TEXT E Many of the most damaging
and life threatening types of weather torrential rains, severe thunderstorms,
and tornadoes(龙卷风,)--begin quickly, strike suddenly, and disappear rapidly,
destroying small regions while leaving neighboring areas untouched. Such event
as a tornado struck the north eastern section of Edmonton, Alberta, in July
1987. Total damages from the tornado exceeded $ 250 million, the highest ever
for any Canadian storm. Conventional computer models of the
atmosphere have limited value in predicting short lived local storms like the
Edmonton tornado, because the available weather data are generally not detailed
enough to allow computers to study carefully the subtle (微妙的)atmospheric changes
that come before these storms. In most nations, for example, weather - balloon
observations are taken just once every twelve hours at locations typically
separated by hundreds of miles. With such limited data, conventional forecasting
models do a much better job predicting general weather conditions over large
regions than they do forecasting specific local events. Until
recently, the observation intensive approach needed for accurate, very short -
range forecasts, or "Now casts", was not feasible. The cost of e quipping and
operating many thousands of conventional weather stations was extremely high,
and the difficulties involved in rapidly collecting and processing the raw
weather data from such a network were hard to overcome. Fortunately, scientific
and technological advances have overcome most of these problems. Radar systems,
automated weather instruments, and satellites are all capable of making
detailed, nearly continuous observation over large regions at a relatively low
cost. Communications satellites can transmit data around the world cheaply and
instantaneously, and modem computers can quickly compile and analyze this large
volume of weather information. Meteorologists(气象学者) and computer scientists now
work together to design computer programs and video equipment capable of
transforming raw weather data into words, symbols, and vivid graphic displays
that forecasters can interpret easily and quickly. As meteorologists have begun
using these new technologies in weather forecasting offices, now casting is
becoming a reality. According to the passage, the word "Now casts" ( paragraph 3 ) means ______.
A．a way of collecting raw weather data B．a forecast which can predict the weather conditions in the small area in an accurate way C．a network to collect instant weather data D．a more advanced system of weather observation