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 2

KBOS · gfs · lead 2

Target day = initialization date + 2 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
tmax00Zbilinear30d27 1 QC2.77 [1.76, 3.83]2.53-1.52 [-2.65, -0.38]3.69 [2.44, 4.76]22% [4%, 41%]44%63%+0.55+0.592026-08-03 → 2026-08-30
tmax00Zbilinear90d27 1 QC2.77 [1.68, 4.02]2.53-1.52 [-2.95, -0.11]3.69 [2.17, 4.93]22% [0%, 41%]44%63%+0.55+0.592026-08-03 → 2026-08-30
tmax00Zbilinear365d27 1 QC2.77 [1.48, 4.14]2.53-1.52 [-3.16, 0.14]3.69 [1.99, 5.06]22% [0%, 43%]44%63%+0.55+0.592026-08-03 → 2026-08-30
tmax00Zbilinearall27 1 QC2.77 [1.61, 4.27]2.53-1.52 [-3.13, -0.03]3.69 [2.14, 5.09]22% [0%, 43%]44%63%+0.55+0.592026-08-03 → 2026-08-30
tmax00Znearest30d27 1 QC3.01 [2.24, 3.86]2.38-2.08 [-3.24, -0.96]3.80 [2.68, 4.78]19% [7%, 33%]33%63%+0.50+0.612026-08-03 → 2026-08-30
tmax00Znearest90d27 1 QC3.01 [1.96, 4.08]2.38-2.08 [-3.52, -0.75]3.80 [2.42, 4.93]19% [3%, 40%]33%63%+0.50+0.612026-08-03 → 2026-08-30
tmax00Znearest365d27 1 QC3.01 [1.88, 4.20]2.38-2.08 [-3.68, -0.62]3.80 [2.25, 5.07]19% [0%, 44%]33%63%+0.50+0.612026-08-03 → 2026-08-30
tmax00Znearestall27 1 QC3.01 [1.95, 4.14]2.38-2.08 [-3.61, -0.70]3.80 [2.35, 5.00]19% [0%, 41%]33%63%+0.50+0.612026-08-03 → 2026-08-30
tmax12Zbilinear30d27 1 QC2.90 [1.73, 4.08]2.91-0.81 [-1.88, 0.28]4.27 [2.25, 5.83]37% [24%, 54%]56%59%+0.52+0.522026-08-03 → 2026-08-30
tmax12Zbilinear90d27 1 QC2.90 [1.57, 4.29]2.91-0.81 [-1.97, 0.38]4.27 [2.05, 6.04]37% [20%, 59%]56%59%+0.52+0.522026-08-03 → 2026-08-30
tmax12Zbilinear365d27 1 QC2.90 [1.47, 4.42]2.91-0.81 [-2.17, 0.43]4.27 [1.93, 6.11]37% [18%, 67%]56%59%+0.52+0.522026-08-03 → 2026-08-30
tmax12Zbilinearall27 1 QC2.90 [1.53, 4.31]2.91-0.81 [-2.08, 0.50]4.27 [2.03, 6.09]37% [20%, 62%]56%59%+0.52+0.522026-08-03 → 2026-08-30
tmax12Znearest30d27 1 QC2.89 [1.75, 4.04]2.75-1.41 [-2.49, -0.30]4.18 [2.20, 5.75]22% [8%, 36%]48%63%+0.52+0.542026-08-03 → 2026-08-30
tmax12Znearest90d27 1 QC2.89 [1.56, 4.25]2.75-1.41 [-2.53, -0.25]4.18 [1.97, 5.99]22% [4%, 38%]48%63%+0.52+0.542026-08-03 → 2026-08-30
tmax12Znearest365d27 1 QC2.89 [1.53, 4.40]2.75-1.41 [-2.75, -0.19]4.18 [1.95, 6.00]22% [4%, 40%]48%63%+0.52+0.542026-08-03 → 2026-08-30
tmax12Znearestall27 1 QC2.89 [1.54, 4.23]2.75-1.41 [-2.62, -0.17]4.18 [1.97, 6.01]22% [6%, 39%]48%63%+0.52+0.542026-08-03 → 2026-08-30
tmin00Zbilinear30d27 1 QC1.77 [1.46, 2.08]1.43-1.26 [-1.78, -0.70]2.20 [1.74, 2.58]33% [20%, 45%]67%81%+0.33+0.462026-08-03 → 2026-08-30
tmin00Zbilinear90d27 1 QC1.77 [1.45, 2.21]1.43-1.26 [-1.90, -0.75]2.20 [1.71, 2.78]33% [18%, 45%]67%81%+0.33+0.462026-08-03 → 2026-08-30
tmin00Zbilinear365d27 1 QC1.77 [1.43, 2.22]1.43-1.26 [-1.97, -0.68]2.20 [1.68, 2.82]33% [17%, 44%]67%81%+0.33+0.462026-08-03 → 2026-08-30
tmin00Zbilinearall27 1 QC1.77 [1.42, 2.22]1.43-1.26 [-1.96, -0.69]2.20 [1.65, 2.85]33% [17%, 44%]67%81%+0.33+0.462026-08-03 → 2026-08-30
tmin00Znearest30d27 1 QC1.56 [1.30, 1.82]1.51-0.89 [-1.45, -0.31]2.01 [1.59, 2.41]37% [27%, 46%]78%89%+0.42+0.432026-08-03 → 2026-08-30
tmin00Znearest90d27 1 QC1.56 [1.29, 1.91]1.51-0.89 [-1.55, -0.36]2.01 [1.56, 2.62]37% [26%, 48%]78%89%+0.42+0.432026-08-03 → 2026-08-30
tmin00Znearest365d27 1 QC1.56 [1.26, 1.97]1.51-0.89 [-1.63, -0.25]2.01 [1.52, 2.68]37% [25%, 50%]78%89%+0.42+0.432026-08-03 → 2026-08-30
tmin00Znearestall27 1 QC1.56 [1.25, 1.97]1.51-0.89 [-1.65, -0.30]2.01 [1.49, 2.67]37% [25%, 47%]78%89%+0.42+0.432026-08-03 → 2026-08-30
tmin12Zbilinear30d27 1 QC1.66 [1.35, 2.00]1.70-0.76 [-1.37, -0.08]2.17 [1.83, 2.52]41% [23%, 61%]63%81%+0.35+0.332026-08-03 → 2026-08-30
tmin12Zbilinear90d27 1 QC1.66 [1.27, 2.04]1.70-0.76 [-1.56, -0.14]2.17 [1.85, 2.55]41% [21%, 67%]63%81%+0.35+0.332026-08-03 → 2026-08-30
tmin12Zbilinear365d27 1 QC1.66 [1.30, 2.11]1.70-0.76 [-1.55, -0.05]2.17 [1.82, 2.62]41% [20%, 65%]63%81%+0.35+0.332026-08-03 → 2026-08-30
tmin12Zbilinearall27 1 QC1.66 [1.32, 2.07]1.70-0.76 [-1.48, -0.10]2.17 [1.83, 2.54]41% [21%, 64%]63%81%+0.35+0.332026-08-03 → 2026-08-30
tmin12Znearest30d27 1 QC1.54 [1.34, 1.79]1.54+0.01 [-0.64, 0.66]1.91 [1.69, 2.16]44% [33%, 56%]74%81%+0.39+0.402026-08-03 → 2026-08-30
tmin12Znearest90d27 1 QC1.54 [1.31, 1.80]1.54+0.01 [-0.82, 0.59]1.91 [1.66, 2.16]44% [33%, 59%]74%81%+0.39+0.402026-08-03 → 2026-08-30
tmin12Znearest365d27 1 QC1.54 [1.34, 1.83]1.54+0.01 [-0.84, 0.72]1.91 [1.68, 2.21]44% [32%, 59%]74%81%+0.39+0.402026-08-03 → 2026-08-30
tmin12Znearestall27 1 QC1.54 [1.31, 1.81]1.54+0.01 [-0.83, 0.64]1.91 [1.67, 2.17]44% [31%, 61%]74%81%+0.39+0.402026-08-03 → 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 2, 00Z bilinear tmax+20+100-10-202026-08-03: -8.39 °F2026-08-04: -2.94 °F2026-08-05: -5.2 °F2026-08-06: -0.89 °F2026-08-07: -0.2 °F2026-08-08: -1.16 °F2026-08-09: +1.64 °F2026-08-10: +3.56 °F2026-08-11: +0.07 °F2026-08-12: -1.32 °F2026-08-13: -0.42 °F2026-08-14: -2.67 °F2026-08-15: +0.08 °F2026-08-16: -0.28 °F2026-08-17: -5.1 °F2026-08-18: -1.13 °F2026-08-19: -2 °F2026-08-20: -10.3 °F2026-08-21: +5.16 °F2026-08-22: -3.31 °F2026-08-23: -2.01 °F2026-08-24: -4.24 °F2026-08-25: -3.65 °F2026-08-26: +3.59 °F2026-08-27: -2.65 °F2026-08-29: +1.27 °F2026-08-30: +1.46 °F2026-08-032026-08-30°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 (28 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.46
2026-08-29+1.27
2026-08-28—
2026-08-27-2.65
2026-08-26+3.59
2026-08-25-3.65
2026-08-24-4.24
2026-08-23-2.01
2026-08-22-3.31
2026-08-21+5.16
2026-08-20-10.30
2026-08-19-2.00
2026-08-18-1.13
2026-08-17-5.10
2026-08-16-0.28
2026-08-15+0.08
2026-08-14-2.67
2026-08-13-0.42
2026-08-12-1.32
2026-08-11+0.07
2026-08-10+3.56
2026-08-09+1.64
2026-08-08-1.16
2026-08-07-0.20
2026-08-06-0.89
2026-08-05-5.20
2026-08-04-2.94
2026-08-03-8.39

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KBOS, lead day 2-20 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: 1 day-8 to -6 °F: 0 days-6 to -4 °F: 3 days-4 to -2 °F: 7 days-2 to 0 °F: 7 days0 to 2 °F: 5 days2 to 4 °F: 2 days4 to 6 °F: 1 day6 to 8 °F: 0 days8 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| 2.01 · P90 |e| 5.17 °F-200+20 °Fn = 27 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
-10.00-8.001
-8.00-6.000
-6.00-4.003
-4.00-2.007
-2.00+0.007
+0.00+2.005
+2.00+4.002
+4.00+6.001
+6.00+8.000
+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
2026-08272.77 -1.52

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-03 → 2026-08-30 27
NCEP GFS2026-08-03 → 2026-08-30 27
NCEP GFS2026-08-03 → 2026-08-30 27
NCEP GFS2026-08-03 → 2026-08-30 27

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 27 -0.62 [-1.70, 0.71] no
Aurora (IFS init) 1 -2.66 [-2.66, -2.66] yes
FourCastNet v2 (IFS init) 1 -4.63 [-4.63, -4.63] yes
GraphCast (IFS init) 26 -0.45 [-1.48, 0.70] no
ECMWF IFS HRES 21 +0.51 [-0.20, 1.76] no
Pangu-Weather (IFS init) 1 -2.38 [-2.38, -2.38] yes
Persistence (baseline) 26 -3.38 [-5.53, -1.38] yes

Cite this page

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

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

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