Tropical Storm Isaias strengthened slightly on Sunday afternoon and a hurricane Watch was issued for a portion of the Carolinas’ coast.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Isaias was located at latitude 27.8°N and longitude 79.8°W which put it about 65 miles (105 km) southeast of Cape Canaveral, Florida.  Isaias was moving toward the north-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 994 mb.

A Hurricane Watch was issued for the portion of the coast from South Santee River, South Carolina to Surf City, North Carolina.  A Tropical Storm Warning was in effect for the portion of the coast from Sebastian Inlet, Florida to Ocracoke Inlet, North Carolina.  A Tropical Storm Watch was issued for the portion of the coast from Ocracoke Inlet, North Carolina to Watch Hill, Rhode Island including Albemarle Sound, Pamlico Sound, Long Island and Long Island Sound.

Tropical Storm Isaias strengthened a little on Sunday afternoon, but the middle level center of circulation was displaced to the northeast of the surface center.  An upper level trough over the central U.S. extended to the Gulf of Mexico and it was producing westerly winds which were blowing toward the top of Isaias.  Those winds were causing moderate vertical wind shear and they were also causing the displacement of the middle level center of Tropical Storm Isaias.  Thunderstorms continued to develop around the middle level center of circulation.  Those storms generated upper level divergence which pumped mass away to the east of the tropical storm.  Winds to tropical storm force extended out 115 miles (185 km) on the eastern side of Isaias.  Tropical Storm force winds only extended out 65 miles (105 km) on the western side of the circulation.

Tropical Storm Isaias will move through an environment somewhat favorable for intensification during the next 24 hours.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  The direction of the upper level winds will shift to the southwest as the upper level trough approaches Tropical Storm Isaias.  That will cause the vertical wind shear to decrease.  Tropical Storm Isaias could strengthen into a hurricane, if the shear decreases.

Tropical Storm Isaias will move around the western end of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Isaias toward the north during the next 12 hours.  The upper level trough will steer Tropical Storm Isaias toward the northeast on Monday.  On its anticipated track Isaias will approach the coast of the Carolinas near Myrtle Beach, South Carolina on Monday night.  Isaias could be a hurricane when it makes landfall.  It will bring gusty winds and locally heavy rain to extreme eastern South Carolina, eastern North Carolina and coastal Virginia.  Isaias will cause a storm surge of 3  to 6 feet (1 to 2 meters) near and to the east of where the center makes landfall.  Tropical Storm Isaias will continue to move up the East Coast toward New England.