Image sequence copyrighted by Fernando Caracena, 1997.
This is the beginning phase of a wet microburst when the precipitation
has not yet reached the ground (virga). However, unlike the dry
microburst where the falling hydrometeors remain virga, in the wet
a gush of rain reaches the surface with high winds, and
produces a brief, surface pressure spike called a pressure nose.
This downward bulge of heavy virga preceeding a severe microburst
was observed at Dallas Ft. Worth International Airport just before
an aircraft was downed by an encounter with the ensuing microburst
(Caracena et al., 1987a).