Hurricanes-The Changing Dynamics in a Climate Change Era By “Wayne Neely ”
Due to climate change, global climate models predict hurricanes will likely cause more intense rainfall due to increased moisture in the atmosphere and have an increased or severe coastal flood risk due to higher storm surge caused by rising seas. Additionally, most scientists speculate that the global frequency of storms may decrease or remain virtually unchanged, but the major hurricanes (Category 3 or higher on the Saffir-Simpson Hurricane Wind Scale) that form are more likely to become more intense, more deadly, and much more destructive. One of the primary reasons for this is that most persons in the North Atlantic and elsewhere are flocking to the vulnerable and hurricane-prone coastal areas because it is considered a ‘status’ symbol to live there. Added to the fact that most of these persons have little or no hurricane experience living there. In addition, they are building more expensive homes at these locations and as a result, the overall monetary damage in a country like The Bahamas has risen exponentially.
Hurricane Andrew in 1992 cost The Bahamas Government in excess of $250 million which at that time was considered an astronomical amount by the then Bahamian Prime Minister Rt. Hon. Hubert Ingraham. Fortunately, local, and international aid and increased government expenditure provided relief for the people of The Bahamas. Fast forward to 2016 Hurricane Matthew cost the Government in excess of $600 million which at that time was an astonishing amount by the then Bahamian Prime Minister Rt. Hon. Perry Christie. Fortunately, once again local, and international aid and increased government expenditure provided relief for the people of The Bahamas. Then the monster of a hurricane called Dorian came along and totally devastated The Bahamas notably Abaco and Grand Bahama and cost the Bahamian people $3.4 billion (IDB Report on Hurricane Dorian), making it the costliest and most powerful hurricane to devastate The Bahamas in the modern era under the leadership of Rt. Hon. Hubert Minnis. Unfortunately, local, and international aid and increased government expenditure provided some relief for the people of The Bahamas but much of the promised aid never materialized because of the worldwide pandemic shortly, thereafter, preventing many governments to hold back on the promised aid simply because they had to cater to their own individual country’s needs dealing with the global pandemic. It is fair to assume that the most powerful hurricanes were to hit The Bahamas (especially the capital city of Nassau, which will perhaps be even higher than $3.4 billion. For example, in 1992 a sheet of plywood cost $16, and today if you were to buy that same sheet of plywood it would be over $50 per sheet.
Unfortunately, this is not a situation unique exclusively to The Bahamas but to most countries in the North Atlantic, especially for small island developing states of the West Indies. As a hurricane researcher, I’ve found out that wealthier nations like the United States are able to absorb economic losses from a hurricane better than many others, such as island nations in the West Indies. Hurricanes have the ability to bring a country to its knees and not just The Bahamas. For example, Hurricane Hugo in 1989 devastated the countries of Dominica and St. Lucia who at the time depended almost exclusively on their banana and sugarcane crops as their main revenue earners, and this hurricane wiped out at least 90% of their crops in one day. The years that followed were extremely rough for the citizens of those two countries. This forced them to cut back significantly on agriculture as their main revenue earners (there were also other economic factors as well that made the situation even worse) and focus on tourism and today both countries are reaping great rewards from their tourism industries. In 1988, the most intense hurricane at the time (until Hurricane Wilma in 2005) was Hurricane Gilbert which struck and devastated the island nation of Jamaica and it basically shut down their tourism industry for over 3 to 5 years (this was the era of declining sales of its then lucrative bauxite product). It took them years to regain their footing in the tourism industry. Finally, Hurricane Mitch in 1998, one of the most powerful hurricanes to hit Central America (Honduras, Nicaragua, Yucatan Peninsula, and others) and destroyed many bridges, roads, and other critical infrastructures set these countries back over fifty years, and to this day some of them are still feeling the negative repercussions from Hurricane Mitch in 1998. The same can be said with Hurricanes Frances, Jeanne, and Wilma in 2004 and 2005 respectively when they struck Grand Bahama and most persons will agree with me that the economy of Grand Bahama to this date has never really fully recovered from these storms 17 and 18 years later respectively.
From June 1 to November 30, many Bahamians turn their eyes to the tropics — not just because they’re dreaming of beach vacations, but because it’s hurricane season. Called by many names depending on where you live (hurricanes, typhoons, cyclones), scientists call these storms tropical cyclones. This is because they are large, rotating storms that need tropical conditions to form — so they originate mostly in the tropics. With that said, let’s talk about some science behind hurricanes and how they may change due to climate change. What is the recipe or main ingredients for a hurricane?
Vertical Wind Shear-This term refers to the change in wind speed and/or direction as you travel upwards in the atmosphere. Why does this matter for a hurricane? Think of the center of a hurricane as a tower of blocks that you push with your hands. If you push the top and bottom in the same direction and with the same strength, the tower can stay intact as it moves along the floor (i.e., low vertical wind shear). If you push the top and bottom in different directions or with different levels of strength, the tower will topple (i.e., high vertical wind shear). Similarly, hurricanes get pulled apart in high vertical wind shear, making it hard for them to grow and strengthen.
Hurricanes need four main ingredients to form and strengthen:
- warm ocean water of 80°F(26.5°C).
- lots of warm moisture in the air.
- low vertical wind shear.
- a pre-existing disturbance (e.g., a cluster of thunderstorms).
Just like making a perfect cookie, a hurricane needs all the ingredients for it to grow. Change any ingredient too much, and the cookie will be too flat, dry, crumbly, etc. The same is true for hurricanes: If any of the four main ingredients changes too much, the storm cannot form or will weaken. These hurricanes are perfect, in the sense that they will only form when the conditions are ideal or perfect. Once a hurricane forms, scientists shift their focus to where it is going and how strong it will be when it gets there. Where a hurricane goes depends mainly on the large-scale weather patterns around it at the time. If it moves over land, it brings with it a fury of strong wind, flooding rainfall, powerful and deadly storm surges and sometimes tornadoes.
With so many moving parts, forecasting a hurricane is a difficult fete within itself because there are so many moving parts and many variables in the hurricane dynamics equation. Large-scale changes in the climate, such as El Niño and La Niña conditions in the tropical Pacific Ocean, also impact hurricanes over an entire season here in the North Atlantic. Thus, trying to determine how climate change will impact hurricanes may seem like an impossible task. However, important tools are in place to help meteorologists tackle it. These include sophisticated global climate and weather models, scientific understanding of how hurricanes form, thrive, and evolve, and expanding observational records of past hurricane activity.
What do the latest weather models show? Even if hurricanes themselves don’t change with regard to climate change, the severe coastal and inland flooding from storm surge events will be made worse by sea-level rise. Furthermore, these dynamic weather models show increases in a hurricane’s rainfall rate by 2100. This means that hurricanes are likely to cause more intense rainfall and severe coastal flooding when they come ashore. Meteorologists have long predicted or forecast that climate change would increase extreme rainfall events. In a warmer world, there is simply more moisture in the atmosphere in the form of gaseous water vapor. Think of heating up a pot of water on the stove. Once the liquid water becomes hot enough, it boils and creates steam (or hot water vapor. This process is called “evaporation,” or when a liquid changes to a gas. A similar dynamic process occurs on Earth’s surface. As surface temperatures rise, more liquid water evaporates from the land and ocean. Evaporation adds moisture to the air. How much water vapor the air can hold is based on its temperature. From physics, it is a known fact that warmer air temperatures can hold more water vapor. The increased moisture in the atmosphere leads to more intense rainfall, especially during extreme events like hurricanes in the tropics.
In a hurricane, spiralling winds draw warm, moist air toward the center of the hurricane, fuelling the towering thunderstorms that surround it. As the air continues to warm due to climate change, hurricanes can hold more water vapor, producing more intense rainfall rates in a storm. In addition, most models show that climate change brings a slight increase in hurricane wind intensity. This change is likely related to warming ocean temperatures and more moisture in the atmosphere, both of which provide additional fuel for hurricanes. While most models show either no change or a decrease in hurricane frequency in a warmer climate, a greater proportion of the storms that form will likely reach very intense (Category 3, 4, or 5) levels. In other words, while there may be fewer storms, the ones that do form have a greater chance of becoming stronger and perhaps more destructive. Meteorologists continue to research and fine-tune these topics along with other important hurricane metrics, including any potential changes in the speed at which hurricanes move across the ocean, how large storms will get, and where hurricanes will go or how fast they will intensify.
What do actual observations show? The record-breaking 2020 hurricane season has shown an increase in the number of storms forming however, this in itself does not provide fuel for the climate change pundits. It must be noted that most of those storms that did form in the 2020 record-breaking season formed because meteorologists now have greater advancements in technology to detect, track and forecast these storms with greater accuracy and precision. If the same conditions occurred about 20 years ago, many of those storms would have gone unnoticed or undetected because of lack of advancement in the field of meteorology. Climate models that help us understand future climatic changes are a key part to the story but have any changes in hurricane activity already been observed in recent years? Since the 1980s, the hurricane record has shown a more active period in the North Atlantic Ocean. On average, there have been more storms, stronger hurricanes, and an increase in hurricanes that rapidly intensify. Thus far, most of these increases are from natural climate variations. However, one recent study suggests that the latest increase in the proportion of North Atlantic hurricanes undergoing rapid intensification is a bit too large to be explained by natural variability alone. This could be the beginning of detecting the impact of climate change on hurricane activity. In contrast, the frequency of hurricanes making U.S. landfall (a subset of North Atlantic hurricanes) has not increased since 1900, despite significant global warming and the heating of the tropical North Atlantic Ocean.
One current focus of hurricane research is sampling hurricanes by flying into them for more accurate data. These higher-quality data are important for improving hurricane model forecasts now and into the future. NOAA partners with NASA to collect measurements of various aspects of hurricanes over time. NASA weather satellites are a powerful tool for observations, as people cannot fly into every storm to gather vital hurricane data. Satellites help expand the observational record. With a longer, more detailed record, scientists can detect changes in long-term data trends over time. For example, scientists may test to see if more detailed data about the ocean’s surface temperature in front of a storm help to accurately predict its intensity. If they find something useful, they can use this information to inform the design of instruments on future satellites. Then as more data are collected, this will lead to a better understanding of forecasting hurricanes and how they may be impacted by climate change.
What do the future of hurricanes and climate change mean for me as a resident of The Bahamas? Anyone who has experienced a hurricane knows how much damage it can cause to life and property. Flooding remains one of the biggest concerns when a hurricane comes ashore, and climate change will likely make that worse. With impacts from climate change (like sea-level rise) already happening, the likelihood of another billion-dollar hurricane disaster from a major hurricane remains very high. Here in The Bahamas over the last few years, we have seen and witnessed severe flooding from just a typical afternoon thunderstorm and in locations that never used to flood like 15 to 20 years ago. If you live in hurricane-threatened areas, the best thing you can do is to be prepared. As we collect more data about hurricanes, we’ll better understand whether models correctly predicted hurricane changes from human-caused global warming. It takes all of us to do our part when seeing changes on the Earth, like the recent pattern of stronger hurricanes, to avoid it becoming something permanent.
Based on my research and experience with past hurricanes, I have found out that those who prepare for a hurricane tend to fare better than those who don’t so my useful advice for this, and every hurricane season is to be prepared and prepare for this season like we are going to be struck by a major hurricane. That means developing a hurricane plan for you and your family, making sure all of your personal properties are fully insured, stocking up on groceries and non-perishable goods, trimming trees that can become a hazard during a hurricane, battening down your home in advance of the hurricane, repair your roof or any part of your building that could become a hazard during a hurricane, fill your vehicles with gas in advance of the storm and fill all prescriptions with an additional two weeks supply of your medications are just a few things that should be done before a hurricane strikes an area. A word to the wise is sufficient!