Case study of a cold-front-dryline merger on May
24th 2002 during IHOP
Tim Trudel
University
of Wyoming
MS Defense
The processes that produce deep
moist convection were investigated in the southern plains, which is an area
often threatened by severe weather during the spring and early summer
months. This study presents
analysis of data taken on 24 May 2002,
which was one of the most active days of IHOP. The focus is on a strong cold front and its
interaction with a dryline on the Texas-Oklahoma
border. Synoptic and mesoscale conditions related to the initiation of deep convection
are described. Observations from
mobile mesonet probes, Wyoming Cloud Radar, soundings,
and radars are used to describe temperature, humidity, airflow, and instability
across radar detected fine-line
boundaries.
Since the cold front was moving
much faster than the dryline, the cold front and dryline collided.
This “merger” process started further north on the Texas
panhandle and progressed southeast during the day. The triple point, visible on Doppler
radar, marked the approximate position where the merger process took
place. The relatively cold dense
air mass behind the cold front lifted the dry air associated with the dryline along with the moist air ahead of the dryline.
Shortly after the merger, severe weather developed near the
Texas-Oklahoma border ahead of the cold front and moved eastward.
Deep mesoscale
lift can rapidly reduce convection inhibition and increase convective available
potential energy of the environment so that the relatively stable environment
changes to one conducive for deep convection. This release of potential instability (i.e.
the erosion of the cap inversion) resulted in a fountain of thermals reaching
the level of free convection, culminating in organized deep convection.