The National Hurricane Center said Sunday that Invest 91L, once flagged as a disturbance to watch in the Central Atlantic, no longer has any chance of tropical development. The system, weakened by dry air and wind shear, has lost the organization needed to become a tropical cyclone.
The dissipation of Invest 91L comes as the climatological peak of the Atlantic hurricane season approaches around Sept. 10. Forecasters at the NHC do not anticipate any new systems forming over the next seven days, though additional tropical activity remains possible later in the month.
Why Did Invest 91L Fail to Develop?
Meteorologists say the collapse of Invest 91L is an example of how hostile atmospheric conditions can overwhelm a tropical wave, even when ocean waters are warm enough to support development.
The Source contacted Glorianne M. Rivera Santiago, a meteorologist at the National Weather Service in San Juan, Puerto Rico, to obtain more information about why Invest 91L did not intensify.
Rivera explained that Invest 91L had been fighting a surge of very dry air across the central Atlantic, along with Saharan dust and vertical wind shear, breaking apart thunderstorms before they could cluster around a center. Without sustained convection or a closed circulation, the disturbance was unable to consolidate, and NHC forecasters dropped formation chances to zero on Saturday night.
Local Weather Effects in Puerto Rico and the USVI
While former Invest 91L is not expected to become a cyclone, the tropical wave is still producing some disorganized thunderstorms as it moves toward the Lesser Antilles. Rivera told the Source that the NWS expects the U.S. Virgin Islands and Puerto Rico to receive some precipitation from the system during the middle part of the week.
Rivera noted that as of Sunday, the NWS does not have an exact estimate of how much rainfall is anticipated. However, the U.S. Virgin Islands could receive about one to two inches of precipitation between Wednesday and Friday.
In addition to the potential for rainfall and thunderstorms associated with the remnants of Invest 91L, Rivera reported that very warm temperatures will continue across the area.
Rivera said that the region is forecast to receive two plumes of Saharan dust in the coming days. The first will arrive Monday and linger through midweek, around the time the remnants of Invest 91L are expected to pass across the local islands. A second round of dust is anticipated by the end of the week and could persist into next weekend.
The NWS also noted that the risk of dangerous rip currents will remain low through Tuesday but could increase to a moderate risk by Wednesday, particularly across St. Croix. Beachgoers and boaters are urged to use caution, as gusty winds may create choppy seas, and isolated thunderstorms with lightning could develop over the coastal waters.
Tropical Development Expected Throughout September
While the NHC expects another brief period of relative inactivity across the Atlantic basin, tropical development is forecast to ramp up throughout September.
According to a Global Tropics Hazards Outlook released on Tuesday, Sept. 2, there will be an elevated chance of cyclonic development across the Atlantic basin. The forecast tool, which is issued weekly by the National Oceanic and Atmospheric Administration’s Climate Prediction Center, provides insight into potential activity across tropical basins up to three weeks in advance.
In its update last week, NOAA said that portions of the Atlantic basin may experience a 20-40% chance of cyclonic development during the “Week Two” outlook period, which runs from Sept. 10 until Sept. 16. A 40-60% chance of tropical cyclogenesis is forecast across the Main Development Region in the “Week Three” outlook, running from Sept. 17 through 23. Areas across the Western Caribbean Sea and the Gulf are also likely to see an increased chance of development.
Stay Informed Throughout Hurricane Season
It is crucial to remember that the forecast can change very quickly. USVI residents and visitors are encouraged to continue to remain prepared. Weather information is available from the NWS, the NHC, and NOAA.
Additionally, the local weather forecast for the U.S. Virgin Islands is regularly updated on the Source Weather Page and VI Source YouTube Channel. A weekly Tropical Outlook article from the Source is also published throughout hurricane season to provide in-depth updates. Residents and visitors can find additional weather alerts and preparedness information from the Virgin Islands Territorial Emergency Management Agency.
