After The Forecast 8 September to 29 September

Rain check · 8 September to 29 September 2026

ECMWF IFS timed tomorrow's rain best at Lakenheath; 3 days ahead, no model scored above 34.8.

Rainfall totals and rain timing are different tests. This report checks the models on both.

Edition No. 6 · The United Kingdom · 22 days of hourly rain at Lakenheath

From 8 September to 14 September 2026, Lakenheath recorded 19.1 millimetres of rain. At least one millimetre fell on 3 of those days; 13 September 2026 was the wettest with 9.7 millimetres. Over the whole period from 8 September to 29 September 2026, the gauge collected 20.6 millimetres, with at least a millimetre on 3 of its 22 days.

Every model was scored on the same 22 days, at every notice its runs reach out to seven days ahead, for timing and for amount. One day ahead, ECMWF IFS timed the rain best, with a score of 57.5; GFS followed at 56.3.

The table below reads each model from a week out down to the day before. One day ahead, the forecasts for those 22 days ranged from 7.3 millimetres by ICON to 29.9 by ECMWF AIFS, against 20.6 measured. With only 28 wet hours in the sample, one shower caught or missed moves a score by several points, so cells a few points apart do not separate two forecasts.

Rain at Lakenheath, 8 September to 29 September, at every noticeFig. 1 · rain score, with forecast rainfall beneath

Rain score and forecast rainfall for every day of the period, by notice
Notice	ECMWF IFS Europe	GFS United States	UKMO United Kingdom	ECMWF AIFS Europe, AI	ICON Germany
7 days ahead	31.564.6 mm	17.87.3 mm	beyond horizon	30.924.5 mm	beyond horizon
6 days ahead	58.826.9 mm	9.913.4 mm	24.826.0 mm	47.722.4 mm	22.121.0 mm
5 days ahead	36.616.1 mm	58.629.2 mm	19.814.7 mm	27.728.8 mm	4.327.1 mm
4 days ahead	41.910.2 mm	21.617.1 mm	30.023.2 mm	34.429.6 mm	16.925.1 mm
3 days ahead	34.822.8 mm	22.419.3 mm	25.915.9 mm	29.930.6 mm	20.522.5 mm
2 days ahead	33.333.6 mm	30.626.4 mm	44.928.7 mm	37.229.3 mm	28.113.6 mm
1 day ahead	57.523.2 mm	56.312.7 mm	47.123.0 mm	40.629.9 mm	26.17.3 mm

Every cell scores the same 22 days at Lakenheath: 509 readable hours, 28 of them wet, 20.6 millimetres measured. The large figure is the rain score, the small one the rain that run forecast over those hours. Public models are read from the 00 UTC run issued that many days before each day. A model whose run does not cover every day at a notice has no cell there. The gauge has no reading for 19 hours (8 September 08:00, 10 September 07:00, 10 September 16:00, 11 September 05:00, 15 September 09:00 to 15 September 10:00, 16 September 18:00, 20 September 02:00, 22 September 17:00, 22 September 22:00, 23 September 10:00, 23 September 13:00 to 23 September 16:00, 24 September 07:00, 24 September 16:00, 25 September 18:00, and 27 September 20:00); those hours are left out for every model.

The wettest day, hour by hour

On 13 September 2026, Lakenheath measured 9.7 millimetres across 8 of the 24 hours it could read. The strip below sets each model's run from the day before against the gauge, hour by hour. ECMWF IFS caught 8 of those 8 wet hours, with 4 false alarms.

13 September 2026, 9.7 millimetresFig. 2 · one day ahead, hour by hour

Rain on 13 September 2026 hour by hour: the gauge, then each model's forecast from the day before
Model	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	Day
Gauge	Dry	Dry	Dry	Dry	0.8	Dry	2.8	1.5	2.0	0.3	Dry	1.0	1.0	0.3	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	9.7 mm
ECMWF IFS	Dry	False alarm	Dry	Within an hour	Caught	Within an hour	Caught	Caught	Caught	Caught	Within an hour	Caught	Caught	Caught	Within an hour	False alarm	False alarm	False alarm	Dry	Dry	Dry	Dry	Dry	Dry	6.2 mm
ECMWF AIFS	False alarm	False alarm	False alarm	Within an hour	Caught	Within an hour	Caught	Caught	Caught	Caught	Within an hour	Caught	Caught	Caught	Within an hour	False alarm	False alarm	False alarm	False alarm	False alarm	Dry	Dry	Dry	Dry	7.0 mm
UKMO	False alarm	Dry	Dry	Dry	Caught	Within an hour	Caught	Caught	Caught	Caught	Within an hour	Caught	Missed	Missed	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	11.7 mm
GFS	False alarm	Dry	Dry	Dry	Caught	Within an hour	Caught	Caught	Caught	Caught	Dry	Missed	Missed	Missed	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	0.8 mm
ICON	Dry	Dry	Dry	Dry	Missed	Dry	Missed	Missed	Missed	Missed	Dry	Missed	Missed	Missed	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	Dry	0.0 mm

The top row is the gauge at Lakenheath, in millimetres per hour; each column is the hour ending at the time above it. Below it is each model's run from the day before. A wet gauge hour is caught when the model had rain within an hour of it and missed when it had none. A forecast wet hour with no rain measured within an hour is a false alarm; one beside measured rain is timing inside the tolerance. The last column is the day's total.

Which model timed tomorrow's rain best?

Across all 22 days, ECMWF IFS offered the best balance between missed rain and false alarms, with a score of 57.5. GFS followed at 56.3. ICON finished last at 26.1: it caught 6 of the 28 wet hours, with 10 false alarms. How ready a model is to forecast rain shows in the hours it called wet, from 15 to 154 over the same 509 hours. For rain at Lakenheath one day ahead, ECMWF IFS was the best choice in this test.

Rain, 8 September to 29 SeptemberFig. 3 · one day ahead

Rain standings, one day ahead
Model	Rain score	Caught	Missed	False alarm	Hours called wet
ECMWF IFS Europe	57.5	20	8	27	52
GFS United States	56.3	20	8	23	43
UKMO United Kingdom	47.1	16	12	27	45
ECMWF AIFS Europe, AI	40.6	26	2	114	154
ICON Germany	26.1	6	22	10	15

Scores for one-day-ahead forecasts across 509 readable hours at Lakenheath; 28 of them were wet. The score rewards hits and penalises misses and false alarms. The gauge has no reading for 19 hours (8 September 08:00, 10 September 07:00, 10 September 16:00, 11 September 05:00, 15 September 09:00 to 15 September 10:00, 16 September 18:00, 20 September 02:00, 22 September 17:00, 22 September 22:00, 23 September 10:00, 23 September 13:00 to 23 September 16:00, 24 September 07:00, 24 September 16:00, 25 September 18:00, and 27 September 20:00); those hours are left out for every model.

About this comparison

The period's wet spell runs from 8 September 2026 to 14 September 2026; its wettest day, 13 September 2026 with 9.7 millimetres, is drawn hour by hour. The other two figures cover every day of the period. Forecasts come from the public models' 00 UTC runs and are compared with the gauge at Lakenheath.

How rain is judged

An hour counts as wet from 0.1 millimetres. A forecast may be 1 hour early or late; when the gauge has no reading, that hour is left out for every model. This is a test at one gauge in Lakenheath, not a verdict on a whole country.

A day enters the sample only when the gauge could be read and all 7 runs before it are in the archive, so every notice is scored on the same 22 days. A model whose run does not cover every one of them at some notice has no score there, rather than a score on fewer days. Each notice is judged on its own. There is no row for how far ahead a model first had the rain: showers do not reduce to one number that a forecast either lands near or misses.

At Lakenheath, the scheduled METAR at 55 minutes past the hour carries a P group for rain during the preceding hour. It is compared with the model hour ending five minutes later. No P group in a scheduled report means dry; no scheduled report means unknown, and that hour is left out. A P0000 group reports a trace, rain too small to measure, and counts as dry.

We compare archived model output with independent station observations. Data is at data.json, the full method at methodology and corrections at corrections.

The live version of this report is an app

After The Forecast comes out on a schedule. VeriSky keeps the rolling scores current for the places you care about and shows how models change with forecast distance.

Download on the App Store Get it on Google Play

Free standings · No account · No cookies