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.
21 October 2020
04 June 2007
by HansPeter Roesli, Jochen Kerkmann (EUMETSAT) and Juma Al-Maskari (Department of Meteorology, Seeb Int. Airport, Oman )
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)
Meteosat-7 IR Images
Meteosat-7 RGB Images
Meteosat-9 HRV Image
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