Cyclone Vayu

Very Severe Cyclonic Storm Vayu () was a strong tropical cyclone that caused moderate damage in India during June 2019. It was the strongest tropical cyclone to affect the Saurashtra Peninsula of northwestern India since the 1998 Gujarat cyclone. Vayu was the third tropical depression, third cyclonic storm and second very severe cyclonic storm of the 2019 North Indian Ocean cyclone season, and the first of which to form in the Arabian Sea. Vayu originated from a low-pressure area that was first noted by the India Meteorological Department (IMD) on 9 June, near the northern Maldives. After consolidating into a depression, the storm tracked slowly north-northwestward over the eastern Arabian Sea, and reached cyclonic storm intensity late on 10 June. Steady strengthening continued into 11 June, and the storm underwent rapid intensification late in the day. Vayu reached peak intensity as a high-end very severe cyclonic storm at 06:00  UTC on 12 June, with three-minute sustained winds of and a minimum pressure of 970 hPa (28.64 inHg). Despite initially being forecast to make landfall in the state of Gujarat, Vayu turned abruptly to the west on 13 June and moved away from the coast. The system weakened gradually as it tracked slowly towards the Arabian Peninsula, then weakened more quickly after beginning to accelerate back towards India on 16 June. Vayu was downgraded to a deep depression the following morning, and further to a depression a few hours later. The system degenerated into a well-marked low-pressure area late on 17 June, just before crossing the Gujarat coast. Vayu's remnants continued inland for several more hours, before dissipating on 18 June.

In total, as many as 6.6 million people in northwestern India were impacted by the cyclone. Approximately 300,000 residents of coastal Gujarat were evacuated on 12 June in preparation for the system's arrival, and thousands of personnel were deployed to the region to assist with preparations, rescue operations and clean up efforts. As of 18 June, eight people are reported to have been killed either directly or indirectly by the cyclone, and at least 12 more injured.

The name ''Vayu'' was provided by India, and is derived from a Sanskrit and Hindi word meaning 'wind'.

Meteorological history

In early June, a strong pulse of the Madden–Julian oscillation (MJO) tracked eastwards into the tropical Indian Ocean, leading to increased cloudiness and rainfall across the region. The presence of the pulse also contributed to enhanced convective activity, and generated conditions which were supportive of tropical cyclogenesis. On 9 June, the India Meteorological Department (IMD) noted the development of a low-pressure area over the southeastern Arabian Sea, to the north of the Maldives. Organisation increased throughout the day, and owing to the improved structure of the system, the United States' Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert at 22:30  UTC. At 00:00 UTC the following day, the IMD indicated that the low-pressure area had consolidated into a tropical depression, and assigned it the designation ARB 01. Conditions were favourable for further intensification, with improving upper-level divergence, and ample energy being provided by extremely warm sea surface temperatures of 31 ° C (88 ° F). Vertical wind shear also continued to decrease as the depression tracked steadily north-northwestwards parallel to the western coast of India under the influence of an anticyclone over central India. Deep convection strengthened around the low-level circulation centre, and the system was upgraded to a deep depression at 06:00 UTC. Six hours later, the JTWC assessed one-minute sustained winds as having reached , and designated the system as Tropical Cyclone 02A. At 18:00 UTC on 10 June, the system strengthened into the third cyclonic storm of the season, and was named Vayu by the IMD.

Vayu continued to steadily strengthen after intensifying into a cyclonic storm. A formative eye began to develop on 11 June, as intense deep convection wrapped tightly around the system. Vayu became a severe cyclonic storm by 12:00 UTC, and reached Category 1 tropical cyclone status on the Saffir–Simpson hurricane wind scale (SSHWS). Shortly afterwards, the cyclone began a period of rapid intensification; however, the rate of intensification was tempered somewhat by strong vertical wind shear. Vayu was upgraded to a very severe cyclonic storm at 18:00 UTC, and continued to strengthen through 00:00 UTC on 12 June, at which point the system became a Category 2-equivalent tropical cyclone on the SSHWS. One-minute sustained winds increased to six hours later as a ragged eye developed on visible-light satellite imagery, surrounded by strong deep convection, particularly in the western semicircle of the storm. The intensification trend then slowed, however, with three-minute sustained winds only increasing further to by 12:00 UTC. Vayu's intensity soon plateaued as ocean heat content began to decrease and drier air began to infiltrate the cyclone's circulation. As Vayu approached the coastline of the state of Gujarat in northwestern India, the influence of a strengthening subtropical ridge over Saudi Arabia caused the system to gradually slow down and turn towards the west. At 12:00 UTC on 13 June, the JTWC indicated that lower vertical wind shear had allowed Vayu to strengthen, noting that the eye had become more distinct. Vayu's intensity was now equivalent to a minimal Category 3 major hurricane on the SSHWS, with one-minute sustained winds of .

Vayu began to weaken on 14 June as it tracked slowly westward, away from the Gujarat coastline. Despite the low wind shear and warm ocean, upper-level outflow from the storm had begun to diminish, allowing the dry air entrainment from the northwest to start eroding the cyclone. The central dense overcast and circulation centre became increasingly ragged and elongated as deep convection diminished and started to become displaced. Vayu weakened to Category 1-equivalent tropical cyclone status at 12:00 UTC, as the loose central convection expanded to leave a ragged eye 55 km (35 mi) in diameter. Vayu's slow westward track through the weak competing steering environment over the northern Arabian Sea brought the system into an environment of high easterly vertical wind shear. The majority of deep convection became confined to the cyclone's southern quadrants, causing the system to weaken to a severe cyclonic storm at 00:00 UTC on 16 June. An approaching mid-latitude trough weakened the areas of high pressure centred to the west and northeast, Vayu recurved sharply to the northeast. Upon weakening further to a cyclonic storm, strong low-level southwesterly flow caused the system to accelerate northeastwards through the break in the blocking high-pressure ridge, back towards the Gujarat coast. Strong vertical wind shear and dry air ingestion from the western semicircle of the storm's circulation continued to erode the cyclone, and Vayu weakened into a deep depression at 03:00 UTC on 17 June, with the JTWC issuing their final advisory at this time. The system was downgraded further to a depression by the IMD six hours later. Soon afterwards, the IMD issued their final advisory on the system after Vayu degenerated into a well-marked low-pressure area, just before crossing the Gujarat coast near the India–Pakistan border. On 18 June, Vayu's remnants slowly moved inland, while continuing to weaken, before dissipating later that day.

Preparations

First approach to land

As the system intensified into a deep depression, the IMD issued a pre-cyclone watch for the coastline of the state of Gujarat. The agency indicated that further strengthening into a cyclonic storm within the following 24 hours was very likely. Fishermen were warned not to venture into the Arabian Sea near the developing system or in the forecast path of the cyclone, and mariners already at sea were urged to return to the coast. The pre-watch for the Gujarat coastline was upgraded to a yellow cyclone alert at 12:00 UTC on 10 June, with forecasts predicting landfall as a very severe cyclonic storm on 12 June. This was further upgraded to an orange alert on 11 June. The IMD warned that thatched houses in the path of the cyclone were likely to be completely destroyed, and that kutcha house