Hurricane Hanna damage
Damage in Matagorda County, Texas, from Hurricane Hanna’s storm surge. (Image credit: Matagorda County Precinct 6 Constable’s Office via Facebook)

Tropical Storm Hanna dissipated over the high terrain of northeast Mexico on Monday morning, July 27, but its remnants were still spreading heavy rains across extreme South Texas and northeastern Mexico.

Hanna made landfall at 6 p.m. EDT Saturday, July 25, about 50 miles south of Corpus Christi, around the Padre Island National Seashore, one of the least populated areas of the Texas coast. A wind gust of 68 mph was measured in Corpus Christi, and a gust of 81 mph occurred at Baffin Bay in the national seashore. Storm surge inundations in excess of five feet occurred in the Corpus Christi area, causing flooding in the downtown district, including flooding of the Art Museum of South Texas. About three inches of water covered the museum’s lower level, but no artwork was damaged, a spokesperson told KRIS-TV.

Figure 1
Figure 1. Radar-estimated rainfall from the Brownsville, Texas, radar from Hurricane Hanna, ending at 10:05 a.m. CDT July 27, 2020. (Image credit: Weather Underground, an IBM Company)

Hanna’s most damaging impacts resulted from the torrential rains it brought to the Texas/Mexico border region, where radar-estimated rainfall amounts in excess of 15 inches occurred in isolated places (Figure 1). The top U.S. 48-hour rainfall amount from Hanna was 14.35″ at Sullivan City, Texas. Brownsville reported 6.73″, McAllen received 7.42″, and Corpus Christi, 2.59″. Sunday’s total of 4.53″ at McAllen was the highest for any calendar day in July records dating back to 1941.

Figure 2
Figure 2. Visible GOES-17 satellite image of 92L at 15Z (11 a.m. EDT) Monday, July 27, 2020. (Image credit: NOAA/RAMMB)

Tropical wave 92L in Central Atlantic expected to become a tropical depression

A large tropical wave in the central tropical Atlantic, designated 92L by NOAA’s National Hurricane Center (NHC), was positioned about 1,000 miles east of the Lesser Antilles Islands at 8 a.m. EDT Monday. The wave was headed west at about 20 mph, and is a threat to develop into a long-track Cape Verde-type hurricane that could threaten North America. An Air Force hurricane hunter aircraft was to investigate 92L on Tuesday afternoon.

Figure 3
Figure 3. Predicted surface wind (colors) and pressure (black lines) at 12Z (8 a.m. EDT) Thursday, July 30, 2020, from the 6Z Monday, July 27, 2020, run of the GFS model. The model predicted that 92L would pass just northeast of the Lesser Antilles Islands as a tropical storm with peak winds of 49 knots (56 mph, light orange colors) and a central pressure of 1007 mb. (Image credit: Tropical Tidbits)

Ventrice tweetThe wave had favorable conditions for development on Monday afternoon, with sea surface temperatures near 28 degrees Celsius (82°F) and moderate wind shear of 10 – 20 knots. The system was embedded in a drying atmosphere with a mid-level relative humidity of 65%. Satellite images on Monday showed that the wave was beginning to have increased signs of organization, with several low-level curved spiral bands beginning to form. According to a tweet by Michael Ventrice, 92L’s development will be aided by the passage of an atmospheric disturbance called a Convectively Coupled Kelvin Wave (CCKW).

The tropical wave will progress westward to west-northwestward at 15 – 20 mph over the next five days, and will have to contend with dry air from the Saharan Air Layer, located to its northwest. The 12Z Monday run of the SHIPS model predicted that the atmosphere surrounding 92L would slowly dry to a relative humidity of 55% by Friday.

The three best models for predicting tropical cyclone genesis – the European, GFS, and UKMET models – all support intensification of 92L into a tropical depression by Thursday, July 30. Steering currents will likely carry the system through or just north of the Lesser Antilles Islands Wednesday evening through Thursday. In an 8 a.m. EDT Monday Tropical Weather Outlook, NHC gave 92L two-day and five-day odds of formation of 80% and 90%, respectively.

The next name on the Atlantic list of storms is an obscure one, “Isaias” (pronounced ees-ah-EE-ahs). The earliest ninth storm in Atlantic tropical history was Irene on August 7, 2005.


7/26 Update: Hanna, Gonzalo, and tropical wave 92L

ISS view of Hurricane Hanna
Hurricane Hanna as seen from the International Space Station around 8 p.m. EDT Saturday, July 25, 2020, about two hours after the hurricane made landfall over South Texas. (Image credit: Col. Doug Hurley)

Tropical Storm Hanna was well inland over northeast Mexico at 11 a.m. Sunday, July 26, headed west-southwest at 9 mph. Hanna’s top winds were down to just 45 mph, but the storm was spreading heavy rains over much of South Texas and northeastern Mexico. The surge flooding from the storm had mostly abated, and Hanna will primarily be a heavy rain threat until it dissipates on Monday over the high terrain of Mexico.

Hanna made landfall at 6 p.m. EDT Saturday, July 25, about 50 miles south of Corpus Christi. At landfall, Hanna was an intensifying category 1 hurricane with 90 mph winds, and would have easily attained category 2 strength if it had spent another 12 hours over water.

Fortunately, the center of Hanna crossed the coast along the Padre Island National Seashore, one of the least populated areas of the Texas coast, so the eyewall winds and highest storm surge missed populated areas. Even so, Hanna brought significant wind and storm surge impacts to the area. A wind gust of 68 mph was measured in Corpus Christi, and a gust of 81 mph occurred at Baffin Bay in the Padre Island National Seashore. Storm surge inundations in excess of five feet occurred in the Corpus Christi area, causing flooding in the downtown district, including flooding of the Art Museum of South Texas.

Figure 1
Figure 1. Radar image of Hurricane Hanna at 6 p.m. EDT Saturday, July 25, 2020, as the storm was making landfall. (Image credit: National Weather Service via Mark Nissenbaum)

Hanna brought torrential rains to a large area of South Texas and northeastern Mexico, flooding streets and highways, leading to numerous water rescues. Twenty-four-hour rainfall amounts in the Corpus Christi area ending at 9 a.m. EDT Sunday ranged from two to five inches, with 2.56″ falling in the city of Corpus Christi. In the Brownsville area, the highest 24-hour rainfall amount ending at 10 a.m. Sunday was 10.64″ at Harlingen.

Hanna’s winds brought down numerous trees and powerlines, and more than 265,000 homes and businesses had no electricity as of 10 a.m. EDT Sunday, according to poweroutage.us. NOAA’s Storm Prediction Center reported that two preliminary tornadoes touched down in Texas on Saturday in Hanna’s spiral bands. On Sunday, an airport manager at the Brownsville South Padre Island International Airport said planes were shoved around and windows blown out of buildings from another possible tornado. The Storm Prediction Center has placed extreme south Texas in a “Slight Risk” area for severe weather on Sunday, and additional tornadoes are possible through the day.

Hanna is the fourth named storm to make landfall in the U.S. this year. Three tropical storms made landfall in the U.S. with 50 mph winds earlier this year: Tropical Storm Bertha in South Carolina on May 27; Tropical Storm Cristobal in Louisiana on June 7; and Tropical Storm Fay in New Jersey on July 10.

The only previous Atlantic hurricane season on record with four U.S. landfalls so early in the year was in 1886, when Hurricane Four hit Florida on July 19. In 2005, the fourth U.S. landfall of the year didn’t occur until August 25, when Hurricane Katrina hit Florida (Arlene, Cindy, and Dennis had made landfalls earlier in the year).

Gonzalo dissipates over the Windward Islands

Tropical Storm Gonzalo dissipated on Saturday afternoon over the southern Windward Islands in the southeast Caribbean, because of dry, stable air. Gonzalo brought heavy rains to Trinidad and Tobago, causing localized flooding and downed trees, but no major damage was reported.

Figure 2
Figure 2. Visible GOES-17 satellite image of 92L at 15Z (11 a.m. EDT) Sunday, July 26, 2020. (Image credit: NOAA/RAMMB)

Tropical wave 92L in Eastern Atlantic is a threat to develop, affect the Caribbean

A strong tropical wave in the eastern Atlantic, designated 92L by the National Hurricane Center (NHC), was positioned about 1,000 miles west-southwest of the Cabo Verde Islands at 8 a.m. EDT Sunday. The wave was headed west at about 20 mph, and is a threat to develop into a dangerous long-track Cape Verde-type hurricane that could threaten the Caribbean and North America.

The wave had favorable conditions for development on Sunday afternoon, with sea surface temperatures near 28 degrees Celsius (83°F) and moderate wind shear of 10 – 20 knots. The system was embedded in a moist atmosphere with a mid-level relative humidity of 70%. Satellite images on Sunday showed that the wave was poorly organized, but had excellent spin and a steadily increasing area of heavy thunderstorms.

Figure 3
Figure 3. Predicted surface wind (colors) and pressure (black lines) at 18Z (2 p.m. EDT) Thursday, July 30, 2020, from the 6Z Sunday, July 26, 2020 run of the GFS model. The model predicted that 92L would be passing just northeast of the Lesser Antilles Islands as a tropical storm with peak winds of 53 knots (61 mph, light orange colors) and a central pressure of 992 mb. (Image credit: Tropical Tidbits)

The wave will progress westward to west-northwestward at 15 – 20 mph over the next five days. Some promising news is that during its trek 92L will have to contend with dry air from the Saharan Air Layer, which is located to its northwest. The 12Z Sunday run of the SHIPS model predicted that the atmosphere surrounding 92L would dry to a relative humidity of 55% by Wednesday, when the system will be approaching the Lesser Antilles Islands. However, the three best models for predicting tropical cyclone genesis – the European, GFS, and UKMET models – all supported intensification of 92L into a tropical depression by Thursday. Steering currents will likely carry the system through or just north of the Lesser Antilles Islands on Thursday, but it is too early to predict which islands might be affected. In an 8 a.m. EDT Sunday Tropical Weather Outlook, NHC gave 92L two-day and five-day odds of formation of 60% and 90%, respectively.

The next name on the Atlantic list of storms is an obscure one, “Isaias” (pronounced ees-ah-EE-ahs).


7/25 Original Post: Hurricane Hanna, first Atlantic hurricane of 2020, plows toward Texas

Hanna radar
Radar image of Hurricane Hanna at 11:21 a.m. EDT Saturday, July 25, 2020. (Image credit: National Weather Service via Mark Nissenbaum).

Hurricane Hanna became the first Atlantic hurricane of the 2020 season at 8 a.m. EDT Saturday, July 25, as it plowed west at 7 mph towards a Saturday evening landfall just south of Corpus Christi, Texas. The average date of the first Atlantic hurricane of the season is August 10; Hanna had already set a record for being the earliest “H” storm of any Atlantic hurricane season.

Figure 1
Figure 1. Visible GOES-17 satellite image of Tropical Storm Hanna at 15Z (11 a.m. EDT) Saturday, July 25, 2020. (Image credit: NOAA/RAMMB)

At 11 a.m. EDT Saturday, Hanna’s top sustained winds were 80 mph, above the 74-mph threshold for a category 1 hurricane, and the eye was clearing out on visible satellite imagery. Radar imagery showed that Hanna was well-organized, with a 35-mile diameter eye and a sprawling set of spiral rainbands that were bringing heavy rains along the South Texas and Northeast Mexico coast. Tide gauge observations at 11 a.m. EDT Saturday showed Hanna bringing a storm surge of 2 – 3.5 feet along most of the Texas coast from Corpus Christi to the Louisiana border. According to an email from storm surge expert Dr. Hal Needham of u-surge.net, as of 10:20 a.m. EDT Saturday, Hanna had generated the highest storm surge in 40 years in Corpus Christi – the eighth highest since 1900. The last time the city experienced a higher surge was in 1980, during Hurricane Allen. Dr. Neeham said he expects a peak surge from Hanna of 3 – 4 feet in Corpus Christi Bay.

Figure 2
Figure 2. As of 10:20 a.m. EDT Saturday, Hurricane Hanna’s storm surge had generated a storm tide 5.82 feet above the NAVD88 datum, which was the eighth highest storm surge since 1900 for the city. The last time the city experienced a higher surge was in 1980, during Hurricane Allen. (Image credit: Dr. Hal Needham of u-surge.net)

Fortunately, the center of Hanna was crossing the coast along the Padre Island National Seashore, one of the least populated areas of the Texas coast. The eyewall winds and highest storm surge will thus mostly spare the densely populated regions of the state. However, Corpus Christi will not be spared Hanna’s heavy rains of 6 – 12 inches, which are likely to cause dangerous flash flooding in the city on Saturday and Sunday.

Keep calm image What to do if you need to evacuate during the COVID-19 pandemic

Unfortunately, South Texas, including Corpus Christi, has the highest rate of COVID-19 hospitalizations of any place in the U.S., according to a New York Times analysis. FEMA has published a detailed 59-page guide on dealing with the pandemic during hurricane season, so South Texas may be ready for a hurricane strike during a pandemic.

Hanna is the fourth named storm to make landfall in the U.S. this year. Three tropical storms made landfall in the U.S. with 50 mph winds earlier this year: Tropical Storm Bertha in South Carolina on May 27; Tropical Storm Cristobal in Louisiana on June 7; and Tropical Storm Fay in New Jersey on July 10.

The only previous Atlantic hurricane season on record with four U.S. landfalls so early in the year was in 1886, when Hurricane Four hit Florida on July 19. In 2005, the fourth U.S. landfall of the year didn’t occur until August 25, when Hurricane Katrina hit Florida (Arlene, Cindy, and Dennis had made landfalls earlier in the year).

Figure 3
Figure 3. Tracks of all category 1 and stronger hurricanes to pass within 100 miles of Corpus Christi, Texas, from 1851 – 2019. (Image credit: NOAA)

Corpus Christi hurricane history

Corpus Christi has led a bit of a charmed life with regard to hurricanes in recent decades. Only three hurricanes have passed within 100 miles of the city during the past 50 years: Hurricane Harvey of 2017, Hurricane Bret of 1999, and Hurricane Celia of 1970. Bret caused less than $1 million in damage to Corpus Christi, but both Harvey and Celia caused major damage to the city.

Figure 4
Figure 4. Visible GOES-17 satellite image of Tropical Storm Gonzalo at 14:50Z (10:50 a.m. EDT) Saturday, July 25, 2020. (Image credit: NOAA/RAMMB)

Gonzalo barely alive as it moves through the Lesser Antilles

Tropical storm warnings were up for the southern Windward Islands of the southeast Caribbean at 11 a.m. EDT Saturday, as Tropical Storm Gonzalo steamed west at 18 mph, featuring top sustained winds of 40 mph. Satellite loops on Saturday afternoon showed Gonzalo to be a small system, with tropical storm-force winds of 39 mph or higher extending out just 25 miles from the center. Gonzalo was struggling to maintain its heavy thunderstorm activity because of dry air, and it barely qualified as a tropical cyclone.

Gonzalo’s primary threat will be heavy rain, with rain totals of up to six inches potentially causing flash floods and mudslides in the southern Windward Islands. The track forecast for Gonzalo is relatively straightforward, with all of the top track models predicting a westerly motion that will take the storm through the Windward Islands on Saturday. Gonzalo is likely to succumb to the dry air bedeviling it and dissipate by Sunday.

Figure 5
Figure 5. MODIS satellite image from Saturday morning, July 25, 2020, of tropical wave 92L over the Eastern Atlantic. Image credit: NASA Worldview)

Tropical wave 92L in Eastern Atlantic is a threat to develop, affect the Caribbean

A strong tropical wave in the Eastern Atlantic, positioned about 400 miles southwest of the Cape Verde Islands at 8 a.m. EDT Saturday, was designated 92L by NHC on Friday afternoon.

The wave had modestly favorable conditions for development on Saturday afternoon, with sea surface temperatures near 28 degrees Celsius (83°F) and moderate wind shear of 10 – 20 knots. The system was embedded in a moist atmosphere with a mid-level relative humidity of 70%. Satellite images on Saturday showed that the wave was poorly organized, and had a modest amount of spin and heavy thunderstorms.

Tweet imageThe wave will progress westward to west-northwestward at roughly 15 mph over the next five days. As shown in the tweet, along a significant portion of its track, 92L will be crossing over waters of record warmth for this time of year:

Some promising news is that during its trek 92L will have to contend with dry air from the Saharan Air Layer, which is located to its northwest. This dry air will likely prevent development into a tropical depression until Monday at the earliest. By Tuesday, July 28, when the system will be approaching the Lesser Antilles Islands, 92L will encounter warmer sea surface temperatures near 28 – 29 degrees Celsius (82 – 84°F), but will still have to deal with dry air and moderate wind shear, according to the 12Z Saturday run of the SHIPS model. The three best models for predicting tropical cyclone genesis – the European, GFS, and UKMET models – all supported intensification of 92L into a tropical depression by Thursday. Steering currents will likely carry the system through the Lesser Antilles Islands on Wednesday or Thursday, but it is too early to predict which islands might be affected. It is also possible that 92L will pass just north of the islands. In an 8 a.m. EDT Saturday Tropical Weather Outlook, NHC gave 92L two-day and five-day odds of formation of 10% and 60%, respectively.

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Topics: Weather Extremes