GOES-16 night microphysics RGB, 19 Dec 2020 03UTC

Early summer convection in central Argentina and Uruguay

18 December 2020 21:00 UTC-19 December 23:00 UTC

GOES-16 night microphysics RGB, 19 Dec 2020 03UTC
GOES-16 night microphysics RGB, 19 Dec 2020 03UTC

Severe convection in central Argentina in December 2020, viewed by GOES-16.

Last Updated

26 January 2021

Published on

11 January 2021

By José Prieto and Jochen Kerkmann (EUMETSAT), Ivan Smiljanic (CGI), Hans-Peter Roesli (Switzerland), Gabriela Ishikame (Servicio Meteorológico Nacional (SMN))

Intensive thunderstorm activity connected to a trough and a cold front affected central Argentina in mid-December 2020. Later it progressed towards Uruguay and southern Brazil.

Cold fronts can sometimes occur in central Argentina in December, quickly weakening as they move north. Around 15 December a trough which formed over the Pacific Ocean started to move across the Andes. Numerical models had predicted the development of a low pressure system in central Argentina. An upper level wave on 18 December in the same area generated intense convection in La Pampa, San Luis and south of Córdoba.

The GOES-16 Night Microphysics RGB (Figure 1) describes the synoptic situation and the Airmass RGB animation (Figure 2) shows the evolution on 19 December, as recorded by the GOES-16 ABI instrument.

GOES-16 night microphysics RGB, 19 Dec 2020 03UTC
Figure 1: Conceptual scene early on 19 December centred close to Buenos Aires, GOES-16 Night Microphysics RGB, 03:00 UTC
Figure 2: GOES-16 Airmass RGB on 1-minute loop centred close to Buenos Aires, 19 December 12:50-15:30 UTC

The night convection RGB animation (Figure 3) shows the main features of this evolution for around six hours starting on 18 December at 21:00 UTC.

Figure 3: Comparison of GOES-16 Night Convection RGB and channel 14, 18 December 21:00 UTC-19 December 03:00 UTC. Location map

A haboob developed on the eastern side of Andes in the afternoon of 18 December. It reinforced and gained speed northwards as the cold air from Andes capped it, see the GOES-16 satellite imagery (Figure 4) and on-ground video (Figure 5)

Figure 4: Haboob raised by the strong convection moving north and strengthening during the night, GOES-16 Geocolor and Visible, 18 December 20:08-22:20 UTC. Credit: RAMMB/CIRA
Figure 5: The haboob seen at ground level. Credit: INUMET

Later the wave progressed towards Uruguay and southern Brazil (Figure 6) at a ground rate of 90 km/h, see Figure 1, and radar image in Figure 7.

GOES-16 Convection RGB with 300 hPa overlaid, 18 Dec 18UTC
Figure 6:  GOES-16 Convection RGB with 300 hPa Geopotential Height overlaid, 18 December 18:00 UTC
Radar 19 Dec 04 UTC
Figure 7: Radar composite, 19 December 23:00 UTC

Anvil-level storm dynamics

Anvil-level temperature dipoles are made of a cold updraft and a warm trough on its lee. They can be noticed around the most persistent or intense updrafts (see right loop in Figure 3 (above) and Figure 8).

GOES-16 NIR10.4 18 Dec 2020 22:35 UTC
Figure 8: Temperature dipoles in the GOES-16 imagery. NIR10.4 infra-red window channel on 18 December 22:35 UTC (local dusk period). 

Next to a 'warm pole', there seemed to be another temperature minimum for the Above-Anvil Cirrus Plume (AACP) in the wake of the strongest updrafts (Figure 9).

Image comparison

GOES-16 Brightness Temperature Difference (BTD) compare1
compare2
 

Figure 9: Maximum temperatures (yellow to green shades, left image) and adjacent minimum brightness temperature differences as a sign of above-anvil cirrus clouds (dark grey shades, right image). GOES-16 IR10.4 channel (left) and BTD (IR12.0-IR10.4) (right), 18 December 22:35 UTC.

These cold areas coincide with the darker red (to black) areas in the Dust RGB (Figure 10). Darker red shades are connected to negative brightness temperature difference between IR window channels (BTD12-10), which generally indicate thin cirrus clouds (e.g. edges of the main storm anvil, or AACP in this case), or even a higher moisture content (e.g. cloud-free area to north of the system) as seen in Figure 9.

 

Image comparison

GOES-16 VIS0.6 compare1
compare2
 

Figure 10: Above-anvil cirrus plumes (AACP) detected through GOES-16 Dust RGB (left) and VIS0.6 channel (right), 18 December 22:35 UTC (local dusk period).

AACPs are colder than warm lee troughs, which are the warm 'pole' of aforementioned temperature dipoles, but seem to be warmer than wider updraft area, best seen from the 'sandwich loop' in Figure 11. Note that wind in the level of storm anvil was westerly.

Figure 11: Animated one hour loop of G-16 'sandwich images' (VIS0.64 channel overlaid with IR10.4), 18 December, 22:20-23:00 UTC, 1 minute Mesoscale Area rapid scanning.

This event was covered by one of the MESO scan sectors of GOES-16 between 19 and 20 December 2020. The Argentinian weather service, Servicio Meteorológico Nacional (SMN), and NOAA have coordinated frequent scans in the past for the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) project. This future the SMN plans to request operational MESO scans to cover hazardous situations like the one presented in this case.


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