Tropical Cyclone Harold Strengthens to Equivalent of Cat. 5 Hurricane

Tropical Cyclone Harold strengthened to the equivalent of a Category 5 hurricane on Monday.  After weakening while the eye crossed the southern end of Espiritu Santo, the core of Harold rapidly intensified and the tropical cyclone became even more powerful.  At 11:00 a.m. EDT on Monday the center of Tropical Cyclone Harold was located at latitude 16.2°S and longitude 169.4°E which put it about 120 miles (195 km) north-northeast of Port Vila, Vanuatu.  Harold was moving toward the east-southeast at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 165 m.p.h.  and there were wind gusts to 200 m.p.h. (320 km/h).  The minimum surface pressure was 912 mb.

The inner core of Tropical Cyclone Harold weakened when the eye moved across the southern end of Espiritu Santo.  For a time the eye was less distinct of satellite images.  However, the eye cleared out quickly after it moved back over water and the core of Harold strengthened further.  By Monday a small, well formed eye was evident infrared satellite images.  The eye had a diameter of 12 miles (19 km).  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Harold.  Storms near the core were generating strong upper level divergence which was pumping mass away from the tropical cyclone.

Winds to hurricane/typhoon force extended out 40 miles (65 km) from the center of Tropical Cyclone Harold.  Winds to tropical storm force extended out 190 miles (305 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Tropical Cyclone Harold was 36.8.  The Hurricane Size Index (HSI) was 16.0 and the Hurricane Wind Intensity Size Index (HWISI) was 52.8.  Harold was capable of causing catastrophic damage.

The core of Tropical Cyclone Harold passed over the southern end of Espiritu Santo.  It then passed near the northern end of Malekula before battering Pentecost and Ambrym.  Harold likely caused catastrophic wind damage in those locations.  Tropical Cyclone Harold also dropped locally heavy rain over Espiritu Santo, Malekula, Pentecost, Maewo, and Ambrym.  Flash flooding probably occurred on those islands.

Tropical Cyclone Harold will move through an environment capable of support an intense tropical cyclone during the next several days.  Harold will move over water where the Sea Surface Temperature is near 30°C.  It will move under the southwestern part of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear.  If a rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Tropical Cyclone Harold to weaken.  Tropical cyclones generally do not maintain Category 5 intensity for an extended period of time.  So, Tropical Cyclone Harold is likely to start to weaken within 24 hours.

Tropical Cyclone Harold will move around the southwestern part of a high pressure system over the South Pacific Ocean.  The high will steer Harold toward the east-southeast during the next few days.  On its anticipated track Tropical Cyclone Harold will move away from Vanuatu.  Harold could approach Fiji within 36 hours and it could still be the equivalent of a major hurricane at that time.