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 3

KBOS · gfs · lead 3

Target day = initialization date + 3 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
tmax00Zbilinear30d26 1 QC3.84 [2.62, 5.51]3.62-2.06 [-3.57, -0.64]5.21 [3.42, 7.40]15% [4%, 29%]35%54%+0.37+0.412026-08-04 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.84 [2.44, 5.88]3.62-2.06 [-3.94, -0.32]5.21 [3.09, 7.74]15% [4%, 31%]35%54%+0.37+0.412026-08-04 → 2026-08-30
tmax00Zbilinear365d26 1 QC3.84 [2.41, 6.02]3.62-2.06 [-4.04, -0.27]5.21 [3.05, 7.67]15% [0%, 33%]35%54%+0.37+0.412026-08-04 → 2026-08-30
tmax00Zbilinearall26 1 QC3.84 [2.33, 6.09]3.62-2.06 [-4.17, -0.32]5.21 [3.02, 7.87]15% [0%, 32%]35%54%+0.37+0.412026-08-04 → 2026-08-30
tmax00Znearest30d26 1 QC4.16 [3.05, 5.81]3.53-2.82 [-4.33, -1.42]5.46 [3.81, 7.53]8% [0%, 17%]31%50%+0.32+0.432026-08-04 → 2026-08-30
tmax00Znearest90d26 1 QC4.16 [2.80, 6.13]3.53-2.82 [-4.72, -1.11]5.46 [3.56, 7.84]8% [0%, 21%]31%50%+0.32+0.432026-08-04 → 2026-08-30
tmax00Znearest365d26 1 QC4.16 [2.75, 6.25]3.53-2.82 [-4.85, -1.10]5.46 [3.45, 7.80]8% [0%, 23%]31%50%+0.32+0.432026-08-04 → 2026-08-30
tmax00Znearestall26 1 QC4.16 [2.84, 6.45]3.53-2.82 [-4.89, -1.16]5.46 [3.46, 8.01]8% [0%, 22%]31%50%+0.32+0.432026-08-04 → 2026-08-30
tmax12Zbilinear30d26 1 QC4.14 [3.13, 5.10]4.05-2.27 [-3.88, -0.68]5.53 [4.48, 6.41]23% [12%, 33%]35%50%+0.32+0.342026-08-04 → 2026-08-30
tmax12Zbilinear90d26 1 QC4.14 [2.82, 5.20]4.05-2.27 [-3.95, -0.36]5.53 [4.05, 6.50]23% [12%, 36%]35%50%+0.32+0.342026-08-04 → 2026-08-30
tmax12Zbilinear365d26 1 QC4.14 [2.63, 5.30]4.05-2.27 [-4.11, -0.25]5.53 [3.85, 6.59]23% [11%, 38%]35%50%+0.32+0.342026-08-04 → 2026-08-30
tmax12Zbilinearall26 1 QC4.14 [2.82, 5.38]4.05-2.27 [-4.21, -0.35]5.53 [4.10, 6.64]23% [10%, 35%]35%50%+0.32+0.342026-08-04 → 2026-08-30
tmax12Znearest30d26 1 QC4.14 [2.91, 5.24]3.64-2.65 [-4.23, -1.19]5.41 [3.96, 6.47]15% [3%, 29%]42%50%+0.32+0.412026-08-04 → 2026-08-30
tmax12Znearest90d26 1 QC4.14 [2.46, 5.35]3.64-2.65 [-4.38, -0.91]5.41 [3.34, 6.53]15% [0%, 33%]42%50%+0.32+0.412026-08-04 → 2026-08-30
tmax12Znearest365d26 1 QC4.14 [2.18, 5.54]3.64-2.65 [-4.53, -0.75]5.41 [2.87, 6.63]15% [0%, 37%]42%50%+0.32+0.412026-08-04 → 2026-08-30
tmax12Znearestall26 1 QC4.14 [2.43, 5.47]3.64-2.65 [-4.59, -0.91]5.41 [3.48, 6.66]15% [0%, 36%]42%50%+0.32+0.412026-08-04 → 2026-08-30
tmin00Zbilinear30d26 1 QC1.78 [1.31, 2.26]1.64-1.07 [-1.56, -0.54]2.25 [1.63, 2.80]38% [23%, 53%]62%85%+0.34+0.392026-08-04 → 2026-08-30
tmin00Zbilinear90d26 1 QC1.78 [1.31, 2.30]1.64-1.07 [-1.59, -0.44]2.25 [1.61, 2.83]38% [22%, 53%]62%85%+0.34+0.392026-08-04 → 2026-08-30
tmin00Zbilinear365d26 1 QC1.78 [1.30, 2.34]1.64-1.07 [-1.66, -0.40]2.25 [1.60, 2.87]38% [20%, 53%]62%85%+0.34+0.392026-08-04 → 2026-08-30
tmin00Zbilinearall26 1 QC1.78 [1.27, 2.37]1.64-1.07 [-1.71, -0.36]2.25 [1.56, 2.90]38% [21%, 54%]62%85%+0.34+0.392026-08-04 → 2026-08-30
tmin00Znearest30d26 1 QC1.60 [1.29, 1.96]1.50-0.62 [-1.05, -0.13]1.98 [1.53, 2.38]35% [19%, 48%]81%88%+0.41+0.442026-08-04 → 2026-08-30
tmin00Znearest90d26 1 QC1.60 [1.27, 2.02]1.50-0.62 [-1.10, -0.10]1.98 [1.51, 2.43]35% [17%, 50%]81%88%+0.41+0.442026-08-04 → 2026-08-30
tmin00Znearest365d26 1 QC1.60 [1.26, 2.06]1.50-0.62 [-1.14, -0.05]1.98 [1.48, 2.47]35% [14%, 50%]81%88%+0.41+0.442026-08-04 → 2026-08-30
tmin00Znearestall26 1 QC1.60 [1.25, 2.02]1.50-0.62 [-1.13, 0.00]1.98 [1.51, 2.45]35% [14%, 50%]81%88%+0.41+0.442026-08-04 → 2026-08-30
tmin12Zbilinear30d26 1 QC2.08 [1.56, 2.60]1.81-1.39 [-2.29, -0.51]2.62 [1.97, 3.17]27% [15%, 39%]50%77%+0.23+0.332026-08-04 → 2026-08-30
tmin12Zbilinear90d26 1 QC2.08 [1.50, 2.76]1.81-1.39 [-2.30, -0.42]2.62 [1.87, 3.28]27% [14%, 40%]50%77%+0.23+0.332026-08-04 → 2026-08-30
tmin12Zbilinear365d26 1 QC2.08 [1.40, 2.83]1.81-1.39 [-2.37, -0.40]2.62 [1.69, 3.37]27% [11%, 41%]50%77%+0.23+0.332026-08-04 → 2026-08-30
tmin12Zbilinearall26 1 QC2.08 [1.43, 2.76]1.81-1.39 [-2.38, -0.42]2.62 [1.67, 3.30]27% [12%, 40%]50%77%+0.23+0.332026-08-04 → 2026-08-30
tmin12Znearest30d26 1 QC1.86 [1.39, 2.37]1.75-0.84 [-1.69, 0.03]2.35 [1.72, 2.89]35% [21%, 50%]65%81%+0.31+0.352026-08-04 → 2026-08-30
tmin12Znearest90d26 1 QC1.86 [1.33, 2.58]1.75-0.84 [-1.85, 0.12]2.35 [1.66, 3.00]35% [19%, 54%]65%81%+0.31+0.352026-08-04 → 2026-08-30
tmin12Znearest365d26 1 QC1.86 [1.29, 2.63]1.75-0.84 [-1.78, 0.15]2.35 [1.51, 3.05]35% [17%, 55%]65%81%+0.31+0.352026-08-04 → 2026-08-30
tmin12Znearestall26 1 QC1.86 [1.25, 2.61]1.75-0.84 [-1.88, 0.14]2.35 [1.48, 3.06]35% [18%, 55%]65%81%+0.31+0.352026-08-04 → 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 3, 00Z bilinear tmax+20+100-10-202026-08-04: -9.52 °F2026-08-05: -15 °F2026-08-06: +6.34 °F2026-08-07: +0.02 °F2026-08-08: -1.82 °F2026-08-09: +1.96 °F2026-08-10: +3.05 °F2026-08-11: +1.21 °F2026-08-12: -3.61 °F2026-08-13: -2.7 °F2026-08-14: -2.82 °F2026-08-15: -0.08 °F2026-08-16: -4.16 °F2026-08-17: -8.44 °F2026-08-18: -2.03 °F2026-08-19: -2.18 °F2026-08-20: -8.14 °F2026-08-21: +4.04 °F2026-08-22: +1.3 °F2026-08-23: -3.21 °F2026-08-24: -2.61 °F2026-08-25: -9.37 °F2026-08-26: +3.57 °F2026-08-27: -0.7 °F2026-08-29: -0.3 °F2026-08-30: +1.65 °F2026-08-042026-08-30°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 (27 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.65
2026-08-29-0.30
2026-08-28—
2026-08-27-0.70
2026-08-26+3.57
2026-08-25-9.37
2026-08-24-2.61
2026-08-23-3.21
2026-08-22+1.30
2026-08-21+4.04
2026-08-20-8.14
2026-08-19-2.18
2026-08-18-2.03
2026-08-17-8.44
2026-08-16-4.16
2026-08-15-0.08
2026-08-14-2.82
2026-08-13-2.70
2026-08-12-3.61
2026-08-11+1.21
2026-08-10+3.05
2026-08-09+1.96
2026-08-08-1.82
2026-08-07+0.02
2026-08-06+6.34
2026-08-05-15.00
2026-08-04-9.52

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KBOS, lead day 3-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 0 days-12 to -10 °F: 0 days-10 to -8 °F: 4 days-8 to -6 °F: 0 days-6 to -4 °F: 1 day-4 to -2 °F: 7 days-2 to 0 °F: 4 days0 to 2 °F: 5 days2 to 4 °F: 2 days4 to 6 °F: 1 day6 to 8 °F: 1 day8 to 10 °F: 0 days10 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| 2.76 · P90 |e| 8.91 °F-200+20 °Fn = 26 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
-16.00-14.001
-14.00-12.000
-12.00-10.000
-10.00-8.004
-8.00-6.000
-6.00-4.001
-4.00-2.007
-2.00+0.004
+0.00+2.005
+2.00+4.002
+4.00+6.001
+6.00+8.001
+8.00+10.000
+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
2026-08263.84 -2.06

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-04 → 2026-08-30 26
NCEP GFS2026-08-04 → 2026-08-30 26
NCEP GFS2026-08-04 → 2026-08-30 26
NCEP GFS2026-08-04 → 2026-08-30 26

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 26 -0.22 [-1.19, 1.18] no
GraphCast (IFS init) 24 +0.69 [-0.55, 2.43] no
ECMWF IFS HRES 21 -0.27 [-0.97, 0.92] no
Persistence (baseline) 26 -2.28 [-4.88, 1.60] no

Cite this page

ShortCastCheck, KBOS gfs lead 3, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KBOS/model/gfs/lead/3/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KBOS (Boston Logan), model gfs, lead day 3. 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/3/

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