What are Some Common Weather Phenomena?

The most common type of weather phenomena is a mid-latitude cyclone. This is a low pressure system which often occurs near the trough of the jet stream in the mid-latitudes (between 30 and 60 degrees north). Depending on the time of year and the temperatures, this weather phenomena can bring severe weather such as damaging winds, tornadoes, and large hail, as well as heavy snow and blizzard conditions. When the jet stream is relatively straight (just moving from west to east), mid-latitude cyclones are not likely to occur.

Tropical Cyclones

Tropical cyclones (often referred to as tropical storms and hurricanes in the Atlantic Basin) are common low pressure systems in the summer and fall months, when the sea surface temperatures are often the warmest. The warm sea surface temperatures act as the “fuel” for tropical cyclones. Tropical cyclones also often occur in the Eastern Pacific, the Western Pacific, and the northern Indian Ocean. Tropical cyclones can bring catastrophic sustained winds of over 150 miles per hour, as well as rising sea levels (often called storm surge) several feet above high tide, and heavy rainfall over 20 inches.

Severe Weather

Types of severe weather phenomena include “supercell” thunderstorms, squall lines, microbursts, tornadoes, large hail, and derechos. Supercell thunderstorms are discrete (isolated/separate), rotating updrafts which often lead to other severe weather phenomena, including tornadoes and large hail. Tornadoes are violently rotating columns of air, which can bring wind speeds from 80 miles per hour in weak tornadoes to over 300 miles per hour in the strongest tornadoes. Hailstones have been recorded as large as eight inches in diameter in the United States, and even small hail can still cause significant damage to crops and property. Squall lines are a line of continuous strong thunderstorms that often lead to strong straight-line winds (winds moving in one direction, not rotating like a tornado), but can also sometimes spin up quick, weak tornadoes. Microbursts are strong damaging winds that occur when air rapidly moves down out of a thunderstorm and hits the ground. Derechos are a special type of long-lived, very strong squall lines that usually cause damage over an area 1,000 miles across or larger.

Winter Weather

The most common type of winter weather is snow, which is caused by mid-latitude cyclones. When snow is falling heavily enough and there are strong enough winds, blizzard conditions can occur, which can knock out power and make travel essentially impossible. One special type of mid-latitude cyclone that creates winter weather is called a Nor’easter. Nor’easters are named due to winds from the northeast; they form and move through the northeastern United States, bringing strong winds and heavy snow. Another common type of winter weather is freezing rain, which is caused by liquid rain that forms above freezing temperatures, but falls and hits the surface where temperatures are below freezing. The rain freezes on contact with the surface and can lead to ice buildup, causing widespread power outages and hazardous travel.