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 6

KBOS · gfs · 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, 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
tmax00Zbilinear30d23 1 QC4.55 [3.47, 5.38]4.58-0.64 [-1.98, 0.98]5.90 [3.93, 7.22]4% [0%, 12%]17%43%+0.30+0.272026-08-07 → 2026-08-30
tmax00Zbilinear90d23 1 QC4.55 [3.34, 5.42]4.58-0.64 [-2.02, 1.33]5.90 [3.87, 7.32]4% [0%, 13%]17%43%+0.30+0.272026-08-07 → 2026-08-30
tmax00Zbilinear365d23 1 QC4.55 [3.32, 5.35]4.58-0.64 [-2.02, 1.24]5.90 [3.80, 7.23]4% [0%, 12%]17%43%+0.30+0.272026-08-07 → 2026-08-30
tmax00Zbilinearall23 1 QC4.55 [3.16, 5.38]4.58-0.64 [-2.00, 1.23]5.90 [3.64, 7.34]4% [0%, 14%]17%43%+0.30+0.272026-08-07 → 2026-08-30
tmax00Znearest30d23 1 QC4.50 [3.33, 5.34]4.52-1.43 [-2.54, 0.18]5.84 [4.04, 7.00]13% [5%, 25%]22%39%+0.31+0.282026-08-07 → 2026-08-30
tmax00Znearest90d23 1 QC4.50 [3.16, 5.37]4.52-1.43 [-2.48, 0.57]5.84 [3.85, 7.08]13% [4%, 27%]22%39%+0.31+0.282026-08-07 → 2026-08-30
tmax00Znearest365d23 1 QC4.50 [3.16, 5.37]4.52-1.43 [-2.50, 0.38]5.84 [3.88, 7.04]13% [0%, 25%]22%39%+0.31+0.282026-08-07 → 2026-08-30
tmax00Znearestall23 1 QC4.50 [2.94, 5.44]4.52-1.43 [-2.48, 0.32]5.84 [3.60, 7.09]13% [0%, 30%]22%39%+0.31+0.282026-08-07 → 2026-08-30
tmax12Zbilinear30d23 1 QC3.94 [2.45, 5.30]4.29-1.20 [-3.00, 1.16]5.49 [2.92, 7.03]22% [9%, 33%]35%57%+0.40+0.322026-08-07 → 2026-08-30
tmax12Zbilinear90d23 1 QC3.94 [2.27, 5.29]4.29-1.20 [-3.02, 1.81]5.49 [2.48, 6.96]22% [7%, 33%]35%57%+0.40+0.322026-08-07 → 2026-08-30
tmax12Zbilinear365d23 1 QC3.94 [2.20, 5.42]4.29-1.20 [-3.25, 1.43]5.49 [2.37, 7.20]22% [4%, 35%]35%57%+0.40+0.322026-08-07 → 2026-08-30
tmax12Zbilinearall23 1 QC3.94 [2.24, 5.48]4.29-1.20 [-3.27, 1.68]5.49 [2.37, 7.31]22% [0%, 35%]35%57%+0.40+0.322026-08-07 → 2026-08-30
tmax12Znearest30d23 1 QC3.84 [2.04, 5.19]4.23-1.73 [-3.45, 0.50]5.68 [2.47, 7.11]26% [9%, 42%]39%57%+0.41+0.332026-08-07 → 2026-08-30
tmax12Znearest90d23 1 QC3.84 [1.83, 5.15]4.23-1.73 [-3.49, 1.19]5.68 [2.14, 7.01]26% [8%, 42%]39%57%+0.41+0.332026-08-07 → 2026-08-30
tmax12Znearest365d23 1 QC3.84 [1.84, 5.23]4.23-1.73 [-3.53, 0.76]5.68 [2.20, 7.08]26% [5%, 43%]39%57%+0.41+0.332026-08-07 → 2026-08-30
tmax12Znearestall23 1 QC3.84 [1.83, 5.38]4.23-1.73 [-3.67, 0.93]5.68 [2.12, 7.15]26% [0%, 43%]39%57%+0.41+0.332026-08-07 → 2026-08-30
tmin00Zbilinear30d23 1 QC2.36 [1.65, 3.12]2.26-0.52 [-1.49, 0.51]2.93 [1.99, 3.74]26% [12%, 41%]57%70%+0.35+0.362026-08-07 → 2026-08-30
tmin00Zbilinear90d23 1 QC2.36 [1.64, 3.15]2.26-0.52 [-1.50, 0.71]2.93 [1.86, 3.74]26% [11%, 44%]57%70%+0.35+0.362026-08-07 → 2026-08-30
tmin00Zbilinear365d23 1 QC2.36 [1.56, 3.21]2.26-0.52 [-1.67, 0.81]2.93 [1.78, 3.81]26% [11%, 44%]57%70%+0.35+0.362026-08-07 → 2026-08-30
tmin00Zbilinearall23 1 QC2.36 [1.52, 3.24]2.26-0.52 [-1.69, 0.64]2.93 [1.75, 3.79]26% [9%, 44%]57%70%+0.35+0.362026-08-07 → 2026-08-30
tmin00Znearest30d23 1 QC2.21 [1.46, 3.01]2.21-0.07 [-1.05, 0.87]2.77 [1.79, 3.53]26% [4%, 46%]61%78%+0.40+0.372026-08-07 → 2026-08-30
tmin00Znearest90d23 1 QC2.21 [1.41, 3.08]2.21-0.07 [-1.06, 1.04]2.77 [1.63, 3.57]26% [0%, 50%]61%78%+0.40+0.372026-08-07 → 2026-08-30
tmin00Znearest365d23 1 QC2.21 [1.35, 3.12]2.21-0.07 [-1.20, 1.02]2.77 [1.59, 3.61]26% [0%, 50%]61%78%+0.40+0.372026-08-07 → 2026-08-30
tmin00Znearestall23 1 QC2.21 [1.34, 3.13]2.21-0.07 [-1.31, 1.04]2.77 [1.60, 3.56]26% [0%, 53%]61%78%+0.40+0.372026-08-07 → 2026-08-30
tmin12Zbilinear30d23 1 QC2.82 [1.83, 3.48]2.50-1.48 [-2.54, -0.10]3.44 [2.28, 4.09]13% [0%, 33%]43%65%+0.23+0.292026-08-07 → 2026-08-30
tmin12Zbilinear90d23 1 QC2.82 [1.45, 3.50]2.50-1.48 [-2.70, 0.42]3.44 [1.82, 4.08]13% [0%, 40%]43%65%+0.23+0.292026-08-07 → 2026-08-30
tmin12Zbilinear365d23 1 QC2.82 [1.55, 3.54]2.50-1.48 [-2.67, 0.30]3.44 [1.96, 4.09]13% [0%, 39%]43%65%+0.23+0.292026-08-07 → 2026-08-30
tmin12Zbilinearall23 1 QC2.82 [1.54, 3.56]2.50-1.48 [-2.68, 0.28]3.44 [1.87, 4.07]13% [0%, 38%]43%65%+0.23+0.292026-08-07 → 2026-08-30
tmin12Znearest30d23 1 QC2.43 [1.58, 3.02]2.26-1.16 [-1.94, -0.23]3.12 [2.00, 3.77]22% [11%, 36%]52%70%+0.33+0.362026-08-07 → 2026-08-30
tmin12Znearest90d23 1 QC2.43 [1.23, 3.01]2.26-1.16 [-2.03, 0.05]3.12 [1.66, 3.77]22% [11%, 40%]52%70%+0.33+0.362026-08-07 → 2026-08-30
tmin12Znearest365d23 1 QC2.43 [1.35, 3.03]2.26-1.16 [-2.04, -0.02]3.12 [1.77, 3.77]22% [10%, 38%]52%70%+0.33+0.362026-08-07 → 2026-08-30
tmin12Znearestall23 1 QC2.43 [1.28, 3.08]2.26-1.16 [-2.10, -0.03]3.12 [1.74, 3.78]22% [10%, 38%]52%70%+0.33+0.362026-08-07 → 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 NCEP GFS at KBOS, lead day 6, 00Z bilinear tmax+20+100-10-202026-08-07: -1.27 °F2026-08-08: -2.97 °F2026-08-09: +3.81 °F2026-08-10: +8.72 °F2026-08-11: +0.36 °F2026-08-12: -2.49 °F2026-08-13: -16.36 °F2026-08-14: -2.56 °F2026-08-15: +2.59 °F2026-08-16: +5.17 °F2026-08-17: -3.53 °F2026-08-18: +4.94 °F2026-08-19: -4.18 °F2026-08-20: -4.39 °F2026-08-21: +2.93 °F2026-08-22: +3.03 °F2026-08-23: +5.42 °F2026-08-24: -5.3 °F2026-08-25: -2.61 °F2026-08-26: +1.34 °F2026-08-27: -14.09 °F2026-08-29: +5.37 °F2026-08-30: +1.28 °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+1.28
2026-08-29+5.37
2026-08-28—
2026-08-27-14.09
2026-08-26+1.34
2026-08-25-2.61
2026-08-24-5.30
2026-08-23+5.42
2026-08-22+3.03
2026-08-21+2.93
2026-08-20-4.39
2026-08-19-4.18
2026-08-18+4.94
2026-08-17-3.53
2026-08-16+5.17
2026-08-15+2.59
2026-08-14-2.56
2026-08-13-16.36
2026-08-12-2.49
2026-08-11+0.36
2026-08-10+8.72
2026-08-09+3.81
2026-08-08-2.97
2026-08-07-1.27

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KBOS, lead day 6-20 to -18 °F: 0 days-18 to -16 °F: 1 day-16 to -14 °F: 1 day-14 to -12 °F: 0 days-12 to -10 °F: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 0 days-6 to -4 °F: 3 days-4 to -2 °F: 5 days-2 to 0 °F: 1 day0 to 2 °F: 3 days2 to 4 °F: 4 days4 to 6 °F: 4 days6 to 8 °F: 0 days8 to 10 °F: 1 day10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.53 · P90 |e| 8.06 °F-200+20 °Fn = 23 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
-18.00-16.001
-16.00-14.001
-14.00-12.000
-12.00-10.000
-10.00-8.000
-8.00-6.000
-6.00-4.003
-4.00-2.005
-2.00+0.001
+0.00+2.003
+2.00+4.004
+4.00+6.004
+6.00+8.000
+8.00+10.001
+10.00+12.000
+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
2026-08234.55 -0.64

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 23
NCEP GFS2026-08-07 → 2026-08-30 23
NCEP GFS2026-08-07 → 2026-08-30 23
NCEP GFS2026-08-07 → 2026-08-30 23

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 23 -0.13 [-1.92, 1.13] no
GraphCast (IFS init) 23 +0.21 [-1.59, 1.72] no
ECMWF IFS HRES 18 +0.04 [-4.13, 2.31] no
Persistence (baseline) 23 -1.97 [-3.28, -0.35] yes

Cite this page

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

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