Question

Why can the scientist predict the weather accurately?

Answer 1

See there is a correction in. ur question and ur questions should be why can the scientist predict the weather accurately? But I m giving u the answer which can be right for both.

Only right prediction can occur through a lot of numerical calculations and requires lot of databases collected from sea, land and air.
And most of the scientists don't go up to this extent.

Hope this helps...

Answer 2

Scientist do not predict weather like fortune foretelling.  They only do forecasting of weather from observed readings of temperature, pressure, composition of atmosphere, vapor percentage, cloud presence, cloud characteristics, wind speeds, wind directions and previous history of weather at the same location.

The weather forecast is only for short term. The forecast is based on numerous measurements done at different locations.  However the observations are not all accurate and not all parameters are known precisely.  Also the atmospheric composition and its behaviour is quite haphazard and rapidly changing.
 
  The volcanic eruptions, global warming, pollution, history of rains, fires, ice caps melting and other parameters perhaps do alter the current atmospheric behavior.  The changes in atmosphere are interdependent and are rapid.
 
   The forecasts are usually good enough for taking predictions. But perhaps the information is not disseminated widely to the affected sometimes.  Many cyclones, tsunamis, tornadoes are now forecast in advance.

    But sometimes rains in summer, autumn, spring and winter are not forecast properly.  Sometimes arrival of rains in monsoon season are not predicted correctly.  Due to wrong or no forecast, many farmers have lost their crops and cultivable lands to ill timed or no rains.  Many farmers have lost their produce on the streets and in the markets.