The dew point at a location 50 km 20° south of west of a recording station is 4°C higher than at the station. If the wind is blowing from the south - southwest (15° west of south) at 12 m s - 1 and net radiation is heating the surface such that evaporation is causing the dew point to increase at 14°F day - 1 , what is the local change in dew point at the station?