The 1998 North Indian Ocean cyclone season was an active season in annual cycle of tropical cyclone formation. The season has no official bounds but cyclones tend to form between April and December. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean. There are two main seas in the North Indian Ocean—the Bay of Bengal to the east of the Indian subcontinent and the Arabian Sea to the west of India. The official Regional Specialized Meteorological Centre in this basin is the India Meteorological Department (IMD), while the Joint Typhoon Warning Center releases unofficial advisories. An average of four to six storms form in the North Indian Ocean every season with peaks in May and November. Cyclones occurring between the meridians 45°E and 100°E are included in the season by the IMD.
With eleven depressions and eight tropical cyclones, this was one of the most active seasons in the ocean along with 1987, 1996, and 2005. The season caused a large loss of life, most of which was from one storm. Over 10,000 people were killed in India when Tropical Cyclone 03A brought a storm surge to the Kathiawar Peninsula, inundating numerous salt mines. Total damages from the storm amounted to Rs. 120 billion (US$3 billion). Tropical Cyclone 01B killed at least 26 people and left at least 4,000 fishermen missing in eastern Bangladesh on May 20. A short lived depression in mid-October killed 122 people after triggering severe flooding in Andhra Pradesh. In November, Tropical Cyclone 06B killed six people and caused property damage worth BTN 880 million (US$20.7 million) in eastern India. An additional 40 people were killed and 100 fishermen were listed as missing after Tropical Cyclone 07B affected Bangladesh.
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Season summary
The first storm of the season developed on May 18 out of an area of low pressure over the Bay of Bengal. It reached its peak intensity with winds of before making landfall near Chittagong, Bangladesh. The storm dissipated shortly after. Later that month, a short-lived storm developed over the Arabian Sea and dissipated the next day without impacting land. The most intense storm of the season formed in early June off the southwestern coast of India. It slowly traveled towards the west, remaining relatively weak before turning towards the north and intensifying. The storm reached its peak intensity with winds of shortly before making landfall near Porbandar in the Indian state of Gujarat. The cyclone rapidly dissipated on the same day.
After three months of inactivity, five storms developed in late September and October. Two of them strengthened into tropical storms, neither of which impacted land. In early November, the sixth tropical cyclone of the season developed in the Bay of Bengal. The storm quickly developed and reached its peak intensity upon landfall with winds of . The storm rapidly dissipated the same day it made landfall. Shortly after 06B dissipated, the remnants of Tropical Storm Chip triggered the development of a new cyclone over the Bay of Bengal. The storm tracked along the edge of a subtropical ridge, reaching its peak intensity over open waters with winds of . The cyclone entered an area of higher wind shear shortly after and rapidly weakened before making landfall. Then it dissipated in Bangladesh. The final cyclone of the season developed in the Arabian Sea during mid-December. It reached its peak intensity with winds of before weakening due to strong wind shear. It made landfall in Oman on December 17 as a minimal tropical storm shortly before dissipating.
Systems
Severe Cyclonic Storm BOB 01 (01B)
The first cyclone in the region developed as a tropical disturbance on May 13 over the southern Bay of Bengal to the southeast of Sri Lanka. At 0700 UTC on May 17, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA). Shortly after, the India Meteorological Department (IMD) declared that the disturbance developed into Depression BOB 01. At 0600 UTC on May 18, the first advisory on Tropical Cyclone 01B was issued by the JTWC, while the IMD upgraded BOB 01 to a deep depression.
Continuing on a northeasterly track, BOB 01 gradually intensified as it neared Bangladesh, strengthened into a cyclonic storm twelve hours later. Early on May 20, BOB 01 reached its peak intensity as a severe cyclonic storm with winds of and a barometric pressure of 972 mbar (hPa). The JTWC assessed the storm to have peaked with winds of , equivalent to a Category 1 hurricane on the Saffir–Simpson Hurricane Scale. An eye developed and the system made landfall several hours later near Chittagong. After making landfall, the storm quickly weakened, dissipating later that day.
Ahead of the storm, officials in Bangladesh relocated an estimated 650,000 people, resulting in a lower loss of life. But BOB 01 adversely affected low-lying areas, destroying 6,000 homes and damaging another 9,945. It produced a storm surge of , inundating coastal towns. At least 35 people were killed by the storm and 504 others were injured.Staff Writer (May 21, 1998). Thousands return home in wake of killer cyclone in Bangladesh Deutsche Presse-Agentur Additionally, an estimated 4,000 fishermen were listed as missing at sea. Two ships owned by the Bangladesh Shipping Corporation sustained significant damage.
Depression ARB 01 (02A)
On May 27, an area of low pressure developed over the central Arabian Sea. Early the next day, the JTWC issued their first advisory on Tropical Cyclone 02A while the system was located about south of Masirah Island. The IMD only briefly monitored the system as a weak depression, designating it as ARB 01. Upon being classified a tropical cyclone, 02A reached its peak intensity. The speed of its winds was . Soon, it began to dissipate due to increasing vertical wind shear. The center of circulation quickly became devoid of convection. The storm weakened below tropical storm intensity later that day before dissipating on May 29 over open waters.
Extremely Severe Cyclonic Storm ARB 02 (03A)
On June 1, an area of low pressure developed over the Laccadive Islands. Two days later, the JTWC issued a TCFA for the system as it became better organized. Early on June 4, the JTWC issued its first advisory on Tropical Cyclone 03A. Around the same time, the IMD began monitoring the system as Depression ARB 02. Shortly after, the depression was upgraded to a deep depression and further strengthened into a cyclonic storm the following day. The small storm moved slowly towards the west and weakened as wind shear began to increase. The storm weakened below tropical storm intensity later that day and the initial final advisory was issued. However, the system redeveloped and advisories resumed the next day. The storm gradually intensified as it moved towards the northwest. Dvorak satellite intensity estimates on June 6 reached T4.0, corresponding to an intensity of . The IMD also marked the increase in intensity, upgrading ARB 02 to a severe cyclonic storm. Around this time, the storm began to turn towards the north and accelerate due to an approaching mid-level trough. As the storm neared the Indian coastline, an eye developed and the storm strengthened into the equivalent of a major hurricane with winds reaching . The IMD assessed the storm to be a very severe cyclonic storm at this time, with winds up to and a barometric pressure of 958 mbar (hPa). After slightly weakening early on June 9, 03A re-strengthened, attaining its peak intensity with winds of . Then it made landfall near Porbandar in the Indian state of Gujarat between 0100 and 0200 UTC. The storm weakened following landfall and the JTWC issued their final advisory later that day. The IMD continued to monitor ARB 02 until June 10, by which time it had weakened to a depression before dissipating.
Tropical Cyclone 03A brought a large storm surge of which devastated coastal communities and salt mines. An estimated 4,000 to 10,000 people were killed by the storm, many of whom were salt mine workers who did not own a radio and received little or no warning of the cyclone. The large loss of life was partially attributed to contractors who wanted to continue making profits and did not inform their workers of the approaching storm. According to the official figures, 1173 people died and 1774 people went missing. Also, the region had witnessed only 17 cyclones since 1890, all of which were weaker than 03A. As a result, its vulnerability was miscalculated by the local population and the disaster management administration. Power supply to numerous residences was lost due to the storms high winds. A microwave tower in Porbandar collapsed, causing widespread disruption in telecommunication. Hundreds of other power transmission towers also fell, causing an estimated loss of Rs 10 billion for the Gujarat Electricity Board. At least 893 people were injured by the storm and over 11,000 animals were killed. Over 162,000 structures were damaged or destroyed throughout the affected area and damages amounted to Rs. 120 billion (US$3 billion). In Kandla, the damages were estimated around . Over the next one month, insurance companies had lost approximately Rs. 13 billion (US$266.5 million). The remnants of the storm produced heavy rains over Pakistan which electrocuted 12 people. In the wake of the storm, the United States Government provided US$25,000 for rehabilitation of the affected population. The Government of Denmark also contributed $72,992 in funds for relief efforts. The Gujarat government deployed approximately 330 medical teams to the affected areas. Local aid, amounting to (US$20.5 million) was provided to assist victims.
Deep Depression BOB 02
On June 13, the IMD began monitoring a depression over the central Bay of Bengal. Tracking towards the west, the depression intensified into a deep depression, peaking with winds of and a minimum pressure of 992 mbar (hPa). Around 15:00 UTC on June 14, the deep depression made landfall near Visakhapatnam. Shortly thereafter, it weakened to a depression and dissipated early the following day.
Depression ARB 03 (04A)
In late September, an area of low pressure developed over the Arabian Sea within an east–west oriented surface trough while located about west of Mumbai, India. The system gradually intensified as it moved slowly towards the west. Early on September 30, the JTWC issued its first advisory on Tropical Cyclone 04A. Its winds peaked at . Located within an area of moderate wind shear, the storm quickly weakened and dissipated early on October 1.
Deep Depression ARB 04
On October 8, the IMD began monitoring a tropical depression located about southwest of Mumbai. The depression was briefly classified as a deep depression with winds of and a minimum pressure of 998 mbar (hPa) as it moved towards the west-northwest. Shortly after reaching its peak intensity, the depression weakened. The last advisory was issued the next day while the storm was over open waters.
Cyclonic Storm ARB 05 (05A)
The IMD began monitoring an area of low pressure over the Laccadive Islands on October 10. The low traveled towards the northwest with little development. On October 15, the JTWC issued a TCFA as the system became better organized. Although wind shear increased, the first advisory was issued the next day. With minimal convection, the storm never intensified past . The system traveled towards the northeast and weakened due to strong wind shear. On October 17, the storm fell below tropical storm status and made landfall on the Kathiawar Peninsula, near the same area where 03A made landfall in early June. The storm dissipated shortly after landfall.