Weather of Arabia - Muhammad Aouina - The Kingdom was affected by an air depression associated with a polar air mass of origin that crossed the Kingdom with the early evening hours of Wednesday 2/17/2021, which brought with it snowfall in large areas of the Kingdom, especially after the late night hours, as snow accumulated in most of the heights Mountains that exceed 750 meters above sea level, and that was according to expectations, thank God.
It was the last snowstorm in the history of the Kingdom affected February 19 2015, which was called the storm Jana at the time, so what are the scientific reasons that prevented this air system from being described as a "snow storm"? We answer that in this report:
Atmospheric systems surrounding the polar mass
The consequences and features of the recovery of the polar vortex in parts of the Arctic Circle, in addition to accelerating changes in the distribution of weather systems in the Arctic Circle, specifically in and around Greenland, and the retreat of Atlantic storms northward towards Greenland, to the excitation of the air height towards important areas in the west and central The European continent, coincides with the affected east of the old continent by a very cold "huge" air mass.
While parts of the central Mediterranean are affected by an Atlantic air depression, this depression worked to attract the polar mass that separates from the parent mass towards the Crete Basin, so that this depression becomes the main driver of the polar mass, which moves towards the Cyprus Island Basin, and in light of this, the pressure decreased Air in the basin of the island of Cyprus, to announce the formation of a deep depression.
Conditions for snow storms in the Kingdom
When delving into the details of a snowstorm, you must know what conditions must be met:
The main elements that must be in place to create a snowstorm
1. Perfect angle of descent and path of the polar mass (not achieved):
The landing path of the cluster directly west of Cyprus is considered the best because the mass retains deep cooling up to the surface, while the Crete path releases a large energy of moisture during condensation, which raises the temperature of the layers, to lose much of their momentum.
The responsible for the deepening of cold air towards the surface is considered a pattern ( PVA, NVA ). PVA occurs when the cold air moves from higher to lower values, and NVA when the air moves from lower values to higher. If the upper dispersion is faster than the convergence and the drop, the cooling deepens further.
When the warm air rises over the cold air mass, and the cold air deepens and flows under the warm air mass, the depression "deepens" (the air pressure becomes lower) and the wind increases around the depression.
2. A regular surface depression for a period of time ranging between 24-48 hours (not achieved):
An air depression formed on Tuesday 16/2/2021 in the northeast of the island of Cyprus, which coincided with the formation of another center in western Cyprus, which is known as the ( twin low pressure system ), due to the irregular surface system that impeded the flow of efficiency with regular isobar lines towards the Kingdom (it became The area is dispersed between more than one system, a wind scattering system and a wind convergence system).
In the hours of the day on Wednesday, 2/17/2021, the depression was concentrated superficially south of the island of Cyprus , where the southwesterly winds prevailed, meaning that they reach Jordan's air across the Sinai, so they are dry and unable to produce precipitation and form dense clouds, which worked exclusively for The air effectiveness on the northern regions, and thus most regions lost important periods during the impact of the depression.
3. Long residence polar mass (check):
The kingdom crossed a cold air front with the hours of Tuesday / Wednesday night in the surface layers of the atmosphere, and the cold front continued to deepen in the lower layers on Wednesday, and with the evening hours on Wednesday , the front began to cross in the upper air layers, which increased the air efficiency in most parts of the Kingdom. Which worked on clear accumulations over the mountain heights until the morning hours, thank God, and thus the polar mass remained for more than 36 hours.
Going back six years back, the cause of the formation of the snowstorm was the eruption of a polar air mass directly from Siberia and reached the eastern basin of the Mediterranean Sea, and worked on the formation of an air depression that lasted for three days , as snow fell in the capital Amman for about 36 hours, which worked on Accumulations exceeded 60 cm, and wind speeds (constant) exceeded 85 km / h.
Despite the weather conditions that the Kingdom experienced from the evening hours of Wednesday until the morning of Thursday 18/2/2021, it does not rise to the term "snow storm", for the reasons we mentioned earlier.
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