Cyclone Onil

Severe Cyclonic Storm Onil

Severe cyclonic storm (IMD scale)
Tropical storm (Saffir–Simpson scale)
Cyclone Onil off the coast of Pakistan on October 2
Formed	September 30, 2004
Dissipated	October 10, 2004
Highest winds	3-minute sustained: 100 km/h (65 mph) 1-minute sustained: 65 km/h (40 mph)
Lowest pressure	990 hPa (mbar); 29.23 inHg
Fatalities	9 total, 300 missing
Areas affected	India and Pakistan
Part of the 2004 North Indian Ocean cyclone season

Severe Cyclonic Storm Onil (India Meteorological Department designation: ARB 03; Joint Typhoon Warning Center designation: 03A) was the first tropical cyclone to be named in the northern Indian Ocean. Forming out of an area of convection several hundred kilometres southwest of India on October 1, 2004, Cyclone Onil quickly attained its peak intensity on October 2 with winds of 100 km/h (65 mph) and a barometric pressure of 990 mbar (hPa; 29.23 inHg). However, dry air quickly entered the system, causing it to rapidly weaken to a depression just off the coast of Gujarat, India. Over the following several days, the system took a slow, erratic track towards the south-southeast. After turning northeastward, the system made landfall near Porbandar on October 10 and dissipated shortly thereafter.

Throughout southeastern Pakistan and northwestern India, thousands of residents were evacuated prior to the cyclone's arrival. In these areas, the storm produced moderate to heavy rainfall, peaking at 145 mm (5.7 in) in Thatta, Sindh, Pakistan. These rains led to flash flooding in several areas. Nine people died in several incidents related to the storm in Karachi. The drainage system of Hyderabad sustained significant damage, leading to several protests and demonstrations by city residents. Offshore, 300 fishermen are believed to have gone missing during the storm; no reports have confirmed their whereabouts since they disappeared.

Severe Cyclonic Storm Onil was first identified as an area of convection early on September 30, 2004 situated roughly 465 km (290 mi) southwest of Mumbai, India. Satellite imagery depicted a poorly organized system with deep convection partially surrounding a low-level circulation. Situated over warm water and within an area of moderate wind shear, the Joint Typhoon Warning Center (JTWC) assessed the system's chances of developing into a tropical cyclone as "fair". Within several hours of being identified, the Indian Meteorological Department (IMD) began monitoring the system as Depression ARB 03. Despite a decrease in convection later on September 30, the IMD upgraded the cyclone to a deep depression, stating that three-minute sustained winds had reached 55 km/h (35 mph). Early the next day, organization substantially improved, prompting the JTWC to issue a Tropical Cyclone Formation Alert. Around 0900 UTC on October 1, the IMD upgraded the deep depression to Cyclonic Storm Onil. Upon being named, the storm became the first tropical cyclone on record to be named in the northern Indian Ocean. The WMO/ESCAP Panel agreed in May 2004 that in September, tropical cyclones in the Northern Indian Ocean attaining gale-force winds would be given names.