Tropical Storm Joaquin strengthens east of Bahamas; East Coast landfall potential still very uncertain

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Stormy Week for East Coast

By WEATHER.com

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.

MORE: Expert Analysis | Hurricane Central

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:

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Tropical Storm Erika
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Tropical Storm Joaquin strengthens east of Bahamas; East Coast landfall potential still very uncertain
A trio of fishermen leave the pier at Clearwater beach in a driving rain as a squall from the remains of tropical storm Erika moves into the area Monday, Aug. 31, 2015, in Clearwater, Fla. (AP Photo/Chris O'Meara)
A beach goer leaves the pier on Clearwater beach as a squall from the remains of tropical storm Erika approaches Monday, Aug. 31, 2015, in Clearwater, Fla. The remnants of the storm is predicted to drop between 3-5 inches on the sunshine state. (AP Photo/Chris O'Meara)
A worker goes out to bring in beach chairs in a heavy rain storm associated with a squall from the remains of tropical storm Erika, Monday, Aug. 31, 2015, in Clearwater, Fla. (AP Photo/Chris O'Meara)
Residents work to salvage personal items from the site of a mudslide in rain-soaked Montrouis, Haiti, Saturday, Aug. 29, 2015. Erika dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, authorities said. In Haiti, one person died in the mudslide just north of Port-au-Prince. (AP Photo/Dieu Nalio Chery)
Commuters on their way to the capital are taxied to a bus, after they were temporarily stranded in Montrouis, Haiti, Saturday, Aug. 29, 2015, the site of a mudslide triggered by Tropical Storm Erika. The deadly storm dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, and parts of Haiti, authorities said. (AP Photo/Dieu Nalio Chery)
Shoes are collected in a standing fan grill, salvaged from a home damaged by a mudslide triggered by Tropical Storm Erika, in Montrouis, Haiti, Saturday, Aug. 29, 2015. Erika dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, and parts of Haiti, authorities said. (AP Photo/Dieu Nalio Chery)
Seven-year-old Redefine Aristile leaps over a puddle where a mudslide partially submerged several homes, in rain-soaked Montrouis, Haiti, Saturday, Aug. 29, 2015. Tropical Storm Erika dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, and parts of Haiti authorities said. (AP Photo/Dieu Nalio Chery)
Residents salvage a mattress from a home partially submerged in mud from a mudslide triggered by Tropical Storm Erika, in Montrouis, Haiti, Saturday, Aug. 29, 2015. Erika dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, and parts of Haiti authorities said. (AP Photo/Dieu Nalio Chery)
A man is given a helping hand as residents evacuate from the site of a mudslide, in rain-soaked Montrouis, Haiti, Saturday, Aug. 29, 2015. Erika dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, and parts of Haiti. (AP Photo/Dieu Nalio Chery)
Residents salvage personal items after a mudslide triggered by Tropical Storm Erika left it partially submerged, in Montrouis, Haiti, Saturday, Aug. 29, 2015. Erika dissipated early Saturday, but it left devastation in its path on the small eastern Caribbean island of Dominica, and parts of Haiti, authorities said. (AP Photo/Dieu Nalio Chery)
A man walks on the shore against strong winds backdropped by a rough sea as Tropical Storm Erika moves away from the area in Guayama, Puerto Rico, Friday, Aug. 28, 2015. The storm was expected to dump up to 8 inches of rain across the drought-stricken northern Caribbean as it carved a path toward the U.S. (AP Photo/Ricardo Arduengo)
A couple of persons take refuge behind a tree against the strong winds of Tropical Storm Erika, as it approaches Santo Domingo, in the Dominican Republic, Friday, August 28, 2015. Tropical Storm Erika began to lose steam Friday over the Dominican Republic, but it left behind a trail of destruction that included several people killed on the small eastern Caribbean island of Dominica, authorities said. (AP Photo/Tatiana Fernandez)
Workers clean highway gutters as Tropical Storm Erika approaches Santo Domingo, in the Dominican Republic, Friday, August 28, 2015. Tropical Storm Erika began to lose steam Friday over the Dominican Republic, but it left behind a trail of destruction that included several people killed on the small eastern Caribbean island of Dominica, authorities said. (AP Photo/Tatiana Fernandez)
Broken traffic lights and street lamps lay on the ground as the strong winds of Tropical Storm Erika approach Santo Domingo, in the Dominican Republic, Friday, August 28, 2015. Tropical Storm Erika began to lose steam Friday over the Dominican Republic, but it left behind a trail of destruction that included several people killed on the small eastern Caribbean island of Dominica, authorities said. (AP Photo/Tatiana Fernandez)
A couple looks out at a rough sea as Tropical Storm Erika moves away from the area in Guayama, Puerto Rico, Friday, Aug. 28, 2015. The storm was expected to dump up to 8 inches of rain across the drought-stricken northern Caribbean as it carved a path toward the U.S. (AP Photo/Ricardo Arduengo)
Two large navigation buoys hit by strong winds and waves, float near the coast, as Tropical Storm Erika moves away from the area in Guayama, Puerto Rico, Friday, Aug. 28, 2015. The storm was expected to dump up to 8 inches of rain across the drought-stricken northern Caribbean as it carved a path toward the U.S. (AP Photo/Ricardo Arduengo)
A boat sits in shallow water as Tropical Storm Erika passes through New Town, Dominica, Thursday, Aug. 27, 2015. Erika was expected to move near Puerto Rico and the Virgin Islands on Thursday and be near or just north of the Dominican Republic on Friday as it heads toward Florida early next week, possibly as a hurricane. (AP Photo/Carlisle Jno Baptiste)
A man walks on the shore backdropped by a rough sea as Tropical Storm Erika moves away from the area in Guayama, Puerto Rico, Friday, Aug. 14, 2015. The storm was expected to dump up to 8 inches of rain across the drought-stricken northern Caribbean as it carved a path toward the U.S. (AP Photo/Ricardo Arduengo)
A man looks out at a rough sea as Tropical Storm Erika moves away from the area in Guayama, Puerto Rico, Friday, Aug. 28, 2015. The storm was expected to dump up to 8 inches of rain across the drought-stricken northern Caribbean as it carved a path toward the U.S. (AP Photo/Ricardo Arduengo)
A large navigation buoys hit by strong winds and waves, floats near the coast, as Tropical Storm Erika moves away from the area in Guayama, Puerto Rico, Friday, Aug. 28, 2015. The storm was expected to dump up to 8 inches of rain across the drought-stricken northern Caribbean as it carved a path toward the U.S. (AP Photo/Ricardo Arduengo)
Tropical Storm Erika in a satellite image on Aug. 28, 2015. (Photo via NOAA)
A couple walks on a pier under cloudy skies as Tropical Storm Erika approaches the island in Naguabo, Puerto Rico, Thursday, Aug. 27, 2015. Erika was expected to move near Puerto Rico and the Virgin Islands on Thursday and be near or just north of the Dominican Republic on Friday as it heads toward Florida early next week, possibly as a hurricane. (AP Photo/Ricardo Arduengo)
TS Erika is hurting lots of us now esp in #Dominica http://t.co/gtGJtzCo8t
Devastating images out of Dominica as tropical storm Erika slammed the country . http://t.co/7rOjGyRg0N http://t.co/FIYs389p2x
People lets 🙏🏽 4 those caught up in #TropicalStormErika in #Dominica #ThisIsNews #caribbean @SkyNews @BBCBreaking http://t.co/d4lo3RLPZg
Tropical Storm Erika in a satellite image on Aug. 27, 2015. (Photo via NOAA)
This visible image of Tropical Storm Erika was taken from NOAA's GOES-East satellite on Aug. 26 at 7:45 a.m. EDT as it headed toward the Lesser Antilles. (Photo via NASA/NOAA GOES Project)
James Franklin, chief hurricane forecaster, looks at an image of Tropical Storm Erika as it moves westward towards islands in the eastern Caribbean, at the National Hurricane Center, Wednesday, Aug. 26, 2015, in Miami. Tropical storm warnings have been issued for Puerto Rico, the U.S. and British Virgin Islands, and the Leeward islands. (AP Photo/Lynne Sladky)
On Aug. 25 at 2:11 a.m. EDT, GPM passed over the northwestern part of the storm and found heaviest rain falling at a rate of 1.1 inches per hour. (Photo via NASA/JAXA/NRL)
On Aug. 25 at 01:59 UTC, the AIRS instrument aboard NASA's Aqua satellite saw cloud tops around Erika's center were near -63F/-53C, indicating strong thunderstorms. (Photo via NASA/JPL, Ed Olsen)
NOAA's GOES-East satellite captured this visible light image of newborn Atlantic Tropical Storm Erika on August 25 at 7:45 a.m. EDT. (Photo via NASA/NOAA GOES Project)
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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.

MORE: Significant Impacts Likely on East Coast

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.

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