Category 4 tropical cyclone Gonu hits the northern coast of Oman (3-8 June 2007)

by HansPeter Roesli, Jochen Kerkmann (EUMETSAT) and Juma Al-Maskari (Department of Meteorology, Seeb Int. Airport, Oman)

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 (see Picture 1 (PNG, 345 KB), Picture 2 (PNG, 459 KB), Picture 3 (PNG, 384 KB)). 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, PNG, 248 KB, 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, PNG, 310 KB, and IR10.8 image, PNG, 172 KB). 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), PNG, 1108 KB, 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, MPG, 10732 KB). 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, PNG, 378 KB), where the eye is less developed than the day before, and by two Metop-A overpasses on June 6 (06:00 UTC image, JPG, 882 KB) and June 7 (05:39 UTC image, JPG, 965 KB).

More information on Gonu and tropical cyclones in the Arabian Sea in general may be found in the following report (PDF, 333 KB). It is copied from material on the Juma Al-Maskari home page where more information and pictures on Gonu can be found.

Meteosat-7 Images Met-7, IR, 04 June 2007, 07:30 UTC Full Resolution (JPG, 273 KB) Animation (hourly, AVI, 29068 KB) 4 June 07:00 UTC - 6 June 15:00 UTC (source: NEMOC, Rota, Spain) Animation (hourly, MPG, 30667 KB) 1 June 00:00 UTC - 8 June 23:00 UTC Met-7, VIS, 04 June 2007, 07:30 UTC Full Resolution (JPG, 208 KB) (source: NEMOC, Rota, Spain) Met-7, RGB VIS-IR, 05 June 2007, 12:00 UTC Full Resolution (JPG, 422 KB) (source: NOAA) Met-7, RGB VIS-IR, 06 June 2007, 12:00 UTC Full Resolution (JPG, 406 KB) (source: NOAA)

Meteosat-9 HRV Image Met-9, 04 June 2007, 08:45 UTC, Channel 12 (HRV) Full Resolution (PNG, 310 KB) Animation (15-min, MPG, 10732 KB) See also: Tropical Cyclone 01A landfall in Oman (Met-5 IR loop, 9-12 May 2002, MPG, 9829 KB) Cyclone in the Indian Ocean (20 May 1999) Cyclone in the Indian Ocean seen in Met-5 Images (5 June 1998)

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