Deep convection, lightning activity and population impact over northwest Mexico: Coastal hotspots from 2009 to 2018

Abstract

Northwest Mexico (NWM) is an extensive region with a humid and unstable environment leading to atmospheric convection during the North American monsoon. Occasionally, extreme events are associated with severe weather, including deep convection, heavy rainfall and frequent lightning. Based on the period from July through September 2009–2018, the present study investigates general characteristics of convection. Geostationary satellites were used to document three‐dimensional cloud cover structures over the mainland, Gulf of California (GOC) and Baja California Peninsula (BCP). The convection developed over the Sierra Madre Occidental (SMO) mountains with a distinct cloud top structure over the southern GOC. In contrast, reduced cloud cover was observed over the peninsula and eastern Pacific Ocean. An active (2014) and inactive (2010) season are examined in more detail; the former had a more favourable environmental setting to support above‐normal convection and rainfall with respect to the 10‐year average. A regional‐scale analysis of lightning was computed with data from a ground‐based sensor network, including date, time and location of more than 16 million records. Major findings include: (1) lightning enhancement occurred in conjunction with deep convection, west of the SMO from the afternoon through the evening, while the gulf entrance became a well‐defined hotspot close to the mainland coastal plains overnight; (2) most lightning‐related deaths were in specific areas near the coastal plains or within isolated regions of the SMO foothills; (3) high exposure is expected in areas with considerable lightning and population located within 100 km from the gulf coastline. These findings are valuable for monitoring monsoon thunderstorms and for improving the ability to provide timely warnings of severe weather.