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Spokane, Washington  Est. May 19, 1883

Tropical storm warnings for parts of Texas, Mexico as storm nears

This radar image shows Potential Tropical Cyclone Four in the Gulf of Mexico on Saturday, Aug. 20, 2022.  (TRIBUNE NEWS SERVICE)
By Matthew Cappucci Washington Post

Tropical storm warnings have been issued in South Texas and the coastline of Tamaulipas, Mexico, ahead of a “potential tropical cyclone” churning toward the Rio Grande. Heavy rainfall, gusty winds and a localized storm surge of a couple feet are probable as the Atlantic begins to awaken after month-long stretch of silence.

Flooding has already been reported in parts of northern Mexico, and another inch or two of rain is likely. The first showers from potential tropical cyclone 4, or PTC4, were also streaming ashore, as well.

Tropical storm warnings are in effect from Boca de Catan, Mexico, to Port Mansfield, Texas.

Although PTC4’s coastal effects are expected to lessen as it dissipates late Sunday or Monday, its real impact won’t come until the middle of next week. That’s when copious rainfall, in some places accumulating half a foot or more, could blossom over Central Texas, southern Oklahoma and Arkansas.

Much of Texas needs the rainfall. The Lone Star State has been plagued by drought as of late, with more than 26 percent of Texas facing a top-tier “exceptional” drought, according to the U.S. Drought Monitor.

As of 1 p.m. Eastern time Saturday, PTC4 was still a tropical depression in the Bay of Campeche. The reasons for that designation are pure technicalities, as the impacts will remain the same.

PTC4 appeared nominally impressive on infrared satellite, with an obvious swirl signifying mid-level rotation. At the surface, however, Hurricane Hunter reconnaissance aircraft have repeatedly been unable to locate a cohesive low-level center of circulation. That means there isn’t a single well-defined central vortex, preventing the classification of PTC4 as a tropical storm. Subsequently, it can’t earn the name “Danielle.”

Otherwise, plentiful shower and thunderstorm activity is evident, and radar indicates a spattering of heavy downpours approaching the coastline. The storm is also displaying healthy outflow aloft, or the exhaust of “spent” air at high altitudes. That’s where the storm is exhaling air that it’s already extracted heat and energy from. The more it breathes out, the more warm, humid air it can ingest from below. That supports its maintenance or intensification.

PTC4 is running out the clock. It only has a few more hours left before making landfall, and its odds of consolidation into a tropical storm are waning. That won’t change the actual impacts though.

Isolated to widely-scattered heavy downpours will pivot ashore in southern Texas and northern Tamaulipas through Saturday evening, when the center of circulation should come ashore. Because the system is poorly-organized, there aren’t any well-structured, unbroken spiral rain bands. Instead, it’s also struggling with a bit of mid-level dry air on the northern half of the storm, thinning out precipitation coverage. That’ll reduce overall amounts to a general inch or two, but not much more - at least in South Texas.

Breezy winds gusting over 30 mph are also expected, and some minor coastal surge up to about a foot in depth is expected. Impacts should be minimal.

The storm should disintegrate by noontime Monday.

Thereafter, the exceptional tropical moisture dragged north by PTC4 will remain in place over Texas. A new system - a surface low forming along a stalled stationary front near the Red River, or the Oklahoma border, will tap into that humidity, resulting in days on end of heavy rainfall.

By the midweek, some places north of Dallas and south of Oklahoma City, including along Interstates 35 and 287, could be looking at six inches or more of rainfall. That’ll put a hefty dent in the existing deficit across that area.

Texas desperately needs the rainfall, as displayed by where the driest conditions are at this point.

Unfortunately, the weakness of PTC4 won’t deliver what’s needed in northeastern Mexico, which is experiencing one of its worst droughts in decades. Reservoirs providing water to the Monterrey metropolitan area, which is home to more than 5 million people, have been tapped dry. Tropical cyclones play a critical role in water supplies in northern Mexico and can contribute up to 50 percent of summer precipitation in some areas, helping to refill dried-up reservoirs. But as the Atlantic hurricane season has had a slow start, much of region, especially the state of Nuevo Leon, has yet to see significant rainfall.