Tropical Storm Isaias has changed little in strength for the last two days, but remains just below hurricane strength as it is expected to make landfall tonight near the border of North and South Carolina. Hurricane Warnings are in effect for parts of the Carolina Coast, and it remains a distinct possibility Isaias could regain hurricane strength before moving inland.

As of 5:00 p.m. EDT Monday, Tropical Storm Isaias was centered near 32.0°N 79.4°W, and was moving north-northeastward at about 16 mph. Maximum sustained winds were 60 knots (70 mph), with an estimated minimum pressure of 993 mb. An Air Force Hurricane Hunter aircraft investigated Isaias this morning and suggested that the pressure had risen to near 1000 mb, but the pressure once again began to drop as the aircraft left. Since that time, an eye-like feature has become apparent on radars, though Isaias does not look much better organized on infrared satellite imagery. The aircraft also did not find any flight-level or surface wind observations that supported hurricane intensity. However, another Air Force Hurricane Hunter aircraft is scheduled to investigate Isaias tonight, which should determine if Isaias attained hurricane strength before landfall. Isaias is expected to continue moving north-northeast towards the mid-Atlantic region and eventually New England while maintaining tropical storm status. Baroclinic forcing should result in weakening at a slower rate than normal for tropical cyclones. Isaias should become post-tropical Tuesday night or Wednesday as it accelerates north-northeastward towards eastern Canada. Tropical Storm Warnings stretch all the way from South Carolina to Maine. During Isaias’ lifespan, the entire eastern United States coastline has been under a Hurricane/Tropical Storm Watch or Warning at some point.

A Hurricane Warning is in effect from South Santee River, South Carolina to Surf City, North Carolina. A Storm Surge Watch is in effect from Cape Fear to Oregon Inlet, North Carolina. A Tropical Storm Warning is in effect from the Savannah River to South Santee River, South Carolina, as well as from Surf City, North Carolina northward to Stonington, Maine. Tropical Storm Warnings are also in effect for several bodies of water, including the Pamlico and Albemarle Sounds, the Chesapeake Bay, Tidal Potomac River, Delaware River, Long Island and Long Island Sound, Martha’s Vineyard, Nantucket, and Block Island. A Tropical Storm Watch has also been issued from Stonington to Eastport, Maine. The maximum storm surge for Isaias is expected to be about 3-5 in the Hurricane Warning region, with much of the other warned areas expected to have a storm surge between 1-4 feet. The highest rainfall totals will be in the mid-Atlantic, where rainfall between 3-6 inches is expected by the National Hurricane Center (NHC) with isolated amounts of 8 inches or more possible. Most importantly, the Carolinas are expected to experience minimal hurricane conditions, while the mid-Atlantic United States, and Northeastern United States are expected to experience tropical storm conditions from Isaias. There will not be a large difference in impacts if Isaias officially makes landfall as a hurricane or high-end tropical storm. Isaias will become the fifth tropical storm or hurricane to make landfall in the United States this season – and the climatological peak of the season has not arrived yet.