From Wunderblog:
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 9:20 am EDT July 3, 2014.
Forecast for ArthurPreviously:
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 5 am EDT Thursday wind probability forecast from NHC gave Cape Hatteras a 34% chance of experiencing hurricane-force winds, and Morehead City a 26% 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....MORE
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