ST JOHN’S, Antigua, Aug 23 2015 – As of late Sunday morning, convection (shower and t-storm activity) was displaced to the north and east of the circulation center due to a “wall of wind shear” near the Caribbean.
Wind shear can blow convection away from the center from a tropical cyclone. If strong enough, it can rip apart existing tropical cyclones. In addition, those increasing west to southwest winds aloft will transport more dry air into the circulation of Danny. This dry air is also stable, meaning it suppresses upward vertical columns of air needed to maintain or form new thunderstorms.
The large-scale atmosphere Danny has moved into, as well as its expected track over land areas of the Caribbean, will induce further weakening with time.
Even though Danny is weakening, numerous tropical storm watches and warnings have been issued for the northeast Caribbean islands. A tropical storm watch is now posted for Puerto Rico and the U.S. Virgin Islands. This means tropical storm conditions are possible there in the next 48 hours.
Danny remains a tiny tropical cyclone, with tropical storm-force winds extending up to only about 60 miles from the center of circulation.
While weakening, Danny will move generally toward the west-northwest the next several days.
Latest forecast indicates the center of Danny would approach the Leeward Islands sometime early Monday morning, most likely as a tropical storm.
Given Danny’s small wind field, the exact track of the center of circulation will determine who will see tropical storm-force winds in the Leewards Monday.
A weakening Danny would then continue toward the Virgin Islands, Puerto Rico and Hispanola Tuesday into Wednesday. It is possible that Danny may be a tropical depression or even a remnant low by that time.
Typical of late-August, the tropical Atlantic has heated up with two more areas of interest that could develop into a tropical depression or tropical storm during the week ahead.
Several hundred miles west of the Cape Verde Islands is an area of low pressure that is swirling westward. The National Hurricane Center says that there is a high chance that this system, dubbed Invest 98-L, will develop into a tropical depression by midweek. By late this week, this system may move to a position near the northern Leeward Islands. Just like we saw with Danny, Invest 98-L will have to battle dry air and wind shear nearby as it tries to organise.
Behind that area of low pressure is a tropical wave that is moving off the west coast of Africa. The National Hurricane Center is giving this system a medium chance of developing over the next five days. By late week, this system should be located over the central Atlantic Ocean.
It’s far too early to know at this time what impacts these systems may bring to the eastern Caribbean or anywhere else
