By Eric Leister, Meteorologist
September 2,2015; 11:15PM,EDT
A stormy weather pattern will prevail through September across much of southern South America; however, some areas that are in need of rain can expect dry weather to persist the next several months.
Needed rain in north-central Chile, including Santiago, will fade quickly through the fall season, while areas farther south will have a wet season.
The active weather in Chile will translate to rounds of rain and occasional severe weather in northeastern Argentina, Uruguay and southeastern Brazil.
Meanwhile, the northern two-thirds of Brazil will continue to receive below-normal rainfall as the drought continues.
JUMP TO: Santiago to Receive Early Season Rain; Storms Shift South by October | Storm Track Brings Frequent Rain, Occasional Severe Storms to Buenos Aires, Montevideo and Asuncion | Drought to Persist for Northern Brazil, Colombia and Venezuela
Santiago to Receive Early Season Rain; Storms Shift South by October
While rain was slow to arrive in Santiago this winter, a one-two punch of storms during the first half of August brought more than a month's rainfall to the city and surrounding areas in just a few days.
The same storm also brought rare rainfall to the Atacama region of northern Argentina. While no measurable rainfall is expected during the spring season in the Atacama region, Santiago and much of central Chile will have multiple storm systems during the month of September that could result in back-to-back months with above-normal rainfall.
People
carry their belongings as they walk on a mud covered street in
Chanaral, Chile, Friday, March 27, 2015. Unusually heavy thunder storms,
torrential rains and overflowing rivers that began on Tuesday left tons
of mud covering communes of northern Chile desert, that left at least
nine dead and villages without water, electricity or communications. (AP
Photo/Pablo Sanhueza)Normal rainfall during the month of September is 30.5 mm (1.20 inches) in Santiago, and normal rain amounts drop off further during the months of October and November.
AccuWeather Meteorologist Rob Miller said, "While much of September will be dry much of the time in Santiago, just one or two significant storm systems can result in above-normal rainfall for month."
While the storm track is expected to shift southward in October, just one significant rainfall can result in near- to above-normal rainfall for Santiago as the normal rainfall for the month is only 15 mm (0.60 inches).
While drier weather builds across central Chile in October and November, an active storm track will continue to bring storm systems through south-central Chile, with areas from Concepcion to Puerto Montt expected to receive above-normal precipitation.
Storm Track Brings Frequent Rain, Occasional Severe Storms to Buenos Aires, Montevideo and Asuncion
An active storm track across south-central Chile during the spring season will translate to a wet and stormy season for northeastern Argentina, Uruguay, southeastern Brazil and southern Paraguay.
Storms tracking across the Andes will often strengthen as they move eastward across the region, resulting in multiple days of heavy rainfall.
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Cities that are at high risk for flooding this spring include Buenos Aires, Cordoba, Montevideo, Asuncion and Porto Alegre.
Surges of warmer air from Brazil will also act as a key ingredient for the development of severe thunderstorms as occasional strong cold fronts press northward from Argentina into southeastern Brazil.
These outbreaks of severe thunderstorms will cause flooding while also producing damaging winds and hail. A few isolated tornadoes will also be possible.
This active pattern, which will persist through November, will likely result in numerous flooding events across the region, which will also have impacts on agriculture following a wet summer in many of the same areas.
"The prolonged periods of wet weather will keep temperatures cool during the day and also keep fields wet, making it difficult to plant spring crops," AccuWeather Senior Meteorologist Jason Nicholls said. The combination or flooding and below-normal temperatures may also hinder crop growth into early summer.
Drought to Persist for Northern Brazil, Colombia and Venezuela
While heavy rain and flooding will be an issue across southern and central parts of the continent, the northern third can expected continued drought conditions.
With El Niño conditions expected to continue through the next three to six months, there will be little pattern change across areas from northern Brazil into Colombia and Venezuela.
Typically from September through November, there is a dramatic increase in rainfall across central and northwest Brazil; however, these rains will be slow to return, and in some areas little or no increase is expected. Areas such as Belo Horizonte, Brasilia and Manaus can expect below-normal rainfall.
A
water system station pumps water from the Atibainha reservoir, part of
the Cantareira System that provides water to the Sao Paulo metropolitan
area, in Nazare Paulista, Brazil, Thursday, Jan. 29, 2015. Southeastern
Brazil is suffering the worst drought in more than eight decades and
authorities put Sao Paulo in a state of alarm when the water utility
director said that rationing could be implemented in a dramatic five
days-off, two days-on system. (AP Photo/Andre Penner)Meanwhile, the typical decline in rainfall across northeastern Brazil has already begun in August and will result in only occasional light rainfall events during the spring months in Recife and Fortaleza.
The abnormally low rainfall will also stretch into Colombia and Venezuela through November. Dry weather has persisted for the past several months in these areas. Drought conditions are expected to become more severe with the dry spring weather anticipated.
Farther south, Rio de Janeiro and Sao Paulo will see occasional frontal boundary reach far enough northward to trigger rain and thunderstorms; however, no drought-busting rainfall is expected. The rain should average out to be near normal and will keep the drought from worsening ahead of the 2016 Summer Olympics in Rio de Janeiro.
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