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: 23/05/2024 04.58 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.

Synoptic situation
A low-pressure area above the north of England hardly changes its position. The associated occlusion around this low extends over the North Sea and the north of Germany. With this low, maritime polar air flows over our area of interest with a southwesterly flow. Above Central Europe, a flat low-pressure area is present that approaches our area of interest via Germany on Friday.

Model evaluation
There have been some light showers. Some showers are now approaching from Belgium. The models are all doing quite well. Diurnal variation and convergence in the boundary layer are triggers. Tomorrow during the day, we will see this happen again. Showers could be a bit more intense. EC even shows some lightning discharges. Harmonies show nothing, KEPS does not exceed 10%. Regarding the cloud cover, in all models we see a new area with SC/ST developing overnight near the west coast due to coastal convergence. During the night towards Friday, we see mist signals in various models due to a diminishing wind and clearings.Points of attention

Wind
Along the west coast occasionally still a 6 Bft. Tomorrow the wind will gradually decrease. Tomorrow, a chance of gusts of 20-25 kn during a shower.

Visibility
Mainly good, moderate to poor visibility in a shower tomorrow. A chance of mist overnight towards Friday.

Temperature
Same air mass tomorrow, slightly more sun and therefore slightly higher max temperature than today.

Cloud cover
Convective clouds, dissolving this evening. Overnight and early tomorrow morning near the west coast a chance of SC/ST. Moving further eastward during the morning and transitioning into CU. In the afternoon and evening, a chance of a few CB's. Tops up to around FL150 are possible.

Precipitation
An occasional shower, especially in the southeast. Thursday in the afternoon/evening again an occasional shower. CAPE values are higher than today. Between 400-700 J/kg according to EC, Harmonies higher. Effective shear is low, around 10-15 kn. Mainly single cells.

valid until Thursday, May 23, 2024 24:00 local time
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Guidance multi-day

Published: 23/05/2024 04.44 uur LT
 
Long term assessment by meteorologist

Synoptic development
The flow pattern remains blocked for the time being with an extensive high over the northwest of Russia, which is connected to high pressure to the west and north of the British Isles. Above the western and central part of the European continent, the flow remains slightly cyclonic with mainly daily development of some rain and thunderstorms, especially coming Friday and Saturday. This pattern will be disrupted from next Sunday when an Atlantic low moves from the north of the British Isles to the Norwegian Sea. The flow in our region will then become (south)westerly. From the middle of next week, high pressure will build up above our region, gradually shifting towards Scandinavia. As a result, it will be (temporarily) less changeable.

Model assessment and uncertainties
It will remain changeable until the middle of next week, with especially a lot of precipitation again coming Friday and Saturday. The situation then seems similar to yesterday, with an extensive shower complex moving across the country from the southeast. There will probably be a total of over 20 mm of rain on both days, with about a 30% chance of 40 mm, but given the showery nature, more may fall locally. A next active disturbance will pass by Monday, but the amounts of precipitation will be lower (40% chance of about 10 mm). Temperatures will generally be around or a few degrees above normal during the day and well above normal at night. From about the middle of next week, it will become temporarily less changeable under the influence of high pressure (there is only 1 cluster, with clearly high pressure influences above our region), but the chance of a rain or thunderstorm remains present (about 30%). Furthermore, temperatures will gradually rise, especially during the day, with a 40-50% chance of summery values inland by the end of May/beginning of June. After that, the changeable weather is likely to return. About 70% of the members show a high trough above our region with an increasing chance of showers and slightly lower daytime temperatures. The rest of the EPS indicates the continuation of the influence of high pressure, with even warmer air being brought in with a south to southwesterly flow.

Summary multi-day period
Fairly changeable with rain and thunderstorms, especially coming Friday and Saturday. Daytime temperatures will be around or slightly above normal.

Summary EPS period
A high chance (70%) of fairly changeable weather with temperatures around or slightly above normal. Furthermore, a 30% chance of dry and (very) warm weather.

Valid from Friday, May 24 to Wednesday, June 05

 

 

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