Weather Systems and Patterns

What types of weather systems does the East Mountain region experience? What global circulation patterns influence those weather systems?

An air mass is a large body of air having a more or less uniform temperature and moisture content covering large regions of the Earth. The different types of air masses are defined and referred to usually based on temperature and moisture content:

Temperature
Tropical – (T) generally hot
Polar – (P) generally cooler
Arctic – (A) generally very cold

Moisture content
Maritime – (m) wet
Continental – (c) dry

The East Mountains, and a good part of New Mexico is typically under a Continental Polar air mass in the winter and a Continental Tropical air mass in the summer. This means that New Mexico is often dry and cold in the winter and dry and hot in the summer. Any variations in the air mass above the East Mountains is due to patterns of global circulation of air in the atmosphere.

One such global circulation pattern is due to the Jet Stream. The Jet Stream occurs when a sharp temperature gradient from a polar front causes a steep pressure gradient and air is under strong pressure gradient force, this causes air to move fast at high altitudes over the. Jet streams usually occur 9 to 12km above sea level. Rossby waves are essentially wiggles in the Jet stream, the top part of the wave is a ridge and the bottom is a trough.

The Polar Jet Stream Across the United States

Generally, where a ridge turns into a trough there is an area of high pressure and where a trough turns into a ridge there is an area of low pressure which is usually indicative of storms.

Because New Mexico is located continentally and no large bodies of water exist in direct proximity to the land, it relies mostly on systems developed and moved by the Jet Stream for moisture containing air that can lead to precipitation and larger storms.

Jet Stream Over New Mexico

 Another factor influencing storm systems in the East Mountains are the Al Niño and La Niña oscillating patterns across the Pacific Ocean. If you have ever heard a weather man say that it is going to be an El Niño winter, you know to expect more precipitation in New Mexico. But what is an El Niño?

Walker circulation is the circulation of air in the atmosphere that is a result of the complex interaction between heating in the atmosphere and heating of the ocean and ocean currents. El Niño and La Niña conditions are caused directly by Walker circulation being either stronger or weaker than usual.

An El Niño is what occurs when the Walker circulation cell weakens and warm pacific waters that are usually blown away from the western coast of the US are allowed to slosh back resulting in cooler than normal temperatures near the Philippines and abnormally warm moist air near the coast of California.

A La Niña is what occurs when the Walker cell is stronger than normal and warm pacific waters are moved even farther than usual resulting in abnormally warm temperatures in the Philippines and abnormally cold and dry weather along the coast of California.

Heat Signatures of the Two Patterns