North America | Polar air masses are rushing to the north of the continent, while a heat dome and a heat wave dominate the rest of the regions.

Arab Weather - Weather forecasters at the Arab Weather Center indicated that the latest computer modeling outputs indicate that large areas of the United States of America, especially the south and west, will continue to be affected by the heat dome phenomenon, which is accompanied by an air mass with high surface heating, such that very hot weather prevails, especially with the increased heating of the air due to the Foehn phenomenon. This is met by the rush of polar air masses towards the north of the continent, causing rainstorms and snowfall.

Tropical High Strengthens, Fueling Heat Dome Over North America (Temperatures Exceed Mid-40s)

According to computer simulations, an upper wave is expected to cross northern North America, leading to the intensification of the tropical high south and east of the continent, which will fuel the heat dome phenomenon, with hot to very hot weather prevailing in various states, especially the southern ones. Daytime temperatures are expected to exceed the mid-forties Celsius in some areas, especially in the plains and low-sea areas.

The rise in temperatures and warming of the air is enhanced by a climate phenomenon called the “Fohn winds,” which will also play a clear role in the severity of the heat in the United States, especially in the plains, slopes, and valleys located east of the American mountain ranges.

North America is affected by a very cold polar mass and winter storms

In stark contrast, North America is affected by a very cold polar air mass coming from the North Pole. Due to the presence of water bodies and the effect of the lake phenomenon, large air pressure differences are formed between the polar mass and the warmer and more humid air, which develops deep depressions and storms that bring strong winds, leading to a significant drop in temperatures and heavy rainfall in many areas. It is also expected that the Rocky Mountains in Canada and Alaska, as well as northern Canada, will witness heavy snowfall in the coming period.

Scientifically: The heat dome and the Foehn winds are two sides of the same coin and they both promote the rise in temperature.

A heat dome is a climatic phenomenon that results from a high-pressure area in the upper atmosphere, which heats the air in the lower atmosphere due to a dynamic process called heating under pressure. As the air in a certain area is compressed under the influence of a high-pressure area in the upper atmosphere, a hot surface air mass is created, the intensity of which varies according to the area, the intensity of the high-pressure area, and also according to the period of its formation during the year.

The high pressure traps the hot air like a lid on a boiling pot. As the hot air expands vertically in the atmosphere, the high pressure pushes it back toward the ground. The air is compressed again under the high pressure area, causing it to gain more heat. This is known scientifically as heating under pressure.

The Foehn phenomenon or Foehn winds is simply the descent of winds from the tops of high mountains towards the lower slopes and valleys, where rapid heating of the air occurs due to this movement of air, as shown in the following diagram.

As a quick mathematical operation in meteorology, the air cools by 1 degree Celsius for every 150 meters we rise above sea level, but it warms by 1.5 degrees Celsius for every 150 meters we descend from sea level. Suppose we are in area (A) with an altitude of 0 meters above sea level and the air temperature is 40 degrees Celsius, and there is a mountain 1000 meters high, and we want to know what the temperature of the same air would be if it moved from point (A) to point (B) behind the mountain at an altitude of 0 meters as well, the operation would be as follows: 40 - (150/1000) * 1 + (150/1000) * 1.5 = 43.34 degrees Celsius, meaning that the air temperature rose by 3.34 degrees Celsius at point (B) due to the process of descending the mountain.

God knows best.