It has been quiet in the Atlantic Basin since mid-June with respect to tropical systems, but now Chantal has reached tropical storm status and is churning towards the Caribbean Sea at a pretty good clip. Chantal developed from a strong easterly wave that slipped off the African west coast a few days ago in what is likely to be a pattern that is frequently repeated over the next few months. The 11AM readings on Chantal have sustained winds at 45 mph with gusts to 60 and rapid movement to the west-northwest at 25 mph. An index that we track here at thesiweather.com called the Madden-Julian Oscillation (MJO) is quite supportive of an active period into at least mid-July as the index will remain in territory (i.e., phases 2 and 3) that favor Atlantic Basin tropical activity. The MJO is a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days.
All indications suggest Chantal will reach the Caribbean Sea within the next 36 hours and then approach the island of Hispaniola later this week. A track over this island would likely, at least temporarily, prevent or slow down intensification of Chantal as mountain peaks tend to interrupt the low-level circulation flow (10,000 foot peaks in Dominican Republic). By the weekend, Chantal could very well be in the vicinity of the Bahamas and, ultimately, it could have an effect on the Southeast US.