21+0.242026-08-10 → 2026-08-30
tmin12Znearest90d20 1 QC3.15 [2.02, 3.77]2.92-0.60 [-2.35, 1.36]3.82 [2.48, 4.60]15% [0%, 25%]40%50%+0.21+0.242026-08-10 → 2026-08-30
tmin12Znearest365d20 1 QC3.15 [2.10, 3.83]2.92-0.60 [-2.26, 1.39]3.82 [2.59, 4.67]15% [0%, 29%]40%50%+0.21+0.242026-08-10 → 2026-08-30
tmin12Znearestall20 1 QC3.15 [1.97, 3.80]2.92-0.60 [-2.26, 1.40]3.82 [2.48, 4.61]15% [0%, 27%]40%50%+0.21+0.242026-08-10 → 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 9, 00Z bilinear tmax+20+100-10-202026-08-10: +6.8 °F2026-08-11: +2.17 °F2026-08-12: -10.55 °F2026-08-13: -12.59 °F2026-08-14: -5.13 °F2026-08-15: +8.04 °F2026-08-16: -3.1 °F2026-08-17: -2.52 °F2026-08-18: +4.24 °F2026-08-19: -10.74 °F2026-08-20: -2.06 °F2026-08-21: +6.87 °F2026-08-22: +15.57 °F2026-08-23: +4.4 °F2026-08-24: -1.54 °F2026-08-25: +4.5 °F2026-08-26: -7.18 °F2026-08-27: -18.01 °F2026-08-29: +0.4 °F2026-08-30: -16.67 °F2026-08-102026-08-30°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 (21 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-16.67
2026-08-29+0.40
2026-08-28—
2026-08-27-18.01
2026-08-26-7.18
2026-08-25+4.50
2026-08-24-1.54
2026-08-23+4.40
2026-08-22+15.57
2026-08-21+6.87
2026-08-20-2.06
2026-08-19-10.74
2026-08-18+4.24
2026-08-17-2.52
2026-08-16-3.10
2026-08-15+8.04
2026-08-14-5.13
2026-08-13-12.59
2026-08-12-10.55
2026-08-11+2.17
2026-08-10+6.80

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KBOS, lead day 9-20 to -18 °F: 1 day-18 to -16 °F: 1 day-16 to -14 °F: 0 days-14 to -12 °F: 1 day-12 to -10 °F: 2 days-10 to -8 °F: 0 days-8 to -6 °F: 1 day-6 to -4 °F: 1 day-4 to -2 °F: 3 days-2 to 0 °F: 1 day0 to 2 °F: 1 day2 to 4 °F: 1 day4 to 6 °F: 3 days6 to 8 °F: 2 days8 to 10 °F: 1 day10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 1 day16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 5.97 · P90 |e| 15.68 °F-200+20 °Fn = 20 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
-20.00-18.001
-18.00-16.001
-16.00-14.000
-14.00-12.001
-12.00-10.002
-10.00-8.000
-8.00-6.001
-6.00-4.001
-4.00-2.003
-2.00+0.001
+0.00+2.001
+2.00+4.001
+4.00+6.003
+6.00+8.002
+8.00+10.001
+10.00+12.000
+12.00+14.000
+14.00+16.001
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08207.15 -1.85

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-10 → 2026-08-30 20
NCEP GFS2026-08-10 → 2026-08-30 20
NCEP GFS2026-08-10 → 2026-08-30 20
NCEP GFS2026-08-10 → 2026-08-30 20

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 20 +0.89 [-0.86, 3.83] no
GraphCast (IFS init) 20 +1.77 [0.05, 4.33] yes
ECMWF IFS HRES 15 +2.65 [0.60, 6.10] yes
Persistence (baseline) 20 -0.80 [-3.96, 3.80] no

Cite this page

ShortCastCheck, KBOS gfs lead 9, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KBOS/model/gfs/lead/9/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KBOS (Boston Logan), model gfs, lead day 9. 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/9/

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