The western Pacific Ocean has had an active typhoon season: 19 storms have been named, nine becoming typhoons, and six Super-Typhoons with winds over 150 miles per hour.
The latest, Vongfong, became the strongest with winds of 180 miles per hour on Tuesday, and is on the same path as last week’s Typhoon Phanfone which raked the Japanese coast and passed directly over Tokyo.
Meanwhile, the Indian Ocean, quiet this summer until now, has a major tropical cyclone (more about names later) named Hudhud, which will reach the equivalent of a major hurricane and strike the east Indian coast on Sunday.
Super-Typhoon Vongfong Spins Towards Okinawa And The Japanese Mainland
Vongfong has moved slowly over the open Pacific the last few days, but has now begun to feel the southern fringe of the jet stream and turned north.
Winds are still 170 miles per hour, and though Vongfong has passed its peak intensity, weakening will be slow until it reaches the colder water closer to Japan and the stronger vertical wind shear (change in wind with height which rips tropical storms apart) of the jet stream.
Vongfong will probably still be a category three storm (winds over 115 miles per hour) as it passes Okinawa, but only a minimal typhoon (winds over 74 miles per hour) when it reaches the southern Japanese main island of Kyushu. It will rapidly weaken further as it accelerates northeastward up the spine of Honshu, steered by increasing jet stream winds.
Tropical Cyclone Hudhud To Hit Western India As Category Three Storm
Tropical Cyclone Hudhud formed Tuesday over the central Bay of Bengal, the eastern lobe of the tropical North Indian Ocean. It is forecast to strengthen rapidly to a 130 mile-per-hour storm by late Friday night, and strike the Indian coast near Visakhapatnam (easy for me to say) late Saturday night.
India is used to monsoon rains in the summer, so the major damage from Hudhud is likely to be from the wind, which will still be over 120 miles per hour at landfall and could maintain hurricane-force well inland.
Tropical Cyclones Not Common In The North Indian Ocean
Hudhud is only the second tropical cyclone of this year (technically there is no tropical cyclone season here).
The other was a minimal tropical storm in the Arabian Sea in June which never affected land. The bifurcation of the North Indian Ocean by the Indian subcontinent reduces the extent of water over which cyclones can travel. Though the water is warm enough for cyclone formation on both sides of India, the window of opportunity is small as storms cannot move very far without encountering land.
This contrasts with the wide Pacific where incubating typhoons can wander for days over warm water without making landfall.
What’s The Story With The Designations?
All hurricanes, typhoons, and other tropical low pressure systems are broadly categorized as tropical cyclones. However, each ocean has different names for these entities:
North Atlantic Ocean: A Tropical Storm is named when winds reach 39 miles per hour; when winds exceed 74 miles per hour it becomes a hurricane. A major hurricane has winds over 115 miles per hour
Eastern North Pacific Ocean: Names are the same as those for the Atlantic.
Western Pacific Ocean: A Tropical Storm is named when winds reach 39 miles per hour. When winds exceed 74 miles per hour, it becomes a typhoon. A typhoon with winds over 150 miles per hour is classified a Super-Typhoon.
North Indian Ocean: A Tropical Cyclone is named when winds reach 39 miles per hour. When the winds exceed 74 miles per hour, the storm becomes a Severe Tropical Cyclone.
What Effect Will Global Warming Have On Tropical Cyclones?
Tropical cyclones are sensitive to water temperature and the vertical structure of the wind field. The simplest prediction is that with the atmosphere warming, the water will warm and there will be more frequent, and more severe, storms. But the atmosphere has feedback mechanisms, and it is possible that these will inhibit tropical storm formation.
One season is not enough to hang a prediction on, but the current tropical Atlantic hurricane season may be instructive. Vertical wind shear (possibly a climate change feedback?) inhibited storm formation. However, of the five storms that formed, four became hurricanes.
Normally only half of all tropical storms become hurricanes.
It is possible that tropical cyclones will become less frequent (inhibited by some atmospheric condition) but stronger (able to use the additional heat of the ocean water when conditions do become favorable). Or it could happen, as it did in the western Pacific this year, that storms will be both more frequent and stronger.
Decoding Science. One article at a time.