Torrential rain hit central Uruguay in June 2019, causing serious flooding.
20, November 2020
By Néstor Santayana (INUMET), Jose Prieto (EUMETSAT) and Sancha Lancaster (Pactum)
More than 8,000 people were displaced due to flooding caused by heavy rains and winds of up to 95 km/h, with peaks of up to 105 km/h in Punta del Este. The Meteosat-11 Coloured HRV (Figure 1) shows one of the systems which brought the heavy rain.
June 2019 was a very rainy month across Uruguay, particularly in central and eastern parts, where rainfall amounts between 200–430 mm were recorded.
Chamangá, in the Flores Department, recorded 430 mm (mainly in seven days — its highest rainfall amount in 100 years; while in the far north, in the city Artigas, only 30 mm was recorded. Figure 2 shows the distribution of the precipitation anomaly.
The main episode of precipitation occurred from 11–18 June. The right-hand panel on Figure 3 shows the amount of precipitable water, which reached 35–45mm above Uruguay, these amounts are considered high for winter.
The left-hand panel of Figure 3 shows a warm air mass advected from the northwest (low level jet) generating a pattern of surface temperature anomalies — high temperatures in what is usually the coldest month of winter.
The animation in Figure 4 shows HRV images of the cloud distribution around 15:00–16:00 UTC (Noon local time), during the peak period of precipitation.
Under a weak, almost neutral El Niño–Southern Oscillation (ENSO) (3.4) and a positive Antarctic oscillation (which limits cold air at high latitudes), a low pressure system with a pronounced trough at medium levels on the surface of central Chile and Argentina sat over the Andes.
The animation in Figure 5 shows Meteosat Dust RGB images during the peak period and the animation in Figure 6 shows the cloud tops from Meteosat channel 10.8 µm, with sliced colour, not producing very cold convection. Most of the precipitation was of a stratiform origin.
For comparison, Figure 7 shows the superior spectral and horizontal resolution by GOES-16 for that region. The temporal resolution is also better, 10 minutes for GOES and 15 minutes for Meteosat-11.
The blocking configuration ultimately led to an extratropical cyclone south-east of Uruguay on 19/20 June, with a peculiar secondary vortex born inside the main one (see Figure 8).
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