Characteristics of mesoscale convection over northwestern Mexico, the Gulf of California, and Baja California Peninsula

Abstract

Mesoscale convective systems (MCSs) are frequent, but understudied, components of the warm season climatology in northwestern Mexico. This study provides an update of previous research on convective development and examines MCS life cycle, structure, and motion from July through September. It focuses on a region south of the North American monsoon core and, from 2009 to 2018 satellite observations, on patterns of cloud tops higher than 10 km above sea level. The diurnal cycle of convection shows cells initiating in the early afternoon over the Sierra Madre Occidental mountains and becoming better organized over the next few hours. These features typically move westward, grow upscale to reach maximum vertical extent near local sunset, and weaken during the night. However, there is a distinct region of deep convection over and off the coast of Nayarit (20-23 N), in the Pacific Ocean, that remains active through the night and into the early morning, producing heavy rainfall and frequent lightning. Occasionally, the inner structure of these MCSs can move across the Gulf of California and reach the southern Baja California Peninsula. One particular long-lived, fast-moving MCS from July 23 and 24, 2014 was selected for in-depth analysis, because it was associated with weather conditions that included unusual precipitation and extreme winds. The MCS caused damage from sustained winds of tropical-storm strength and an intense gust front in the Los Cabos area, in the southern tip of the peninsula. This extraordinary MCS developed in the most unstable and humid environment recorded during the 1976-2018 period, and was supported by a collocated upper-level, inverted trough and a lower-troposphere tropical wave. We also found that the 10 most unstable conditions have all occurred after 2011, possibly indicative of a trend toward more frequent and favourable environments to spawn MCSs over the Gulf of California entrance.

Thunderstorm and hailstorm environments in Mexico

“…Particularly in the NW subregion, the influence of the NAM in summer and autumn is observed with high environmental instability, consistent with previous reports of MCS (Farfán et al, 2021). Over the GM subregion, the highest CAPE environments during spring (medians around 2000 J·kg −1 for thunderstorms and hail) have been associated with a change in wind patterns from the Gulf of Mexico (León‐Cruz et al, 2022) coincident with the beginning of a severe weather season in northeastern Mexico and the southern United States.…”

“…Particularly in the NW subregion, the influence of the NAM in summer and autumn is observed with high environmental instability, consistent with previous reports of MCS (Farf an et al, 2021). Over the GM subregion, the highest CAPE environments during spring (medians around 2000 JÁkg −1 for thunderstorms and hail et al, 2009) and the role of easterly waves and tropical cyclones in the continental portion of Mexico (Dominguez et al, 2020).…”

“…In this regard, some studies have examined deep convective clouds related to severe weather. For example, mesoscale convective systems (MCS) over northwestern Mexico have been widely analysed during the North American monsoon (NAM) (Farfán et al, 2021; Ramos‐Pérez et al, 2022; Valdés‐Manzanilla, 2015). Likewise, the spatiotemporal distribution of precipitation and deep convective clouds over FV has been analysed, illustrating that both events are related to the orographic features (Brito‐Castillo et al, 2022; León‐Cruz et al, 2021).…”

Effect of the Trans‐Volcanic Axis on meridional propagation of summer precipitation in western Mexico

“…6a). In the Baja California Peninsula, a September peak is observed due to the approach of tropical cyclones, which reach the northernmost position in September (Farfán et al ., 2015) and the development of organized thunderstorms also known as Mesoscale Convective Systems (Farfán et al ., 2021).…”

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

“…The present study used the location and number of individual strokes to find convective cells with a spatial and temporal resolution comparable or even better than the one from GOES imagery. Characteristics of convection in Mexico, with the WWLLN dataset, have been examined for the development of meteorological phenomena from a multiyear perspective (e.g., Kucie nska et al, 2010;Kucienska et al, 2012;Raga et al, 2014) and short-term, regional-scale events (Barrett et al, 2017;Farf an et al, 2021;Clouthier-Lopez et al, 2022). The present study examined the number of detections within a fine-scale grid of 5.6 × 5.6 km to determine stroke density per unit area across the mainland, peninsula and surrounding oceanic regions.…”