Can a wet winter lead to a drier monsoon? (Part II)

Previously, I went over how strong landscape heating generates a seasonal wind shift called the North American Monsoon. The resultant large-scale relative low pressure at the surface becomes paired with the simultaneous development of high pressure aloft. Thus, moist low-level winds originating from surrounding moisture sources in proximity to the “thermal low” region are drawn inwards overland, while winds rotating clockwise around the upper-level high pressure circulation entrain additional subtropical moisture found near Mexico to better support deeper atmospheric moisture profiles available for thunderstorms.

In a prior explainer post, I described why established snowpack is difficult to naturally remove. Importantly, snowpack is an incredibly efficient natural heat sink (high sunlight reflectivity, high heat absorption potential, and high heat storage capacity). As snow does begin to melt, wet soils and runoff continue to delay full surface heating potential since liquid water still has greater heat storage capacity versus dry soils and evaporative cooling effects!

Consequently, it makes sense why research has demonstrated through observational correlations and modeling simulations that the presence of widespread and deep snowpack in the southern Rockies can be a significant lead indicator for a delayed and weakened summer monsoon circulation setup, especially northwards over the “Four Corners” region (AZ, UT, CO, and NM). What this all boils down to is the natural chain of events leading to the development and overall strength of the anticipated North American Monsoon wind pattern is susceptible to the intensity and areal coverage of surface heating throughout the southwestern U.S. between the spring transition into summer.

The monsoon timeframe (June 15th – September 30th) is significant producing between ~30% to 50% of annual precipitation for many locations in Arizona and New Mexico. Therefore, any summer precipitation reduction feedback response linked to wet and cold winters goes beyond just the interest of meteorologists and would likely be on the radar for those involved in regional management of water, land, and energy resources.

Photo Credit: Jonny William Malloy