Tropical Depression Four has formed in the western Atlantic Ocean over the Turks and Caicos Islands, packing winds of 35 MPH. The storm is expected to steadily strengthen into Hurricane Cristobal this week, potentially threatening the southeastern coast before turning out to sea.
Hurricane Hunters have been surveying the system for the past couple of days, and the disturbance teetered on the brink of becoming a tropical storm but failed to develop a closed center of circulation at the surface. As the system now has a closed center, the National Hurricane Center pulled the trigger and declared it a tropical depression on Saturday afternoon.
Given how close the system is expected to track to the southeastern coast, it bears close watching for folks from Florida to North Carolina. As of this evening's model runs, it looks like they're starting to come into close agreement that the storm will track parallel to the Florida coast before starting to curve out to sea later in the week. The NHC notes the uncertainty in its discussion of the system: "Given the spread in the guidance and the recent formation of the system, confidence in the details of the track forecast is lower than normal."
The storm will recurve, but how soon it turns out to sea determines what impacts it will have on coastal areas, if it has any at all.
Even though the current forecast shows the storm staying off the coast, a good portion of the southeast is in the cone of uncertainty. The cone is the margin of error in historical hurricane track forecasts — the center of the storm winds up inside the cone 66% of the time, on average. Since this is the forecast track for the center of the storm, there could still be some impacts to the coast aside from heavy surf and rip currents. If the center tracks farther west than currently anticipated, coastal areas could see the outer edges of what will soon become Cristobal.
Since Tropical Depression Four is so close to land, the National Hurricane Center will issue advisories (forecasts) every three hours. The next intermediate advisory is at 2 AM EDT, followed by a full advisory at 5 AM EDT.
[Map by the author, satellite via GOES | The graphics were updated at 7:45 PM and again at 10:57 PM to reflect the latest advisories from the NHC.]