“This is a special tropical coverage that started from November 27 and ended on December 2!”

According to the Joint Typhoon Warning Centre (JTWC), there had been a total of five tropical storms in the North Indian ocean this year with four in the Arabian sea while one in the Bay of Bengal, a rare tropical activity year indeed. According to the Indian Meteorological Department, there had been only a one cyclone this year that too from the Arabian sea that was Cyclone Keila in early November. Following are the main cyclone related articles made by Pakistan Weather Portal (PWP) in different months;

• Cyclone VS Karachi Saint
• Cyclone goes gaga over Sindh
• Detailed history of Cyclones in Pakistan (Updated!)
• Cyclone hits Karachi, India – War with Ghazi deepens!
• History of cyclones in the Arabian sea
• Monsoon 2011 and Cyclones – Sub-continent’s coastal threat?
• Super cyclones – The future of the Arabian sea!!
• Hypercanes – Can they happen?
• The Bhola cyclone – Not so “Bhola” at all!
• Cyclone Yemyin – The untold story!
• Is Arabian sea getting ready to give birth to “Tropical storm 2A”?

Depression ARB 04 is the ninth tropical depression of the 2011 North Indian ocean cyclone season and the fourth depression from the Arabian sea while also the fourth tropical storm from the Arabian sea.

History of ARB 04

On November 23, a low pressure over south-west Bay of Bengal was detected at 1008 mbar and the next day it intensified and showed improved convection. On November 25, it intensified into a well-marked low pressure at 1006 mbar and due to favourable sea temperatures. The next day, the system was declared a tropical storm 04A and a Depression ARB 04 at a pressure of 1002 mbar near Maldives and southern India, during the same day it caused torrential rainfall in Srilanka that killed some 20 people in the country. On November 27, the depression slightly moved in a NW direction.

Forecast from Pakistan Weather Portal

ARB 04 near peak intensity on November 29, weak eye could also be seen!

Pakistan Weather Portal (PWP) estimates that ARB 04 is likely to intensify further into a deep depression on November 27 late/November 28 (Happened) and it may further intensify into a cyclonic storm on November 28 depending upon the conditions (Did not happen) surrounding the system (sea temperature in the eastern Arabian sea around 28°C – 30°C) at peak intensity of atleast 55 – 60 mph, it is not forecasted to intensify beyond that stage and weaken gradually from that point due to intense vertical wind shear in the north-western parts that would tear the system apart and cause the pressure to rise; and cool sea temperatures in the western sector of the Arabian sea also likely to hamper further intensification (Happened).

The storm is expected to move in a WNW direction atleast by November 28 (Happened) but then a mid-latitude trough may cause the storm to re-curve in a NW to eventually N/NE direction towards Pakistan (as a much weaker system), however having said that if the mid-latitude wave fails to do so, the storm will continue to move towards in a western direction towards Oman and would dissipate there. But there is a good hint that in what ever direction it would move, the mid-latitude trough would eventually force the storm to recurve, but this process would cause the storm to weaken and it would start to lose intensity and may become a remnant before finally dissipating. (Happened) If the storm intensifies into a cyclonic storm, it would be given a name that is next on the list;

• Thane – Name from Burma, meaning ‘feudal lord’.

Timing of updates – 6:30 pm PKT (evening) and 9:00 pm PKT (night)

This is the final update regarding this tropical system!

Update issued on December 2 at 2:30 pm PKT

Remnants of ARB 04 dissipated near Pakistani coastline. Few high levels clouds persists over Makran coast that are likely to dissipate. Following is the amount of rainfall that occurred due to ARB 04 in Pakistan on December 1;

• Balochistan
• Pasni got 3 mm
• Ormara also got 3 mm
• Sindh
• Karachi got TR.

Update issued on December 1 at 6:30 pm PK

Yesterday’s depression ARB 04 has further weakened into a well-marked low pressure over northern and adjoining westcentral Arabian sea. It is expected to dissipate near Pakistani coast in 24 to 36 hours as the low is moving in a N/NE direction. The remaining clouds are passing from Makran to Sindh coast and south-eastern Sindh. Mid-latitude trough has also absorbed its moisture; 35 – 40  knots  winds and cold water were responsible for rapid weakening  of the tropical storm. It is not a significant storm now.

Update issued on November 30 at 6:30 pm PKT

Yesterday’s deep depression has weakened into a depression ARB 04 and has re-curved in a N/NW position, it is expected to continue to move in this position during 24 to 48 hours before rapidly dissipating. The storm is 850 km SSW of Karachi, however the wind shear is now 35 knots – 40 knots. Following are the main features of the tropical storm as of now;

• Movement: NW
• Winds: 30 mph (47  km/h)
• Pressure: 1002 mbar
• Under threat now: None

Update issued on November 29 at 9:00 pm PKT

The period of intensification is now over as the ARB 04 is now over cold waters with strong wind shear (30 knots). Mid-latitude trough is passing over the north-western parts that is very likely to cause the storm to weaken rapidly. The storm might curve in a N/NW direction before dissipating. The storm is 1050 km south of Karachi. Following are the main features of the tropical storm as of now;

• Movement: NW
• Winds: 35 mph (56 km/h)
• Pressure: 999 mbar
• Under threat now: None

Mostly cloudy weather expected in Sindh coast from November 29 with chances of drizzle along the Pakistani coast on November 30, with windy condition. Spiral bands of ARB 04 are now over Balochistan extending to Islamabad and adjoining extreme northern  Oman. Clouds from ARB 04 have covered south-eastern Sindh including Karachi. Weak thundercloud SE of Karachi and south of Keti bandar, lying over Arabian sea. However there is no direct affect to any country that is near this storm.

Update issued on November 29 at 6:30 pm PKT

Yesterday’s deep depression further intensified for short period of time into a strong deep depression with weak eye taking shape that is visible through satellite image. The system is present just 1050 km south of Karachi. Following are the main features of the tropical storm as of now;

• Movement: NW
• Winds: 39 mph (63 km/h)
• Pressure: 998 mbar
• Under threat now: None

Mostly cloudy weather expected in Sindh coast from November 29 with chances of drizzle on November 30.

Update issued on November 28 at 9:00 PKT

Deep depression ARB 04 is over east central Arabian sea and its spiral bands are extending into Sindh-Gujarat coast while other half is over south-western Arabian sea. The storm at present is located in the area of mild wind shear (10 knots) and sea temperature is 29 °C thus chances of intensification in 12 hours persists but after that intense wind shear (30 knots) would eventually cause the storm to weaken rapidly. The Storm will move over cold waters of Arabian after 12 hours. Following are the main features of the tropical storm as of now;

• Movement: WNW
• Winds: 35 mph (56 km/h)
• Pressure: 1000 mbar
• Under threat now: None

Mostly cloudy weather expected in Sindh coast from tonight with chances of drizzle on November 30.

Update issued on November 28 at 6:30 pm PKT

Yesterday’s depression over south-east Arabian sea has slowly intensified into a deep depression and may further intensify, conditions at the moment are favourable over the surrounding area. Following are the main features of the tropical storm as of now;

• Movement: WNW
• Winds: 35 mph (56 km/h)
• Pressure: 998 mbar
• Under threat now: None

Mostly cloudy weather expected in Sindh coast from tonight with chances of drizzle on November 30.

Update issued on November 27 at 9:00 pm PKT

Depression ARB 04 is present over south-east and east central Arabian sea near Lakshadweep Island, the weather depression would intensify in 36 hours into a deep depression and move in a WNW direction. Following are the main features of the tropical storm as of now;

• Movement: WNW
• Winds: 30 mph (47 km/h)
• Pressure: 1002 mbar
• Under threat now: None

Since the system is moving westwards the rainfall activity would decrease by tomorrow morning in Lakshadweep however isolated showers might continue.

Update issued on November 27 at 1:30 pm PKT

Depression ARB 04 is over India’s Lakshadweep Islands and adjoining Maldives, the weather depression may further intensify in 36 hours into a deep depression and move in a WNW. Following are the main features of the tropical storm as of now;

• Movement: WNW
• Winds: 30 mph
• Pressure: 1002 mbar
• Under threat now: Lakshadweep Island (India)

Heavy rainfall with strong gusty winds expected in Maldives especially the Lakshadweep Islands where one to two series of heavy rainfall is expected till night with decrease afterwards as system moves in open sea waters. Significant rainfall has occurred in the south-western coast of India, ranging from 80 mm – 160 mm.

21st century cyclones in the month of November

Only five cyclones have formed in the month of November in the Arabian sea with Phyan and Keila bringing spotty drizzle to Pakistan;

• 2003: November 12 – A category-1 hurricane with winds up to 85 mph, it dissipated near the horn of Africa.
• 2004: November 2 – A tropical storm (Deep depression) moved and dissipated near the coast of Africa.
• 2004: November 29 – Cyclone Agni, a category-1 hurricane, it became the nearest a tropical cyclone that has ever approached to the equator. It hit Somalia, it had winds up to 75 mph.
• 2009: November 4 – Cyclone Phyan, a tropical storm, it created panic in Mumbai. It had winds up to 60 mph.
• 2011: November 1 – Cyclone Keila formed over western Arabian sea and brought unusual flooding rainfall to Oman.
• 2011: late November ?

Tropical Storm 04A: Your thoughts!