Tropical Storm Sinlaku is intensifying as it approaches the coast of Vietnam. At 7:00 p.m. EST on Friday the center of Tropical Storm Sinlaku was located at latitude 12.8°N and longitude 111.7°E which put it about 200 miles east-southeast of Quy Nonh and about 310 miles southeast of Da Nang, Vietnam. Sinlaku was moving toward the west at 12 m.p.h. The maximum sustained wind speed was 65 m.p.h. and there were gusts to 80 m.p.h.
As the forward motion of Sinlaku slowed, the wind shear decreased. Warm Sea Surface Temperatures (SSTs) and well developed upper level outflow created an environment favorable for intensification and the inner core of the tropical storm became better organized. A ring of convection is forming around the center of the circulation and there are some satellite indications that an eye may be forming. Sinlaku will remain over warm SSTs as it moves toward Vietnam and further intensification is likely. It is possible that Sinlaku could reach typhoon intensity before it makes landfall.
Sinlaku is being steered toward the west-northwest by a subtropical ridge to its north. That steering pattern should remain in place and Sinlaku could make landfall in 12-18 hours. It will bring strong winds to the coast of central Vietnam and it could produce locally heavy rainfall over parts of Southeast Asia as it moves inland.
Spiral banding and other organizational features have increased around Tropical Depression 21W and it has intensified into Tropical Storm Sinlaku. At 7:00 p.m. EST on Thursday the center of Tropical Storm Sinlaku was located at latitude 10.9°N and longitude 117.3°E which put it about 360 miles southwest of Manila, Philippines and about 650 miles east-southeast of Quy Nohn, Vietnam. Sinlaku was moving toward the west-northwest at 23 m.p.h. The maximum sustained wind speed was 40 m.p.h. and there were gusts to 50 m.p.h.
Sinlaku is being steered to the west-northwest by a subtropical ridge located to its north and that steering pattern is expected to continue for the next two or three days. Sinlaku could be near the coast of Vietnam in about 42 hours. The spirals bands of thunderstorms are increasing in organization and the upper level outflow is increasing. Sinlaku will remain over warm Sea Surface Temperatures as it moves toward Vietnam. The environmental factors suggest further intensification is likely, although the rapid forward motion of Sinlaku could limit the rate of intensification. If Sinlaku were to move more slowly, then a faster rate of intensification night be possible.
Sinlaku is likely to bring some gusty winds to the coast of central Vietnam and it could produce locally heavy rainfall over parts of Southeast Asia as it moves inland in two or three days.
Tropical Depression 21W (TD 21W) is bringing rain to parts of the Central Philippines as it moves toward the west-northwest. At 7:00 p.m. EST on Wednesday the center of TD 21W was located at latitude 9.8°N and longitude 122.9°E which put it about 70 miles east of Cebu and about 350 miles south-southeast of Manila. TD21W was moving toward the west-northwest at 20 m.p.h. The maximum sustained wind speed was 35 m.p.h. and there were gusts to 45 m.p.h.
TD 21W appears to be developing some spiral bands of showers and thunderstorms and it could become more organized as it moves away from the Philippines. It is over warm Sea Surface Temperatures and upper level outflow appears to be developing. As a result of those factors TD 21W could intensify into a tropical storm during the next 24-36 hours. Available guidance suggest that TD 21W will continue to move in a general west-northwesterly direction and it could approach the coast of Vietnam in about three days.
A small circular symmetric low pressure system developed over the southern Mediterranean Sea on Friday. The low had an eye-like feature in its center and spiral bands of convection which made its structure look somewhat similar to a tropical cyclone. The low brought wind gusts to 64 m.p.h. and a pressure of 986 mb to Malta. At 3:00 p.m. the center of the low was near 32°N and longitude 15°E which put it about 300 miles south of Syracuse on the island of Sicily. The low was moving toward the east-northeast and it was passing just south of the island of Sicily.
There have been other low pressure systems over the Mediterranean Sea that were similar to the current system and they often start debates about how they should be classified. Some aspects of their structure (i.e. an eye-like feature in the center and spiral bands of clouds) are similar in structure to tropical cyclones. The strongest winds are usually found close to the center of circulation and the pressure falls rapidly near the center, which are characteristics also seen in tropical cyclones. The convection in the Mediterranean lows is usually not as deep as the convection in tropical cyclones and it is difficult to determine if they have a warm core in the middle and upper troposphere, which is part of the definition of a tropical cyclone. Some of the lows are very similar to tropical cyclones from other parts of the world while other Mediterranean lows appear less like tropical cyclones of the deep tropics and more like subtropical cyclones or some other type of hybrid mesoscale low pressure system. In any case they do bring winds which are strong enough to cause damage and they can produce heavy rainfall, especially when the cross mountainous regions.
Although the upper level wind shear is increasing over Hurricane Vance it has maintained its intensity today. At 10:00 p.m. EST on Monday the center of Hurricane Vance was located at latitude 17.4°N and longitude 110.6°W which put it about 485 miles southwest of Mazatlan, Mexico. Vance was moving toward the north-northeast at 13 m.p.h. The maximum sustained wind speed was 110 m.p.h. and the minimum surface pressure was 965 mb. A Tropical Storm Watch has been issued for the portion of the coast from Mazatan to Topolobampo, Mexico.
An upper level trough approaching southern California is generating southwesterly winds that are starting to affect Hurricane Vance. The outflow is being inhibited on the western side of the hurricane and the upper level cirrus clouds show indications of being pushed toward the northeast. It is possible that the circulation around Vance is beginning to tilt toward the northeast with height. In addition, it looks like some drier air may be wrapping around the southwestern side of the circulation. Increased wind shear and drier air should start weakening Vance and the shear could be strong enough to weaken it quickly at times.
The southwesterly winds in the upper level trough are expected to pull Vance toward the northeast and the center could reach the coast of Mexico in 36-48 hours. Vance is likely to be much weaker when it gets to the coast but a Tropical Storm Watch has been issued as a precaution. Moisture associated with the circulation around Vance is likely to enhance the rainfall over parts of Mexico during the middle portion of the week.
After an extended period when drier air and wind shear inhibited the organizational processes in Tropical Storm Vance, it has intensified rapidly in recent hours and it is now a hurricane. At 10:00 a.m. EST on Sunday the center of Hurricane Vance was located at latitude 11.9°N and longitude 107.5°W which put it about 535 miles south-southwest of Manzanillo, Mexico. Vance was moving toward the northwest at 15 m.p.h. The maximum sustained wind speed was 80 m.p.h. and the minimum surface pressure was 990 mb.
Vance is moving around the western end of a ridge of high pressure over Mexico. A large upper level trough west of California will begin to affect Vance as it moves farther north. The trough is expected to turn Vance toward the northeast early next week. The track forecast becomes more challenging for the period when Vance could be approaching the coast of Mexico. Much of the guidance from the numerical models suggests that the upper level winds could be strong enough to separate the upper portion of Vance’s circulation from the lower level rotation. If that happens, then the middle and upper portions of the circulation could be transported across Mexico, while the surface low gets left behind and meanders southeast of Baja California.
Vance is over water where the Sea Surface Temperature is near 29°C and the upper level winds are relatively light. So, the period of rapid intensification could continue for another 12-24 hours. When the upper level trough approaches Vance from the northwest on Monday, the wind shear will increase and Vance will start to weaken and it could weaken quickly. Even if the low level center of Vance does not make landfall, moisture in the middle and upper portions of the circulation could enhance precipitation over Mexico next week.
Typhoon Nuri intensified rapidly and it has now reached Super Typhoon status. At 1:00 p.m. EST on Sunday the center of Nuri was located at latitude 17.9°N and longitude 132.3°E which put it about 650 miles south-southeast of Okinawa. Nuri was moving toward the north-northwest at 8 m.p.h. The maximum sustained wind speed was estimated to be 175 m.p.h. which made Nuri the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.
Nuri is moving around the western end of a subtropical ridge. It is anticipated that the upper level westerly winds in the middle latitudes will begin to turn Nuri more toward the northeast over the next few days. The guidance from numerical models suggest that Nuri will pass southeast of Japan during the middle of next week.
Nuri has been over warm Sea Surface Temperatures and in an area where the upper level winds are light. It has well developed outflow and the energy from the ocean has allowed it to strengthen rapidly. It is possible that Nuri become a little stronger during the next few hours. Once Nuri moves farther north, the upper level westerly winds will increase the wind shear and inhibit outflow on the western side of the circulation. Those factors will put Nuri on a weakening trend that will continue until it makes a transformation into an extratropical cyclone as it passes south of Japan.