Tropical Storm Hernan (2020)
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Tropical Storm Hernan was a short-lived
tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...
that brought widespread flooding and destructive
mudslide A mudflow, also known as mudslide or mud flow, is a form of mass wasting involving fast-moving flow of debris and dirt that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/ ...
s to southwestern
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
in late August 2020. Hernan was the thirteenth tropical cyclone and eighth
named storm Tropical cyclones and subtropical cyclones are named by various warning centers to simplify communication between forecasters and the general public regarding forecasts, watches and warnings. The names are intended to reduce confusion in the ...
of the
2020 Pacific hurricane season The 2020 Pacific hurricane season was a near average Pacific hurricane season in terms of named storms, featuring 17 (including one unnamed tropical storm which was operationally classified as a tropical depression), but well below average season ...
. The system developed from a
low-pressure area In meteorology, a low-pressure area (LPA), low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. It is the opposite of a high-pressure area. Low-pressure areas are commonly associated with incle ...
to the southwest of Mexico on August 26, as a low-end tropical storm. Moving generally northward and paralleling the west coast of Mexico, Hernan was hindered by a high
wind shear Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical ...
environment and only slightly strengthened. The cyclone achieved its peak intensity around 06:00
UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...
on August 27 with
maximum sustained winds The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a certain distance from the center, known as the radius of ma ...
of and a minimum barometric pressure of . Passing just offshore of the state of
Jalisco Jalisco, officially the Free and Sovereign State of Jalisco, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entities of Mexico. It is located in western Mexico and is bordered by s ...
, Hernan turned west and degenerated to a remnant low on August 28. The low passed near the southern tip of the Baja California Peninsula later that day and dissipated shortly thereafter. Despite Hernan's short existence, it dropped more than 280 millimeters (11 inches) of rain across many areas of southwestern Mexico, with accumulations peaking at in Jalisco. Multiple highways had to be shut down due to dangerous conditions, including mudslides and rivers overflowing their banks. Several schools suffered damage in the state of
Colima Colima, officially the Free and Sovereign State of Colima, is among the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima is a small state of western Mexico on the cen ...
, and in the city of Manzanillo, homes, businesses, and streets were damaged and covered in mud. Nearly 20,000 people were greatly affected by Hernan in Jalisco, and 1,674 houses and 9 schools suffered severe damage. In that state, a man fell off his roof and died while inspecting it for damage following the storm. Severe damage was also reported in
Guerrero Guerrero, officially the Free and Sovereign State of Guerrero, is one of the 32 states that compose the administrative divisions of Mexico, 32 Federal Entities of Mexico. It is divided into Municipalities of Guerrero, 85 municipalities. The stat ...
, with the most significant flooding taking place in the Costa Grande region. Lesser effects of the storm were felt in several other coastal states across western Mexico. Recovery efforts were undertaken by the
Mexican Armed Forces The Mexican Armed Forces () are the military forces of the United Mexican States. The Spanish crown established a standing military in colonial Mexico in the eighteenth century. After Mexican independence in 1821, the military played an import ...
across several states. Total damage in Mexico was calculated at Mex$1.1 billion (
US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...
51.4 million).


Meteorological history

In late August 2020, the
monsoon trough The monsoon trough is a convergence zone between the wind patterns of the southern and northern hemispheres. It is a portion of the Intertropical Convergence Zone in the Western Pacific,Bin WangThe Asian Monsoon.Retrieved 2008-05-03. and is dep ...
over the Eastern Pacific
tropical cyclone basin Traditionally, areas of tropical cyclone formation are divided into seven basins. These include the North Atlantic Ocean, the eastern and western parts of the North Pacific Ocean, the Southwest Pacific, the Southwest and Southeast Indian Oceans, ...
became active, following the passage of
Hurricane Genevieve The name Genevieve has been used for seven tropical cyclones in the Eastern Pacific Ocean. * Hurricane Genevieve (1984) - A Category 3 hurricane that passed offshore Mexico and dissipated near the southern tip of the Baja California Peninsula * Hur ...
. As Genevieve weakened west of the Baja California Peninsula, the monsoon trough, aided by a pulse of the Madden–Julian oscillation, developed three separate areas of low pressure. One of the lows formed on August 21, to the southwest of mainland Mexico. The low moved slowly eastward, initially unable to organize its
convective Convection is single or multiphase fluid flow that occurs spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
(shower and thunderstorm) activity due to its large size. However, beginning on August 24, the low and its associated shower and thunderstorm activity began to slowly become better organized and defined within marginally favorable conditions for
tropical cyclogenesis Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropics, tropical cyclogenesis occur are distinctly different from those through which temperate cyclogenesis occu ...
. After developing a cyclonic circulation and
gale-force The Beaufort scale ( ) is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. It was devised in 1805 by Francis Beaufort a Hydrography, hydrographer in the Roy ...
winds on August 26, the low became a tropical storm around 06:00
UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...
that day, about 545 kilometers (340 miles) southwest of the municipality of Cabo Corrientes. However, the United States-based
National Hurricane Center The National Hurricane Center (NHC) is the division of the United States' NOAA/National Weather Service responsible for tracking and predicting tropical weather systems between the IERS Reference Meridian, Prime Meridian and the 140th meridian ...
(NHC) operationally did not recognize the system as having reached tropical storm strength until 21:00 UTC that day, at which time it was named ''Hernan''. Upon naming Hernan, the NHC noted that the storm was also located on the eastern side of a broad monsoon
gyre In oceanography, a gyre () is any large system of ocean surface currents moving in a circular fashion driven by wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction determine the ...
, causing it to move in an eastward-to-northward fashion. Additionally, the system was facing strong easterly
wind shear Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical ...
and was slightly elongated from northeast to southwest, inhibiting potential strengthening. Despite these unfavorable conditions, cloud tops south and west of Hernan's center cooled to between as its convection increased, allowing the cyclone to strengthen slightly. Hernan achieved peak intensity at 06:00 UTC on August 27 with
maximum sustained wind The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a certain distance from the center, known as the radius of ma ...
s of and a minimum barometric pressure of . Continuous wind shear caused Hernan to weaken shortly thereafter, restricting convection to the western portion of the storm's circulation. Continuing to move counterclockwise around the monsoon gyre, Hernan passed over the
Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...
and turned to the west early on August 28. The system weakened to a tropical depression at 12:00 UTC that day as most of its associated convection dissipated. Hernan degenerated to a
remnant low Remnant or remnants may refer to: Religion * Remnant (Bible), a recurring theme in the Bible * Remnant (Seventh-day Adventist belief), the remnant theme in the Seventh-day Adventist Church * ''The Remnant'' (newspaper), a traditional Catholic n ...
six hours later just off the southern coast of
Baja California Sur Baja California Sur, officially the Free and Sovereign State of Baja California Sur, is a state in Mexico. It is the 31st and last state to be admitted, in 1974. It is also the second least populated Mexican state and the ninth-largest state by ...
. The remnants of Hernan continued westward around the gyre, which contained Tropical Storm Iselle, another tropical cyclone located to the south. By 00:00 UTC on August 29, the remnants of Hernan were completely absorbed by the gyre.


Preparations, impact and aftermath

No tropical storm watches or warnings were issued in advance of Hernan despite its close proximity to land. However, over 400 people were evacuated ahead of the storm in the states of
Jalisco Jalisco, officially the Free and Sovereign State of Jalisco, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entities of Mexico. It is located in western Mexico and is bordered by s ...
and
Colima Colima, officially the Free and Sovereign State of Colima, is among the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima is a small state of western Mexico on the cen ...
due to anticipated flooding. A total of 30 people were evacuated in high-risk areas in the city of Manzanillo in the latter state. Another 211 residents were evacuated to six shelters across
Guerrero Guerrero, officially the Free and Sovereign State of Guerrero, is one of the 32 states that compose the administrative divisions of Mexico, 32 Federal Entities of Mexico. It is divided into Municipalities of Guerrero, 85 municipalities. The stat ...
. Approximately 97,000 people across Colima,
Michoacán Michoacán, formally Michoacán de Ocampo, officially the Free and Sovereign State of Michoacán de Ocampo, is one of the 31 states which, together with Mexico City, compose the Political divisions of Mexico, Federal Entities of Mexico. The stat ...
, and Jalisco lost electricity due to Hernan. At least seven people across the coast were rescued by air following inundation of their houses by flood waters. Over 250 state and federal workers were dispatched to areas affected by Hernan, while workers from different agencies traveled by helicopter to bring food and supplies.
Secretary of the Navy The Secretary of the Navy (SECNAV) is a statutory officer () and the head (chief executive officer) of the Department of the Navy, a military department within the United States Department of Defense. On March 25, 2025, John Phelan was confirm ...
José Rafael Ojeda Durán José Rafael Ojeda Durán (born 3 February 1954) is the former Mexican Secretary of the Navy in the Cabinet of Andrés Manuel López Obrador. He has worked in the Mexican Navy in various positions for nearly 50 years. He is a member of the Mexi ...
implemented the
Mexican Navy The Mexican Navy () is one of the components of the Mexican Armed Forces. The Secretariat of the Navy is in charge of administration of the navy. The commander of the navy is the Secretary of the Navy, who is both a cabinet minister and a career ...
's Marine Plan, under which naval personnel carried out the evacuation of people trapped by flooding, removed debris, cleaned beaches, and transferred food and equipment to victims of the storm. Over 450 units (vehicles) of army machinery were used to carry out the Marine Plan: 60 maritime units, 6 aircraft, and 391 land units.


Jalisco

Rainfall in Jalisco peaked at in
Cihuatlán Cihuatlán is a coastal municipality in the Mexican state of Jalisco. Its main city is also named Cihuatlán. Etymology The word Cihuatlán is compounded of two words of Nahuatl origin, a language spoken in central Mexico since the seventh centu ...
and in Apazulco during August 26–28. At least 630 houses and 9 schools experienced severe damage in the state. Torrential rains and landslides affected coastal areas of Jalisco, including the resort city of
Puerto Vallarta Puerto Vallarta ( or simply Vallarta) is a Mexican resort city near the Bahía de Banderas on the Pacific coast of the Mexico, Mexican state of Jalisco. Puerto Vallarta is the second largest urban agglomeration in the state after the Guadalajara ...
, where the Ameca River flooded, and forced the closure of the San Sebastián del Oeste-Mascota highway. The severe flooding prompted the closure of five federal highways between Jalisco and the neighboring states of Colima and
Nayarit Nayarit, officially the Free and Sovereign State of Nayarit, is one of the 31 states that, along with Mexico City, comprise the Political divisions of Mexico, Federal Entities of Mexico. It is divided in Municipalities of Nayarit, 20 municipalit ...
. Heavy rains left 30 communities in Jalisco without power; 18 people took shelter on their roofs during the flooding and had to be rescued by armed forces members. Landslides and mudslides covered parts of federal highways 80 and
200 Year 200 ( CC) was a leap year starting on Tuesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Severus and Victorinus (or, less frequently, year 953 ''Ab urbe condita''). The denomination 200 for this y ...
and required clearing by federal workers. In the towns of Melaque and La Manzanilla, heavy flooding caused the nearby Cuixmala River to overflow, while rising waters in the El Pedregal stream led to flooding that prompted the opening of three temporary storm shelters in Jaluco and Melaque. Citizens in Melaque had to travel by boat to navigate flooded streets. Severe flooding of homes and roads in Cihuatlán and La Huerta prompted the opening of four temporary shelters in the former
municipality A municipality is usually a single administrative division having municipal corporation, corporate status and powers of self-government or jurisdiction as granted by national and regional laws to which it is subordinate. The term ''municipality' ...
, which held 365 displaced residents. 250 homes were damaged in Cihuatlán, while another 228 were damaged in La Huerta. A man died in La Huerta when he fell from his roof while checking for damage from Hernan. Over 350 people from Cihuatlán and
Tomatlán Tomatlán (meaning "Tomato land" or "place of tomato" from Nahuatl) is a town and municipalities of Jalisco, municipality, in Jalisco south of Cabo Corrientes (Mexico), Cabo Corrientes in central-western Mexico. The municipality covers an area ...
had to be transferred to temporary storm shelters. Damage in Jalisco amounted to Mex$470 million (US$21.9 million). At least 19,968 people were impacted and in need of support across Jalisco following Hernan. The Jalisco State Emergency Committee declared states of emergency in the municipalities of Tomatlán, Casimiro Castillo, Cihuatlán, La Huerta,
Villa Purificación Villa Purificación is a town and municipality, in Jalisco in central-western Mexico. The municipality covers an area of 1,848 km². As of 2005, the municipality had a total population of 10,975. History In 1532 Nuño Beltrán de Guzmán se ...
, Cabo Corrientes and Cuautitlán de García Barragán after the passage of the cyclone. Resources from both the federal government's Fondo Nacional de Desastres Naturales (National Fund for Natural Disasters) and Jalisco's Fondo Estatal de Desastres Naturales (State Fund for Natural Disasters) were given to the seven aforementioned municipalities. Food pantries, mats, hygiene kits, and water were among the supplies given to the residents of 1,674 damaged homes. The federal legislature requested that the (National Water Commission) carry out studies and take further preventive actions to address the lack of storm-resistant infrastructure in many coastal municipalities of Jalisco.


Colima

Torrential rainfall from Hernan led to numerous rivers overflowing their banks across Colima, which resulted in severe and widespread flooding across coastal portions of the state. Structures and roadways along the coast saw serious damage as roofs collapsed and flood waters swept away cars, toppled trees, knocked over power lines, and battered buildings. Waves of up to 4 meters (13 feet) occurred off the coasts of Manzanillo,
Tecomán Tecomán is a city and seat of the municipality of Tecomán in the Mexican state of Colima, about 50 km south of the city of Colima. In the 2005 census the city had a population of 112,726 people. It is the third-largest community in the st ...
, and Armería. Several schools were affected by Hernan's passage, experiencing flooding, leaks, and fallen tree branches, though none suffered serious damage. A parota tree blocked a road in the town of Tamala in the municipality of Ixtlahuacán, and residents across the area were advised to stay home by local government authorities during the storm's passage. Flooding was particularly heavy in the city of Manzanillo; rainfall in the city peaked at . Hundreds of homes, businesses, and streets were covered in mud, and several roads collapsed or were rendered impassable immediately following Hernan's passage. The president of Manzanillo's Planning and Tourism Commission, Luis Rogelio Salinas Sánchez, stated that both urban and rural areas around Manzanillo were severely affected by the storm. Torrential rain fell across the area, and strong
rip currents A rip current (or just rip) is a specific type of water current that can occur near beaches where waves break. A rip is a strong, localized, and narrow current of water that moves directly away from the shore by cutting through the lines of bre ...
occurred along the city's beachfront. Sand and debris were stirred up throughout the streets of Manzanillo by strong winds as Hernan passed offshore. Civil protection authorities carried out damage assessments statewide following the storm.


Guerrero

Destructive rains from Hernan and its precursor spread into Guerrero in conjunction with the
Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ , or ICZ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the t ...
(ITCZ), a large area of converging thunderstorms, for several days in late August. The combined effects of the weather systems caused at least of rainfall along the coastline of the state during August 26–28. The most serious damage occurred in the Costa Grande region, mostly due to the overflowing of rivers in
Zihuatanejo Zihuatanejo (), and/or Ixtapa-Zihuatanejo, is the fourth largest city in the Mexican state of Guerrero. It was known by 18th-century English mariners as Chequetan and/or Seguataneo. Politically the city belongs to the municipalities of Mexico, m ...
, La Unión, Coahuayutla, San Jerónimo, Coyuca de Benítez and
Petatlán Petatlán is a city in the municipality of Petatlán located along the Pacific Coast of the Mexican state of Guerrero. It is part of the Costa Grande region between Zihuatanejo and Acapulco. The city is known for the Sanctuary of the Padre Jes ...
, with over 100 houses experiencing damage in the last city. Over 400 houses were damaged in the town of Hacienda de Cabañas, where there were initial reports of a missing person due to the storm. A resident of the municipality of Cacalutla had to be rescued after being washed into an overflowing river. The large port city of
Acapulco Acapulco de Juárez (), commonly called Acapulco ( , ; ), is a city and Port of Acapulco, major seaport in the Political divisions of Mexico, state of Guerrero on the Pacific Coast of Mexico, south of Mexico City. Located on a deep, semicirc ...
experienced heavy rains, falling trees, and several landslides. Severe damage occurred along Cayaquitos beach, where garbage, debris and animal corpses were washed up. Wind gusts and torrential rainfall tore the roofs off of businesses. In the municipality of
Juxtlahuaca Juxtlahuaca (), or Xiuxtlahuaca (), is a cave and archaeological site in the Mexican state of Guerrero containing murals linked to the Olmec motifs and iconography. Along with the nearby Oxtotitlán cave, Juxtlahuaca walls contain the earlie ...
, located on the border of Guerrero and
Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federative Entities of the Mexico, United Mexican States. It is divided into municipalities of Oaxaca, 570 munici ...
, the Mixteco River overflowed its banks, inundating homes nearby. Secretary Ojeda Durán activated
Plan DN-III-E The Plan DN-III-E or Civil Relief and Aid Plan for Disasters (Spanish: ''Plan de Auxilio a la Población Civil en Casos de Desastre'') is a series of measures implemented primarily by the Mexican Ministry of National Defense, specifically the Mexic ...
to provide aid to individuals affected by Hernan in Guerrero and Oaxaca, and sent military personnel to the states to assist in recovery and cleanup efforts. The storm caused Mex$634 million (US$29.5 million) in damage to the state.


Elsewhere

Disruptions and flash flooding were occurred in Michoacán, with over 100 homes suffering damage in the town of El Bejuco in that state. Up to 600,000
sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerh ...
eggs in Marine Turtle Sanctuary in Michoacán were swept away or destroyed by Hernan, including those of the threatened
Olive Ridley turtle The olive ridley sea turtle (''Lepidochelys olivacea''), also known commonly as the Pacific ridley sea turtle, is a species of turtle in the family Cheloniidae. The species is the second-smallest and most abundant of all sea turtles found in t ...
, making for a large environmental loss. Flooding, hail, minor mudslides, and debris were reported in southern coastal areas of the state of
Sinaloa Sinaloa (), officially the (), is one of the 31 states which, along with Mexico City, compose the Federal Entities of Mexico. It is divided into 18 municipalities, and its capital city is Culiacán Rosales. It is located in northwest Mexic ...
. The city of
Mazatlán Mazatlán () is a city in the Mexican list of states of Mexico, state of Sinaloa. The city serves as the municipal seat for the surrounding , known as the Mazatlán Municipality. It is located on the Pacific Ocean, Pacific coast across from th ...
closed its port and beaches on August 28 due to hostile weather conditions from Hernan. Flooding occurred along the coast of
Bahía de Banderas Bahía de Banderas (, Spanish language, Spanish for ''Bay of Flags'') is a bay on the Pacific Coast of Mexico, within the Mexican states of Jalisco and Nayarit, being the westernmost municipality in Nayarit. It is also the name of an administrati ...
and in the city of San Blas in Nayarit, and rainfall across the state exceeded . A mudslide occurred near a populated neighborhood in the city of
Xalisco Xalisco () is a city and its surrounding municipality of the same name in the Mexican state of Nayarit. The city had a population of 21,899 in the 2005 census while the municipality has an area of 290.6 km2 (112.2 sq mi) and a populati ...
, though no serious damage resulted.


See also

* Weather of 2020 *
Tropical cyclones in 2020 2020 was regarded as the most active tropical cyclone year on record, documenting 104 named tropical systems. During the year, 142 tropical cyclones formed in bodies of water known as tropical cyclone basins. Of these, a record-high of 104, ...
* List of Eastern Pacific tropical storms * Other storms named Hernan


Notes


References


External links

*The National Hurricane Center'
advisory archive on Tropical Storm Hernan
{{DEFAULTSORT:Hernan (2020) Eastern Pacific tropical storms 2020 Pacific hurricane season 2020 in Mexico Hernan Hurricanes in Sinaloa Hurricanes in Nayarit Hurricanes in Jalisco Hurricanes in Colima Hurricanes in Michoacán Hurricanes in Guerrero Hurricanes in Oaxaca