Tropical Depression 10W strengthened into Tropical Storm Maria on Wednesday and a Tropical Storm Warning was issued for Guam. At 5:00 a.m. EDT on Wednesday the center of Tropical Storm Maria was located at latitude 12.7°N and longitude 145.9°E which put it about 95 miles (155 km) southeast of Guam. Maria was moving toward the north-northwest 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 1000 mb. Tropical Storm Warnings were in effect for Guam and Rota. Tropical Storm Watches were in effect for Saipan and Tinian.
The center of circulation in former Tropical Depression 10W became more well organized on Wednesday and the Japan Meteorological Agency designated the system as Tropical Storm Maria. The circulation was still increasing in organization. There was a distinct low level center of circulation. Numerous bands of showers and thunderstorms were revolving around the center of circulation. Storms near the center were generating upper level divergence which was pumping mass away from the tropical storm.
Tropical Storm Maria will move through an environment very favorable for intensification during the next few days. Maria will move over water where the Sea Surface Temperature is near 30°C. Tropical Storm Maria will move under the western end of an upper level ridge that is between two upper level lows which are east and west of the ridge. The upper level winds will be relatively weak and there will be little vertical wind shear. The combination of the ridge and two upper level lows will increase the upper level divergence. Tropical Storm Maria will continue to strengthen. Maria will become a typhoon later this week. It could intensify rapidly once an eye forms and the inner core is well developed.
Tropical Storm Maria is moving around the western end of a subtropical ridge which is steering Maria toward the north-northwest. On its anticipated track the center of Tropical Storm Maria will move near Guam and Rota later today. A general motion toward the northwest is forecast for the next several days. Maria could move in the direction of the Ryukyu Islands at the end of the week.
Tropical Storm Maria will bring gusty winds and heavy rain to the southern Mariana Islands. The strongest winds and heaviest rain will affect Guam and Rota. Gusty winds and heavy rain will also affect Saipan and Tinian. Heavy rain could produce flash floods.
Elsewhere over the Western North Pacific Ocean, Tropical Storm Prapiroon was moving over the Sea of Japan. Prapiroon was bringing wind and rain to the northern Islands of Japan including Hokkaido and Honshu. At 5:00 a.m. EDT on Wednesday the center of Tropical Storm Prapiroon was located at latitude 39.6°N and longitude 135.6°E which put it about 360 miles (585 km) west-southwest of Misawa, Japan. Prapiroon was moving toward the northeast at 25 m.p.h. (40 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were winds gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 987 mb.
An upper level low is pulling Typhoon Lionrock toward a landfall in northern Japan. At 8:00 p.m. EDT on Monday the center of Typhoon Lionrock was located at latitude 36.1°N and longitude 142.5°E which put it about 150 miles (240 km) south-southeast of Sendai, Japan. Lionrock was moving toward the north-northwest at 24 m.p.h. (39 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure was 965 mb.
An upper level low west of Japan was pulling Typhoon Lionrock back toward the west-northwest. At its current track and speed Typhoon Lionrock would make landfall on the northeastern coast of Honshu near Sendai in about six hours.
The structure of Typhoon Lionrock is changing as a result of cooler Sea Surface Temperatures and more vertical wind shear. Lionrock is making a transition of a tropical cyclone to an extratropical cyclone. The circulation is becoming more elongated and the typhoon is pulling cooler drier air into the western half of the circulation. The wind field will tend to expand as the typhoon becomes extratropical.
Typhoon Lionrock will be capable of producing minor wind damage along its path. It could also cause locally heavy rainfall and flash floods over northern Honshu. It will pass over some of the same areas recently affected by Typhoon Mindulle.
Tropical Storm Chanthu brought wind and rain to the east coast of Honshu as the center passed east of Tokyo on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Chanthu was located at latitude 37.4°N and longitude 141.6°E which put it about 105 miles (170 km) northeast of Tokyo, Japan. Chanthu was moving toward the north-northeast at 12 m.p.h. (19 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 995 mb.
Tropical Storm Chanthu is starting the transition from a tropical cyclone to an extratropical cyclone. It is still moving over water where the Sea Surface Temperature (SST) is near 26°C, but Chanthu will move over colder water during the next 24 hours. An upper level trough west of Japan will sweep northwesterly winds over the top of Tropical Storm Chanthu. The increased vertical wind shear will tilt the circulation of Chanthu toward the northeast. The trough also contains cooler air. A combination of cooler SSTs, more vertical wind shear and cooler air aloft will alter the structure of Chanthu and it will begin to look more like an extratropical cyclone on Wednesday.
The upper level trough will steer Chanthu in a generally north-northeasterly direction during the next 24 hours. On its anticipated track Tropical Storm Chanthu will move roughly parallel to the coast of Honshu. Chanthu is expected to move across Hokkaido later on Wednesday.
The rainbands in Tropical Storm Chanthu are capable of producing locally heavy rainfall. Some flooding is possible in eastern Honshu and Hokkaido. Wind damage should be minimal although fishing boats and other vessels along the northeast coast of Japan will have to deal with wind and waves.