Synopsis
On the south flank of a high above the Norwegian Sea, an eastern flow of continental polar air leads. A small, filling layer northwest of Brittany moves northwest and is no longer recognizable on Wednesday morning. A corresponding W-O oriented occlusion travels north over the Netherlands Wednesday morning. Activity is low. This occlusion slowly migrates further north but decreases due to the diffuse flow in activity and meaning and dissolves Wednesday evening above our country. A new layer to the northwest of Spain descends and moves northwest, leaving the current to the east on Wednesday (and Thursday) (south) and gradually bringing warmer air. The corresponding occlusion reaches the south on Thursday morning and moves north over the Netherlands after which the current becomes southwest. A wave in the cold front over France draws northeast and passes in the night to Friday Holland.

Model assessment
The activity of Wednesday's occlusion remains low in exports. The activity of Thursday's occlusion is somewhat greater, the hourly probability of precipitation is about 30%. Uncertainties are whether or not to reach the convection temperature and the forcing. The wave in the night to Friday is active, but also here the activity shifts quite into the output.Attention

Wind
For the average wind, the Harmony output is usable. During showers Thursday during the day, any outliers seem to be limited to about 20 kn, in the night to Friday there is locally 40 kn in the export, which is realistic. Here too, the output is shifting strongly.

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No details.

Temperature
Also Wednesday probably some underestimate of the daily course in exports.

Cloud
At the occlusion of Wednesday alto, possibly convective in nature. At Thursday's occlusion there is a chance of some CBs. Base is probably high, around 7000 ft, peaks in the most active case up to FL350. At the wave in the night to Friday mainly CB remains, but there are enough CBs with peaks up to FL400.

Precipitation
At the occlusion of Wednesday local light rain, possibly a showery character. In most places it stays dry. Thursday's convection seems to remain spatially limited, but the showers that have arisen are active, there is a signal for hail in Harmony output. There should be sufficient force as there is often an inversion between FL050-1000 vt in the progtemps. CAPE is 1000-2000 J/kg and the shear is about 25 kn, i.e. mainly multicells. At the wave in the night to Friday there seems to be a MCS-like complex. The forcing comes mainly from convergence in the lower layers of the wave. There may also be forced movement of the left exit of the beam current, but this pattern is also strongly disturbed by the complex. On the north side of the complex the CAPE is still about 1000 J/kg, but in the complex the output of CAPE is not usable, as is that of the wind shear. The activity in Harmony exports is clearly higher than in EC exports. The location and time of the most active showers within the complex shifts strongly. Locally, 30-50 mm can fall to Friday at night, where the uncertainty over the location is high.

Synopsis
A steering low is on Thursday 27 August northwest of Spain. At altitude the current is south to southwest, in the lower levels the current is first southeast with the supply of warm air. From Thursday on Friday the corresponding wavy cold front passes. In the course of Friday, we will be faced with a southwest current and maritime supply on the flank of the previously mentioned layer which then went to the North Sea via the British Isles. This is the beginning of a period with a large-scale sunny pattern (NAO+ from Sunday), which seems to last until the end of next week. A train of low pressure areas travels across North-West Europe and disturbances pass us almost daily. At the end of the period the current seems to meander more and we see more and more solutions with a height back above our environment.

Model assessment and uncertainties
Thursday is the warmest day of this period with in the east and south about 28°C. Thursday and Friday there is a chance of some heavy thunderstorms and code yellow. Then there is also a small chance of heavy thunderstorms (heavy winds, large hail, a lot of precipitation in a short time), especially in the (south) eastern half. Deep wind shear comes well into the multicell regime and Friday afternoon there is also a chance of low-top supercells in the east. From Friday, temperatures are slightly above the long-term average and remain wet, with daily 80-90% probability of precipitation. Only in the course of the next week after that, the precipitation opportunities decrease slightly. The sun will also be shown in between. It is a relatively wet period, with until 8 September cumulatively about 50 mm in the southeast, 60 mm in the middle and 80 mm in the northwest, about one and a half to twice as the climate average for this period.

Multi-day Summary
Thursday warm but also an increasing chance of heavy thunderstorms. From Friday less hot and regular showers.

EPS Period Summary
First great chance of variable weather with every day 80-90% chance of precipitation. From the beginning of September, daily precipitation rates decrease to 40-70% with the highest probability in the northwest. The temperature is probably around the long-term average.

Valid from Thursday 27 August to Tuesday 08 September