Tag Archives: Ryuku Islands

Typhoon Lan Intensifies Into Equivalent of a Major Hurricane

Typhoon Lan intensified into the equivalent of a major hurricane on Friday.  At 11:00 a.m. EDT on Friday the center of Typhoon Lan was located at latitude 20.9°N and longitude 130.3°E which put it about 450 miles (720 km) south-southeast of Okinawa.  Lan was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h).  The minimum surface pressure was 942 mb.

Typhoon Lan has a large and powerful circulation.  There is a large circular eye at the center of circulation.  The eye has a diameter of 60 miles (96 km) and it is surrounded by a ring of strong thunderstorms.  The strongest winds are occurring in that ring of storms.  Multiple bands of showers and thunderstorms are revolving around the core of the circulation.  Typhoon Lan is generating strong upper level divergence which is pumping mass away to the northeast of the typhoon.  Winds to typhoon force extend out about 100 miles (160 km) from the center of circulation.  Winds to tropical storm force extend out about 330 miles (530 km) from the center.

The Hurricane Intensity Index (HII) for Typhoon Lan is 20.6.  The Hurricane Size Index (HSI) is 37.2 and the Hurricane Wind Intensity Size Index (HWISI) is 57.8.  Those indices indicate that Typhoon Lan is capable of causing widespread major damage.

Typhoon Lan will move through an environment that will be favorable for further intensification during the next 24 hours.  Lan will move over water where the Sea Surface Temperature is near 31°C.  An upper level ridge centered east of Lan is producing southerly winds which are blowing toward the top of the circulation.  There are also southerly winds in the lower levels of the atmosphere and thus there is not much vertical wind shear.  The southerly winds in the upper levels are actually enhancing the upper level divergence to the northeast of Typhoon Lan.  Warm water and little vertical wind shear will allow Typhoon Lan to strengthen during the next day or so.  When Lan moves farther north, it will reach the upper level westerly winds in the middle latitudes.  The vertical wind shear will increase at that time, and Typhoon Lan will start to weaken.

Typhoon Lan is moving around the western end of a subtropical ridge which is steering the typhoon toward the north.  As Typhoon Lan moves farther toward the north, it will begin to move toward the north-northeast.  When Lan reaches the upper level westerlies on Sunday, it will turn more toward the northeast.  On its anticipated track the center of Typhoon Lan will pass east of Okinawa and the Ryuku Islands on Saturday.  Typhoon Lan will approach Honshu in about 48 hours.

Typhoon Lan will still be a large powerful typhoon when it approaches Honshu.  Lan will be capable of producing strong gusty winds and very heavy rainfall.  Flash floods could occur when Typhoon Lan moves across Japan.