Did you predict that many students （） up for the dance competition

M: Well, you didn't expect it to be warm, did you？

W: Of course not, but I just heard the National Weather Service's prediction for the next 90 days. They said it's sup- posed to be much colder weather than usual.

M: Yeah, maybe. Personally, I think those long-range forecasts are useless.

W: Not as useless as you think.

M: Oh, come on, when you're talking about what's going to happen three months later, you might as well just pick a forecast out of our hat. W: Well, you are half-right. They aren't very good for the amount of rain. But they are a lot better for temperatures especially for this time of the year.

M: Really, so I should take them seriously about the cold but not count too much on a lot of extra snow？

W: Un-huh.

M: But what did you say about this time of the year？ Do some seasons really give them more problems in making forecasts？

W: Autumn is the worst, apparently weather patterns change so much then, just think how variable our weather has been the last three months.

M: Come to think of it. That's true. It probably would have been hard to predict all those changes back in the summer. You know, you're beginning to convince me there is more to forecast than I thought. How come you know so much about it？

W: I get my information from an expert. My sister's a meteorologist.

On what aspect of weather forecasting is the conversation about？

(20)

A．How much its accuracy has improved recently.

B．How reliable long-range forecasts are.

C．How difficult it takes to make a good forecast.

D．How the current forecast causes troubles.

M: Well, you didn't expect it to be warm, did you？

W: Of course not, but I heard the national weather service's prediction for the next 90 days. They said it' s supposed to be much colder weather than usual.

M: Yeah, maybe. Personally, I think those long-range forecasts are useless.

W: Not as useless as you think.

M: Oh, come on, when you' re talking about what' s going to happen three months later, you might as well just pick a forecast out of our hat.

W: Well, you are partly right. They area' t very good at the amount of water falling on the earth. But they are much better for temperatures especially for this time of the year.

M: Really？ So I should take them seriously about the cold but not count too much on a lot of extra snow？

W: Exactly.

M: But what did you say about this time of the year？ Do some seasons really give them more problems in making forecasts？

W: Autumn is the worst; apparently weather patterns change so much then. Just think how variable our weather has been the last three months.

M: Come to think of it, that' s true. It probably would have been hard to predict all those chan ges back in the summer. You know, you' re beginning to convince me there is more to fore casting than I thought. How come you know so much about it？

W: I get my information from an expert--my sister.

(23)

A．The foundation.

B．The reliability.

C．The history.

D．The source.

M: Well, you didn't expect it to be warm, did you？

W: Of course not, but I just heard the national weather services prediction for the next 90 days. They said it's supposed to be much colder weather than usual.

M: Yeah, maybe. Personally, I think those long-range forecasts are useless.

W: Not as useless as you think.

M: Oh, come on, when you are talking about what's going to happen three months later, you can not count on the long- range weather forecasting.

W: Well, you are half way right. They aren't very good for rainfall. But they are a lot better for temperatures especially for this time of the year.

M: Really, so I should take them seriously about the cold but not count too much on a lot of extra snow？

W: Ahha.

M: But what did you say about this time of the year？ Do some seasons really give them more problems in making forecast.

W: Autumn is the worst; apparently weather patterns change so much then. Just think how variable our weather has been the last three months.

M: That's true. It probably would have been hard to predict all those changes hack in the summer, you know, you are beginning to convince me of the value of weather forecasting. How come you know so much about it？

W: I get my information from an expert. My sister works at weather bureau.

(20)

A．The amount of snow.

B．The amount of cloud covering.

C．The wind condition.

D．The temperature.

M: Well, you didn't expect it to be warm, did you.'？

W: of course not, but I just heard the National Weather Service’s prediction for the next 90 days. They said it's supposed to be much colder weather than usual.

M: Yeah, maybe. Personally, I think those long-range forecasts are useless (23) .

W: Not as useless as you think.

M: Oh, come on, when you're talking about what's going to happen three months later, you might as well just pick a forecast out of our hat.

W: Well, you are half-right. They aren't very good for the amount of rain. But they are a lot better for temperatures especially for this time of the year (24) .

M: Really, so I should take them seriously about the cold but not count too much on a lot of extra snow？

W: Un huh.

M: But what did you say about this time of the year？ Do some seasons really give them more problems in making forecasts？

W: Autumn is the worst, apparently weather patterns change so much then, just think how variable our weather has been the last three months (25) .

M: Come to think of it. That's true. It probably would have been hard to predict all those changes back in the summer. You know, you're beginning to convince me there is more to forecast than I thought. How come you know so much about it？

W: I get my information from an expert. My sister's a meteorologist.

(20)

A．How much its accuracy has improved recently.

B．How reliable long-range forecasts are.

C．How difficult it takes to make a good forecast.

D．How the current forecast causes troubles.

The first of these methods is the persistence method; the simplest way of producing a forecast. The persistence method assumes that the conditions at the time of the forecast will not change. For example, if it is sunny and 87 degree today, the persistence method predicts that it will be sunny and 87 degree tomorrow. If two inches of rain fell today, the persistence method would predict two inches of rain for tomorrow. However, if weather conditions change significantly from day to day, the persistence method usually breaks down and is not the best forecasting method to use.

The trends method involves determining the speed and direction of movement for fronts, high and low pressure centers, and areas of clouds and precipitation. Using this information, the forecaster can predict where he or she expects those features to be at some future time. For example, if a storm system is 1,000 miles west of your location and moving to the east at 250 miles per day, using the trends method you would predict it to arrive in your area in 4 days. The trends method works well when systems continue to move at the same speed in the same direction for a long period of time. If they slow down, speed up, change intensity, or change direction, the trends forecast will probably not work as well.

The climatology method is another simple way of producing a forecast. This method involves averaging weather statistics accumulated over many years to make the forecast. For example, if you were using the climatology method to predict the weather for New York City on July 4th, you would go through all the weather data that has been recorded for every July 4th and take an average. The climatology method only works well when the weather pattern is similar to that expected for the chosen time of year. If the pattern is quite unusual for the given time of year, the climatology method will often fail.

The analog method is a slightly more complicated method of producing a forecast. It involves examining today's forecast scenario and remembering a day in the past when the weather scenario looked very similar (an analog). The forecaster would predict that the weather in this forecast will behave the same as it did in the past. The analog method is difficult to use because it is virtually impossible to find a predict analog. Various weather features rarely align themselves in the same locations they were in the previous time. Even small differences between the current time and the analog can lead to very different results.

What factor is NOT mentioned in choosing a forecasting method？

A．Imagination of the forecaster.

B．Practical knowledge of the forecaster.

C．Necessary amount of information.

D．Degree of difficulty involved in forecasting.

M: Well, you didn't expect it to be warm, did you？

W: Of course not, but I just heard the national weather services prediction for the next 90 days. They said it's supposed to be much colder than usual.

M: Yeah, maybe. Personally, I think those long-range forecasts are useless.

W: Not as useless as you think.

M: Oh, come on, when you're talking about what's going to happen three months later, you might as well just pick a fore cast out of our hat.

W: Well, you are half way right, They arch't very good for precipitation. But they are a lot better for temperatures, especially for this time of the year.

M: Really, so I should take them seriously about the cold but not count too much on a lot of extra snow？

W: Ahha.

M: But what did you say about this time. of the year. Do some seasons really give them more problems in making forecast.

W: Autumn is the worse, apparently, weather patterns change so much then. Just think how variable our weather has been the last three month.

M: Come to think of it. That's true. It probably would have been hard to predict all those changes back in the summer. You know, you' re beginning to convince me there is more to forecasting than I thought, How come you know so much about it？

W: I get my information from an expert. My sister is a meterologist.

On what aspect of weather forecasting does the conversation focus？

A．How much it has improved in recent years.

B．How reliable long-range forecasts are.

C．How long it takes to become a meteorologist.

D．How the current forecast will affect the speakers.

Forecasting Methods

There are several different methods that can be used to create a forecast．The method a forecaster chooses depends upon the experience of the forecaster, the amount of information available to the forecaster, the.level of difficulty that the forecast situation presents,and the degree of accuracy or confidence needed in the forecast.

The first of these methods is the persistence method; the, simplest of producing .a forecast．The persistence method assumes that the conditions at the time of the forecast will not change．For example, if it is sunny and 37 degrees today, the persistence method predicts that it will be sunny and 37 degrees tomorrow．If two inches of rain fell today, the persistence method would predict two inches of rain for tomorrow．However, if weather conditions change significantly from day to day, the persistence method usually breaks down and is not the best forecasting method to use.

The trends method involves determining the speed and direction of movement for fronts, high and low pressure centers, and areas of clouds and precipitation (降雨量)．U-sing this information, the forecaster can predict where he or she expects those features to be at some future time For example, if a storm system is 1000 miles west of your location and moving to the east at 250 miles per day, using the trends method you would predict it to arrive in your area in 4 days．The trends method works well when systems continue to move at the same speed in the same direction for a long period of time．If they slow down,

speed up, change intensity, or change direction, the trends forecast will .probably not work as well.

The climatology (气候学) method is another simple way of producing a forecast．This method involves averaging weather statistics accumulated over many years to make the forecast．For example, if you were using the climatology method to predict the weather for New York City on July 4th, you would go through all the weather data that has been recorded for every July 4th and take an average．The climatology method only works well when the weather pattern is similar to that expected for the chosen time of year．If the pattern is quite unusual for the given time of year,the climatology method will often fail.

The analog method(类推法)is a slightly more complicated method of producing a forecast．It involves examining today's forecast scenario and remembering a day in the past when the weather scenario(天气状况)looked very similar (an analog)．The forecaster would predict that the weather in this forecast will behave the same as it did in the past．The analogy method is difficult to use because it is virtually impossible to find a predict analog．Various weather features rarely align themselves in the same locations they were in the previous time．Even small differences between the current time and the analog can lead to very different results.

第 41 题 What factor is NOT mentioned in choosing a forecasting method？

A．Imagination of the forecaster.

B．Necessary amount of information.

C．Practical knowledge of the forecaster.

D．Degree of difficulty involved in forecasting.