North Carolina will receive hurricane warnings (a significant notch above watches) within a few hours, as the forecasted path for earl shift a bit to the west than previously thought and b) becomes less certain.
From NOAA/Hurricane Prediction Center:
North of Surf City North Carolina to Parramore Island Virginia including the Pamlico and Albermale Sounds
Tropical Storm Warning for San Salvador
Tropical Storm Watch for North Carolina Coast from Cape Fear to Surf City
You can expect, approximately, for the first of these watches to be upgraded to a warning soon.
Thursday night or Friday Morning, Earl, which is a physically very large hurricane and a fairly strong one, will be located off the North Carolina coast and that coastal region will be experiencing hurricane force winds. Over the subsequent two days, over the weekend, Earl will bring tropical storm or hurricane force winds to parts of the US east coast as it speeds up and weakens, moving towards the north by northwest, with what is left of the center hitting or even going west of Nova Scotia. The storm may well still be a hurricane as it comes dangerously close to, or directly impacts, Cape Cod.
The current forecast indicates that there is a 40 % chance or less that part of the Carolina coast will be impacted by hurricane force winds, but the forecast has been shifting to the west. Do not be surprised if the forecasts issued later today or early tomorrow morning show a better than even chance of this happening. But also, be wary of forecasts of forecasts!
Similarly, there is about a 30% chance or less of hurricane force winds hitting Cape Cod, which juts out into the Atlantic forming the southern margin of Massachusetts Bay, but the forecasts are less certain and shifting as we speak.
Earl is currently a Category Three hurricane and is not expected to change to a Category Four. The models indicating Earl’s future strength indicate on one hand a stable energy level or slight increase (based on some information) or a weakening (based on different information) over the next day or two. As Earl affects the Carolina coast, it will probably have hurricane force winds of over 100 miles per hour as a Category Two hurricane, but these winds will likely be pretty far off shore. As Earl reaches the vicinity of Cape Cod it will not be much weakened, and will likely remain a Category Two hurricane, according to current predictions.
This could either be a bad storm or a bad scenario for the east coast. A hurricane that plows directly into the continent dissipates very quickly. A hurricane that stays off the coast and grazes it may cause flooding condition over a very large area, hit a few places with very bad winds, and although there will not be a storm surge if it stays off the coast, very high surf over several days can do serious damage to barrier islands and other coastal landforms.
At the moment, sea surface temperatures off the Atlantic are quite warm, as usual, though they are not as warm as they ae in the gulf. In fact, Western Atlantic SST’s are anomalously high this year (i.e., in a given spot, warmer than expected though again, not warmer than the Gulf of Mexico, which is always warm this time of year, but not anomalously so right now). This will keep Earl strong while it moves roughly in parallel with the coastline.
Meanwhile, Fiona is a tropical storm and will remain so as it reorients to the north and blows out to sea. Fiona is expected to be dissipated by early next week or so.
Out in the middle of the Atlantic there is a reasonably well organized and highly energetic system blowing up, which has a very high probability of being the next named system. If so, this will likely happen before the weekend.