Weathering Changes Visit a National Weather Service Office
By: John Shepler
The Doppler radar for the National Weather Service needs to
be recalibrated twice a year. It's not to compensate for changes
in the electronic circuitry. It's because the leaves fall off
the trees in autumn and new ones reappear in late spring. The
ultrasensitive radar sees this as a change in the terrain and
loses track of what is permanent and what is moving.
On
the radar screen inside the Chicago office, 100 feet below the
28 foot dome housing the Doppler radar's antenna, the meteorologists
on duty scan patterns of reds and greens, looking for shifts
in the wind. This is what differentiates Doppler from other types
of radar. It not only tells you how far away things are but also
how fast they are moving. The green areas represent winds blowing
toward the radar. The reds are winds blowing away. The stronger
the colors, the faster the winds are moving.
For most of the year, the radar tells forecasters exactly
how fast the winds aloft are moving. But twice a year this part
of the radar also goes out of calibration. In the spring, when
birds migrate north, the south to north winds appear to be blowing
faster than they really are. It's because the birds' velocity
is added to that of the wind. In the fall, the north to south
winds are equally out of calibration. I stare at the screen in
amazement that flocks of birds miles or dozens of miles away
can affect what shows up on weather radar screens. Yet, this
seeming oversensitivity in the equipment becomes well worth the
occasional nuisance when violent storms are in the area. Every
shift in wind patterns can be critical to aircraft landing at
nearby O'Hare International Airport. Those colored patterns could
also be locating the characteristic hooked signature of a tornado
forming overhead.
This past weekend, my wife Barbara and I were invited to visit
the National Weather Service office that serves our area from
Romeoville, IL, in the flat fields southwest of Chicago. We got
our invitation over our personal weather radio from a voice with
a curiously electronic sound. We headed that way, hoping to find
out who that odd announcer was and why he seemed to be on at
all hours of the day and night.
This was the first ever open house of the Chicago weather
forecast office in their state of the art facilities in Romeoville.
Chicago has had a forecast office since 1894, shortly after the
weather service transferred from the Army Signal Corps to the
Department of Agriculture. In 1940, weather forecasting responsibility
transferred again to the Department of Commerce and is now part
of NOAA, the National Oceanic and Atmospheric Administration.
The Chicago office started at the Post Office downtown, moved
to Rosemont to be near O'Hare Airport, and then moved again next
to Lewis University Airport near Romeoville in 1991, when that
location was picked as the best spot for the $2 million Nexrad
Doppler Radar.
Our
tour began with an explanation of how the NOAA weather radio
works and the important features that have been added just recently.
For instance, did you know that a digital coding called SAME
(Specific Area Message Encoding) will turn on weather radios
only for the locations you have programmed? If your radio has
that feature, you can set your radio to wake you up only if there
is a watch or warning for your specific county. This technology
is so useful that has been adopted for the country's new national
Emergency Alert System.
We met our mystery announcer in the next room. He's known
affectionately as "Iron Mike," and he is indeed a computerized
voice. Mike is what's known as a text to voice translator. As
the meteorologists develop a new forecast, they type it into
their computers and it becomes available to airports, police
stations, radio and TV stations, newspapers and Iron Mike. Mike
instantly converts the text of the forecast or weather data into
spoken words that go out phone wires to a weather radio transmitter
within 40 miles of you. Previously, meteorologists had to take
extra time to go into a little studio and record tapes for the
broadcasts. Mike does that for them now, saving 10 or 20 minutes
that could be critical in a rapidly developing emergency.
At National Weather Service offices such as Romeoville, the
traditional weather forecasting instruments still have an important
role. While a geostationary satellite hovers overhead sending
moving pictures of the clouds, the familiar anemometer cups spin
to measure wind just outside the building. A weather vane swings
back and forth to sense the wind's direction, and a metal rain
bucket gathers precipitation and measures it to within a hundredth
of an inch. They still use weather balloons to carry instruments
with radio transmitters, known as radiosondes, up through the
atmosphere. We got to touch one, and oddly enough they feel "gooey"
to the touch. The special material expands as the balloon rises
until it finally bursts at about 35,000 ft. and the radiosonde
parachutes to earth. Oh, yes, these balloons get so large and
under certain conditions reflect sunlight so well that even today
they are still routinely reported as UFOs. Not everything in
the weather service has changed.
Books of Interest:
The Weather Book by Jack Williams, USA Today. The best,
most readable and visually stimulating guide to our nation's
weather--featuring the full-color graphics of the most popular
section of America's most popular newspaper.
Weather: An Explore Your World Handbook by H. Michael
Mogil, Discovery Channel. This new book was created by the Discovery
Channel to help you understand how our weather works in a clear
and easy to follow format. It contains over 300 photographs that
explain the inner workings of hurricanes, tornadoes, thunderstorms,
weather fronts and more. The up to date information is provided
by professional meteorologists.
The Weather Tracker's Kit by Gregory C. Aaron. Budding
meteorologists will enjoy the giant cloud chart plus a functional
weather station that includes a wind direction and speed indicator,
a rain gauge, a thermometer, and a wind-chill chart. An illustrated
handbook teaches all about weather lore.
Also visit these related
sites:
NOAA - Facebook Page of the
National Oceanic and Atmospheric Administration of the Department
of Commerce, which operates the National Weather Service, National
Ocean Service and other important agencies.
National Weather Service - The mission of NWS is "Provide weather, water, and climate data, forecasts and warnings for the protection of life and property and enhancement of the national economy."
Tornado Themed Gifts - A dangerous tornado or “twister” touches down and is captured on film by storm chasers from the National Severe Storms Laboratory of NOAA. This twister has a dust and debris cloud forming at the ground surface in tornado alley.
what is moving.
