Visible, AVHRR, ASCAT scatterometer winds, Infrared, High Resolution Visible, Natural Colour RGB, Convection RGB, Brightness Temperature
This case study combines a number of examples of tropical cyclones that formed and travelled over the Indian Ocean in the early 2000s. We have tracked them using various satellite data and recorded some of the impacts they made in countries such as Myanmar, Madagascar and Mauritius.
13 March 2023
08 March 2023
By Juma Al-Maskari (Department of Meteorology, Seeb Int. Airport, Oman), Jochen Kerkmann and HansPeter Roesli
According to Wikipedia, Tropical Cyclone Nargis was a strong tropical cyclone that caused the deadliest natural disaster in the recorded history of Myanmar.
The cyclone made landfall in the country on 2 May 2008, causing catastrophic destruction and at least 90,000 fatalities with a further 56,000 people missing.
Total damage is estimated at over $10 billion (USD), which made it the most damaging cyclone ever recorded in this ocean basin. It was also Burma's worst natural disaster overall, as well as being the deadliest.
Nargis developed on 27 April in the central area of the Bay of Bengal. Initially it tracked slowly northwestward and, encountering favourable conditions, it quickly strengthened (see upper image below). Dry air temporally weakened the cyclone on 29–30 April (see Metop-A AVHRR image below).
But, after beginning a steady eastward motion, Nargis rapidly re-intensified to attain peak winds of at least 215km/h (source: JTWC), making it a category 4 cyclone on the Saffir-Simpson scale. The cyclone moved ashore in the Ayeyarwady Division of Burma at peak intensity, see bottom image and Met-7 IR animation (27 Apr 12:00 UTC– 03 May 12:00 UTC), and, after passing near the major city of Yangon (Rangoon), the storm gradually weakened until dissipating near the border of Burma and Thailand.
On 3–8 June 2007 a tropical cyclone developed into category 4 storm Gonu and, travelling from the Arabian Sea into the Gulf of Oman, hit the northern Omani coast without making landfall.
Strong winds and rainfall causing many flash floods severely affected the modern infrastructure of the Capital area and the surrounding districts.
Thanks to the excellent weather forecast many people were evacuated in time reducing loss of life to a relatively small number. After hitting Oman, Gonu crossed the Gulf northwards and weakened rapidly once it reached the Iranian coast (see track of Gonu, source: Department of Meteorology, Oman).
The storm track was very well out on the limb of the Meteosat-9 field-of-view, whereas it was close to the centre of that of Meteosat-7. Thus, Meteosat-7 was mainly used to support forecasting of the storm track and to monitor its physical evolution. Examples of Meteosat-7 images processed by NOAA and NEMOC (see images below) show the day-to-day progress of Gonu and a detailed view on 4 June.
Nevertheless, Meteosat-9 has also been very useful for monitoring the storm. Although in such an extreme (limb) geographical position RGB schemes loose performance, the IR10.8 and HRV channels, in particular, may still add useful information (see HRV image and IR10.8 image). The cloud top temperature measured by channel IR10.8 is as low as -70°C over a large area around the eye.
The Meteosat-9 HRV image compares favourably to the AQUA-MODIS image (see channel 01 image (250 m resolution), source: NASA). Remarkable are the eye structure with the hot towers in the eye wall, and the fact that channel 01 of MODIS is saturated over a wide area of the storm. HRV's strength, of course, shows best in an animated sequence on 4 June (see animation).
Beside showing the evolution of the eye during the day other cloud systems give some insight into local convection and differential advection around the Hadjar mountain ranges that run parallel to the northern Omani coast. Also quite spectacular is the very bright spot in the eye that pops up in the local afternoon and persists until sunset. Most probably it is a very high hot tower containing very small ice particles.
The evolution of Gonu on the days following 4 June is illustrated by a Meteosat-9 HRV snapshot on 5 June (see 02:15 UTC image), where the eye is less developed than the day before, and by two Metop-A overpasses on June 6 (06:00 UTC image) and June 7 (05:39 UTC image).
More information on Gonu and tropical cyclones in the Arabian Sea in general may be found in the following report (source: Juma Al-Maskari)
20 Dec 2006, Seychelles, Madagascar
The Metop-A AVHRR image below shows Tropical Cyclone Bondo, a category 4 tropical cyclone on the Saffir-Simpson scale, one day before it hit the Farquhar atoll, part of the 115-isle Seychelles archipelago in the Indian Ocean.
Thirty-five people were evacuated from this remote atoll, which lies some 800km southwest of the Seychelles' main island, Mahe.
A few days later, on 25 December 2006, two people were killed as now weakened Tropical Cyclone Bondo hit the northern coast of Madagascar and continued to lose strength as it moved southwest across the island (see track of TC Bondo, source: Wikipedia).
The severe Tropical Cyclone Gafilo was one of several cyclones to affect Madagascar in the 2003/2004 season.
With 1-minute averaged wind speeds of about 250 km/h and gusts of up to 330km/h, this cyclone struck the northeast coast of Madagascar early on the morning of 7 March 2004, in particularly, the city of Antalaha. There was massive destruction and 85% of the city was destroyed). 237 lives were lost, with 181 missing persons and 879 injured (official figures as of 30 March 2004).
Of the total of 237 fatalities, more than 110 persons were killed on the ferry 'Le Samson' from the nearby Comoro Islands that was reported to have capsized in heavy seas. More than 304,000 people were left homeless by the storm and more than six thousand hectares of agricultural land were flooded, resulting in major crop losses. According to the Multi-Satellite Precipitation Analysis (MPA) product from the NASA Goddard Space Flight Center, total rainfall for the period 3–10 March 2004 reached values of up to 500 mm in an area from the central Mozambique Channel eastward along the northwest coastline of Madagascar.
The upper two Meteosat-8 images below show Tropical Cyclone Gafilo about 18 hours before it made landfall. These two images have been re-projected into Mercator projection, which provides a better presentation for images that are viewed at very large satellite viewing angles.
The lower two images are presented in the original satellite projection. The lower right Meteosat-8 image shows the Tropical Cyclone on 7 March 2004, after landfall and when it had already weakened somewhat.
The Meteosat-8 images from 6 March show the marked spiral structure of Gafilo and a relatively large eye, with the eyewall and the Central Dense Overcast (CDO) region. They also show areas of small ice particles/intense precipitation (in yellow colour on the RGB images) within the CDO region and the spiral bands. The Meteosat-8 visible and infrared images, however, do not reveal an eyewall replacement cycle, which could only be observed in microwave imagery (e.g. AMSU on NOAA, TMI on TRMM, AMSR on Aqua or SSMI on DMSP). The two examples from 6 March 2004 that show the double eyewall structure are also presented below.
27 Dec 2002, Madagascar, Mauritius, Réunion
Tropical Cyclone Crystal passing nearby Mauritius seen by Meteosat-5 over the Indian Ocean on 27 December.
As in previous years, throughout the season 2002–2003 tropical cyclones continued to pose a severe threat for the population of Madagascar, Réunion and Mauritius, in the Southern Indian Ocean.
On 23 December, Tropical Cyclone Crystal formed at about 11 °S and 66 °E moving in a south-westerly direction, initially directly towards Mauritius. On 24 December, the warnings issued by the Joint Typhoon Warning Center predicted a position of the cyclone very close to Mauritius with maximum sustained winds of 160km/h and gusts up to 200km/h.
In the following days, Mauritius was preparing for the worst, but at the last moment the cyclone turned to the south passing the island at a distance of about 200km (see the track of Tropical Cyclone Crystal Source: Joint Typhoon Warning Center). The meteorological stations on Mauritius reported maximum sustained winds of 128km/h, with gusts of up to 157km/h, and a maximum significant wave height of about 6.3m.
In the afternoon of 27 December the cloud wall around the eye of the storm started to weaken in all quadrants. As expected, in the following days Crystal tracked south-southeastward along the western edge of the low to mid-level subtropical ridge of high pressure. Finally, on 29 December, Crystal became an extra-tropical cyclone.
Meteosat-5, operating at 63 °E and providing EUMETSAT's Indian Ocean Data Coverage Service, plays a key role in tracking and predicting the path of tropical cyclones in the Indian Ocean. This service has been extended until the end of 2005.
8-10 March 2002, Madagascar
The images below show Tropical Cyclone Hary on 8 March, two days prior to its near landfall in Madagascar on 10 March (see track of Hary below).
At 12:00 UTC on 8 March Hary was located at approximately 430km northeast of Madagascar, moving west-southwestwards at a speed of 20km/h. Maximum sustained winds at this time were about 200km/h with gusts up to 250km/h. The Meteosat-5 images depict the outflow of the tropical cyclone at high levels and the formation of a concentric eye of about 15–20km diameter.
On 10 March, Hary skirted the eastern shore of Madagascar bringing heavy rain and strong winds. However, no substantial damage was reported.
In Antalaha two bridges were destroyed and one person died. In Maroantsetra the risk of flooding resulted in evacuations from low-lying areas. In Fenerive East district one road was cut due to a destroyed bridge. As of 11 March, the storm moved east-southeast away from the island.
In 2000, more than 160 Madagascans were killed and tens of thousands driven from their homes by cyclones Eline and Gloria.
19 Feb 2002, Madagascar, Mauritius, Réunion
Tropical Cyclone Guillaume developed east of Madagascar and initially tracked northeast then east as it intensified (see track below). The cyclone eventually made a southward turn to the east-northeast as it steered around a mid-level ridge of high pressure.
Guillaume attained maximum intensity (maximum sustained winds of 215km/h, gusts up to 260km/h) as it passed within 150km of Mauritius while moving southward. Subsequently, the cyclone began to move more southeastward while undergoing transition to an extratropical storm. Fortunately, minimal damage and no casualties were reported from Mauritius.
Animated infrared images from Meteosat-5 indicate a 15–2 km irregular eye with deep convection around the centre. It should be noted that the eye of the cyclone does not follow a straight path, but performs a spiral movement, this behaviour has been observed in other Tropical Cyclone cases.
Meteosat-5, operating at 63 °E and providing EUMETSAT's Indian Ocean Data Coverage Service, plays a key role in tracking and predicting the path of Tropical Cyclones in the Indian Ocean. This service has been extended until the end of 2005.
6 Jan 2001, Madagascar, Mauritius, Réunion
The tropical cyclone season 2001 in the southern Indian Ocean started early on 2 January when Tropical Cyclone Ando was born at about 11 °S and 61 °E. This is approximately 1, 200km east of the northern tip of Madagascar. It is in the area of the southern Intertropical Convergence Zone (ITCZ), which, at the start of the year, was positioned between the equator and 10°S.
In the beginning, Ando moved to the south-west, towards the central part of Madagascar. The system rapidly intensified as it tracked beneath the subtropical ridge. Luckily, on 5 January, Ando turned to a more southerly direction, moving at 8–10 knots, so that it passed right between Madagascar and the island of Réunion, at a distance of only 240km from Réunion.
If Ando had hit one of the islands it would have most probably caused severe damage. Its intensity can be seen from the above Meteosat-5 infrared satellite image. Ando reached its maximum intensity on 6 January with a central pressure of less than 930hPa (Tropical Cyclone category 5), wind maxima of 225km/h and gusts up to 270km/h, as reported in the warning of the Joint Typhoon Warning Centre located on Guam Island. Maximum reported significant wave height was 6m.
The satellite images depict a well-organised symmetric storm system with a concentric eye of about 40km and intense, solid core convection. Further features of Ando, as depicted by animated water vapour images and QuikSCAT data, include a symmetric wind field with 35 knot wind radius extending to about 280km and an impressive high-level outflow over the storm system.
One day later, on 7 January 2001, Ando started weakening caused by a quasi-stationary long-wave trough situated over South Africa. It finally disappeared on 11 January, in the area south-east of Southern Madagascar.
Meteosat-5, operating at 63 °E under EUMETSAT's Indian Ocean Data Coverage service, played a key role in the tracking and predicting the path of Ando. The service was recently extended to continue until the end of 2005.