Record heat waves and widespread drought are ravaging the Southwest US, thanks to a missing climate pattern that normally brings relief to the region.
The monsoon is a seasonal shift in wind that brings rain and cooler temperatures to northern Mexico and the intermountain region of the Southwest United States. Much of the region counts on the monsoon to deliver over half of their annual rainfall.
Without a monsoon, drought conditions often lead to intense wildfires, dwindling groundwater, dangerous heat waves, and huge losses to the agricultural industry – which contributes more than $29 billion to Arizona and New Mexico’s economies each year. In 2018, New Mexico’s surface water supply almost ran out when parts of the Rio Grande came to the brink of running dry.
“The monsoon pattern just has not set up this year at all,” CNN Meteorologist Chad Myers said. “Most people think the desert Southwest is always dry and hot. That is not the case. In the summer it gets very humid and clouds and storms pop up from that humidity.”
How the monsoon operates
During the monsoon, incoming winds shift from dry land areas to the moisture rich areas of the Gulf of California and Eastern Pacific. When this air hits the mountains, it’s lifted, bringing rain to the region. However, this year a ridge of high atmospheric pressure near the US-Mexico border has prevented the seasonal shift in winds.
The lack of a monsoon so far this year has led to scorching heat and drought in Arizona, New Mexico and the surrounding region. Almost 65% of the Western United States is in drought, largely due to the missing monsoon, according to the latest US Drought Monitor. Close to 95% of New Mexico, and over 80% of Arizona are also in drought.
“Drought coverage across just Arizona since the end of June has increased from 13.5% to over 80%,” Brad Pugh, a meteorologist at the Climate Prediction Center, said. “And that’s going to increase further this week.”
Phoenix is already sweating through its hottest summer in recorded history. The average high temperature has been almost 108 degrees. Phoenix also registered a record-tying seven consecutive days with a low temperature above 90 degrees in July.
Though the drought situation is dire, the region may get much needed rain from the tropics. East Pacific hurricanes and tropical storms can often move into the Southwestern United States after making landfall in Mexico, helping bring moisture to the region. New developments in the eastern Pacific could bring much needed rain to the desert Southwest if they track in that direction.
“If one of those tropical cyclones takes a northward track near the Baja of California, that would likely lead to a northward surge of moisture from the gulf of California into the desert Southwest,” Pugh said.