英语翻译five-day forecasts today are as good as two-day forecast

如今五日内天气预报 与（大约） 20年前 二日内天气预报一样好（GOOD在这里即准确的意思）.
five-day forecasts today are as good as two-day forecasts were.个人认为,这也可以成为一句话,就是表达的不完整,需要加上状语部分予以限定,于是about twenty years ago就出来了.如果没有about,也能说得通,那就是只比确切地20年前的二日天气预报要好.
两个谓语动词,都是系动词,good是are和were的共同表语.
再问： five-day forecasts today are as good as two-day forecasts about twenty years ago 去掉were不行吗？加个were总觉得多余
再答： 这是一个比较状语从句，当两个句子的动词相同、时态一致的话，就可以省掉了。如：He is as quick in answering as his sister (is). 他回答的和她姐姐一样快。因此，这里的were不可以省略！ 谢谢！