An area of disturbed weather that is moving through the eastern Caribbean Sea has the potential to develop into a tropical depression or tropical storm this week.
The National Hurricane Center (NHC) said that the system - designated Invest 97-L - has a medium (50 percent) chance of developing during the next two days, and a high (70 percent) chance of developing during the next five days.
This naming convention is used by the NHC to identify features that are being monitored for potential future development into a tropical depression or a tropical storm.
(MORE: What is an Invest?)
Invest 97-L Satellite and Position
Tropical waves are batches of energy and general spin in the atmosphere that develop due to temperature contrasts on either side of Africa's Sahel region. They then move west across the Atlantic Ocean.
Sometimes tropical waves develop into a closed area of surface low pressure with collocated shower and thunderstorm activity. Once this occurs, a tropical depression or storm can develop, and that's what we'll be monitoring Invest 97-L for.
(MORE: What is a Tropical Wave?)
The
NHC said that this system's fast movement was a negative to development
in the near term. The dry air in the region also may be playing a role
in keeping convection rather disorganized.
Once Invest 97-L
reaches the western Caribbean Sea in a few days, it will have a greater
chance to develop into a tropical depression or tropical storm.Computer Model Track Forecast For Invest 97-L
Puerto Rico Radar
Forecast Rainfall Associated with 97L
Technically, the Atlantic hurricane season runs from June 1 through Nov. 30. Much of the tropical activity occurs between the second week of August and the second week of October. In late July and early August, we begin to keep an eye on the eastern Atlantic as it begins to show signs of life.
(MORE: Gulf of Mexico Hurricane Drought Likely to Become the Longest in 130 Years)
August and September: More Favorable For Development
Tropical waves that emerge off the African coast often develop around or after passing the Cape Verde Islands.Meteorologists make frequent references to the "Cape Verde" season, which is essentially a season within the overall hurricane season. Most Cape Verde storms develop from mid-August until late September.
Expanding
high pressure ridge creates a more favorable environment for tropical
systems to develop and move westward in the Alantic
There
are so many "mouse traps" (unfavorable conditions) in the Atlantic that
very few of these Cape Verde tropical storms and hurricanes ever make
it all the way to the United States. But there have been some notable
Cape Verde storms that made it to the East Coast of the U.S., such as
the 1938 Hurricane, Hurricane Hugo in 1989 and Hurricane Andrew in 1992.Development of tropical waves into tropical storms or hurricanes is determined by several environmental factors that can range from somewhat favorable to extremely favorable, including:
- Ocean temperatures
- The orientation of ridges (high pressure) and troughs (low pressure) aloft
- A moist environment
Tropical systems like to have winds that are roughly the same speed and direction through a depth of the atmosphere for maximum development. Wind shear - changing winds with height - tends to break up tropical systems that are trying to develop, displacing convection away from a center of circulation.
This often occurs when a trough of low pressure aloft is to the west of a tropical weather system, such that west to southwest winds aloft combine with the typical tropical east-northeast trade winds to produce wind shear.
In August and September, a high-pressure ridge aloft, known as the Bermuda-Azores high, often expands and creates a more favorable environment for development. Atlantic systems are often steered toward the western Atlantic, Caribbean Sea and sometimes all the way to the U.S.
Since the area from Africa to the eastern Atlantic looks quite active already and we now have a tropical system of interest, it'll be interesting to see what the rest of the hurricane season will have in store.
MORE: Retired Atlantic Hurricanes and Tropical Storms
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