[--MAIN HOME--] [--ALL HABYHINTS--] [--FACEBOOK PAGE--] SEVERE STORM STRUCTURE: FORWARD FLANK AND REAR FLANK DOWN DRAFT METEOROLOGIST JEFF HABY The forward flank downdraft is the outflow from the rain-cooled air of the storm's downdraft. The rear flank downdraft is air from aloft that is transported down to the surface from colliding with the storm. The rear flank downdraft air tends to be dry and warm since the air warms by adiabatic compression as it sinks to the surface. Adiabatically warmed air will also decrease in relative humidity if no precipitation falls into the air. The rear flank downdraft tends to be warmer than the forward flank downdraft also since rain and evaporative cooling is not as common in the rear flank. Shear is enhanced along these flanking downdraft boundaries and the shear can be magnified along where the two flanks merge. The right balance of shear and instability release can lead to tornadogenesis. The diagram below shows the forward and rear flank downdrafts at "H". The rear flank downdraft is on the left side and the forward flank is on the right side of the diagram.