South America Summer Forecast: El Nino to Bring Flooding Rain to Argentina, Uruguay and Southeast Brazil

By Eric Leister, Meteorologist

October 28,2015; 10:19AM,EDT

 

 

The ongoing El Niño will continue to be a major factor in the weather across South America as frequent rainfall leads to new flooding events in parts of Argentina, Uruguay and Brazil this summer.
Elsewhere, infrequent rainfall will bring little or no relief to drought-stricken Chile and northern Brazil. Surges of heat that build across the interior of Brazil will frequent Sao Paulo and Rio de Janeiro and result in numerous uncomfortable days throughout the summer.

JUMP TO: Wet Weather to Continue Through Summer From Northern Argentina to Paraguay and Southeast Brazil | Drought to Worsen Across Northern Brazil as Summer Heat Builds | Chile: Sparse Rain, Warm Stretches for Central and Northern Regions | Frequent Storms to Target Ecuador to Bolivia
Wet Weather to Continue Through Summer From Northern Argentina to Paraguay and Southeast Brazil
Frequent storm systems have brought flooding rain to parts of Argentina, Uruguay and southeast Brazil during the spring months and will be the predominant pattern throughout the summer.
Rainfall averaged 100-250 percent of normal from August through the middle of October and similar numbers are expected over the next several months.
A man paddles his kayak on a flooded street in Lujan, Argentina, Wednesday, Aug. 12, 2015. More than 11,000 people had been evacuated by Tuesday from parts of Argentina's largest province after heavy weekend rain caused rivers to rise precipitously, a top official said. (AP Photo/Natacha Pisarenko)
Slow-moving cold fronts will be the primary weather feature from northern Argentina through Uruguay, southeast Brazil and Paraguay and will produce bouts of heavy rainfall and occasional severe thunderstorms.
Frontal boundaries will often stall across this region resulting in several days of locally heavy rainfall. Warm air will provide the fuel for strong thunderstorms as the fronts initially push northward.
The most powerful thunderstorms will be capable of producing damaging winds, flash flooding and large hail. Cities at risk for occasional severe weather events during the summer months include Buenos Aires and Cordoba in Argentina, Asuncion, Paraguay, Montevideo, Uruguay and Puerto Alegre, Brazil.
While severe weather will be infrequent, flooding events are expected to be more common resulting in numerous impacts throughout the region, ranging from travel to agriculture.
Even though rainfall is typically favorable for crops during the summer months, a wet spring into summer can cause planting delays and poor crop quality.
Drought to Worsen Across Northern Brazil as Summer Heat Builds
While parts of the continent experience flooding rain events from December through February, northern Brazil will once again face prolonged periods of dry weather.
Another season of below-normal rainfall will worsen drought conditions from northern Brazil into Colombia and Venezuela.
Rainfall since August has averaged 50 percent or less of normal across this entire region and similar percentages are forecast for the coming months.
The ongoing drought combined with infrequent rainfall and above-normal temperatures will also cause a heightened risk for wildfires across northwest Brazil.
In this Oct. 30, 2014 photo, a water gage stands on the receding shore of the nearly empty Itaim dam in Itu, a commuter city outside of Sao Paulo, Brazil. (AP Photo/Andre Penner)
The building drought over the past several years has had adverse effects across the region limiting water supplies, impacting hydro-electric power and also causing low crop yields.
The cocoa crop, focused in southeast Brazil, is expected to continue to experience below-normal rainfall and above-normal temperatures and cause significant impacts on yields to this year's crop that will lower this year's yield.
The warm and dry weather may also have a negative impact on Brazil's important coffee crop. Brazil ranks as the top exporter of coffee worldwide and any significant impacts to the crop can result in global price increases.
The long stretches of dry weather will also foster oppressive heat across the interior of Brazil. This heat will occasionally creep southward, resulting in several consecutive days of unseasonable heat for Brasilia, Belo Horizonte, Rio de Janeiro and Sao Paulo.
Chile: Sparse Rain, Warm Stretches for Central and Northern Regions
Despite an increase in rainfall during the late winter and spring across central and north-central Chile, a long-term drought continues.
While rainfall is typically very limited during the summer months in Chile, "A few light rainfall events are possible as weak upper-level storm systems arrive from the Pacific Ocean," stated AccuWeather Senior Meteorologist Jason Nicholls.
Generally, rainfall is forecast to be light from the these storms, averaging less than 6 mm (0.25 of an inch) in any given location. Even light rainfall events will be welcome to areas still trying to recover from several years of below-normal rainfall.
While central and northern Chile typically experience long periods of dry weather during the summer months, rainfall typically remains a constant in southern Chile. However, fewer storm systems are expected to cross the South Pacific this summer, resulting in below-normal rainfall from Puerto Montt and the surrounding Los Lagos Region southward into Patagonia.
This below-normal rainfall could result in a higher threat for wildfires across the region.
RELATED:
South America Weather Center
Chile Weather Center
Brazil Weather Center
Frequent Storms to Target Ecuador to Bolivia
The building warmth of Pacific Ocean waters off the coast of northwest South America will yield an increase in rainfall for Ecuador.
This moisture will often advance southeast through the Andes and cause thunderstorms and torrential downpours through Peru and into Bolivia.
These storms can quickly cause flash flooding and result in deadly mudslides in the region's mountainous terrain.
Temperatures will also average above normal as the increased moisture will often lead to more cloud cover at night, making it feel balmy throughout the night.