|The Difficulties of Forecasting|
Tornadic Activity in South Florida
In respect to the United States, Southern Florida has a climate all it's own and residents of
this area are used to experiencing severe weather on a regular basis. Amongst the myriad of
weather phenomena that occur in the southern most portion of the continental United States,
South Florida is probably most well known for the tropical cyclones that frequently hit the
peninsula. It may come as a suprise to some people that this region is also very prone to the
development of tornadoes which can be difficult to pinpoint and forecast over the unique
landscape. There are several ways that tornadoes form over the southern tip of Florida: They
can develop from thunderstorms interacting with the sea breeze front and other air mass
collisions, tropical cyclones can generate tornadic activity, and when waterspouts move on
shore they are classified as tornadoes. Each of these types of tornadic development create a
separate set of difficulties for forecasters.
The most common way that tornadoes form over Southern Peninsular Florida is from
severe thunderstorms, which are very typical in this region, colliding with the sea breeze or
other air mass boundaries. These Strong thunderstorms can produce tornadoes if there is
sufficient vertical wind shear, low level moisture advection, instability,and a trigger mechanism
such as an interacting boundary. However, even when all of these favorable elements are in
place, it does not necessarily mean that tornadic activity will occur. There area many days in
South Florida when all of the ingredients are present and conditions are ripe for severe
thunderstorms to generate tornadoes and it just doesn't happen. On the other hand, there are
instances when tornadoes have formed over the peninsula when the conditions were not as
favorable. For example, tornadoes have formed in the summertime when the wind shear was
very low, but enough instability was present for tornadic activity, catching forecasters off
When conditions are favorable and tornadoes are expected on a given day, Meteorologists
must utilize the doppler radar in order to identify rotation within a severe thunderstorm
capable of producing tornadic activity. This can be difficult to pinpoint on radar and even if
there is significant rotation visible on the doppler, it does not indicate for certain that there is
an actual tornado touching the ground. "Doppler radar signatures can tell warning
meteorologists a great deal about a thunderstorm's structure, but usually can't see the tornado
itself. This is because the radar beam gets too wide to resolve even the biggest tornadoes
within a few tens of miles after leaving the transmitter." (1) Some other tools forecasters use
are storm spotter reports, but even when multiple spotters report a tornado over a certain
area, Meteorologists still have to wait for the National Weather Service to survey the damage
and make the official decision as to whether or not it really was a tornado.
Tornadoes can also form over South Florida when spawned from tropical cyclones moving
over the peninsula, particularly from the feeder bands associated with hurricanes.
Meteorologists look at each storm for the favorable elements necessary for tornadic
development. As a general rule for some Meteorologists, when forecasting tornadoes
generated from tropical cyclones, the bigger and stronger the wind field, the deeper the
vertical wind shear which heightens the probability of severe thunderstorms capable of
producing tornadic rotation. Similarly, this type tornadic development also depends on the
amount of instability, moisture, and lift in the vicinity of the tropical cyclone. Predicting this
type of tornadic development, associated with tropical cyclones, can be challenging for
forecasters due to the very fast motion of the associated tornadic cells. Also, each tropical
cyclone has different characteristics so Meteorologists are faced with a new set of possible
outcomes with each storm. "Andrew (1992), for example, spawned several tornadoes across
the Deep South after crossing the Gulf, but produced none during its rampage across South
Florida. Katrina (2005) spawned numerous tornadoes after its devastating LA/MS landfall, but
only one in Florida (in the Keys)." (2) Another difficulty is, when a tropical cyclone is
approaching an area, Meteorologists can become overwhelmed just getting the public through
tropical cyclone itself because these storms affect such a large area and often forecasting
associated tornadoes is then added to an already full agenda.
Tornadic waterspouts as well as fair weather waterspouts have been known to develop
over the ocean and make their way over the land which then classifies them as tornadoes.
Tornadic waterspouts usually develop from strong thunderstorms over the ocean and then
move onto the peninsula, whereas Fair Weather Waterspouts form during relatively calm
weather, with light winds, within cumulus congestus clouds. These are generally very weak
tornadoes that deteriorate quickly after coming onshore. Both types of waterspouts that move
onshore have the potential to be very destructive. Though it is rare for Fair Weather
Waterspouts to make landfall or move far inland when they do. These tornadoes are possibly
the most difficult type of all to forecast because they occur on such a small scale that they can
usually only be "spotted" by the naked eye.
Although tornadoes in South Florida usually remain below EF2 on the Enhanced Fujita
Scale, they can be very destructive and even deadly. Even with weaker tornadoes, it is not
uncommon for their violent rotation to knock down power lines, uproot trees, and break gas
lines or water mains. They can even contribute to the outbreak of fires. Because of the
destruction that tornadoes can cause and the fact that they develop and move so quickly,
there is little time to warn the public when they are forming. Florida is one of the
only tornado prone states that does not have sirens to warn the public when a tornado is
approaching. This is a dangerous scenario because it is so warm in South Florida, the chance
for severe thunderstorm development and tornadic activity is just as likely at night when
people are sleeping as it is in the daytime hours.
One way to improve the capabilities of forecasting tornadoes and identifying tornadic
rotation early on in order to better warn the public, is to improve resolution on radar imagery.
This of course is much easier said then done. Tornadoes are very small scale features and so
you need tools that can accurately analyze imagery on a small scale without it becoming
pixilated and unreadable. This will probably happen in time as our technology continues to
advance. Also, as Research Meteorologists including those who work at the Storm Prediction
Center in Oklahoma continue to improve their knowledge base of tornadoes and how exactly
they develop, forecasting capabilities will improve as well. In the meantime, making weather
radio's available to every household in South Florida would aid in the protection of human life
since these storms are so difficult to predict and can occur at any time of the year.
Edwards, Roger, Storm Prediction Center. "The Online Tornadoe FAQ." Tornado Forecasting.
Edwards, Roger, Storm Prediction Center. "The Online Tornadoe FAQ."
Do Hurricanes and Tropical Storms Produce Tornadoes?