Final Advisory Issued For Danny; New Tropical Depression Developing?

August 24,2015

Highlights

• The National Hurricane Center wrote its final advisory on Danny Monday at 11 a.m. EDT. Data from a Hurricane Hunter aircraft revealed that Danny had degenerated into a trough of low pressure, meaning it no longer had the closed circulation center needed to qualify as a tropical cyclone.
• Danny's remnants will continue to track west through the Leeward Islands on Monday, and will then pass south of Puerto Rico and the Virgin Islands Monday night through Tuesday. This may bring some welcome rainfall to drought-stricken Puerto Rico and the Virgin Islands.
• A new tropical depression may form later today east of Danny in the central Atlantic. A second area of interest has a low chance of development near the Cape Verde Islands.

The National Hurricane Center issued its final advisory for Danny at 11 a.m. EDT on Monday, stating that there was no longer a closed circulation center based on Hurricane Hunter data. That said, rain and gusty winds from Danny's remnants will still impact the Caribbean.

We are also monitoring two other areas of interest in the Atlantic for possible tropical development. One of those tropical systems could develop into a tropical depression later on Monday, and eventually a tropical storm at some point this week.

Below we have a look at what to expect from Danny's remnants, followed by details on the potential for a new tropical depression to form later today.

Danny's Remnants: Drought-Helping Rains For Puerto Rico

Danny Rainfall Outlook

Danny's remnants will continue to move through the Leeward Islands on Monday. Locally heavy rain and gusty winds are expected as Danny passes through.

The remnants of Danny will then move south of the Virgin Islands, Puerto Rico and Hispanola Monday night through Tuesday.

It seems probable at least some bands of much needed locally heavy rain will wrap into parts of the Virgin Islands and Puerto Rico.
(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.

New Tropical Depression Developing?

Enhanced Satellite

Model Tracks: Invest 98-L

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 midweek, this system may move to a position near or north of the 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 has moved 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.

Danny's weakening Saturday-Monday has been due to a "wall of wind shear" near the Caribbean.

Wind shear can blow convection (shower and t-storm activity) away from the center from a tropical cyclone. If strong enough, it can rip apart existing tropical cyclones. In addition, those west to southwest winds aloft transported 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.

(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 wasn'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.
Senior meteorologists Nick Wiltgen and Jonathan Erdman and meteorologists Chris Dolce and Quincy Vagell contributed to this report.

MORE: Hurricanes by the Numbers