Weather chronicle | Return of the April frost in 2022: will we survive the nightmare of April 2021?

From 1uh February 2021, temperatures above the seasonal average. In recent days, many regions of France have been holding 20°C for several days in a row… just like in 2021. You would understand: this year the picture of 2021 is repeated. A sharp drop of cold air is expected from 1uh April. What damage is expected?

February and March 2022 under sweetness

Numerous January frosts made it possible to remove vernalization, i.e., the need for cold, from crops. Thereby, the softness seen in February and March allowed the buds to open, that is, the opening of the buds. First, on average or even slightly ahead, vegetation was well ahead of the past week with amazing softness, but no major breaking records. On fig. 1 shows deviations from the standards of the national thermal indicator.

Specifically, Paris is currently moving towards a series of 5 days with temperatures of at least 20°C.. Looking at at least equivalent series (until April), we see that there were 3 over a period of 130 years at Montsouris (1873-2002), and that this series is the 3rd in 20 years (2003-2022). ). In 2021, the monthly record is 26°C!

A sharp descent of cold air is expected during the 1st.uh April

In the week leading up to 2021, weather patterns will change overnight. From March 29 to April 2, local temperatures may drop by more than 25°C.. This cold air is driven from northeast Europe by a depression falling from England into France.

This cold will a priori be wet and windy at first. The risk of snow is even present on some weather models. It will be advective cold (cold at all altitudes of the atmosphere), which will be very difficult to fight. Then from April 2 it will be drier and less windy. This will allow the subsequent installation of radiant cold (accumulation of cold on the ground), accentuating the cold in the first meters of the atmosphere.

Meteorological situation on March 27, 2022.

Weather forecast for Saturday, April 2, 2022 by GFS model

There are still many uncertainties regarding these weather patterns. especially :

  • The presence of clouds and/or wind can block the exacerbation due to the installation of radiative cold.
  • The presence of snow on the ground can drastically lower the temperature. However, this layer of snow protects arable crops, but much less forestry.
  • Not all models are consistent with minimum temperatures. The gel has been received, but the intensity has not stabilized yet. The American GFS model is significantly colder than its European CEP counterpart. Indeed, the European model provides more maritime air (less cold and more humid) than the American one (colder and drier).
  • The lower Rhone valley would be protected a priori by the Mistral (a mixture of air that slows down the drop in temperature). However, it will be necessary to keep an eye on the upper Rhone valley, where the wind will allow a potentially destructive black frost to set in: apart from sprinkler irrigation, there is no means of combating black frost.
  • The spread of frost to the southwest is still poorly determined by models.
  • The duration of the event is still poorly defined. This a priori should apply to France at least until April 4th.

Therefore, these forecasts will be updated in future bulletins.

Will this event be similar to the 2021 freeze?

At the moment, the duration and scope are similar to the event from 6 to 8 April 2021. IThere is still uncertainty about frost forecasts. For apricots, plums, pears, kiwis and even cherries, if forecasts are correct, this April 2022 event will be comparable to the April 2021 event.

This is how an agro-climatological map of damage to fruit trees (without grapes and apple trees) from frost in the worst case (GFS scenarios) could look like. At the moment, it is not possible to refine the zonation of damage until all models are consistent with each other.

Pessimistic scenario

Optimistic scenario

Are April frosts a common occurrence in meteorology?

It is not frost that causes these exceptional agro-climatic events with dramatic consequences for production, but mild winters that allow early vegetation to emerge.

Climate change sends us a new warning. A World Weather Attribution science paper attributes the April 2021 episode to climate change and points to a 60 percent increase in the likelihood of a similar episode by 2050 with continued climate change.

Prevent: a new tool from ITK

Starting with the April 2021 freeze, ITK has been working to take into account the impact of frost on production, which it makes available from its Prevent app. It quantifies and characterizes the intensity of the future hazard, which it combines with data on the sensitivity of crops depending on the stage of development, site by site. He also recommends taking various protective measures depending on the intensity and weather conditions. Frost alerts are configured and sent according to the predicted crop loss rate calculated by the tool. Given the announced weather conditions, the vineyard and apple tree already included in the Prévent program can be managed with the utmost precision.

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