The month of July is considered to be the hottest month of the year. This occurs a month after the summer solstice. The summer solstice is the longest day of the year.
Time will tell if July is the hottest month this year. In some years, June or August can be hotter. Because of the upper level pattern (jet stream) we are experiencing very dry conditions and a moderate drought this year.
The jet stream has been taking a lot of the heavy rain to our south and west. Last month, we saw the dangerous flooding and damage caused by the flooding in West Virginia.
In the opposite, brush (wild fires) can occur due to a lack of rain. The difference in getting rain in the summer versus the other seasons is that not all areas receive the same amount of rain. One area of the country could get an inch of rain within a half hour while not too far away, little or no rain occurs.
This is why Meteorologists use the phrase “scattered showers” during the summer months. In the summer, scattered showers and thunderstorms can often occur with the approach and passage of a cold front. Also an upper level disturbance can cause scattered showers and thunderstorms to form. As a cold front approaches, showers and thunderstorms can occur.
What effects the extent of the showers and thunderstorms?
The amount of dry air in the mid-upper levels of the atmosphere will effect the development and extent of the overhead showers and thunderstorms.
How humid is the air mass?
The more humid the air mass, the more showers and thunderstorms can develop. Thunderstorms like to form in a hot and humid air mass.
Instability in the atmosphere?
The more instability in the atmosphere the greater the chance of thunderstorms. Instability occurs when the sun heats the ground and this warm (hot) air rises and meets with cooler air above.
This process causes clouds to form and as the process continues to get repeated the clouds grow and get larger.
Eventually they become cumulonimbus clouds, the clouds that produce thunderstorms. A stable atmosphere, which is the opposite of an unstable atmosphere, occurs when there is warm air aloft above cooler air near the ground. This stable atmosphere does not allow thunderstorms to form or if there are strong thunderstorms that move into this stable atmosphere, they can quickly weaken.
An example of this is the sea breeze along coastal areas. The sea breeze cools the air nearer the ground while warmer air is above. This causes a stable atmosphere. Thunderstorms have trouble sustaining themselves when they move into this stable environment.
Thunderstorms like to form in a warm (hot) unstable environment. In an unstable environment, cooler air is above and warm humid air is located nearer the ground. Remember, warm air is lighter, less dense and as a result, it rises.
Cool air is heavier, more dense and as a result it sinks, as colder, more dense air likes to be below the less heavy warmer air. This scenario is a stable environment.
When the atmosphere becomes unstable, there is a lack of balance and the atmosphere is not happy. As a result of this, strong to severe thunderstorms can occur. Also, for severe storms to form we need strong winds in the upper atmosphere changing direction with height (shear).
With higher shear values this can cause severe thunderstorms to develop causing strong damaging winds. These damaging winds can cause trees or tree branches to fall on power lines causing power outages.
When there is the potential for severe thunderstorms to occur, a severe thunderstorm watch will go into effect for a given county. When severe thunderstorms occur, a severe thunderstorm warning will go out. This same logic is for a tornado watch versus warning. When thunderstorms occur, you should get inside a sturdy building (home) and away from the windows.
Email your weather questions to Al, (he loves to hear from his readers!).