It’s a failure, as sometimes happens with the weather. Even if forecasts, especially in the short term, are increasingly reliable and rarely faulted, certain phenomena go under the radar of detection and anticipation. This is what happened on Wednesday in the north of France.
The highest temperatures in Île-de-France and Hauts-de-France, as well as nearby, did not reach the 15°C mark. They even timidly crossed the 10°C threshold near the sea. Until late in the morning, however, it was forecast that it would be up to 6°C to 7°C warmer. In the case of Lille, it was 13°C against 16°C expected. In Paris and its region, it should be around twenty degrees like in most regions of the North-West. However, the thermometer remained limited between 12°C and 14°C, a level at the end of March or the beginning of October. In addition, the clouds did not dissipate, although the sun should have been there.
This map provided by Météociel allows you to visualize the situation around 5 p.m., at the hottest time of the day in the northwest quarter of the country. As expected, it was around twenty degrees, or a little more, except in the capital region and to the north of it. A cooler air mass has imposed itself.
As the Météo-villes site explains, it is the anticyclone currently located in the country which is to blame. On Wednesday, it swelled over the United Kingdom, causing a movement of air masses. It thus caused an arrival of humidity from the north of France. This humidity contributed to the maintenance of clouds, limiting the rise in temperatures.
In May, the sun normally rises high enough to dissipate low-lying clouds. The humidity took over on Wednesday. The weather models had not sufficiently taken its level into account, hence the forecast error. Only human observation and analysis by professionals during the morning made it possible to correct the forecast. The automatic models persisted in the error until the afternoon. For example, it was visible on the mobile application used by default on certain smartphones.
This Thursday, the situation should not happen again. Even if the morning was once again cloudy and quite cool in part of the north of France, the sun will take over. As explained by The Weather Channel, the (weak) wind shifts to the east, therefore coming from the continent and not from the sea. This helps to dry out the air mass. It should therefore be, this time, around twenty degrees, or even a little more, from Lille to Paris.
