A hurricane warning remains in effect between Port Mansfield and Baffin Bay. A tropical storm warning covers remaining coastal communities from the U.S.-Mexico border north through Port O’Connor. Some of the same areas that were struck by Category 4 Hurricane Harvey on Aug. 25, 2017, are being hit again.
On Saturday afternoon, the National Weather Service reported “significant structural damage” in Port Mansfield with winds gusting over 80 mph. “Severe damage” was reported to a pier on North Padre Island where nearby winds topped 100 mph. PowerOutage.us indicated over 150,000 customers without power in South Texas as of Saturday evening.
A dangerous storm surge is affecting areas just north of where the center is coming ashore. The surge is the storm-driven rise in ocean water above normally dry land at the coast. Storm surge warnings extend from near Baffin Bay to Sargent, where the water may rise up to 2 to 6 feet above normally dry land, resulting in coastal inundation. The maximum surge of 4 to 6 feet was predicted between Baffin Bay and Corpus Christi Bay, where the surge was expected to be the highest since Hurricane Allen in 1980.
Images from social media showed water inundating parts of downtown Corpus Christi Saturday afternoon.
In addition to coastal flooding, South Texas will also be subjected flash flooding from heavy rain as well. Up to 18 inches of rain are expected as Hanna’s torrential rain bands focus deep tropical moisture. As of Saturday evening, already 8 to 11 inches of rain had fallen along the South Texas coast in the area just south of Port Mansfield, where a flash flood warning was in effect. A flash flood warning was also issued for areas farther inland including for Harlingen and Weslaco, Texas.
The National Weather Service warned the “intense rainfall this evening into the overnight hours could be significant and life-threatening at times.”
A local state of disaster was declared in Hidalgo County, which borders Mexico and is located to the west-northwest of Brownsville, given “expected catastrophic flooding.”
Hanna’s impending landfall comes at a time when the United States continues to be gripped by the coronavirus pandemic; Texas ranks second among the states with the most new cases in the past week, and South Texas has been hit particularly hard. According to the Texas Department of Health and Human Services, the seven counties from Corpus Christi south to Brownsville and inland along the Mexican border, which are likely to see Hanna’s strongest winds and heaviest rains, have diagnosed a total of 18,420 active covid-19 cases. Many of these cases have occurred in the past few weeks.
The pandemic complicates storm shelter and relief operations as social distancing requirements and other prevention efforts are taken into account, with FEMA and state agencies tasked with responding to both the coronavirus and hurricanes.
Hidalgo County has recorded the third-highest number of fatalities statewide, with at least 433.
More than 2,000 miles to the east, another storm — Gonzalo — was gasping for life as it trekked west, bound for the Windward Islands. A tropical storm warning was up for St. Vincent and the Grenadines, Tobago, and Grenada, where gusty winds and several inches of rain are possible.
Simultaneously, a third Atlantic system south of the Cape Verde islands bears watching and has an increasing likelihood of tropical development once it approaches the Lesser Antilles during the first half of next week.
As of 10 p.m. central time Saturday, Hanna was centered 35 miles west of Port Mansfield, heading west-southwest at 9 mph. Due to interaction with land, its peak winds had dropped to 75 mph.
Hanna had intensified at an impressive clip since Friday morning, its peak winds increasing 50 mph from a low-end tropical storm (with 40 mph maximum winds) to a high-end Category 1 hurricane with 90 mph maximum winds at landfall.
On Saturday afternoon, an eye also became visible at the center of the storm, indicating intensification was continuing through to landfall. Wind gusts had topped 100 mph at Laguna Madre, Texas, which is adjacent to South Padre Island.
The storm’s peak winds will continue to gradually weaken as it moves further inland and it is likely to be downgraded a tropical storm by Sunday morning.
Rainfall and flood threat
In South Texas, a broad 6 to 12 inches of rainfall is likely, with localized 18-inch amounts. Rainfall rates of up to 4 inches per hour could occur. This rainfall output, the Weather Service warned, could prompt “many evacuations and rescues” as waterways rapidly overflow, roads and parking lots become “rivers of moving water,” and floodwaters enter structures.
Farther north, a spattering of tropical downpours were affecting the Houston-Galveston area, while another cluster of rains was deluging the Golden Triangle of Port Arthur, Beaumont and Orange. In this zone, lesser amounts are predicted, with 2 to 4 inches likely. However, if the storm’s rain bands pass repeatedly over the same area, a couple isolated amounts exceeding 6 or 7 inches, could lead to flooding.
Wind and surge
As Hanna makes landfall, wind gusts over 100 mph may be possible near the storm’s center. Winds will decrease away from the immediate center but could still cause power outages.
Where the strongest winds occur, the Weather Service warned of the possibility of “considerable roof damage,” “large trees snapped,” and “roads impassable from large debris.”
North of where the center comes ashore, the onshore wind is expected to generate a substantial storm surge. In Corpus Christi, Aransas Bay, Copano Bay and Matagorda Bay, a 4- to 6-foot surge is anticipated. Farther north toward Galveston Bay, a 1- to 2-foot surge is more probable.
These magnitudes will be realized if the greatest surge occurs around high tide. High tide will be at 7:18 p.m. Saturday in Corpus Christi.
The surge, the Weather Service warned, could cause damage to buildings, wash out roads, cause major beach erosion and result in “moderate damage to marinas, docks, boardwalks, and piers.”
A few tornadoes and waterspouts are also possible within the feeder bands north of Hanna’s center. The organization of tropical cyclones, which features counterclockwise near-surface inflow and clockwise outflow, or exhaust, produces an environment of high wind shear. Wind shear is a change of wind speed and direction with height.
That shear can be enhanced when systems make landfall. Any feeder-band thunderstorms embedded in that highly sheared atmosphere can rotate, presenting the risk for a few tornadoes and waterspouts.
A tornado warning was issued about 40 miles west southwest of Houston shortly before 7 a.m. local time Saturday.
The National Weather Service Storm Prediction Center has drawn a level 2 out of 5 “slight risk” for severe weather — in the form of tornadoes — for South Texas.
A waterspout or two can’t be ruled out elsewhere along the Gulf Coast, as far north as Louisiana.
Tropical Storm Gonzalo was sputtering westward Saturday morning, centered about 180 miles east of Trinidad. On satellite, a small, disheveled clump of thunderstorms was all that marked Gonzalo’s presence. The storm appears barely capable of surviving another day, and, after bringing a couple inches of rain and breezy winds to the southern Windward Islands on Saturday will likely disintegrate on Sunday.
A third system to watch
As if the twin cyclones were not enough to keep track, a third tropical wave emerged off the coast of Senegal in Africa.
When Gonzalo moved through earlier in the week, it helped transport water vapor into the upper atmosphere. By saturating the air column, Gonzalo was able to pave an easier path for this new fledgling tropical wave to trek westward, while fending off dry air encroaching from the “Saharan Air Layer.” That gives it better odds of development.
The National Hurricane Center currently estimates a 50 percent likelihood the wave of low pressure will consolidate into a tropical depression, the precursor to a tropical storm.
It will continue moving west in the coming days, probably moving into a favorable environment for strengthening. Given its eventual path and potential to affect land, it bears watching.
A bigger picture
As a whole, the tropics are blistering with activity, in stark contrast to the ominous quiescent that enveloped the Atlantic Basin just one week ago. Hanna’s formation on Thursday evening demolished the previous record for a season’s earliest “H” storm — formerly held by Tropical Storm Harvey, which formed on Aug. 3, 2005 — as the latest domino to topple in a record-busy start to hurricane season.
The season has already featured the earliest “C,” “E,” “F” and “G” storms on record — Cristobal, Edouard, Fay and Gonzalo.
A season’s eighth named storm typically doesn’t develop until closer to late September.
As the season’s first hurricane, Hanna comes about two weeks early. The average first hurricane in the Atlantic basin forms around Aug. 10.
Hanna’s central pressure, which dropped to at least 973 millibars, marks the lowest pressure for a storm in the Gulf of Mexico during July since Hurricane Alex in 2010. The lower the pressure the strong the storm in most cases.
Atmospheric scientists had been warning that the 2020 Atlantic hurricane season could be a hectic one, with large-scale atmospheric circulations and patterns, like a developing La Niña, favoring an increased number of storms.
Meanwhile, ultra-warm waters could help make those that form more intense and wetter, with a greater potential for storms to undergo rapid intensification.
The warming seas are largely a symptom of human-induced climate change.