Where do Hurricanes come from? We know that they come slamming into our coasts from the oceans, I intend to show that most of them start in the same spot and why that is. I will show that most Hurricanes that make it to the United States, start in the exact same spot. Specifically, a spot just off the coast of the African Cape Verde islands. (Macdonald, 2017).
Let’s look at what the atmospheric conditions are like to get the hurricane started in the first place.
The Atlantic hurricane season is May-November with the largest number of hurricanes generated in August through September. (Dorst, n.d.) (Picture 3). An Atlantic hurricane begins as a small tropical disturbance, which is defined as a thunderstorm that has organized activity stretching over one hundred miles and stays true to form for a period of over twenty-four hours. (Plumer, B., 2017).
Scientists will watch these cells as they start to move westward from the African coast.
If conditions are right, this disturbance will develop and begin to spin around a low-pressure center, and then it becomes classified as a tropical depression or a cyclone. This stage of the form requires some very specific conditions, the water temperature, for instance, must be eighty degrees Fahrenheit or warmer in order to fuel the system, there also must be plenty of moisture in the lower and middle part of the atmosphere. There must also be winds that are set up to allow the depression to spin, too much wind can break up a depression that is starting to form.
The next thing to happen is the pressure towards the center of the system drops, air rushes in, and creates strong winds. Once the system gains enough strength and winds reach speeds over thirty-nine miles per hour, the storm is considered a tropical storm and is then given its name.
The US National Hurricane Center makes the call for when the system moves from a mere depression and becomes a tropical storm that is worthy of a name. As the storm moves and passes over a region of especially warm water such as that near this “spot” and does not meet any wind shear to tear it apart, the pressure in the center continues to fall and winds pick up tremendously. This is when the system forms more clearly and the “eye” is noticeable. Once all of this happens and the wind speeds pass seventy-four miles per hour, the system is officially a hurricane. Hurricanes get categorized by the Saffir-Simpson Scale (picture 1), this bases the storm on wind speed and the potential for damage.
It is important to note also that a hurricane can also become weaker and be downgraded again to a tropical storm. An example was hurricane Hermine in 2016, it was downgraded to a tropical storm just as it reached the Florida coast, however, soon after as it made its way back out to the Atlantic Ocean the record-warm temperature of the ocean there caused the hurricane to regain its strength. Keep in mind that even a tropical depression is capable of massive rainfall, dangerous surf, erosion, high winds, and even flooding. 2012’s Sandy was downgraded before it hit the East Coast, but it caused significant damage to the New York and Jersey Coasts. The most recent hurricane Florence was downgraded several times even broke apart at one point only to re-energize and become a Category 5 at one point in its lifespan.
From my research, I found nine Atlantic hurricanes Camille, Allen, Andrew, Isabel, Ivan, Dean, Felix, Irma and Maria that all reached Category 5 level and then they weakened. They all have another thing in common, they were back to a Category 5 more than once. Six of those nine attained Category 5 status twice during their lifespans, the remaining three, reached Category 5 three different times during their lifespans. Three times for this back and forth from a 5 is the most, none have done so four times, yet. So far only 3 hurricanes that attainted Category 5 status have ever hit the United States, 2017’s Irma, another Cape Verde hurricane, came close. It was downgraded to a 4 before it made landfall in Florida. This is just the United States, several hurricanes have hit landfall before they make the US or even break apart before they hit us. Irma specifically, made landfall as a Category 5, seven times at islands along the way causing catastrophic damage and a death toll of 134, and nearly 2 million people felt the effects of Irma. (NOAA, 2014).
Research has shown that a majority of the ‘monster storms that hit the US and Canada start out as a distinct weather pattern in the atmosphere over western Africa, specifically a spot off the coast of the African Cape Verde Islands.’ (Macdonald, 2017). (Picture 2). According to Macdonald’s article, eighty-five percent of the intense hurricanes that make landfall and affect the US and Canada, get their start as a disturbance in the atmosphere over western Africa. Once the disturbance is noticed and it begins to spread over a large enough area, the hurricane’s chances of becoming dangerous only take one to two weeks’ time. In that time how far they travel, how much energy they gather, and if the storm can avoid any wind shear determines the Category they will have by landfall. Landfall itself generally causes downgrading, but that does not imply there is no damage. Also, about sixty percent of all tropical storms and hurricanes rated Category 1 and 2 are triggered by the waves in this area. (Erdman, 2018).
While only about 10 percent of the disturbances that begin over Cape Verde yearly, actually turn into hurricanes, the few that do, have the chance to soak up enough energy while they move over the warm waters of the Atlantic Ocean. Lending a hand to them having the potential to become some of the most powerful hurricanes and creating a lifespan to make their way to the United States and Canada. (NOAA, 2014). NOAA also writes that not all hurricanes form in the exact spot near the Cape off of Africa, however, it has been where most major hurricanes that make their way to the US begin.
The correlation of these Cape Verde hurricanes to one of the driest places on Earth, the Sahara Desert accounts for the interaction between the hot dry air, and the cooler more humid air that comes from the Gulf of Guinea to the South. This forms what is known as the African easterly jet, blowing east to west across Africa. Inside this jet is where the disturbances known as tropical waves begin to form and move off the west African coast past Cape Verde. These waves begin to interact with the warm water of the Atlantic which triggers columns of warm moist air to rise from the ocean. The storms which now have two of the necessary ingredients to become a full-fledged hurricane. The third ingredient is the Earth’s rotation, if it can get those winds above seventy-four miles per hour, you have the total recipe for a category 1 hurricane.
When we consider hurricanes and preparedness, it is interesting to know that a desert that is half way around the world can influence the formation of such severe weather and the impact to the coasts here in the US is catastrophic. It is best to be armed with as much information as soon as possible to plan for safety and be prepared. NOAA stays prepared for hurricanes and encourages all to create their own hurricane plan which they provide downloadable information to do just that. (NOAA, 2014).
Hurricane Florence, the most recent deadly hurricane, is a prime example of a downgraded, upgraded and again downgraded storm. A strong tropical wave began to emerge off the west coast of Africa on August 30, 2018. It fluctuated for several days over the open ocean and rapidly intensified September 4 and 5 when Florence became a Category 4, sustaining winds over 130 mph. Just 2 days later the storm was torn apart with wind shear and downgraded to a tropical storm. At this point, it once again began building strength as it continued west and on September 10, it was returned to a Category 4. Florence weakened again only to rebuild itself, and strengthen its eyewall, and by September 13 again it was downgraded to a 1.
Then came the “stall”, as the storm came closer to the coast it seemed to slow down and wait, but as it approached the Carolina coast in the early hours of September 14, 2018 hurricane Florence made its impact on the United States as a “mere” Category 1. Florence as expected, slammed the coast, wreaking havoc although it continued to be downgraded and was finally absorbed by another frontal storm on the 19th. The aftermath: 53 fatalities, nearly 18 billion in damages, and 35.93 inches of rainfall at its highest in Elizabethtown. Damage continued to mount due to massive flooding and continued to affect many that were miles inland from the coast. The massive amounts of water over-filled streams and rivers caused flooding in states as far inland as the Tennessee boarder. North and South Carolina, Virginia and even West Virginia had an impact from the water. Because Florence was driven by warm air its capacity to carry water was much higher. “Any time it comes off Africa, they have two weeks’ worth of warm water to build up,” (Gibbens, 2018).
The African jet off the coast of Africa and the Cape Verde influence I have been discussing and its responsibility of the formation of some of the worst hurricanes to make landfall in the United States is no myth. It is a reality. The warm temperatures of the Atlantic accounting for the ability for them to continue to build strength for those that manage to avoid being blown apart by the wind shear. The dry air from the Sahara Desert along with this has created a perfect environment. The fact that hurricanes seem to be more frequently occurring and stronger plays to my belief that global warming is a reality as well. That is another paper, however, if we continue to add the necessary ingredients to the mix, such as warmer water temperatures, this trend will likely continue.
“These are not acts of God,” says meteorologist Alan Gadian, senior scientist at the U.K.’s National Centre for Atmospheric Sciences, “but a direct consequence of making the atmosphere more unstable due to seawater being warmer than average. They will occur again.”
Researchers everywhere are continually working on way to better predict which storms need to be watched and what preparations need to be made. Imagine if they could predict a hurricane before it forms, it takes weeks to reach land, the number of precautions that could be taken could be life-saving.
The damage from rainfall and flooding alone is enough for concern, not to mention the wind damage from a hurricane. Expecting global warming to change or reverse itself is foolish, so being prepared no matter where you live is essential. People in the path of the wind and waves need to install shutters or the hardware to do so quickly, close all interior doors, bring in loose objects that could become airborne and act as a deadly projectile, always make sure your buildings and structures do not have loose pieces that can come flying off, sump pumps and generators should be tested before the storm arrives as well. (disastersafety.org, 2018). Above all, listen to the warnings and if evacuations are ordered, do so. There have been many proposed ways to stop a hurricane from forming or assist in breaking it up before it makes landfall, so far nothing. Until that technology exists, if it is even possible, be prepared.