St. Croix Gets A Few Heavy Showers From Outer Bands Of Invest 99-L
CHRISTIANSTED — The outer bands of Invest 99-L dropped a little bit of rain on St. Croix early Tuesday morning.
Two disturbances in the central and eastern Atlantic Ocean, Invest 99-L and Invest 90-L, are being monitored for potential development into the next tropical depression or tropical storm over the next few days.
These are both behind Fiona, which is succumbing to the twin tropical nemeses of dry air and wind shear far from land in the central Atlantic Ocean.
Invest 99-L is currently a tropical wave — an area of low pressure without a closed, counterclockwise surface circulation — located about 900 miles east of the Lesser Antilles.
So far, 99-L has had to battle against dry air, similar to Fiona ahead of it. In the last day or so, some thunderstorm clusters have been bubbling up near the disturbance.
For a tropical cyclone to form, there needs to be persistent convection (thunderstorm activity) near a surface low-pressure circulation.
Sometimes the first system – Fiona in this case – becomes a sacrificial lamb, helping to prime the atmosphere behind it for the next system.
The National Hurricane Center says this system has a medium chance of development into a tropical depression or tropical storm over the next five days. An Air Force Reserve Hurricane Hunter aircraft is tentatively scheduled to investigate Invest 99-L on Tuesday.
For now, a tight consensus of our guidance suggests the disturbance should continue in a general west or west-northwest trajectory the next several days. It should reach the Lesser Antilles by late Tuesday or early Wednesday, and then spread through the northeast Caribbean Islands into Thursday.
Regardless of whether it is 99-L, a tropical depression or tropical storm, this system could bring heavy rain to the Lesser Antilles beginning late Tuesday. After that, it may lead to an uptick in locally heavy rain across Puerto Rico and the U.S. Virgin Islands.
Beyond that, it’s possible this system may threaten the Bahamas, then eventually some portion of the U.S., but it’s simply far too soon to determine.
The uncertainty is, in part, due to the fact we don’t yet have a closed circulation with which numerical guidance can use as a starting point. It’s hard to know where you’re going if you don’t know where you are.
Secondly, any low center that does form may spend time interacting with land areas of the Caribbean, which may further inhibit development.
Following the birth of Tropical Storm Gaston off the African coast, Hermine may form over the Atlantic Ocean this week, posing a threat to islands in the northern Caribbean Sea.
Tropical Depression Seven formed off the coast of Africa on Monday afternoon and strengthened to Tropical Storm Gaston on Monday evening.
Conditions are favorable for rapid development of Gaston into the weekend.
“Gaston will become a hurricane and could become the first major hurricane of the season in the Atlantic Ocean,” according to AccuWeather Hurricane Expert Dan Kottlowski.
Indications are that Gaston would take a northwestward path toward the central Atlantic over the next week, perhaps very similar to that of Fiona.
Such a path by Gaston would not pose an immediate threat to land. However, beyond the next week there is some potential for the system to be drawn close to Bermuda.
“A second tropical disturbance, dubbed 99L, was located about 400 miles east of Barbados, in the Windward islands, and could become Tropical Depression Eight this week,” Kottlowski said.
This disturbance is moving on a more westerly path than Gaston, which will bring showers, thunderstorms and rough seas to the Leeward islands Tuesday and the British and United States Virgin islands and Puerto Rico on Wednesday.
Gusty showers and thunderstorms may continue to spread northwestward over the Bahamas and northern Caribbean islands during the balance of the week. The system could approach Florida later this weekend.
How much rain and wind occur will be dependent on how quickly 99L strengthens. Most likely this disturbance will remain relatively weak into the middle of the week due to disruptive winds and dry air in the vicinity of its path. However, even a tropical depression or tropical storm is capable of producing heavy rainfall, flash flooding, mudslides, dangerous surf and damaging wind gusts.
From midweek on, the disruptive winds may ease, but interaction with the larger islands in the northern Caribbean, such as Puerto Rico and Hispaniola, may continue to hinder development or could cap strengthening.
“If 99L passes too close to Hispaniola with its mountainous terrain, it may never become an organized tropical system,” Kottlowski said.
If the path of 99L ends up north of the major islands in the Caribbean, then more significant and rapid development could occur prior to the system approaching United States’ waters.
Following Gaston, the next name on the list of tropical storms in the Atlantic for this season is Hermine.
People living in, traveling to or cruising around the Caribbean islands and the southeastern coast of the U.S. should monitor the progress of 99L this week and into next week.
Meanwhile, Fiona continues to produce showers and thunderstorms, despite its weak structure.
Fiona will continue to drift on a northwesterly path over the central Atlantic through the balance of the week and could regain some strength.
During this weekend, Fiona or its leftover showers and thunderstorms could wander southwest of Bermuda, Kottlowski stated.