Tropical Storm Matthew strengthened into a hurricane on Thursday as it moved over the eastern Caribbean Sea.  At 8:00 p.m. EDT on Thursday the center of Hurricane Matthew was located at latitude 14.2°N and longitude 68.1°W which put it about 150 miles (240 km) north-northeast of Curacao.  Matthew was moving toward the west at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 987 mb.

Tropical Storm Watches are in effect for Curacao, Bonaire and Aruba.  The government of Columbia has also issued a Tropical Storm Watch for the portion of the coast from the Columbia/Venezuela border to Riohacha.

The structure of Hurricane Matthew became much better organized on Thursday.  A primary rainband wrapped around the center of circulation.  An eye appears to be forming.  A ring of strong thunderstorms surrounds the eye on all sides except to the south.  Additional bands of thunderstorms developed in the northern and eastern parts of the circulation.  The storms near the eye generated upper level divergence which pumped out mass to the north and east of Hurricane Matthew.  The upper level divergence pumped out enough mass to allow the minimum pressure to decrease by 17 mb during the past 24 hours.

Hurricane Matthew will be moving into an environment that will be favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough over the western Caribbean Sea and an upper level ridge just east of Matthew are producing southwesterly winds which are blowing across the top of the hurricane.  The vertical wind shear made Hurricane Matthew’s structure asymmetrical earlier today, but the shear has been less in recent hours.  The effect of the wind shear will be to slow the rate of intensification, but it will not prevent intensification.  Hurricane Matthew will pass just north of the cost of South America and drier air could also slow the rate of intensification.

A strong subtropical high pressure system to the north of Matthew is steering the hurricane toward the west and that general motion is expected to continue for about another 48 hours.  When Hurricane Matthew reaches the western end of the ridge, it will turn toward the north.  Guidance from the numerical models continues to be quite divergent about when, where and how sharp the turn will be.  If Hurricane Matthew turns sooner and sharper, it could move over Haiti early next week.  On the other hand, if Matthew turns later and more gradually, it could affect Jamaica and eastern Cuba.  It is too early to know which scenario will eventually occur.

Hurricane Matthew could become a major hurricane over the Caribbean Sea and interests in the Greater Antilles should monitor its progress.