Meteorological Piracicaba/2013 Piracicaba Macroburst

The storm that hit Piracicaba, in the interior of the state of São Paulo, Brazil, on July 21, 2013 (known as the 2013 Piracicaba Macroburst) was a notable phenomenon for the city. It was accompanied by a macroburst, which is a type of downburst that reaches an area greater than 4 km, unlike microbursts, which reach an area of less than 4 km. A downburst is a downdraft of air that spreads horizontally when it hits the ground, causing high winds and property damage. This article will analyze the causes, characteristics and consequences of the macroburst of July 21, 2013 in Piracicaba.

The characteristics of the storm in Piracicaba were notorious. Winds reached a maximum speed of 128.5 kilometers per hour (80 miles per hour), according to INMET, which is equivalent to a category 1 hurricane on the Saffir-Simpson scale. The rain was accompanied by large hailstones, with a diameter of more than 4 centimeters. The storm lasted less than 10 minutes, but it was enough to wreak havoc on practically the entire city. This was the worst windstorm recorded in Piracicaba since the 2006 tornado. After the macroburst of July 21, 2013, there was never again a record of something of such proportion in the municipality.

Statistics

Time of occurrence: 4 pm on July 21, 2013.
Kind: Storm with heavy rain, strong downdraft and large hail.
Main areas affected: City of Piracicaba and district of Artemis.
Approximate duration: 5-8 minutes.
Max. wind speed: 128 km/h (80 mph).
Precipitation: Not reported.
Hail Size: Some ice stones measured 4 cm in diameter, but the value is believed to have been higher.
Cause: Arrival of a cold front associated with a cold wave, which met with a warm air mass.
Fatalities: 0
Injured: 4
Homeless or displaced: 0

Aftermath and affected areas

The consequences of the 2013 Piracicaba Macroburst were serious. The wind resulted in the fall of trees, branches, walls, poles, signs and electrical wires on the streets, in addition to the unroofing of homes, breaking of windows, interruption in the electrical network, damage to vehicles, among others. CPFL Paulista reported that 52.4 thousand homes were without electricity.

In the Alto neighborhood, almost all streets had damage, from falling trees to breaking windows. It was the hardest hit neighborhood, and perhaps the epicenter of the macroburst, although there is no confirmation. The Piracicaba City Center was also intensely affected, although the damage was slightly less compared to that recorded in the Alto neighborhood. In José Bonifácio Square, a 20-meter tree was uprooted. A dweller said that his antenna was even blown away by the wind.

In Rezende Village neighborhood, near the Piracicaba City Center, a tree fell under a car and hit the power grid, in addition to traffic lights that stopped working due to the lack of electricity. In Jardim Europa, which officially belongs to the Cidade Jardim neighborhood, a tree fell under a vehicle, injuring a 46-year-old woman. On Independência Avenue, between Bairro Alto and Monteiro Village, part of the wall of the Saudade Cemetery fell, in addition to a newsstand near the entrance to the cemetery that collapsed and injured two people.

In Piracicamirim, a resident filmed the storm from the beginning. In the same neighborhood, there were tree falls behind the region's bus terminal and the Army War Shooting. A dweller of the place reported that her neighbor's house was unroofed with the force of the wind. 7 km from the Piracicaba City Center, a resident of the Cecap neighborhood reported that some wooden houses even flew off.

The macroburst also reached the Vale do Sol neighborhood and the district of Artemis. In Vale do Sol, in the Northwestern Piracicaba, a resident recorded the hailstones falling in a local park. In Artemis, there was also a record of hail and damage.

Causes

The 2013 Piracicaba Macroburst was caused by a cumulonimbus cloud, or Cb, in its abbreviated form. The Cb was very charged and dense, which caused a strong downdraft to break free from the cloud, resulting in a windstorm that reached a maximum speed of 128 km/h (80 mph).

The occurrence of storms like this during the period was influenced mainly because of the encounter between a cold front of a strong cold wave and a warm air mass predominant. The encounter resulted in an intense atmospheric instability, which favored the formation of an isolated but well-developed storm cell. It is worth mentioning that this combination is mainly responsible for the formation of supercells and tornadoes.