Structure of an Atmospheric River over the Gulf of Mexico Observed during the NASA CPEX Campaign

The NASA Convective Processes Experiment (CPEX) was a one-month
aircraft field campaign that took place in the North Atlantic-Gulf of
Mexico-Caribbean Oceanic region during the early summer of 2017. A
total of 16 missions were conducted, in which dropsondes, among
multiple other instruments, were used to collect data, to better
understand convective initiation, organization, and growth
processes. The fifth of these missions was conducted on June 2, 2017
to investigate the moist flow moving to the NE over the Gulf of
Mexico from the remnants of the East Pacific tropical storm
Beatriz. This system consisted mainly of heavy stratiform cloudiness
and widely scattered large convective cells as seen from a satellite
view-point. The transport of moisture into the Gulf of Mexico from the
E Pacific, due to atmospheric rivers, enhanced the interest in this
specific mission. A total of 23 dropsondes were launched over a
rectangular pattern of 1 degree by 9 degrees in the Central Gulf of
Mexico, covering a cross-section of this disturbance. To obtain
meteorological parameter values in the entire observational volume, a
three dimensional variational analysis (3D-Var) method was used.
Saturation fraction and instability index plots, obtained from 3D-Var
calculated parameters, indicate a region particularly susceptible to
deep convection centered at longitude 91 degrees W. This longitude
crosses the Bay of Campeche, which is the region where the remnants of
Beatriz crossed over from the E Pacific into the Gulf of Mexico. The
presence of cold pools at low levels in the Central Gulf of Mexico, is
also investigated.