|TEXAS DRYLINE PROPAGATION ON MODELS
METEOROLOGIST JEFF HABY
The dryline is a boundary that separates
tropical moist air from
tropical dry air. A dryline is located by the
distinct dewpoint gradient and wind shift that occurs at its leading boundary. The dryline tends to be most
discernible in the spring and often traverses across Oklahoma and Texas.
The dryline has a few distinct characteristics that make it different from a front. A dryline moves east
during the day and then retreats back west at night. Typical fronts tend to move in one direction and thus do
not retreat. The forward motion of a dryline occurs due to the mixing out of shallow moist air near
the dryline boundary. Daytime heating initiates the mixing out of moist air along the dryline boundary. Since there
is no daytime heating at night, the moist air ahead of the dryline undercuts the dry air and thus the dryline boundary
retreats back west. Unlike a front which tends to have a strong density gradient, the density gradient is
not as strong along a dryline. Hot and dry air has a similar density to warm and moist air. The difference
in density between warm and cold air is much more pronounced, such as along a cold front.
A dryline is similar to a front in that it can generated uplift along its boundary. The amount of
along the dryline boundary will determine the amount of uplift. In a situation is which there is strong west
winds behind the dryline and strong southeast winds ahead of the dryline, the convergence along the dryline
will be significant.