METEOROLOGIST JEFF HABY
The dryline is a dramatic weather changer and can be a convergence zone for severe storms to fire up. A dryline separates air masses
with very different moisture characteristics. Since the dryline is more noted for its advancing stage instead of retreat stage, it
is known as a dryline instead of a moistline. The dryline typically advances during the day and then retreats at night. In the advancing
stage, the dryline will replace warm and humid air with warm and dry air. The dryline is found most notable in the spring and is a
relatively common feature in Western Texas, Oklahoma, and Kansas. The dryline can advance to the east of this region but it will
inevitably retreat back toward the source region after sunset.
The dryline is a dewpoint change line and a convergence axis. The dewpoint can vary dramatically from one side to the other. For example,
the dewpoint could be 68 F on the moist side and 25 F on the dry side. The passage is often accompanied by gusty winds, dust and
sometimes storms if enough convergence takes place. The dryline can change a humid hot day into a dry dusty day in just moments
after passage. Storms can fire up on and near the dryline boundary thus the storms represent another sudden change that can occur
in the weather.
A dryline separates warm and moist mT air (warm and moist Gulf of Mexico ocean air mass known as maritime tropical) from high plains and high
elevation cT air (warm and dry continental tropical air). The cT air will flow over the mT air, thus the influence of the dry air mass
can extend well east of the surface dryline boundary. This dry air aloft produces convective instability when it flows over the top of
warm and humid air. Thus, the dryline environment is often associated with a severe storm environment, especially when the dryline is
being forced forward by a developing low pressure system.