Times of the Islands Fall 2018

In the wake of such a devastating season, many
Islanders will frequently be checking in online with the
National Hurricane Center, ever cognizant that the next
big one might be on the way. Many will wonder if the
2018 hurricane season will have more challenges in store
for the Islands. As of early September, thankfully, the season
has been rather quiet, with only seven named storms,
all of which have had no impact on the Turks & Caicos.
Statistically speaking, nearly 80% of all tropical
storms and hurricanes in the Atlantic Basin occur between
August 15 and about October 20. So this means we
shouldn’t expect hurricanes to form after late October,
right? Unfortunately, no. In order to understand why hurricanes
do continue to form late in the season, we must
take a look at some of the parameters that go into hurricane
formation.
When we are discussing hurricane environment, there
are a number of things that meteorologists and other
atmospheric scientists are looking for. Some of the most
important information is gleaned from whether the upper
level environment is calm (light winds) or if wind shear is
present, the current Sea Surface Temperatures (SSTs) and
current pressure patterns in the Atlantic.
In order for low pressure systems to develop and
thrive in a specific environment, it is important that very
little to no wind shear is present. Wind shear effectively
will destroy the top of a hurricane in short order the stronger
the shear becomes. Think of the top of a hurricane as
you would the exhaust pipe on a car. At the surface of a
hurricane, warm air is being sucked into the middle and
upper levels of the hurricane. Once it reaches the top, it is
able to evacuate the center of the storm and the process
continues. With a car, the exhaust pipe allows gases to
escape the engine. When wind shear is present, this effectively
disturbs the ability of the hurricane to evacuate all
of the mass (warm air) it is sucking into the storm. Over
time, much like a car, it begins to choke, and eventually
begins to weaken and then to be torn apart. In a car, if
you plug the exhaust the car will soon die, as it is not able
to get rid of the by-products of combustion.
With regard to Sea Surface Temperatures, the Turks &
Caicos Islands (and other nearby islands) enjoy very shallow
banks. This can be a double-edged sword. Shallow
banks contribute to the beautiful colors of the waters that
draw tourists from around the world. That is the good
side. The not-so-good side is that these shallow waters
tend to get very, very warm during the summer and into
the fall season. Traditionally, the water in these areas as
well as the Caribbean Sea and Gulf of Mexico continue
Sea surface temperatures play a role in hurricane formation. This map
shows the SSTs in the region as of August 9, 2018.
to have temperatures above 80ºF heading into the later
portions of hurricane season. Water temperatures above
80ºF are generally needed to sustain tropical activity. This
provides the fuel that is needed should low pressure be
in the area.
Lastly, the other important criteria is the current
pressure situation in the region. During the later portion
of the season, traditionally we will not find storm development
occurring well out in the Atlantic Basin (east of
the Leeward Islands) due to poor atmospheric and water
conditions. Generally we will be looking at the Bahamas,
the TCI and Hispaniola to Puerto Rico, as well as the
Caribbean Sea and Gulf of Mexico areas. As we head
into late October and, especially, November, cold fronts
from the lower 48 states will move into the Caribbean as
they weaken. These frontal systems are essentially a low
pressure trough that meanders in the warm waters of the
Caribbean as they begin to decay. With warm waters and
light winds, these troughs sometimes can generate low
pressure which can continue to grow and develop into a
tropical system with time.
The reason these are normally few and far between
during the later six weeks of the season is due to the
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