A tropical storm warning has been issued from Port Mansfield, Texas to Boca de Catan, Mexico, according to the National Hurricane Center. The warnings are associated with a system the National Hurricane Center has designated as Potential Tropical Cyclone Four, located in the southern Gulf of Mexico, about 400 miles south-southeast of the mouth of the Rio Grande.
The hurricane center uses the potential tropical cyclone designation to issue warnings for a system prior to it actually being named.
“Since the system is likely to develop further and make landfall as a tropical storm in less than 36 hours, advisories are being initiated on Potential Tropical Cyclone Four with tropical storm warnings being issued for portions of the coasts of northeastern Mexico and South Texas,” the Hurricane Center said in its forecast discussion.
Regardless of development, the system is expected to bring heavy rain to northeastern Mexico and extreme southern Texas. Rainfall amounts of up to eight inches are possible in Mexico, and one to three inches expected in far South Texas.
Meanwhile, the rest of the desert Southwest, an area dealing with long-term megadrought, is bracing for a moderate risk, Level 3 of 4, of extreme rainfall, which could lead to flash flooding Friday and Saturday.
“A multi-day significant rainfall event is forecast across the Southwest US this weekend,” the Weather Prediction Center said. “Impactful rainfall is most likely across parts of southeast Arizona into southwest New Mexico with storm total amounts approaching 5-6 inches.”
Flood watches are posted for nearly 10 million people across the Southwest, including Tucson, Phoenix, Albuquerque, and El Paso, through Saturday.
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Zack Taylor, a senior meteorologist at the Weather Prediction Center, pointed out there are multiple factors creating the new surge of moisture, including the remnants of a tropical wave currently over northern Mexico embedded within the larger-scale monsoon.
One thing making the particular event different is the timing of the storms. Typically, monsoon storms are diurnally driven, meaning they occur in the afternoon and early evening. This time, the chance for rain will be around the clock. Storms will fire up in the afternoon and early evening as usual, but will also occur Friday overnight and early Saturday morning.
There are also two timelines as far as the impact goes with the next system: the short term, which would be flash flooding, and the long term, which would be the influence on the rivers, creeks, and streams in the area.
“The main concern is with the flash flooding initially,” Jeff Davis, senior meteorologist for the National Weather Service office in Tucson told CNN. “But we’re transitioning into a situation where we may have some of the larger washes that are normally dry and some of the main stem rivers starting to see significant flows by Monday.”
By the end of the weekend, the rain will spread east into Texas, another state experiencing significant drought. By early next week, 3-5 inches of rain is possible from Lubbock, Texas, to Shreveport, Louisiana, increasing the potential for flash flooding in those areas.
Monsoon rains are helping the drought, but not enough
While the desert Southwest may not be known as a wet part of the country, this time of the year is when it is most likely to get rainfall. The rainy season helps the Southwest, but it often leads to superficial improvement.
The drought-plagued region is already dealing with a water crisis, so they need the rain, but it may not be as beneficial as it appears.
One of the concerns with the upcoming heavy rain is it is not expected to surge far enough north or west where the water is needed most: California, Nevada, Oregon, and northern Utah.
“Several large areas of improvement were noted this week, with the heaviest rains and most widespread improvement covering Arizona,” the latest US Drought Monitor details. “After an extended period of serious drought, the heavy rains have prompted broadscale improvement in monsoon-affected areas.”
The recent rains have helped, but only for some areas of the West. Roughly 70% of the West is still in some level of drought, down from 90% just three months ago. Most of the improvements have been in just two states, Arizona and New Mexico. The recent rains have helped those two states even more.
“Monsoonal rains are only a fraction of the water needs of the West,” said Chad Myers, CNN meteorologist. “That said, the recent rains have raised the level of Lake Mead by 1.8 feet over the past three weeks.”
Myers pointed out the main driver for water in this region is the melting winter snowpack, but it doesn’t mean the rainfall isn’t beneficial.
“Although the heaviest of the upcoming rain will miss the Colorado River basin and Lake Mead, plenty will still fall in Utah and Colorado directly into the upper drainage basin of the river,” Myers said.
The US Southwest monsoon officially runs from June 15 to September 30, putting the region beyond the halfway point of the season.
The recent rain in Las Vegas has brought its monsoon total up to 1.29” marking the wettest monsoon season in a decade. However, the city is still well below where it should be at this time in the year, having received just over half of its average rainfall up through mid-August. The 1.29” this season already makes 2022 Vegas’ third-wettest monsoon in the 21st century. It comes just two years after the driest monsoon on record back in the summer of 2020 when there was no measurable rain.
Down the road in Tucson, they’ve had a roller coaster of monsoon seasons recently. 2020 was the second-driest on record (1.62”) while 2021 managed to be the third wettest (12.79”). So far this season, a little over 2” has fallen in the city, below the average to date of 3.48”.
Salt Lake City has had 6.70” so far this year, but their average is more than 10 inches. It is an ever-present sign of how bad the drought has been over the last few decades in the region that we are celebrating getting a little more than half of what is normal.
CNN Meteorologists Pedram Javaheri and Tom Sater contributed to this story.