Synoptic assessment of weather models

Every day, KNMI meteorologists analyze and interpret the results of the Hirlam, ECMWF and Harmonie weather models. Below you can read their findings, particularly educational material for those who want to understand more about the weather on the maps and in the graphs.
 
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Short-term to + 48 hours | Guidance multi-day model review
 



Models overall rating up to +48 hours

Published: 22/03/2025 05.56 uur LT
 
Guidance model assessment for the Netherlands, the Dutch coastal waters and the North Sea, based on the HIRLAM run of 12 UTC and the other mentioned models and guides with associated run time.

Synopsis
Low pressure area Martinho is located near Brest and attracts very slow and slightly full east over Brittany. This is why we have a southeast current. The frontal zone belonging to Martinho slowly pushes north over France and Belgium, reaches on Saturday to the southwest of our country, swings northwards and leaves on Sunday to the north of the country. To the southwest of the layer there is a next cold front, which begins to rotate south around the low and in the night to Sunday and Sunday from south to north over the land.

Model assessment
For the wind in the coastal districts we keep the models, which also better match the measured wave heights. The wind measurements reduced to 10 m on the platforms a little closer to the coast show too high values. On Saturday evening (thunderstorms) thunderstorms are approaching from the frontal system from northern France in a diffuse upper current. Because of this and also through daily passage, these showers hardly seem to reach our country. However, on Saturday evening above our country we see some showers (born), probably triggered by heat advice for the cold front and therefore also fed from some heights. We see this image both in Ha43 and in EC. However, Harmony is very varied with each run between light to moderate showers and heavier showers with thunderstorms. The last few runs keep it moderate. If there are some heavier showers, the chance of wind blows of 30-35 knots increases due to water loading. Sunday we see in Harmony a strong St-signal above the sea north of the Wadden (see also PASCAL), which is possibly exaggerated due to too much evaporation above land (too high dew points). It is not surprising that EC St calculates and also the EC progtemps for EHAK and EHFD remain relatively dry at the bottom. It is still quite far away, but taking the too high dew points in Ha43 we assume only a small St-chance Sunday.Issues

Wind
6 Bft on the North Sea and a 7 Bft in the north of the FIR and possibly in the north of districts Texel and Rottum. Sunday morning the 6 Bft disappears.

Visibility
In the north of the FIR above the sea, local moderate visibility first. Saturday in moderate showers risk moderate vision.

Temperature
Lower afternoon temperatures than Friday due to significantly more clouds.

Cloud
At the cold front a crumbled whole, lowest base above sea probability of sct/bkn Sc 1000-1500 vt, above land mostly sct/bkn Sc/Ac/As 5000-7000 vt. for the cold front out also chance of Cbs from any height, peaks FL200, Saturday evening possibly some higher peaks, FL300. At the second cold front we see more or less the same thing happening, see the model assessment for the St-Opportunity. After that, there's a chance for some TCUs on Sunday.

Precipitation
This morning in the southwest half local rain, part of what the radar shows still evaporates at the bottom. Later today by heat advection at low altitude also an increasing CAPE, to several hundred J/kg. Especially Saturday night a little higher CAPE, 400-700 J/kg. Effective wind shear 10-15 kn, so chances of single or multicells. Thunderstorm probability small but not completely zero. At the second cold front we see the same image. Then there's a chance of a light shower on Sunday.

valid until Sunday 23 March 2025 24.00 local time



 

Guidance multi-day

Published: 22/03/2025 04.58 uur LT
 
Long term assessment by meteorologist

Synoptic development
The flow pattern remains blocked for the time being, with an altitude level above the Western Mediterranean on Monday and an Atlantic altitude back reaching the British Isles. On the ground, the current is still cyclonal. Around Wednesday, a back of the Azores reaches the northwest from our surroundings. Weak fronts can still pass our environment in a weak northwest current. In the course of the next week, the altitude level will draw to the Balkans and the altitude back will level above our surroundings. By flattening the ridge, more active disturbances from the northwest can reach our environment, especially around Saturday 29 March. A new Atlantic ridge could build around Sunday 30 March above the British Isles, leading to a weakening northwest current. This development is uncertain. As of Saturday 29 March there are 5 or 6 clusters that continue to differ but which generally show a permanently blocked image.

Model assessment and uncertainties
In the coming period little detail can be expected. The temperature is still above Monday, but then near the long-term average. Due to the fairly quiet weather with the supply of maritime air, local fog can occur on most days in the night and morning during clearances, especially Tuesday in the east. The daily probability of precipitation is not great. On Monday, mostly inland showers can occur on the daily course due to the presence of a fore. Then a weak front sometimes passes, for example later on Tuesday. Around Saturday, March 29th, the probability of precipitation is temporarily quite large if more active disturbances can reach us from the northwest. Much wind does not seem to be included. In the longer term, the probability of precipitation is decreasing again. A total of 15-25 mm of rain is expected in the next two weeks. At the beginning of April the high pressure influence of the north is likely to increase with a weak preference for northeast wind, more sun than average and also slightly higher temperatures.

Multi-day Summary
Quiet spring weather with regular sunshine and sometimes some rain. First on the soft side, gradually afternoon temperatures around the long-term average.

EPS Period Summary
At first, pretty volatile. Early April, the high pressure influence of the north is likely to increase with possibly more sun and also slightly higher temperatures than average.

Valid from Monday 24 March to Saturday 05 April

 

 

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