Appearance in Satellite Data

Different types of clouds associated with cold fronts in southern South America can be distinguished by the combined use of information given by the different channels of the GOES-E satellite.

  • Visible (VIS): thick frontal clouds are very bright white.
  • Infrared (IR): areas with convective clouds are shown in brighter tones than clouds at lower levels which are in shades of grey.
  • Water Vapor (WV): the frontal zone is seen as a darker band associated with dryness in the mid- and high levels of the atmosphere. At the leading edge of this band, there are cloud areas of greater thickness which are shown in lighter tones.
  • RGB: the advantage of these images is that different types of clouds can be identified easily. Yellow colors show low level clouds. Thick clouds are shown in white, bright shades and the high level translucent cirrus are shown in shades of blue.

Cloud patterns associated with cold fronts differ between the warm and cold seasons. Two examples are given below, to compare the cloudiness in each case. The schematics show the general features and do not necessarily correspond fully to the case studies presented.


a) Summer

There are thick convective clouds ahead of summer cold fronts, generally due to the occurrence of Mesoscale Convective Systems (MCS) when the South American Low Level Jet (SALLJ) is present.
20 December 2014/17:45 UTC - GOES 13 VIS 0.65 image
20 December 2014/17:45 UTC - GOES 13 IR 10.7 image
20 December 2014/17:45 UTC - GOES 13 WV 6.75 image
20 December 2014/17:45 UTC - GOES 13 RGB image (0.65, 0.65 and 10.7)

The following animation shows the passage of a cold front over Argentina on 6 February, 2014. It shows how the cold front reaches Argentina from the south Pacific and moves rapidly to the east towards the Atlantic Ocean.

Press "Play Button" to see the loop; 5 February 00 UTC - 6 February 21 UTC - GOES 13 IR 10.7

b) Winter

Cloudiness related to cold fronts in winter possesses the following characteristics:

  • The presence of extensive bands of stratiform cloudiness with a NW-SE orientation.
  • In some cases deep convection is embedded in the stratiform clouds.
  • When cold fronts reach lower latitudes (~20°S), the persistence of low-level clouds (Stratus) is frequent in the northwest of Argentina, close to the eastern slopes of the Andes mountain range.
05 July 2014/14.45 UTC - GOES 13 VIS 0.65 image
05 July 2014/14.45 UTC - GOES 13 IR 10.7 image
05 July 2014/14.45 UTC - GOES 13 WV 6.75 image
05 July 2014/14.45 UTC - GOES 13 RGB image (0.65, 0.65 and 10.7)

The following animation shows the passage of a cold front over Argentina on 22 August, 2013. In this case, it can be seen that the cold front reaches further north than in summer, up to Paraguay and Bolivia, triggering deep convection around 00 UTC on 23rd August.

Press "Play Button" to see the loop; 22 August 00 UTC to 22 August 21 UTC - GOES 13 IR 10.7

c) Cold air cloudiness behind Argentinean cold fronts

There are often open cell-type convective clouds within the cold front and behind it. These clouds mainly affect the coastal regions of Argentina in winter, bringing ice pellets or sleet, snow or rain showers.
26 July 2014/18.00 UTC - Aqua/MODIS RGB image (0.65, 0.56 and 0.47)

The following time-lapse shows the cloud top temperature development of the open cell cloud tops over Argentinian coast on 11 September, 2015.

Press "Play Button" to see the loop; 22 August 00 UTC to 22 August 21 UTC - GOES 13 IR 10.7