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Lionrock Becomes a Typhoon East of Okinawa

Tropical Storm Lionrock intensified into a typhoon east of Okinawa on Tuesday.  At 8:00 p.m. EDT on Tuesday the center of Typhoon Lionrock was located at latitude 25.3°N and longitude 132.8°E which put it about 340 miles (550 km) east-southeast of Okinawa.  Lionrock was moving toward the south-southwest at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 965 mb.

Lionrock is a fairly small typhoon.  Winds to tropical storm force only extend out about 150 miles (240 km) from the center.  The circulation of Typhoon Lionrock is very well organized.  A small distinct eye is visible on satellite imagery.  The eye is surrounded by a ring of strong thunderstorms.  Additional spiral rainbands are rotating around the core of Lionrock.  The thunderstorms around the eye are generating upper level divergence which is pumping out mass in all directions.

Typhoon Lionrock is in an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 30.5°C.  The upper level winds are weak and there is little vertical wind shear.  A small typhoon like Lionrock can intensify very quickly and it appears to be doing so.

An upper level ridge over China is steering Typhoon Lionrock slowly toward the south-southwest and that general motion is expected to continue for another day or two.  Lionrock could move into an area where the steering winds are weak and it could stall for a period of time.  Eventually, an upper level trough is expected to approach the area from the west and begin to pull Lionrock toward the north.

Tropical Storms Lionrock and Kompasu Spin Up Near Japan

A large cyclonic atmospheric gyre near Japan spun up two more tropical storms at the end of the week.  The Japan Meteorological Agency named two smaller circulations within the larger gyre Tropical Storm Lionrock and Tropical Storm Kompasu.

At 2:00 p.m. EDT on Saturday the center of Tropical Storm Kompasu was located at latitude 37.8°N and longitude 142.3°E which put it about 75 miles (120 km) east of Sendai, Japan.  Kompasu was moving toward the northwest at 26 m.p.h. (42 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 996 mb.

At 2:00 p.m. EDT on Saturday the center of Tropical Storm Lionrock was located at latitude 30.6°N and longitude 135.7°E which put it about 530 miles (860 km) east-northeast of Okinawa.  Lionrock was moving toward the west-southwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 994 mb.

Tropical Storm Kompasu is located farther north and it is beginning to make a transition into an extratropical cyclone.  Kompasu is moving over water where the Sea Surface Temperature (SST) is near 26°C, but it is moving rapidly toward cooler SSTs.  Most of the thunderstorms are in a single primary rainband that wraps around the southern part of the circulation.  An upper level trough west of Japan is pulling southwesterly winds across the top of Tropical Storm Kompasu and the vertical wind shear is increasing.

The upper level trough is expected to turn Tropical Storm Kompasu toward the northeast.  On its anticipated track Tropical Storm Kompasu will move across Hokkaido in about 18 hours.  It will bring locally heavy rain and some wind.

Tropical Storm Lionrock is more well organized.  Several spiral bands of thunderstorms are wrapping around the southern and east sides of the center of circulation.  There is drier air in the western portion of the circulation and there are few thunderstorms in that part of Lionrock.  The thunderstorms east of the center are generating upper level divergence that is pumping mass toward the northeast away from core of Tropical Storm Lionrock.

Tropical Storm Lionrock is in an environment that is somewhat favorable for additional intensification.  It is moving over water where the SST is near 30°C.  The upper level trough west of Japan is generating some vertical wind shear.  The drier air in the western part of the circulation will also inhibit intensification, but Lionrock could gradually get better organized.  Upper level outflow from stronger Tropical Storm Mindulle, which is southwest of Lionrock, could produce enough vertical wind shear to weaken Lionrock at times.

The large atmospheric gyre is steering Tropical Storm Lionrock toward the west-southwest.  Lionrock could be pulled more toward the south as the larger, stronger Tropical Storm Mindulle passes east of it.  Tropical Storm Lionrock is expected to remain south of Japan during the next several days.  An alternative scenario would be for Tropical Storm Mindulle to intensify into a typhoon and grow large enough to absorb the circulation of Lionrock.