Environmental Characteristics of Coastal Convection in the Houston Region

Convection initiation (CI) patterns over Houston, Texas, are complicated due to interactions between the coastal and urban environments. The Gulf of Mexico, Galveston Bay, and Trinity Bay all impact the local sea and land breeze circulations. Additional environmental heterogeneities arise from the urban heat island produced by Houston. As part of preparations for the Experiment of Sea Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) field campaign, a CI climatology was developed using radar reflectivity and environmental data for the month of June during the 2017-2022 period.

Preliminary observations indicate that CI patterns can be classified into three different regimes based on the location of cell formation: gulf only, land only, and both land and gulf. RAP model analyses were used to characterize their mesoscale environments. Although thermodynamic environments are similar for each category, there are subtle differences in forcing mechanisms around each regime. For example, the gulf only regime is more likely to have a cold front, stationary front, or outflow boundary within 100 miles of Houston than the other regimes. Consistent diurnal cycle differences between 0Z and 12Z soundings were observed, with 12Z soundings having lower lifting condensation levels and levels of free convection. This pattern was seen among all three regimes.

Radar reflectivity data show abundant convection in the region, with two hotspots to the east northeast and south southwest, relative to the city of Houston. It also shows differences in time of initiation, dissipation, and duration (initiation to dissipation) between all three regimes, with gulf convection happening earlier in the day than land convection. Typically, the gulf regime initiates early in the morning and dissipates in early afternoon, while the land regime initiates in the afternoon and dissipates in the early morning. Additionally, the both regime had a longer duration of about 17 hours, spanning the typical times of both land and gulf regime convection, which is around 8 hours. The both regime initiates similarly to the gulf regime, and ends similarly to the land regime. Based on this climatology, radar and sounding data from the field campaign could greatly enhance the understanding of mesoscale processes contributing to convection initiation in the Houston region.