Invest 91L draws 90% development odds as early models show potential East Coast threat
National Hurricane Center says the Atlantic disturbance could become Tropical Storm Gabrielle; ensemble 'spaghetti' tracks indicate possible impacts from Florida through the Carolinas to Virginia.
A broad tropical disturbance in the central Atlantic that the National Hurricane Center is monitoring as Invest 91L has a high probability of developing into a tropical cyclone and is being plotted by early model runs that show a potential threat to the U.S. East Coast.
The NHC has given the system a 90 percent chance of developing into a tropical depression, the first organized stage of a tropical cyclone, and warned that it could strengthen into the next named storm—Gabrielle—if sustained winds reach 39 mph. Presently, the disturbance is an unorganized system with winds around 23 mph and limited structure, according to forecasters and synoptic observations.
Early ensemble or “spaghetti” model runs shared publicly by private meteorologists, including Tony Mainolfi on X, display a range of possible tracks. Several of those runs show a trajectory that would take the system toward Florida and up the southeastern seaboard through Georgia, the Carolinas and into Virginia. Those model ensembles, if realized, would put tens of millions of residents along the Eastern Seaboard within the range of potential impacts, with some estimates used in early reporting suggesting as many as 30 million people could be affected.
Meteorologists stress that significant uncertainty remains in the storm’s eventual path and intensity. Ensemble tracks illustrate a wide cone of possibilities that typically narrows as a system becomes better organized and as the forecast period shortens. The timeline for development and any U.S. impacts will depend on changes in the disturbance’s structure, steering currents in the Atlantic and environmental factors such as wind shear and ocean temperatures.
If Invest 91L organizes into a tropical depression and then a tropical storm, it would receive the name Gabrielle. A further increase to sustained winds of 74 mph or more would classify it as a hurricane. Those thresholds are standard nomenclature used by forecasters to describe stages of tropical cyclone development and the system’s potential hazard level.
The disturbance is forming during the climatological peak of the Atlantic hurricane season, when warm ocean waters and atmospheric patterns more often favor tropical development. Forecasters routinely caution that early model divergences are common; different models and ensemble members can diverge in their representation of a system’s intensity and steering, producing a variety of plausible tracks.
The NHC and local National Weather Service offices will continue issuing regular updates, watches and warnings as conditions warrant. Emergency management officials in coastal states generally advise residents and businesses to maintain awareness of official forecasts, review preparedness plans and follow local guidance if watches or warnings are issued.
As with all developing tropical systems, forecasters said the situation could change rapidly and urged those in the potential path to monitor updates from the NHC and their local weather services. Private forecasters and media outlets will continue to plot ensemble runs and deterministic model solutions; however, forecasters emphasize reliance on official advisories for decision-making regarding preparations and potential evacuations.