Rather than drawing isobars (lines joining places of equivalent mslp), or contours (lines joining places of equivalent geopotential height), it is sometimes better to describe graphically the wind flow by drawing lines with arrows showing the direction of the wind at any level...often used on / near the surface. Although long used in tropical / sub-tropical areas, ( where isobaric analysis is of dubious value ), streamlines are also very useful at mid-latitudes, for instance to determine likely areas of convective activity due to convergent triggering.
Meaning of STREAMLINES in English
Weather and meteorology English vocabulary. Английский словарь погоды и метеорологии . 2012