The National Hurricane Center has begun tracking a weather disturbance over the Atlantic Ocean that it says has a 70 percent chance to become a tropical depression or storm over the next five days.
The disturbance does not yet have a name, but if it becomes better organized and attains maximum sustained winds of at least 39 mph, it will become Tropical Storm Don.
Right now, the disturbance appears as a disheveled mass of thunderstorms about 1,000 miles west of the coast of Africa, but environmental conditions are mostly favorable for it to intensify:
- Wind shear is lower than normal. This is important because wind shear at this time of year is normally high, frequently tearing apart fledgling disturbances.
- Waters are warm. Developing tropical weather systems require warm water, and sea surface temperatures are warmer than normal.
Dry air positioned to the system’s north is a factor which may limit its potential to intensify substantially.
Still, by late this week, many forecast models predict the disturbance to strengthen enough to become Tropical Storm Don.
— Ryan Maue (@RyanMaue) July 3, 2017
Most models track this system north of the Caribbean by Friday or Saturday; however, track forecasts become much less reliable beyond three days or so.
The stronger the system becomes, the more likely it is to track more to the north and get caught up in high-altitude steering currents. Whereas, if it is weaker, it may undercut those currents and continue on a path toward the Caribbean.
Assuming the system tracks north of the Caribbean, it is premature to speculate where it would go beyond that and whether it could potentially threaten the U.S. coast.
How I'm communicating 94L this AM at work: If it forms, low confidence in any direction/impact at this time. Slow burn ahead. No hysterics. pic.twitter.com/ztm6THkTjx
— Bryan Wood (@bryanwx) July 3, 2017
The long-term intensity forecast is tricky. Weather.com’s Jonathan Erdman notes that it would be rare, but not unprecedented, for this system to turn into a hurricane. He found that since 1950, only six disturbances that became tropical cyclones east of the Caribbean at this time of year reached hurricane strength.
Stay tuned for more updates on this system.