WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Hurricane Arthur Intensifying as it Approaches North Carolina
Hurricane warnings are flying for most of the North Carolina coast as Hurricane Arthur accelerates north-northeastwards. Arthur is the first Atlantic July hurricane since Hurricane Alex of 2010, and arrives over a month prior to the typical August 10 arrival of the season's first hurricane. Heavy rains from the intensifying hurricane have already begun this morning along the southern North Carolina coast at Wilmington, and will spread northeastwards along the North Carolina coast today. Long-range radar out of Wilmington shows that Arthur has developed an imposing area of heavy rains, and is expanding in size. The Hurricane Hunters were in Arthur this morning, and an Air Force aircraft measured a minimum pressure of 983 mb at 7:03 am EDT. At 7:36 am EDT, a NOAA aircraft measured 82 mph winds at the surface using a dropsonde, but stronger winds of 109 mph were recorded just 110 meters above the surface. The Air Force aircraft noted that the eyewall had a gap in the southwest quadrant, so Arthur is still having issues with dry air infiltrating its core. Satellite loops on Thursday morning showed a much more impressive storm than yesterday, with a large area of intense thunderstorms with cold cloud tops, and an intermittent eye. An excellent outflow channel has developed on the east side, but outflow is still restricted on the west side, where dry air is interfering with the storm. Wind shear continued to be a light 5 - 10 knots. Arthur is riding along the axis of the Gulf Stream, taking advantage of the narrow ribbon of very warm waters the current carries.
Figure 1. Long-range radar out of Wilmington, North Carolina at 11:14 am EDT July 3, 2014.
Forecast for Arthur
Given the Category 2 winds of 109 mph that the Hurricane Hunters found just above the surface, we can expect that these winds will begin to mix down to the surface later today as the storm continues to organize, bringing the storm to the threshold of Category 2 strength: 95 - 100 mph winds. With the eyewall still showing gaps due to dry air infiltration, rapid intensification into a Category 3 hurricane appears unlikely. The 12Z Thursday run of the SHIPS model predicted that wind shear will remain light to moderate, 5 - 15 knots, between now and Friday morning, then rise steeply. The model predicted a 21% chance of rapid intensification--a 30 mph increase in winds in 24 hours, and I put the odds Arthur becoming a Category 3 or stronger storm at 20%. The four main intensity models used by NHC--the LGEM, SHIPS, GFDL, and HWRF--continue to be in remarkable agreement, predicting that Arthur will be a borderline Category 1/Category 2 hurricane with 95 - 100 mph winds at 8am EDT on Friday. The models are also in good agreement on the track of Arthur. A trough of low pressure passing to the north accelerate the storm northeastwards Thursday night and Friday, and the Outer Banks of North Carolina are at risk of a direct hit. The 11 am EDT Thursday wind probability forecast from NHC gave Cape Hatteras a 72% chance of experiencing hurricane-force winds, and Morehead City a 51% chance. The 00Z Thursday runs of our top two track models, the GFS and European (ECMWF), showed the eye of Arthur passing over North Carolina's Outer Banks between 3 am - 7 am EDT Friday, July 4.
Figure 2. Screenshot of the experimental NHC Potential Storm Surge Flooding Map for the North Carolina Outer Banks, generated at 5 am EDT Thursday July 3. Inundation of the land to a depth of 3 - 6 feet (yellow colors) has a 10% chance of occurring near the vulnerable section of Highway 12 near Rodanthe, and at the Bonner Bridge over Oregon Inlet. The bridge was forced to close in December 2013 for 12 days of emergency repairs due to dangerous scouring around the support pillars. The image was generated using using NOAA's Probabilistic Hurricane Storm Surge (P-Surge 2.0) model. P-Surge 2.0 uses multiple runs of the NWS Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model to create an ensemble of possible inundations, by varying the hurricane's landfall location, intensity, size, forward speed, and angle of approach to the coast. The image shows where the storm surge has a 10% chance of inundating the coast at 3, 6, and 9 feet above ground level. The model does not take into account wave action, freshwater flooding from rainfall, and breaching or overtopping of levees.
North Carolina's Outer Banks at risk of getting cut off
Hurricane Sandy pummeled the Outer Banks of North Carolina in late October 2012, causing $13 million in damage, and wiping out the protective dunes along a long section of coast. Coastal Highway 12 that connects North Carolina's Outer Banks to the mainland was cut for nearly two months, until repairs were completed in December 2012. Residents of the Outer Banks were forced to take a 2-hour ferry ride to get to the mainland when Highway 12 was cut. Nor'easters and storms repeatedly caused overwash and road damage to NC-12 during the winter of 2012 - 2013, but a temporary barrier was erected in 2013 that has been successful at keeping the road open during the past year (though minor overwash occurred during storms on October 10, 2013 and March 18, 2014, and Tropical Storm Andrea closed the road to all but 4-wheel drive vehicles on June 7, 2013.) Emergency post-Sandy federal funding of $20.8 million was secured to construct a barrier designed to last three years, but the project is up for bid, and has not yet begun.
Figure 3. Top: Coastal Highway 12 in North Carolina, which connects the Outer Banks to the mainland, as seen at 5:43 pm EST on Tuesday, November 13, 2012, near Rodanthe. Hurricane Sandy wiped out most of the protective dunes along the coast, allowing the ocean to directly pound the road during high tide. Bottom: the same view as seen in June 2014, after a temporary repair was made to the beach destroyed by Sandy. Image credit: North Carolina DOT. Live views of Highway 12 road cams are available from the NCDOT web site.
NC 12 is once again in danger of being cut, due to the storm surge and wave action of Arthur. Also at risk is Highway 12's Bonner Bridge over Oregon Inlet on the Outer Banks, which was forced to close for 12 days in December 2013 for emergency repairs, when scans revealed excessive sand erosion (scour) around some of the support columns. The bridge will be subjected to a double storm surge from Arthur--one when the hurricane approaches, as onshore winds drive water into Pamlico Sound, and another as the storm passes, when the winds will reverse to offshore, driving the accumulated water out of the sound and back into the ocean. It is often this reverse surge that causes the greatest erosion to barrier islands. With sea level rise steadily increasing the damage that storms like Arthur can do to the vulnerable Highway 12, some very expensive long-term solutions are being studied for keeping Highway 12 open.
Links
Wrightsville Beach, NC webcam
Carolina Beach, NC webcam
Jeff Masters
Figure 1. Long-range radar out of Wilmington, North Carolina at 11:14 am EDT July 3, 2014.
Forecast for Arthur
Given the Category 2 winds of 109 mph that the Hurricane Hunters found just above the surface, we can expect that these winds will begin to mix down to the surface later today as the storm continues to organize, bringing the storm to the threshold of Category 2 strength: 95 - 100 mph winds. With the eyewall still showing gaps due to dry air infiltration, rapid intensification into a Category 3 hurricane appears unlikely. The 12Z Thursday run of the SHIPS model predicted that wind shear will remain light to moderate, 5 - 15 knots, between now and Friday morning, then rise steeply. The model predicted a 21% chance of rapid intensification--a 30 mph increase in winds in 24 hours, and I put the odds Arthur becoming a Category 3 or stronger storm at 20%. The four main intensity models used by NHC--the LGEM, SHIPS, GFDL, and HWRF--continue to be in remarkable agreement, predicting that Arthur will be a borderline Category 1/Category 2 hurricane with 95 - 100 mph winds at 8am EDT on Friday. The models are also in good agreement on the track of Arthur. A trough of low pressure passing to the north accelerate the storm northeastwards Thursday night and Friday, and the Outer Banks of North Carolina are at risk of a direct hit. The 11 am EDT Thursday wind probability forecast from NHC gave Cape Hatteras a 72% chance of experiencing hurricane-force winds, and Morehead City a 51% chance. The 00Z Thursday runs of our top two track models, the GFS and European (ECMWF), showed the eye of Arthur passing over North Carolina's Outer Banks between 3 am - 7 am EDT Friday, July 4.
Figure 2. Screenshot of the experimental NHC Potential Storm Surge Flooding Map for the North Carolina Outer Banks, generated at 5 am EDT Thursday July 3. Inundation of the land to a depth of 3 - 6 feet (yellow colors) has a 10% chance of occurring near the vulnerable section of Highway 12 near Rodanthe, and at the Bonner Bridge over Oregon Inlet. The bridge was forced to close in December 2013 for 12 days of emergency repairs due to dangerous scouring around the support pillars. The image was generated using using NOAA's Probabilistic Hurricane Storm Surge (P-Surge 2.0) model. P-Surge 2.0 uses multiple runs of the NWS Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model to create an ensemble of possible inundations, by varying the hurricane's landfall location, intensity, size, forward speed, and angle of approach to the coast. The image shows where the storm surge has a 10% chance of inundating the coast at 3, 6, and 9 feet above ground level. The model does not take into account wave action, freshwater flooding from rainfall, and breaching or overtopping of levees.
North Carolina's Outer Banks at risk of getting cut off
Hurricane Sandy pummeled the Outer Banks of North Carolina in late October 2012, causing $13 million in damage, and wiping out the protective dunes along a long section of coast. Coastal Highway 12 that connects North Carolina's Outer Banks to the mainland was cut for nearly two months, until repairs were completed in December 2012. Residents of the Outer Banks were forced to take a 2-hour ferry ride to get to the mainland when Highway 12 was cut. Nor'easters and storms repeatedly caused overwash and road damage to NC-12 during the winter of 2012 - 2013, but a temporary barrier was erected in 2013 that has been successful at keeping the road open during the past year (though minor overwash occurred during storms on October 10, 2013 and March 18, 2014, and Tropical Storm Andrea closed the road to all but 4-wheel drive vehicles on June 7, 2013.) Emergency post-Sandy federal funding of $20.8 million was secured to construct a barrier designed to last three years, but the project is up for bid, and has not yet begun.
Figure 3. Top: Coastal Highway 12 in North Carolina, which connects the Outer Banks to the mainland, as seen at 5:43 pm EST on Tuesday, November 13, 2012, near Rodanthe. Hurricane Sandy wiped out most of the protective dunes along the coast, allowing the ocean to directly pound the road during high tide. Bottom: the same view as seen in June 2014, after a temporary repair was made to the beach destroyed by Sandy. Image credit: North Carolina DOT. Live views of Highway 12 road cams are available from the NCDOT web site.
NC 12 is once again in danger of being cut, due to the storm surge and wave action of Arthur. Also at risk is Highway 12's Bonner Bridge over Oregon Inlet on the Outer Banks, which was forced to close for 12 days in December 2013 for emergency repairs, when scans revealed excessive sand erosion (scour) around some of the support columns. The bridge will be subjected to a double storm surge from Arthur--one when the hurricane approaches, as onshore winds drive water into Pamlico Sound, and another as the storm passes, when the winds will reverse to offshore, driving the accumulated water out of the sound and back into the ocean. It is often this reverse surge that causes the greatest erosion to barrier islands. With sea level rise steadily increasing the damage that storms like Arthur can do to the vulnerable Highway 12, some very expensive long-term solutions are being studied for keeping Highway 12 open.
Links
Wrightsville Beach, NC webcam
Carolina Beach, NC webcam
Jeff Masters
Tropical Storm Arthur - Infrared
First Bands, Part 2: Tropical Storm Arthur
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.