Tropical Cyclone Amphan Rapidly Intensifies Into Equivalent of Major Hurricane

Tropical Cyclone Amphan rapidly intensified into the equivalent of a major hurricane over the Bay of Bengal on Sunday night.  At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone Amphan was located at latitude 13.3°N and longitude 86.4°E which put it about 675 miles (1090 km) south-southwest of Kolkata, India.  Amphan was moving toward the north at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 919 mb.

Tropical Cyclone Amphan rapidly intensified into a large powerful tropical cyclone on Sunday night.  A small circular eye was at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Amphan.  Storms near the core were generating strong upper level divergence which was pumping mass away from the tropical cyclone in all directions.

The circulation around Tropical Cyclone Amphan grew in size on Sunday.  Winds to hurricane/typhoon force extended out 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out 210 miles (335 km) from the center.  The Hurricane Intensity Index (HII) for Tropical Cyclone Amphan was 31.6.  The Hurricane Size Index was 16.8 and the Hurricane Wind Intensity Size Index (HWISI) was 48.4.  Tropical Cyclone Amphan was capable of causing widespread significant damage.

Tropical Cyclone Amphan will remain in an environment capable of supporting a strong tropical cyclone during the next 36 to 48 hours.  Amphan will move over water where the Sea Surface Temperature is near 31°C.  It will move under an upper level ridge.  The upper level wind will be weak and there will be little vertical wind shear.  The ridge will actually enhance the upper level divergence.  If a rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Tropical Cyclone Amphan to weaken.  Tropical Cyclone Amphan is likely to remain a large, powerful tropical cyclone during the next 48 hours.

Tropical Cyclone Amphan will move around the western end of a high pressure system over Southeast Asia.  The high will steer Amphan toward the north.  On its anticipated track Tropical Cyclone Amphan could approach the coast of Bangladesh in 48 hours.  Amphan is could still be the equivalent of a major hurricane when it reaches Bangladesh.  Tropical Cyclone Amphan could generate a significant storm surge at the coast.  Amphan will cause major wind damage and heavy rain could cause freshwater flooding.