Brewing tropical rainstorm sailing westward across the Atlantic waters

The tropics are heating up this week as a cluster of showers and thunderstorms located several hundred miles off of the west coast of Africa continues to show indications of organization. AccuWeather forecasters are closely monitoring the tropical rainstorm for development over the coming days, saying that it is not out of the question for a tropical depression to form in the Atlantic sometime early this week.

This robust tropical rainstorm, designated as Invest 92L by the National Hurricane Center, is currently tracking westward across the open waters of the Atlantic. All eyes will be on this feature as it pushes into the central Atlantic and moves across a zone of abnormally warm sea surface temperatures.

For tropical formation to occur, sea surface temperatures must meet a minimum threshold value of at least 80 degrees Fahrenheit, or around 26 degrees Celsius. Currently, the ocean water temperatures from the Cabo Verde Islands to the Windward Islands range between 80 to 82 F, or 27 to 28 C, at the surface. Compared to typical mid-June sea surface temperatures, values observed this week are trending several degrees higher than the historical average.

An important factor that has allowed the sun’s rays to warm the Atlantic waters quicker than in previous years is the reduced amount of Saharan dust present. An abundance of Saharan dust across the Atlantic basin can be a limiting factor in suppressing tropical formation. It will result in a very dry air mass overhead and reduces the sun’s energy reaching the ocean’s surface.

A snapshot of the AccuWeather Enhanced RealVue™ Satellite showing the tropical rainstorm in the eastern Atlantic, captured on Sunday, June 18.

During its westward trek across the Atlantic waters, forecasters say that the tropical rainstorm will encounter varying levels of wind shear.

“Currently, this feature is in a pocket of low wind shear, which helps to create an environment conducive to development. However, shear is expected to increase once it approaches the Leeward Islands, and further development may become a challenge,” explained AccuWeather Meteorologist Alex DaSilva.


Wind shear is the change in direction and speed of winds throughout the various levels of the atmosphere. It can critically influence how vertically stacked and organized a storm can become. As a tropical feature becomes more vertically stacked, it can strengthen and become more organized over the warm ocean waters. Strong vertical wind shear is typically bad news for tropical elements, as it can rip apart the layers stacked throughout the atmosphere.

Through midweek, forecasters are highlighting a high potential for the tropical rainstorm to strengthen into a tropical depression as it pushes across the central Atlantic Ocean.

“On this westward track, it could be near the northeastern Caribbean late in the week and next weekend. As a result, anyone with interests in the eastern Caribbean will want to continue monitoring the progress of this system,” explained AccuWeather Senior Meteorologist Adam Douty.

Once reaching the vicinity of the Windward Islands, the tropical rainstorm can take a general track to the west-northwest and skirt the northern Lesser Antilles by late in the week and this weekend. If the storm tracks near the Islands, gusty winds and heavy rain could result in sporadic damage, such as downed tree branches, minor roof damage and isolated flooding in low-lying areas.

Forecasters say that as the system passes by the northeastern Caribbean, wind gusts of 40-60 mph (65-80 km/h) can occur in close proximity to the storm with an AccuWeather Local StormMax™ of 70 mph (115 km/h). Bands of rain that spread to the Lesser Antilles can result in general rainfall totals of 1-2 inches (25-50 mm) with an AccuWeather Local StormMax™ of 5 inches (125 mm).

Following directly behind the tropical rainstorm is a separate tropical wave that is closely being monitored this week into this weekend. There are some indications that it could be the next piece of energy to watch for potential organization; however, at this time it just remains a zone of loosely organized showers and thunderstorms.

The next tropical storm name on the list in the Atlantic basin will be Bret.

AccuWeather meteorologists are also monitoring a potential development zone in the East Pacific basin over the next day or so. An area of low pressure located well off the coast of southwest Mexico has been producing a wide swath of showers and thunderstorms with a low chance of forming into a tropical system. Although conditions are likely to become less favorable by midweek and regardless of development, this feature should not directly impact land.

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