Atlantic Disturbance Could Become A Tropical Depression Before Reaching Caribbean


A disturbance tracking through the central Atlantic could form into a tropical depression over the next several days as it marches closer to the Caribbean.

The disturbance, which rolled off the coast of Africa on Monday, will make its long voyage westward across the open Atlantic over the next week.

Possible NHC Development
T​his system has been designated Invest 95L by the National Hurricane Center (NHC). It’s a naming convention used by the NHC to identify tropical disturbances that have some chance to develop into a tropical depression or storm.

The NHC has given Invest 95L a medium chance of development over the next seven days. If development does occur during this period, it is more likely late this weekend or next week.

Warm water is abundant, but dry air is a factor against development. Despite the headlines of record warm water temperatures in the Atlantic, the atmosphere still has to cooperate for tropical development to occur.

This particular wave will have to persevere through dry air over the next several days in order to reach the Caribbean or western Atlantic.

Across much of the Atlantic, there is a deep well of both dry air and Saharan dust that stretches from northwestern Africa to Hispaniola. Each factor degrades the moisture content surrounding disturbances and makes it more difficult for them to develop.

Relative Humidity
Such hostile conditions are typical in July and sometimes into August in that stretch, which is known as the Main Development Region (MDR).

In order for the MDR to become more favorable for tropical storms and hurricanes, these tropical waves often have to venture off Africa and clear out the dry air like an atmospheric dust plow. Each successive tropical wave is more successful than the last one at getting across the Atlantic.

This is one reason why tropical activity ramps up in August as this traffic route from tropical waves gets easier to navigate.

What happens next week? Under the great assumption that this tropical wave gets across the Atlantic with moisture intact, it would arrive in the Lesser Antilles by early to midweek.

In what form this arrival would look like remains to be seen. It is more likely to be a ragged system that brings an enhanced chance of showers and thunderstorms for some islands.

Beyond that, like a one-two punch, the system may trade dry air for wind shear in the Caribbean. A common nemesis of systems in the Caribbean is accelerating winds at the low levels in the atmosphere, but this year – and recently – wind shear has been moderately strong, in part, due to El Niño.

This system’s prospects to survive long-term are not good, but we will continue to monitor the situation since changes are possible in the coming days.

Tropical waves are a hurricane’s first step at life. Tropical waves, often called African easterly waves, are the building blocks for much of the tropical storm and hurricane activity in the Atlantic and even Pacific basins. These are not waves in the ocean in the sense that you can play in them at the beach, but the ocean does play a large part in pumping moisture into these tropical waves that exist from near-surface level to 10,000 feet above the ocean.

According to the NHC, 60 tropical waves track across the Atlantic Ocean each year. Roughly one in five of these tropical waves becomes an Atlantic Basin tropical cyclone, and a few of these waves become tropical storms or hurricanes in the eastern Pacific.


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