Monday, September 2, 2019

Dorian to threaten landfall in Carolinas as it slowly moves up coast with damaging winds, heavy rain

By Alex Sosnowski, AccuWeather senior meteorologist




States of emergency have been declared and millions are facing evacuation orders from Georgia to North Carolina as dangerous Hurricane Dorian, a Category 4 storm, continues to grow in size.
After paralleling the Florida Atlantic coast during the first part of this week, Dorian is forecast to turn northeastward and parallel the Carolina coast with battering winds, pounding waves and torrential rain later this week.
AccuWeather meteorologists continue to believe that the center of Dorian will remain east of Florida, but have concerns for a direct strike on the Carolinas and significant impact is in store for coastal areas even if landfall is avoided.
Dorian cat 4 11 am Sept.2
The extent of loss of life and devastation in the northern Bahamas will become more clear in the coming days and weeks. Since Dorian stalled over Grand Bahama during Monday morning, exactly when and how fast the hurricane begins northward motion will affect the timing and exact track of the storm over the balance of the week.
"Even though Dorian is forecast to gradually lose intensity near the eye, the hurricane will gradually grow in girth in the coming days," according to AccuWeather Hurricane Expert Dan Kottlowski.
The cloud shield and spiral bands are already considerably larger in size, when compared to late last week.
Dorian IR Monday Sept. 2, 2019
This infrared image shows Category 5 Hurricane Dorian centered along the northern shore of Grand Bahama Island on Monday, Sept. 2, 2019. (NOAA/GOES-East)
"This means that the areal extent of hurricane and tropical storm conditions will increase as Dorian encounters the United States," Kottlowski said.
This trend began over the Bahamas this past weekend and will continue until the storm moves over the cold waters of the North Atlantic during the upcoming weekend.
Dorian will remain an ordeal for residents, visitors, officials, shipping and cruise interests much of this week along the Atlantic seaboard.
"People are urged to heed evacuation orders when issued," Kottlowski said.
Preparations to protect property need to be completed as soon as possible. Small craft should be secured in port. Cruise and shipping interests should avoid the path of Dorian.
Storm surge and flooding rainfall are the leading causes of fatalities as a hurricane approaches land.
Dorian Impacts 9 am
"People can expect a storm surge of 4-7 feet with locally higher inundation from east-central Florida to southeastern Virginia associated with Dorian," Kottlowski said.
While a waterspout or tornado can occur anywhere in the spiral bands of the hurricane, the greatest risk will be in the northeastern quadrant of the storm as it nears the coast in North Carolina.
What can Florida, southeastern Georgia expect?
Over the Florida Peninsula and southeastern Georgia, people should expect hurricane conditions with strong sustained winds, powerful gusts and torrential rain to develop and spread northward from Interstate 95 eastward, starting near West Palm Beach, Florida, and expanding through Savannah, Georgia, during the first half of this week.
This is expected, even though the center of Dorian is likely to remain offshore.
It is possible that the outer eyewall with Category 2-3 hurricane conditions may brush Cape Canaveral, Florida, on Tuesday, with widespread power outages and considerable urban and coastal flooding.
Dorian Gusts 9 am
The coastal flooding will be greatest around the inlets, back bays and Intercoastal Waterway.
Tropical storm conditions with sporadic power outages and isolated urban flooding are possible as far west as U.S. Routes 27 and 301 in Florida and Georgia.
Rainfall of 4-8 inches with an AccuWeather StormMax™ of 12 inches is forecast for the immediate upper Atlantic coast of Florida and the Georgia coast.
Carolinas, especially North Carolina, still at risk for a direct hit
Depending on exactly how close to the coast the storm tracks, the eye may make landfall along North Carolina's capes Fear, Lookout and Hatteras.
The current AccuWeather RealImpact™ Scale for Hurricanes for Dorian is a 5 on the Bahamas but a 2 on the mainland U.S.
AccuWeather RIS
While the Dorian will lose some intensity due to friction of the large landmass of North America and increasing wind shear, the hurricane may track so close that a slight shift in the track or wobbles with the center may result in multiple landfalls in North Carolina.
Dorian is forecast to slowly weaken along much of its route from Florida waters to North Carolina waters. The hurricane is likely to be a Category 3 off the northeastern Florida coast on Tuesday night and a Category 1 near Cape Hatteras during Friday morning.
During the middle to latter part of this week, the hurricane is forecast to increase its forward speed.
Dorian TS Arrival times 8 am
However, the initial slow movement and ongoing proximity to the coast may be almost as bad as a fast-moving, intense hurricane farther offshore.
Well ahead of the hurricane, stiff northeasterly breezes will create above-normal tides and an uptick in the strength and frequency of rip currents. Large swells propagating outward from the storm will create dangerous surf.
Due to increasing onshore winds, each high tide cycle is likely to be progressively worse in terms of coastal flooding ahead of the day when the storm is nearest.
Rather than lasting a few hours, an entire day's worth of damaging winds, pounding waves, coastal flooding, and heavy rain will take its toll on beach communities and areas over the mainland with exposure to the back bays and coastal rivers.
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Cities, such as Charleston, South Carolina, that experience flooding during high astronomical tides should expect significant flooding as the week progresses. Conditions may not improve until the hurricane has passed to the northeast and winds on the back side are pushing water away from the coast.
However, there will be a period late this week where the Outer Banks is likely to experience flooding on the west side from Pamlico Sound.
Rainfall is likely to be much less intense, when compared to Matthew, over central portions of the Carolinas and somewhat less intense in the coastal areas of the Carolinas.
"But, enough rain is still likely to fall when combined with high tide levels to lead to major flooding in the coastal streams and rivers of the Carolinas and southeastern Virginia," Kottlowski said.
Dorian Rainfall 7 am
"Rainfall of 8-12 inches with an AccuWeather Local StormMax™ of 15 inches is forecast in these areas," he added.
Could the storm hit northeastern US or Atlantic Canada?
While the long-range track is likely to take the storm east of the mid-Atlantic, interests in Cape Cod, Massachusetts, Maine, Nova Scotia and Newfoundland should monitor the progress of Dorian.
Interaction with non-tropical systems in such a way could bring the storm close to eastern New England and perhaps onshore in Canada later this weekend.
Even though Dorian may be a shell of what is has been in the tropics, it would still be a natural force to be reckoned with in terms of rainfall, rough seas and wind.
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