Met-11 SCON with isolines

Tropical Cyclone Eloise

21 January 2021 00:00 UTC-30 January 09:00 UTC

Met-11 SCON with isolines
Met-11 SCON with isolines

In mid-January 2021 Category 2 Tropical Cyclone Eloise brought devastation to many countries in south east Africa - the second tropical storm in that month.

Last Updated

23 April 2021

Published on

18 March 2021

By Ivan Smiljanic (CGI), Jochen Kerkmann and Jose Prieto (EUMETSAT)

During southern hemisphere summer season 2020/2021, there were two similar tropical low pressure systems in the short time span, both crossed Madagascar and restrengthened over the Mozambique Channel, hitting Mozambique in the region of Beira. The first was Tropical Storm Chalane, which was weaker in intensity but had interesting track, traversing the entire breadth of the southern African subcontinent. The second was Tropical Storm Eloise, which was stronger (Category 2), but moved along a shorter track (Credit: CIMSS). Two consecutive International Charter Calls, and numerous other warnings on severe rainfall, floods and landslides, were raised for affected countries: Madagascar, Mozambique, Zimbabwe, South Africa, Eswatini, even Botswana (Figure 4)

Figures 1-3 show the moments when strong re-intensification of the system took place over very warm waters in the Mozambique Channel, accompanied by clusters of strong convection around a low pressure centre.

Met-11 SCON with isolines
Figure 1: H700 ECMWF model isolines over Meteosat-11 Severe Convection RGB product, pointing out position of cyclone center. 21 January 2021, 09:00 UTC. Credit: EUMeTrain.
Met-11 HRV 21 Jan 2021
Figure 2: Meteosat-11 Natural Colour RGB product over high resolution visible channel (HRV), 21 January 08:00 UTC, showing high-reaching cloud bands around cyclone centre.
Figure 3: Meteosat-11 IR10.8 window channel with H-SAF Rain Rate product (H03B) overlaid, 21 January 00:00-09:00 UTC, 15 minute time step.


Met-11 Airmass with h700, 24 Jan 2021
Figure 4: H700 ECMWF model isolines over Meteosat-11 Airmass RGB product, pointing out the position of cyclone center on 24 January 2021, 18:00 UTC. Credit: EUMeTrain.

The H-SAF rain rate product points out intense rainfall region associated with that convection (Figure 3). This product is based on infrared (IR) brightness temperatures (BT), with calibration against microwave data, and becomes saturated when the BTs are very low. Therefore, it is no surprise that when zooming in on the convective system at the south western flank of Eloise (bright yellow system in Figure 1, or saturated feature in Figure 3), BTs of cloud tops reach 180 K (ca. -93 °C) (Figure 5). Comparing that to local temperature profiles, but also performing dual-view visual assessment, it was estimated these clouds reached heights of around 20 km (+/- 3 km).

It is interesting to note is that higher resolution IR sensors read even lower temperatures of the coldest parts of convective system (overshooting tops), below 180 K (saturated white pixels in Figure 6).

Met-11 IR BT
Figure 5: Brightness Temperature readings (up to -93°C) of convective system cloud top, sensed by Meteosat-11 IR10.8 window channel, 21 January 10:45 UTC.
Figure 6: Brightness Temperature readings (less than 180 K, in white pixels) of convective system cloud tops, sensed by NOAA-20 VIIRS IR window channel , 21 January. Same convective system as in Figure 4. Credit: NOAA.

TC Eloise developed a pronounced eye feature, best seen in the Meteosat-11 Night Microphysics animation that shows landfall moment on 23 January, around 03:00 UTC (Figure 7).

Figure 7: Moments prior to TC Eloise landfall captured by animation of Meteosat-11 Night Microphysics RGB, 22 January 16:00-23 January 02:00 UTC.

Using high-resolution, visible spectral channels, the flooded areas in the Beira region, close to the mouth of Pungwe river, could be clearly seen. The MODIS True Color RGB reveals the muddy colours of water in flooded basin (Figure 8), while the SEVIRI HRV channel shows reduced reflection in the same region (Figure 9).

MODIS True Color comparison

27 January 2020 compare1

Figure 8: Flooded areas. Comparison between high resolution True Color RGB on 27 January 2021, and year earlier, taken by Terra MODIS instrument. Credit: NOAA.

Met-11 HRV 30 Jan 2021
Figure 9: Meteosat-11 HRV, 30 January 09:00 UTC. Flooded areas in darker grey shades.