Tag Archives: Walaka

Hurricane Walaka Rapidly Intensifies to Category 5

Hurricane Walaka rapidly intensified to Category 5 on the Saffir-Simpson Scale on Monday.  At 11:00 p.m. EDT on Monday the center of Hurricane Walaka was located at latitude 13.2°N and longitude 169.8°W which put it about 240 miles (390 km) south of Johnston Atoll.  Walaka was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h).  The minimum surface pressure was 920 mb.

A Hurricane Warning is in effect for Johnston Atoll.  A Hurricane Watch is in effect for the Papahanaumokuakea Marine National Monument from Nihoa to French Frigate Shoals to Maro Reef.

The circulation of Hurricane Walaka is very well organized,  There is a circular eye at the center of Walaka.  The eye is surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Hurricane Walaka.  Storms near the core were generating strong upper level divergence which was pumping mass away from the hurricane in all directions.

Winds to hurricane force extended out about 50 miles (80 km) from the center of Hurricane Walaka.  Winds to tropical storm force extended out about 185 miles (300 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Walaka was 35.0.  The Hurricane Size Index (HSI) was 16.4 and the Hurricane Wind Intensity Size Index (HWISI) was 51.4.

Hurricane Walaka will remain in an environment very favorable for strong hurricanes for several more days.  Walaka will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds will be weak and there will be little vertical wind shear.  If a rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Hurricane Walaka to weaken.  In several days Walaka will move into an area where the upper level winds are stronger and the vertical wind shear will increase.  Hurricane Walaka will weaken more quickly when the shear increases.

Hurricane Walaka is moving around the western end of a subtropical high pressure system.  The high pressure system will steer Walaka toward the north during the next several days.  On its anticipated track Hurricane Walaka will pass near Johnston Atoll on Tuesday.

Tropical Storm Walaka Forms South of Hawaii

Tropical Storm Walaka formed south of Hawaii on Saturday afternoon.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Walaka was located at latitude 11.5°N and longitude 159.1°W which put it about 680 miles (1095 km) south of Honolulu, Hawaii.  Walaka was moving toward the west at 15 m.p.h. (24 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 1005 mb.

A distinct low level center of circulation formed within an area of thunderstorms south of Hawaii on Saturday and the Central Pacific Hurricane Center designated the system as Tropical Storm Walaka.  The circulation around Walaka was still organizing.  Most of the thunderstorms were developing in bands south and east of the center of circulation.  Bands north and west of the center consisted primarily of showers and lower clouds.  Storms south and east of the center were beginning to generate upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Walaka will be moving through an environment that will be favorable for intensification.  Walaka will move over water where the Sea Surface Temperature is near 29°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Walaka will strengthen into a hurricane and it could intensify rapidly once the inner core is well organized around an eye.

Tropical Storm Walaka will move south of a subtropical high pressure system over the Central Pacific Ocean during the next two or three days.  The ridge will steer Walaka in a general westward direction.  On its anticipated track Tropical Storm Walaka will remain south of Hawaii.