Thus, north is facilitated to its displacement in direction, that after to reach mountain range of Andes it divides itself in two, Polar Mass of the Pacific (MPP) and Massa Polar Atlntica (MPA). Of this form, the MPP associates it the cold sea chain of Humboldt, if dislocating until next the line to the tropic of Capricrnio not influencing in the climate of Brazil. While, the MPA acts on the portion center-south-east of the South America, arriving at the times to exceed the line of the Equator. According to Mendona (the 2007), when it reached the latitude of the river Silver subdivides itself in two, first one associates it thermal fall of winter and the reduced indices of air and of rainfall in the interior of Brazil. To another one it is dislocated for the coast and one associates it the MTA provoking rains in the Brazilian east, mainly it enters the winter and summer ends. With this, it is verified that the performance of the Atlantic polar mass is sufficiently active, therefore when joining the tropical air of the Atlantic one (MTA) it generates a discontinuity, and it is changedded into the Atlantic polar front (FPA) and when it arrives at Brazil is on the form of cold front, causing rains weighed and thunderstorms, to the times it gains latitude and arrives until the Amazon region. FRONTS Are the meeting of two air masses of different characteristics, especially in terms of density, temperature, humidity and pressure, generating a discontinuity surface. This phenomenon is called frontogenesis, while its waste is the frontolysis.
According to Blacksmith (2006), the mixture of hot air with cold air provokes the rise of a mass on the other, causing to variation in the temperature and difference in the air density. This atmospheric instability generates cloudiness sufficiently, causing much rain. A cold or hot front always occurs enters two centers of high pressures, being proper it a common place of low pressures, thus an area frontal, always will determine a ciclnica circulation, surrounded for anticyclonic circulaes.