The Role of Tropical Cyclones in Precipitation Over the Tropical and Subtropical North America

Abstract

Tropical cyclones (TCs) are essential elements of the hydrological cycle in tropical and subtropical regions. In the present study, the contribution of TCs to seasonal precipitation around the tropical and subtropical North America is examined. When TC activity over the tropical eastern Pacific (TEP) or the Intra Americas Seas (IAS) is below (abovenormal), regional precipitation may be below (above-normal). However, it is not only the number of TCs what may change seasonal precipitation, but the trajectory of the systems. TCs induce intense precipitation over continental regions if they are close enough to shorelines, for instance, if the TC center is located, on average, less than 500 km-distant from the coast. However, if TCs are more remote than this threshold distance, the chances of rain over continental regions decrease, particularly in arid and semi-arid regions. In addition, a distant TC may induce subsidence or produce moisture divergence that inhibits, at least for a few days, convective activity farther away than the threshold distance. An analysis of interannual variability in the TCs that produce precipitation over the tropical and subtropical North America shows that some regions in northern Mexico, which mostly depend on this effect to undergo wet years, may experience seasonal negative anomalies in precipitation if TCs trajectories are remote. Therefore, TCs (activity and trajectories) are important modulators of climate variability on various time scales, either by producing intense rainfall or by inhibiting convection at distant regions from their trajectory. The impact of such variations on water availability in northern Mexico may be relevant, since water availability in dams recovers under the effects of TC rainfall. Seasonal precipitation forecasts or climate change scenarios for these regions should take into account the effect of TCs, if regional adaptation strategies are implemented.

Easterly wave contributions to seasonal rainfall over the tropical Americas in observations and a regional climate model

“…Tropical cyclones (TCs) are also important moisture carriers. Arid or semi-arid regions can benefit greatly from a single TC event because one system can produce such intense precipitation (Dominguez and Magaña 2018). TCs are well known for transporting moisture from the tropics to the subtropics and mid-latitudes, but they also can induce drying conditions in regions that are remote to their circulation, approximately more than 500 km (Dominguez and Magaña 2018).…”

“…This drying effect has been rarely explored and quantified. It is explained in terms of weak subsidence outside the core of the system that is forced mechanically and may produce clear skies and moisture divergence in neighboring regions to the TC system (Emanuel 1997;Dominguez and Magaña 2018). In other words, while some arid or semi-arid regions are favored by TC occurrence, other distant regions from the TC center can be adversely affected in their accumulated seasonal rainfall.…”

“…We hypothesize that high TC activity over the MDR, produce more TCs developing from EWs, and transport moisture into the subtropics, leading to dry summer seasons over the TAs by means of the TC drying effect and few EWs reaching the continental NSA. TCs act as drying agents for the TAs when they are over the mid-Atlantic Ocean because they transport moisture from the tropics to the subtropics, causing negative anomalies of moisture in this region, mainly over NSA (Dominguez and Magaña 2018), and reducing the chances of rainfall over the TAs continental landmass. In addition, more EWs becoming TCs over the MDR mean that few EWs arrive at the TAs and consequently, this could impact the seasonal precipitation over NSA.…”

The contribution of tropical cyclones to the atmospheric branch of Middle America’s hydrological cycle using observed and reanalysis tracks

“…Prat and Nelson (2013a) found that near 15% of yearly rainfall over Mexico's Pacific Coast is related to TCs; later, Prat and Nelson (2016) quantified that up to 32% of the precipitation is associated with TCs along the Gulf of Mexico and 50% in southern Baja California; TCs accounted for almost all daily accumulations above 100 mm day −1 over Baja California. Over semiarid regions of Mexico TCs may contribute up to 50% of the seasonal rainfall (Domínguez and Magaña 2018). To complement these previous studies, we analyse the monthly climatology of the contribution of TCs over Middle America, including the effect of TCs on extreme rainfall.…”

Tropical cyclone—Induced heavy rainfall and flow in Colima, Western Mexico

“…The contribution of TCs to rainfall in Mexico has been demonstrated on a broad scale (e.g., Englehart and Douglas, 2001;Agustín Breña-Naranjo et al, 2015;Khouakhi et al, 2017;Dominguez and Magaña, 2018). Agustín Breña-Naranjo et al, 2015 found that TCs in Mexico may contribute between 20 and 60% of the observed seasonal rainfall for some coastal regions.…”