Disasters: Hurricanes in Mexico's Coastal Areas

The word "hurricane" comes from hunraken, which among the Mayas means "god of storms", although the word urican was also used among the ancient inhabitants of some Caribbean islands.

In the North Atlantic Ocean basin and the northeastern Pacific Ocean basin the northeast Pacific Ocean basin, tropical cyclones are called hurricanes, while typhoon is used to identify these same phenomena. is used to identify the same phenomena in the northwest Pacific Ocean basin, baguios in the Philippine Islands, cyclones in India, and willy-willies in India. India and willy-willies in Australia.

Birth of a hurricane

These atmospheric phenomena can occur in maritime areas where the sea surface temperature is higher than 26°C, where winds do not have abrupt variations with height, and in areas located between 5°C and 25°C north or south. These conditions can be found in the so-called inter-tropical convergence zone (ITCZ) that surrounds the Earth near the equator, where the northeast trade winds and southeast trade winds converge. In the summer this ITCZ rises in latitude and can produce tropical disturbances that in turn can evolve into a tropical cyclone.

This is the case of the hurricanes that occur in the waters of the Gulf of Tehuantepec and move towards the northwest, threatening the western coasts of the national territory.

The so-called easterly waves, which occur in the Atlantic Ocean, can also give rise to a tropical disturbance since in the summer the waters of this sea have very high temperatures and meet the conditions for it to evolve into a tropical depression, characterized by winds of less than 34 knots or 62 km/h, or to the category of a tropical storm with winds of 34 to 63 knots, i.e. greater than 63 km/h but less than 113 km/h or even to hurricane whose winds have an intensity greater than 64 knots, but less than 82 knots, i.e. between 114 km/h and 184 km/h.

At the southern end of a cold front, conditions for the creation of a tropical cyclone are also present, mainly in late October and early November in the Atlantic, since these cold fronts break through to very low latitudes where ocean temperatures are still conducive to the development of these phenomena. Since the fronts are followed by a trough in the upper levels, they create a divergence zone in height that reinforces the convergence in the low levels, which is necessary for the intensification of the cyclonic circulation of the hurricane.

The origin of a tropical cyclone is still under discussion; the conditions under which a disturbance becomes a hurricane are not clear. conditions under which a disturbance becomes a hurricane are not clear. In 1964 Charney and Eliassen concluded that for a tropical disturbance to develop, the interaction of convective cumulus clusters with large-scale fields must produce an unstable atmospheric zone.

Hurricane growth

Most cumulus clusters seen in satellite imagery are monitored daily at national weather centers, but not all may develop into hurricanes.

When they achieve this, a process of latent heat release begins high up, creating a divergence in the upper levels; this causes a loss of weight in the atmospheric column, resulting in a pressure drop at the surface. This results in a low-pressure zone at the surface where the winds converge, carrying large amounts of water vapor towards the center of the storm, where they begin their ascent and the release of latent heat that heats the center of this column.

A mature hurricane has winds that rotate cyclonically, that is, counterclockwise, and has a radius that varies between 100 and 1000 km in diameter, at its center the temperature is relatively high and the pressure relatively low; that is, a mature hurricane is a warm-core low. The most intense winds are found at the surface, at low altitudes, and are more intense in the vicinity of the eye. When the air near the eye rotates so rapidly that it cannot be carried to the center, it has to rise about 7 km where it disperses outward.

The eye of a hurricane is circular and inside it, the meteorological weather is calm winds and free of cloudiness; immediately after follows a zone of cumulonimbus clouds that is called the eye wall, which converge in spiral form the cloud bands of the storm, which also indicate the intensity of the hurricane. If these bands are very curled, it is an intense hurricane, but if the bands are approximately straight, the hurricane is in the dissipation stage.

Hurricane track forecast

There are several methods for forecasting the path of these phenomena. In the first instance, it is known that hurricanes move westward with an average speed of 20 km/h and are rising in latitude due to the Coriolis effect, which deflects bodies moving on the Earth's surface to the right.

Meteorologists use synoptic maps where they analyze mainly the pressure, temperature, and wind fields, both at the surface and at different altitude levels, identifying meteorological systems that establish guiding currents that are in charge of displacing the tropical cyclone. Although stationary cyclones are frequently found or with an erratic trajectory that makes forecasting difficult.

At present, numerical models of the atmosphere have been developed as a modern and powerful tool that, together with satellite images and modern communication systems, allow meteorological services to make accurate forecasts in advance. When these forecasts reach the population promptly, they make it possible to save a large number of human lives through timely evacuations, even though the material damage caused by hurricanes cannot be reduced.

Disasters due to hurricanes

Of all meteorological phenomena, hurricanes are the ones that cause the greatest loss of human lives and the material damage they leave in their wake is immense. The winds of more than 100 km/h and the low pressures registered in their center can be so strong that trees are uprooted, so one can imagine the damage caused to houses and in general to the entire infrastructure of a city.

The swell that forms at sea during a hurricane is another factor that causes substantial losses since it forms real mountains of water that lash out against the populations located on the coasts. The rainfall associated with a hurricane causes considerable damage; even when the hurricane is already on land and the winds are significantly reduced, the rains may continue for one or more days, thus raising the level of rivers and streams and flooding riverside populations.

Most hurricane casualties occur in coastal populations. Gilberto, in 1988, has been one of the most fearsome hurricanes in recent years; with a central pressure of 888 MB and a westward trajectory in the Caribbean Sea and the Gulf of Mexico, it affected the states of Quintana Roo, Yucatan, Tamaulipas, and Nuevo Leon. Paulina, in 1997, originated south of the Gulf of Tehuantepec and, with a west-northwest trajectory, affected the states of Oaxaca, Guerrero, and Michoacán, causing the death of 120 people, 10,000 victims and producing material losses of more than 300 million pesos.

In 1995, Roxanne, with an erratic trajectory in the Caribbean and Gulf of Mexico, caused havoc in Tabasco, Quintana Roo, Veracruz, and Yucatán. The damage caused to the national oil industry was in the order of 27 million dollars a day, even without coming ashore. Ismael, in 1995, originated in the waters of the Pacific Ocean, south of the Revillagigedo Islands. With an erratic trajectory during the first days, it posed no threat to the national coasts, but on September 15 of that year, it moved so fast that in less than 24 hours it reached land, off Topolobampo, in Sinaloa, causing incalculable losses to the shrimp fleet by sinking most of its ships.

In the Caribbean Sea, Hurricane Mitch devastated several Central American countries, causing considerable damage mainly in the sister republics of Honduras, Nicaragua, El Salvador, Belize, and Guatemala. In 1991, in Bangladesh (Southeast Asia), some 118,000 people died as a result of a cyclone that caused flooding from storm surges (wind-driven sea level rise). In monetary terms, the strongest impact of a hurricane was due to the landfall of Hurricane Andrew in the south of the Florida peninsula on August 22, 1992, causing economic damage of approximately 25 billion dollars.

In Mexico, which is located between 15°N and 30°N and between 87°W and 117° W, tropical cyclones or hurricanes are a constant threat during the summer, being the Yucatan Peninsula is one of the regions most susceptible to be affected by one of these phenomena, which have their origin in the warm waters of the Caribbean Sea.

Hurricanes that originate in the warm zone of the Gulf of Tehuantepec or south of the coasts of Michoacán and Jalisco, mainly affect the southern part of the Baja California peninsula, although almost all of our coastal populations are susceptible to being affected by a tropical cyclone to a greater or lesser degree.

As previously mentioned, systems have been created to warn populations threatened by a tropical cyclone to save as many human lives as possible, although material damage cannot be reduced. In the Mexican Republic, civil protection systems are in charge of alerting the inhabitants of the position, intensity, and possible trajectory of a hurricane and, if necessary, evacuating the population.

By Marcial Orlando Delgado Delgado, Source: Correo del Maestro No. 31.