Danny Weakening As It Moves Into the Caribbean; Two More Atlantic Systems May Develop

August 23,2015

Highlights

• Danny has weakened substantially over the last day or so after reaching Category 3 hurricane status on Friday. Maximum sustained winds were at 40 mph as of 11 p.m. EDT Sunday. 
• Tropical storm watches and warnings are in effect for portions of the Leeward Islands.
• Danny will track west to west-northwest, reaching the Leeward Islands by early Monday, then Puerto Rico and the Virgin Islands Monday night or early Tuesday morning. A weakened Danny should bring welcome rainfall to drought-stricken Puerto Rico and the Virgin Islands.
• The National Hurricane Center is monitoring two other areas of interest in the Atlantic for possible development well east of Danny the next few days.

Storm Stats and Satellite

After reaching Category 3 hurricane status on Friday, Danny has weakened significantly as it moves through a hostile environment east of the Leeward Islands. To the east of Danny, we are also monitoring two other areas of interest in the Atlantic for possible tropical development. Below we have a look at the specifics on Danny, followed by details on the Atlantic tropical disturbances.

Tropical Storm Watches, Warnings

Projected Path

(MORE: Track Danny with our Interactive Storm Tracker)

Danny: More Weakening Expected

As of Sunday evening, 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. 

Danny has grown in size but remains a small tropical cyclone, with tropical storm-force winds extending up to only about 105 miles from the center of circulation. Comparisons were made Thursday to the much larger west Pacific typhoons Goni and Atsani.

(INTERACTIVE: Satellite Loop of Danny)

While weakening, Danny will move generally toward the west to west-northwest over the next few days. Our latest forecast indicates the center of Danny would approach the Leeward Islands sometime early Monday morning.

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 likely that Danny may be a tropical depression or even a remnant low by that time.

Danny Rainfall Outlook

That said, it seems probable at least some bands of locally heavy rain will wrap into parts of the Virgin Islands and Puerto Rico. This could end up being too much of a good thing in the drought-stricken region.
(FORECAST: San Juan | St. Croix)
NBC News reported six more municipalities in Puerto Rico were declared federal disaster areas Wednesday, bringing the total number of municipalities declared a disaster area to 36.
The U.S. Geological Survey says roughly 45 percent of the public water supply in Puerto Rico is supplied by reservoirs.
The eastern half of the island territory, as well as the U.S. Virgin Islands, are classified as in either severe or extreme drought, according to the U.S. Drought Monitor analysis.
San Juan, Puerto Rico, (-10.20 inches) and St. Croix (-11.91 inches) have significant year-to-date rain deficits through Sunday, a large chunk of those since June 1. Dating to 1951, it has been the driest year-to-date on record at Henry E. Rohlsen Airport on St. Croix, picking up only 7.31 inches of rain through August 20.

Two More Areas to Watch in the Eastern Atlantic

Enhanced Satellite

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.
(MORE: Heart of the Hurricane Season is Here)
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 early this week. 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 organize.
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 low 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. Check back with The Weather Channel and weather.com for updates during the week ahead.

Danny History

Danny peaked as a category 3 hurricane with maximum sustained winds up to 115 mph Friday afternoon, becoming the first major hurricane of the 2015 Atlantic hurricane season.

(MORE: Expert Analysis | Hurricane Central)

Friday afternoon, a NOAA research plane not only sent back near real-time radar images from a hurricane for the first time.

Incidentally, while small, Danny isn't the smallest tropical cyclone on record. According to the NOAA's Hurricane Research Division, Tropical Storm Marco in 2008 had gale-force winds extending only 12 miles from the center.  Danny's tropical storm-force winds extended up to an estimated 60 miles from the center, as of Friday morning.
Danny became only the fourth named storm to become a hurricane in the strip of the Atlantic Ocean from off west Africa to the Lesser Antilles since the start of the 2011 season. Gonzalo (2014), Humberto (2013) and Katia (2011) were the only others to do so in that stretch of over four seasons.
Friday, Danny was the first hurricane to strengthen to Category 3 intensity in that Lesser Antilles to west Africa strip of ocean since 2010's Julia.
Stay tuned to The Weather Channel and check back with weather.com for updates on this system.
Senior meteorologists Nick Wiltgen and Jonathan Erdman and meteorologists Chris Dolce and Quincy Vagell contributed to this report.

MORE: Hurricanes by the Numbers