Forecast accuracy: forecast vs observations

ICON forecast (nearest point, lapse-rate corrected) vs METAR/SYNOP at valid time. MAE — mean absolute error; bias — mean (forecast − observed); ±2° — share within 2 °C. · 2992137 pairs, 7957 stations, since 24.08 17:00 UTC

1 d 3 d 7 d 30 d

Model accuracy — temperature (short range)

Model	MAE T, °C	Bias T	N
DWD NWP 🥇	1.33	-0.12	43963
ECMWF	1.6	-0.46	47724
GFS	1.92	-0.25	47724

Lower MAE = more accurate. Matched METAR/SYNOP, short range; at 3-7 days the ranking usually differs (ECMWF stronger). Updated hourly.

All stations

Lead time	N	MAE T, °C	Bias T	±2°	MAE wind, m/s	MAE P, mmHg
1–6 h	375050	1.2	-0.2	82%	1.2	0.6
7–12 h	378813	1.3	-0.2	80%	1.2	0.7
13–24 h	698221	1.3	-0.2	79%	1.3	0.7
25–48 h	999809	1.4	-0.3	77%	1.3	0.7
49–72 h	467560	1.5	-0.2	74%	1.3	0.8
73–120 h	35681	1.7	-0.4	69%	1.4	0.9

SYNOP stations

Lead time	N	MAE T, °C	Bias T	±2°	MAE wind, m/s	MAE P, mmHg
1–6 h	192406	1.3	-0.3	81%	1.2	0.7
7–12 h	190882	1.3	-0.3	80%	1.2	0.7
13–24 h	349718	1.3	-0.3	79%	1.3	0.7
25–48 h	493716	1.4	-0.4	77%	1.3	0.8
49–72 h	220777	1.5	-0.4	74%	1.3	0.8
73–120 h	14263	1.7	-0.5	68%	1.4	0.9

Airports (METAR)

Lead time	N	MAE T, °C	Bias T	±2°	MAE wind, m/s	MAE P, mmHg
1–6 h	182644	1.2	-0.2	82%	1.2	0.5
7–12 h	187931	1.3	-0.2	80%	1.3	0.6
13–24 h	348503	1.3	-0.2	80%	1.3	0.6
25–48 h	506093	1.4	-0.2	77%	1.3	0.6
49–72 h	246783	1.5	-0.1	74%	1.4	0.7
73–120 h	21418	1.7	-0.2	69%	1.4	0.8

By country (≤24 h)

Country	N	MAE T	Bias
Andorra	219	5.2	-5.2
Tajikistan	2345	2.9	-2.5
Liechtenstein	524	2.8	-2.7
Haiti	215	2.8	-2.7
Nepal	702	2.5	-2.2
Svalbard and Jan Mayen	530	2.4	-2.4
Bosnia and Herzegovina	3130	2.4	-0.9
Sao Tome and Principe	253	2.3	-2.3
Reunion	798	2.3	-1.6
Albania	930	2.2	-1.2
Aland Islands	1054	2.1	+0.7
Namibia	3261	2.0	-1.1
Mali	1368	2.0	+0.1
Honduras	2873	2.0	-0.9
Belize	370	2.0	+0.4
Turks and Caicos Islands	270	1.9	-1.7
Colombia	13621	1.9	-0.7
Ecuador	3334	1.9	-1.1
Chad	1552	1.8	-0.0
U.S. Virgin Islands	268	1.8	+1.0

Largest errors (≤24 h)

Station	Country	N	MAE T	Bias
Svobodnyj S31445	Russia	18	14.4	+14.4
Beni-Saf S60518	Algeria	119	13.6	+12.0
Darvaz S38856	Tajikistan	83	13.4	-13.4
Madri-Colmenar S08219	Spain	219	12.8	+12.8
Ishkashim S38957	Tajikistan	88	11.3	-11.3
Turgen S36889	Kazakhstan	83	10.9	+10.9
Izana S60010	Spain	234	10.7	-10.7
Garmsar S40756	Iran	175	10.0	+10.0
Bunji S41518	Pakistan	37	9.9	-9.9
Rushan S38951	Tajikistan	79	9.9	-9.9
Khorog S38954	Tajikistan	84	9.8	-9.8
Chinchorro S85405	Chile	234	8.9	+8.9
Vorogovo S23973	Russia	62	8.8	+8.6
Quetzaltenango S78629	Guatemala	30	8.7	+8.7
Houei-Sai * S48926	Laos	42	8.7	+8.7

Typical causes: mountain/coastal siting, elevation mismatch, nocturnal inversions, urban heat island.