F6 Inconceivable 319-379 mph <1% Such tornadoes are highly unlikely; the
tornado (513-610 kph; areas they damage would not be
277-329 knots) recognizable and evidence for them would
probably only be detected through
engineering studies; such areas would likely
be surrounded by areas damaged by F5
forces, with cars, large appliances, and other
large objects causing additional damage
What is numerical weather prediction?
Numerical weather prediction is forecasting the weather using numerical models.
Because of the complexity of the mathematics involved—not to mention the number of
variables needed to predict the weather—all numerical model studies are run on high-
speed computers. The computer solves a set of equations, resulting in a computer
model of the atmosphere showing how weather conditions will change over time.
How do computer modelsattempt to predict the weather?
In general, computer models used to predict weather use around seven equations that
govern how the basic parameters—temperature, pressure, and so on—change over time
in the atmosphere. Scientists call the
study of how they can physically and
mathematically represent all the processes
in the atmosphere dynamics.
In reality, everyone knows computer
models can’t perfectly predict the weath-
er at this time. This is because of several
factors, including errors in the initial
conditions (or the observations the model
gets to begin making its forecast) and
errors inherent in the model (a computer
model can’t take into consideration all
the factors controlling the weather).
Long-term forecasts are even more inac-
curate because these two errors are com-
pounded mathematically over time.
What are some examplesof weather
prediction models?
Because there is more than one group
carrying out weather predictions, there 313
MATH IN THE NATURAL SCIENCES
The strength of a tornado is rated on the Fujita-
Pearson Tornado Intensity Scale, which takes into
account wind speeds and damage created by the
twister. The Image Bank/Getty Images.