The monsoon brings much-needed rain to the southwest

0

For about three months each year, the desert southwest transforms into a magical landscape of pastels, flashes of light, and oases of life in an otherwise sandy, cactus-studded chaparral. Some communities collect half of their annual rainfall in a few short afternoons, while others are inundated when dry arroyos turn into bubbling rapids.

The culprit? The southwest monsoon — a seasonal wind shift that pumps moisture from the Gulf of Mexico and Pacific Ocean north to New Mexico, Arizona, and parts of southern California, Nevada, Utah, and Colorado. The moisture surge will bring isolated thunderstorms sweeping across the region, with high cloud bases offering spectacular views of pinpoint lightning strikes. This year’s monsoon has a rapid onset, coming weeks earlier than planned and with a greater intensity than expected.

A rare flash of lightning shook California with 66,000 strikes

Along with the elegance and beauty comes concerns about flash floods and debris flows, particularly the burn scars from wildfires that have ravaged the South West in recent years.

A busy start to the monsoon season

At the start of the busy start to the season, Chuck Jones, a senior meteorologist at the National Weather Service in Albuquerque, said the monsoons will last for months.

“It started on June 17, so almost two weeks early,” he said in a phone interview. “Generally we are talking about starting near July 4th and at least Labor Day, but we have an official monsoon season that lasts from June 15th to September 30th. It was early and consistent.”

One way to diagnose the monsoon is to look at the dew point — a measure of how much water is in the air. In Albuquerque, the summer dew point averages 47 degrees. It rose above it in June and only recently fell again.

“I noticed that our average dew point went down around the 40s yesterday,” Jones said. “The last time our 24 hour dew point average was below 50 was on June 16th. That’s 20 days in a row.”

Heavy rainfall and flooding are a concern

Accompanying the souped-up atmosphere has been copious amounts of precipitation. Albuquerque has received 2.38 inches of rain since the monsoon began on June 17. The average for the entire month of June is 0.57 inches.

Albuquerque’s average annual precipitation is 8.84 inches, meaning more than a quarter of the city’s annual precipitation fell during a two-week window.

“A good part of western and central part of [New Mexico sees] 50 percent or more” of their annual rainfall from the monsoons, Jones said. It was a blessing in disguise for a drought-stricken state gripped by its desperate need for water. “This year has been incredible. Most of the state improved one drought category.”

While rain is welcome, it can cause problems — especially when it comes all at once. Even half an inch of rain per hour can be problematic for sandy soils that struggle to absorb excess runoff.

“You know what, the first 10 days to two weeks it wasn’t convective but lighter to general moderate rain and that helped a lot of places,” Jones said. “It didn’t do much damage to the last few burn scars.”

He said things have changed in the last week or so and that precipitation is increasingly convective in nature – or consists of showers and thunderstorms with torrential downpours.

“In the last week or so it turned into a more regular monsoon with rain surges and storms in the afternoon and evening,” Jones said. “They get weaker overnight and are usually done by the next morning, but we start around noon and do it all over again. But we have some issues with burn scars and flooding, mainly in the last 10 days.”

Since the monsoon began, his office has issued 47 flash flood warnings.

While most of the monsoon’s influence has so far been relegated to the Land of Enchantment, Arizona has caught on a bit, too. Phoenix saw 0.32 inches of rain in June, which sounds underwhelming, but keep in mind that 0.02 inches is the monthly average.

Farther north and west, monsoonal moisture in the middle layers of the atmosphere has helped produce some storms, but a dry near-surface layer evaporated much of the precipitation before it hit the ground. The result? A spate of “dry thunderstorms,” ​​some of which produced lightning that ignited new wildfires.

More than 60,000 lightning bolts lit up the skies over central and southern California in the penultimate week of June. One of the attacks killed a woman walking her dog through a park in the Los Angeles metropolitan area.

Share.

Comments are closed.