In late March 2018 severe thunderstorms hit parts of South America.
By Néstor Santayana (UNIMET) and Jose Prieto (EUMETSAT)
On 23 March an active cold front moved from the area of Buenos Aires towards Uruguay, bringing hail and intense precipitation over the Argentinean capital.
In the early hours of 24 March, the humidity advection of a low level jet from the north west, helped organise the convection and generate further hail and lightning over the borders of Argentina, Uruguay and Brazil. In the northern part of Uruguay, 140 mm of rain was reported in a few hours.
On the evening of 24 March the system became linear, but kept its intensity over Paraguay, northern parts of Argentina, and central Brazil.
On 25 March the frontal low pressure on a long wave trough, plus the high pressure centre between Uruguay and central Argentina, intensified winds, with gust fronts up to 80 km/h. Small hail showers built up from the humidity from the La Plata river.
The GOES-16 Night Microphysics RGB (Figure 2) shows the progress of the storms on 23–24 March.
Figure 2: Night Microphysics RGB from ABI, 23 March 16:00 UTC–24 March 21:00 UTC.
The GOES-16 near-infrared (NIR) band around 1.37 µm (Figure 3) is spectrally a water vapour absorption region. It does not sense the lower troposphere, where most of the atmospheric water vapour resides, so provides excellent daytime sensitivity to high, very thin cirrus, especially in warm, moist atmospheres. Figure 3 shows the aftermath of the convection in Uruguay on 25 March.
Figure 3: ABI 1.37 µm NIR animation, 25 March 10:30 UTC–20:45 UTC.
The 2.2 µm NIR band (Figure 4), in conjunction with other bands, enables cloud particle size estimation. Cloud particle growth is parallel with cloud development and the intensity of the convection.
Figure 4: ABI 2.25 µm animation, 25 March 10:30 UTC–20:45 UTC.
Channels at both near-infrared wavelengths will be available in the Flexible Combined Imager (FCI) of the Meteosat Third Generation satellites, due to be ready for operations in the 2020s.