“Any hurricane is an enormous challenge,” Gov. Greg Abbott said in a news conference Saturday. “This challenge is complicated and made even more severe, seeing that it is sweeping through an area that is the most challenged area in the state for Covid-19.”
Hanna made landfall Saturday evening on Padre Island, south of Corpus Christi, according to the National Hurricane Center. It was the first hurricane of the season in the Atlantic and had sustained winds of 90 mph, making it a high-end Category 1 hurricane.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain or squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (), typhoon (), tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.”Tropical” refers to the geographical origin of these systems, which form almost exclusively over tropical seas. “Cyclone” refers to their winds moving in a circle, whirling round their central clear eye, with their winds blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The opposite direction of circulation is due to the Coriolis effect. Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface, which ultimately recondenses into clouds and rain when moist air rises and cools to saturation. This energy source differs from that of mid-latitude cyclonic storms, such as nor’easters and European windstorms, which are fueled primarily by horizontal temperature contrasts. Tropical cyclones are typically between 100 and 2,000 km (62 and 1,243 mi) in diameter.
The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth’s rotation as air flows inwards toward the axis of rotation. As a result, they rarely form within 5° of the equator. Tropical cyclones are almost unknown in the South Atlantic due to a consistently strong wind shear and a weak Intertropical Convergence Zone. Conversely, the African easterly jet and areas of atmospheric instability give rise to cyclones in the Atlantic Ocean and Caribbean Sea, while cyclones near Australia owe their genesis to the Asian monsoon and Western Pacific Warm Pool.
Coastal regions are particularly vulnerable to the impact of a tropical cyclone, compared to inland regions. The primary energy source for these storms is warm ocean waters. These storms are therefore typically strongest when over or near water, and weaken quite rapidly over land. Coastal damage may be caused by strong winds and rain, high waves (due to winds), storm surges (due to wind and severe pressure changes), and the potential of spawning tornadoes. Tropical cyclones also draw in air from a large area—which can be a vast area for the most severe cyclones—and concentrate that air’s water content (made up from atmospheric moisture and moisture evaporated from water) into precipitation over a much smaller area. This continual replacement of moisture-bearing air by new moisture-bearing air after its moisture has fallen as rain, may cause multi-hour or multi-day extremely heavy rain up to 40 kilometers (25 mi) from the coastline, far beyond the amount of water that the local atmosphere holds at any one time. This in turn can lead to river flooding, overland flooding, and a general overwhelming of local man-made water control structures across a large area.
Though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They also carry heat energy away from the tropics and transport it toward temperate latitudes, which may play an important role in modulating regional and global climate.
Hurricane Hanna weakens to tropical depression after making …
By Sunday evening it was downgraded to a tropical depression, with maximum sustained winds of 35 mph, and was slowly dying over the mountains of northern Mexico. However, it still posed a threat for rain in the drenched Rio Grande Valley, where more than a foot of rain has fallen.
A flash flood emergency remained in effect for Hidalgo County, Texas, as roads and highways are underwater, prompting water rescues.
Hurricane Hanna weakens to tropical depression after making …
Widespread rainfall totals are between 4-6 inches, but some places have seen a foot of rainfall. There is still the chance for 2-4 inches of rain in parts of southern Texas as well as the chance of isolated tornadoes through the rest of Sunday.
Abbott issued a disaster declaration for 32 counties in the state and has also issued a federal emergency disaster declaration request. Urging extreme caution, Abbott warned residents across the state not to forget about the virus because of the storm.
FEMA approved a Federal Emergency Declaration following the storm’s landfall, Gov. Abbott’s office said in a news release on Sunday.
Officials in Hidalgo County, where several of the affected cities are located, reported overwhelmed hospitals last week filled to capacity and a judge ordered residents to shelter at home following upticks in both coronavirus cases and hospitalizations.
“This is a time in response to a hurricane where sometimes people will come together, come together to shelter, come together just as close family come together, as friends come together to respond,” Abbott said. “That coming together will continue to provide the ability for Covid-19 to transmit from one person to another.”
‘Dramatic’ flooding, governor says
Some of the southernmost parts of Texas received more than a foot of rain as the center of the storm crossed over to northeastern Mexico, CNN meteorologist Derek Van Dam said.
This led to widespread flooding in the Rio Grande Valley town of Mission, where the National Weather Service declared a flash flood emergency. There were numerous reports of water rescues, mainly from cars stuck in rising flood waters. Parts of US Highway 83 were impassable.
“We’ll continue to see dramatic waves of flooding including flash flooding that will come upon people suddenly. One moment they will be in an area … where it seems like there’s a little rain and then moments later, they could be washed in water up to their doors, if they’re in their cars, up to their knees, if they’re walking around,” the governor said Saturday.
Even as the storm weakens in the mountains of northern Mexico, additional rainfall is possible overnight. There is also a risk of isolated tornadoes. A confirmed EF0 tornado, with winds between 70-75 mph, struck the Brownsville airport early Sunday.
Meanwhile, another potential tropical system that could develop over the next five days was trekking behind Hanna across the Atlantic Ocean, Van Dam said.
Thousands without power
Tropical storm-force winds in parts of Texas could cause power outages and damage to buildings and trees, the weather service said. Along with the possibility of brief spin-up tornadoes, Van Dam said, and there will still be dangerous rip currents and localized beach flooding along the coast.
In Mission, officials said early Sunday morning emergency responders had already been dispatched to several homes for water rescues. A tornado warning was issued through early Sunday morning and officials reported thousands of residents were left without power, after heavy winds caused damage to power lines and traffic signals.
“Electricity crews must shelter in place due to wind speeds the rain,” the City of Mission said on Twitter. “You’re asked to only report downed power lines or safety hazards. Crews will continue to respond to outages when it’s safe to do so.”