Hurricane Kirk strengthened to Category 4 on the Saffir-Simpson Scale over the Tropical Atlantic Ocean on Thursday.  At 11:00 p.m. EDT on Thursday the center of Hurricane Kirk was located at latitude 21.5°N and longitude 47.5°W which put the center about 1670 miles (2685 km) southwest of the Azores.  Kirk was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 935 mb.

Hurricane Kirk rapidly continued to intensify on Thursday.  Kirk reached Category 4 on the Saffir-Simpson Scale.  A circular eye with a diameter of 17 miles (28 km) was at the center of Kirk’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms revolved around the center of Hurricane Kirk.  Storms near the center of Kirk generated strong upper level divergence that pumped large quantities of mass away from the hurricane.  The removal of large amounts of mass caused the pressure to continue to decrease.

The core of Hurricane Kirk contracted as Kirk intensified on Thursday.  Winds to hurricane force extended out 35 miles (55 km) from the center of Kirk’s circulation.  Winds to tropical storm force extended out 185 miles (295 km) from the center of Hurricane Kirk.

The Hurricane Intensity Index (HII) was 29.9.  The Hurricane Size Index (HSI) was 13.0 and the Hurricane Wind Intensity Size Index (HWISI) was 42.9.

Hurricane Kirk will move through an environment favorable for intensification during the next 24 hours.  Kirk will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the middle of an upper level ridge over the central Atlantic Ocean.  The winds are weak near the middle of the upper level ridge and there will be little vertical wind shear.  Hurricane Kirk is likely to intensify during the next 24 hours unless the inner end of a rainband wraps around the existing eye and eyewall.  If concentric eyewalls form, then an eyewall replacement cycle would cause Kirk to weaken.  If an eyewall replacement cycle does not occur, then Hurricane Kirk could strengthen to a Category 5 hurricane.

Hurricane Kirk will move around the western part of a subtropical high pressure system over the Atlantic Ocean.  The high pressure system will steer Kirk toward the north-northwest during the next 24 hours.  On its anticipated track, Hurricane Kirk will remain far from any land area.

Elsewhere over the Atlantic Ocean, the upper level divergence from Hurricane Kirk was inhibiting the intensification of Tropical Storm Leslie.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Leslie was located at latitude 10.0°N and longitude 32.0°W which put the center about 610 miles (980 km) west-southwest of the Cabo Verde Islands.  Leslie was moving toward the west at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1001 mb.