01/06/99- Updated 06:10 PM ET -
"To the often-heard question, 'Why can't we make better weather
forecasts?' I have been tempted to reply, 'Well, why should we be able to make any
forecasts at all?' " - Edward N. Lorenz in The Essence of Chaos.
Lorenz is the MIT atmospheric science researcher whose work led to the
development of the idea of chaos in physical systems. In meteorology, one of the important
implications is that small differences in the initial conditions of the atmosphere can
lead to big differences in the weather that results only a few days later. These
differences can be too small to detect. This is why scientists say that day-to-day
forecasts of the weather for more than about two weeks ahead will never be possible.
Today, five days is about the limit of useful day-to-day forecasts. And, forecasts for
five days ahead are, at best, little better than using "normal" climatic values.
All weather forecasts begin with observations of what the weather is doing all
over the world. These observations are then fed into super computers that use mathematical
models of the atmosphere to make predictions. In the United States, these computers are
operated by the National Weather Service. The resulting forecasts are used by all weather
forecasters, both those with the National Weather Service, those at television stations,
and those at private forecasting companies, such as Weather Services Corp. in Lexington,
Mass., which does all of USA TODAY's forecasts.
The links below will tell you more about how all of this is done.
Basics of forecasting
The University of Illinois' Online Meteorology section on
is the best way to begin understanding the topic.
and activities section gives teachers and students good ideas for learning more about
weather and forecasting.
forecasts page has links to information that explain what forecasters mean and how to
read weather maps.
If you want to try your hand at doing some of your own weather forecasting,
first check out the University of Illinois site listed above, then go to articles from a
National Oceanic and Atmospheric Administration gopher server, which USA TODAY has posted
on our site. First, don't count on most
weather proverbs to tell you
what's likely to happen. But the combination of readings from a
barometer and wind direction can
often give good clues what to expect.
Once you learn some of the basics of weather forecasting and how to read the
different weather maps, you will want to visit the University of Michigan's WeatherNet
weather maps page, which has both
surface and upper-level weather maps
The information that had been here on what forecasting terms mean and how to
read weather maps is now part of our new
understanding forecasts page.
Many computer models have been developed the past three decades, which help
meteorologists forecast weather. A USA TODAY Online text file gives a brief history of
models and their role in
Another USA TODAY text file briefly describes some of the
models currently in use.
The National Weather Service Western Region has an introduction to
Numerical Weather Prediction
A good way to access the images and text produced by these models is on the
Ohio State University Forecast
Weather Images page. Links from this page will take you not only to the U.S. models,
but also some from other parts of the world.
The University of Michigan also has links to many of the different forecast
to access the WeatherNet's computer model forecast page.
Forecasts have improved tremendously the past three decades with the explosion
of computer technology. Whether or not this rapid improvement in weather forecasts
continues depends on
The ability to observe the atmosphere is crucial for improving forecasts. The
National Centers for Environmental Predictions (NCEP) is improving
observations of the atmosphere by
modernizing observation techniques and using new technology.
The National Weather Service's Office of Meteorology has a Web site with
more information on changes being made in
The National Oceanic and Atmospheric Administration's Forecasting Systems Lab
in Boulder, Colo., has several projects designed to improve forecasting.
Click here to go to a web
page with links to more information about these projects.
A big question for forecasters always is, "how reliable is this
prediction?" A basic idea from chaos theory as it applies to weather forecasting is
that small differences in the initial conditions of the atmosphere can lead to big
differences in the weather that results only a few days later. But, some times small
differences can make more difference that at other times. That is, sometimes the weather
is more predictable than at other times. To find out whether the atmosphere is more or
less predictable at a particular time, forecasters run their computer models several times
to produce the same forecast. But, they change the initial conditions slightly for each
run. If the results of the model runs with different conditions are close to each other,
the forecasters know the atmosphere is behaving well and the forecasts have more chance of
turning out well.
- More about this is found in the second edition of the USA TODAY Weather Book, published in
Hurricane forecast limits
hurricane model led
to vast improvements in hurricane forecasting in the 1995 season. However, meteorologists
say there are
limitations on the
accuracy and time range of hurricane forecasting.
The National Weather Service issues long-range forecasts for weeks and months
ahead. These forecasts are not detailed and can not tell you if it will rain on a
particular day next month. A USA TODAY online file describes
what long-range forecasts can and
can not tell you. Another file contains some answers to
commonly asked questions about long
Long range forecasts often depend on seasonal variations in the sea surface
temperature of the oceans, such as those that are a part of El Nino.
homepage has links to some long-range forecasts issued by NCEP and some more
information about long range forecasts.
Often, climatic "normals" - or 30-year averages - are a more useful
guide to planning than any kind of long-range forecast. USA TODAY's weather averages page has more
information and links to averages for places around the world.
The USA and other nations support many research projects in atmospheric science
in order to better understand some of laws and processes that govern the earth's
atmosphere and oceans. One major project is the ongoing research into
VORTEX Experiment was
another major research project, which was designed to try to better understand tornadoes.
A USA TODAY Online graphic gives more
details about how the VORTEX Experiment
was set up and some of the results.
The explosion in technology is one of the key factors that have improved
forecasts. One of the new tools, which have enhanced observations of the atmosphere, is
Hurricane hunter aircraft have
been used the past several years to observe hurricanes and to aid forecasters in
predicting hurricane landfall. A new
high altitude jet craft is
expected to be ready by August 1996. The new jet will likely lead to a major improvement
in hurricane landfall forecasts.
technology homepage describes
some of the technology in use and being developed for weather forecasting.