Research Article Projections of Heat Waves Events in the Intra-Americas Region Using Multimodel Ensemble Moises Angeles-Malaspina , 1 Jorge E. González-Cruz , 2 and Nazario Ramírez-Beltran 3 1 Mechanical Engineering Department, Polytechnic University of Puerto Rico, San Juan, PR 00918, USA 2 NOAA-CREST, City College of New York, New York, NY 1031, USA 3 Department of Industrial Engineering, University of Puerto Rico, Mayag¨ uez, PR 00680, USA Correspondence should be addressed to Jorge E. Gonz´ alez-Cruz; jgonzalezcruz@ccny.cuny.edu Received 22 June 2017; Revised 11 December 2017; Accepted 18 December 2017; Published 22 January 2018 Academic Editor: Annalisa Cherchi Copyright © 2018 Moises Angeles-Malaspina et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Significant accelerated warming of the Sea Surface Temperature of 0.15 ∘ C per decade (1982–2012) was recently detected, which motivated the research for the present consequences and future projections on the heat index and heat waves in the intra-Americas region. Present records every six hours are retrieved from NCEP reanalysis (1948–2015) to calculate heat waves changes. Heat index intensification has been detected in the region since 1998 and driven by surface pressure changes, sinking air enhancement, and warm/weaker cold advection. is regional warmer atmosphere leads to heat waves intensification with changes in both frequency and maximum amplitude distribution. Future projections using a multimodel ensemble mean for five global circulation models were used to project heat waves in the future under two scenarios: RCP4.5 and RCP8.5. Massive heat waves events were projected at the end of the 21st century, particularly in the RCP8.5 scenario. Consequently, the regional climate change in the current time and in the future will require special attention to mitigate the more intense and frequent heat waves impacts on human health, countries’ economies, and energy demands in the IAR. 1. Introduction e intra-American region encompasses Northern South America, Central America, Gulf of Mexico, the Caribbean region, and the Western Atlantic [1–3], where a complex interaction among synoptic atmospheric/oceanic patterns drives the rainfall activity in the region [4–7] (see Figure 1(a)). In tropical regions, the Sea Surface Temperature (SST) is one of the variables that drive rainfall, with a weak impact when SST is less than 26 ∘ C and a stronger effect when SST is between 26 ∘ C and 29.5 ∘ C. e relationship between SST and rainfall is not linear, so precipitation tends to decrease when SST is greater than 29.5 ∘ C [8]. Consequently, SST modulates the intra-Americas region (IAR) rainfall development from May to July, while in the next months the vertical wind shear (VWS) impacts the thermal vertical convection and cyclogenesis activity [5, 9, 10]. An additional variable in the IAR is the Bermuda-Azores high-pressure system (one pole of the North Atlantic Oscillation Index, NAO) which interacts with the Caribbean low-level jet, causing a downward dry air, hindering precipitation, and warming the surface [4, 11, 12]. A direct consequence of the high-pressure system oscillation is the development of stronger/weaker easterly winds causing cooler/warmer SST leading to a drier/wetter region [4, 13, 14]. is relationship is known as the wind- evaporation-SST feedback pointing out a direct relationship among wind speed, evaporation, and sea level pressure (SLP) [15]. Furthermore, a deep subsidence from Central America to the Caribbean region could play an additional role in the IAR rainfall activity [4, 16]. Moreover, Saharan dust episodes from June to August are likely to generate a rainfall deficit due to aerosol interaction with cloud condensation nuclei and dry air coming from the northwest African desert [17]. ese complex relationships lead to a bimodal rainfall pattern in the IAR during the rainy season [4, 5, 18–21]. is rainy season is divided into the Early Rainfall Season (ERS) defined from April to July (which contains the first rainfall peak) and the Late Rainfall Season (LRS) from August to November, Hindawi Advances in Meteorology Volume 2018, Article ID 7827984, 16 pages https://doi.org/10.1155/2018/7827984