Hurricane Olaf intensified rapidly on Monday and it reached Category 4 on the Saffir-Simpson Scale.  At 11:00 p.m. EDT on Monday the center of Hurricane Olaf was located at latitude 10.1°N and longitude 139.5°W which put it about 1235 miles (1985 km) east-southeast of Hilo, Hawaii.  Olaf was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 949 mb.

Olaf is a small but well organized hurricane.  The core is very symmetrical.  Hurricane Olaf has a clear eye with a diameter of about 12 miles (19 km/h) and the eye is surrounded by a ring of strong thunderstorms.  Several spiral rainbands are rotating around the inner core of the hurricane.  Upper level outflow channels to the northeast and southwest of Olaf are carrying mass away from the center of circulation, which is allowing the surface pressure to decrease.

Hurricane Olaf is moving just south of a band of stronger upper level westerly winds.  It is in an area of modest vertical wind shear.  The ocean beneath Hurricane Olaf has Sea Surface Temperatures  near 29°C.  The compact structure of Olaf allowed the hurricane to efficiently convert energy it extracted from the ocean to kinetic energy associated with higher wind speeds.  Olaf could remain in a favorable environment for another day or two, which may allow for further intensification.  However, if eyewall replacement cycles begin to occur, they will cause fluctuations in the intensity of Hurricane Olaf.

A subtropical ridge north of Olaf is steering the hurricane toward the west and that general steering motion is expected to continue for another day or two.  The western end of the subtropical ridge is expected to weaken later this week and that should allow Olaf to turn toward the north.  On its anticipated track, Olaf would turn toward the north before it reaches the Hawaiian Islands.

The core of the circulation of Olaf consolidated on Sunday and the National Hurricane Center upgraded it to a hurricane.  At 11:00 a.m. EDT on Sunday the center of Hurricane Olaf was located at latitude 9.5°N and longitude 133.2°W which put it about 1620 miles (2610 km) east-southeast of Hilo, Hawaii.  Olaf was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 989 mb.

The circulation of Hurricane Olaf consists of a small core of thunderstorms around the center of circulation and a primary rainband that spirals around the western and southern sides of the hurricane.  The core of thunderstorms is producing some upper level divergence, but upper level winds are inhibiting the outflow on the western side of the center.

Hurricane Olaf is moving over water where the Sea Surface Temperature is near 30°C and there is plenty of energy in the upper ocean to support intensification.  However, an upper level trough north of Olaf is producing westerly winds which are blowing over the top of the hurricane.  The upper level winds are blocking upper level outflow on the western side of Olaf and the vertical wind shear is inhibiting the intensification of Olaf.  If the wind shear decreases, then further intensification will be possible.

A subtropical ridge is steering Hurricane Olaf toward the west and that general motion is expected to continue for another day or two.  When Olaf reaches the western end of the ridge, it will start to turn more toward the north.