A weakening Tropical Storm Douglas moved away from Hawaii on Monday. At 11:00 p.m. EDT on Monday the center of Tropical Storm Douglas was located at latitude 22.9°N and longitude 163.3°W which put it about 200 miles (325 km) east-southeast of French Frigate Shoals. Douglas was moving toward the west at 18 m.p.h. (30 km/h). The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h). The minimum surface pressure was 993 mb.
Tropical Storm Douglas weakened on Monday. An upper level trough west of Hawaii produced southerly winds which blew toward the top of Douglas’ circulation. Those winds caused strong vertical wind shear. The wind shear caused former Hurricane Douglas to weaken even though it was moving over water where the Sea Surface Temperature was near 27°C. The low level center of circulation was surrounded by showers and lower clouds. The only thunderstorms were occurring on the northern periphery of the tropical storm. Bands in the other parts of Douglas consisted of showers and lower clouds. Winds to tropical storm force extended out about 100 miles (160 km) from the center of circulation.
Tropical Storm Douglas will move south of a subtropical high pressure system over the North Pacific Ocean. The high will steer Douglas toward the west during the next few days. On its anticipated track Tropical Storm Douglas will move across the International Date Line and over the Western North Pacific Ocean later this week. The upper level trough will continue to cause vertical wind shear and Douglas will continue to weaken.
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.