Tropical Storm Joaquin strengthens east of Bahamas; East Coast landfall potential still very uncertain
Tropical Storm Joaquin underwent a period of noticeable strengthening Tuesday afternoon over the western Atlantic Ocean, and it appears likely to become a hurricane just east of the Bahamas before a complicated atmospheric pattern makes its future track – including any potential landfall on the U.S. East Coast – extremely difficult to forecast.
Residents along the East Coast of the U.S. should pay close attention to the forecast now through this weekend. It's a particularly difficult forecast that hinges on the behavior of several different atmospheric features over North America and the North Atlantic Ocean.
Computer forecast models (see graphic below) – and the meteorologists who rely on them for guidance – are grappling with a complex interaction between Joaquin, a cold front near the East Coast, the remnants of Tropical Storm Ida, a strong bubble of high pressure aloft over the North Atlantic Ocean, and a potentially strong area of low pressure aloft digging into the southeastern U.S. later this week.
Joaquin's future depends critically on the position and relative strength of those players – not to mention its own strength. Strong wind shear had kept most of Joaquin's thunderstorm activity (convection) south of its center of circulation, but that changed Tuesday afternoon as thunderstorms developed over the circulation center.
Look back at Tropical Storm Erika:
Air Force reconnaissance aircraft flew into the storm as that happened. The crew reported a central barometric pressure of 990 millibars – considerably lower than most forecast models had expected this early in Joaquin's evolution – signaling a robust tropical cyclone gaining strength. (Lower central pressure generally corresponds to higher wind speeds in tropical cyclones.)
Regardless of the ultimate outcome of Joaquin's path, portions of the East Coast will still see multiple impacts from the evolving large-scale weather pattern, including flooding rainfall, gusty winds, high surf, beach erosion and some coastal flooding. Click the link below for more information on that story.
In addition, Joaquin could move far enough southwest to bring rain and wind impacts to the northeast Bahamas during the latter half of the week. Interests there should follow the progess of Joaquin very closely.
Here's what we know about Joaquin:
- Tropical Storm Joaquin's center is located about 405 miles east of the northwestern Bahamas as of 5 p.m. EDT Tuesday.
- Maximum sustained winds jumped to 65 mph Tuesday afternoon.
- As wind shear over the storm lessens, Joaquin should strengthen further and may become a hurricane Tuesday night or Wednesday.
- This system is moving slowly to the west-southwest and this is expected to continue over the next day or so, before turning north Friday into Saturday.
- Watches or warnings may be issued Tuesday evening for parts of the Bahamas, which could see rain and wind impacts from Joaquin depending on how far southwest the storm moves.
- While the official National Hurricane Center five-day forecast track no longer includes the U.S. East Coast, Joaquin may directly or indirectly affect the East Coast late this weekend or early next week, and a landfall cannot be ruled out beyond the five-day forecast window.
- Moisture and/or energy associated with Joaquin could enhance rainfall along the cold front in the Northeast late this week. Regardless, the East Coast will see significant impacts from the larger scale weather pattern taking shape.
- Tropical Depression Eleven strengthened into Tropical Storm Joaquin Monday night after forming Sunday evening.