Conventional satellite imagery depicted an upper low digging slowly southeast into the Central Rockies. Meanwhile, an active subtropical jet was focused farther south underneath it lifting northeast across northern Mexico and downstream across the wind across the Gulf Coast states.
While there was broad warm air advection, instability and a very moist airmass focused across the western Gulf Coast region, there were no identifiable features on the larger scale in conventional satellite imagery that suggested a forcing mechanism for organized convection to initiate. However, upon closer inspection of morning GOES-RGB airmass imagery, a subtle and small scale, but identifiable feature appeared that reflected a shortwave impulse. This impulse was tracked crossing the Rio Grande river at 12Z/16, and in conjunction with deep moisture and diurnal instability proved to be the catalyst for increasingly organized convection after 18Z/16 that continued past 00Z/17 along the Upper Texas coast and coastal areas of southern Louisiana. The result was 4 to 8 inches of rain, and flash flooding in the suburbs of Houston, TX.
Thanks for reading!
~ Andrew Orrison (WPC)