Hurricane Earl

Pre-Landfall 4 | Summary
Posting Date: September 2, 2010, 8:45:00 AM

Hurricane Earl is once again a Category 4 hurricane on the Saffir Simpson Wind Scale. Aircraft reconnaissance reported a significant drop in central pressure last night, which is currently estimated at 932 mb, consistent with Category 4 wind speeds. As of the National Hurricane Center's 8 am advisory, Earl's maximum sustained winds are 145 mph. While convection in the eye wall is somewhat less organized—suggesting that Earl may have reached its peak intensity—it is likely to remain a major hurricane (Category 3 or higher) as it tracks past North Carolina's Outer Banks. The forecast track is largely unchanged, with Earl expected to pass just east of North Carolina's Cape Hatteras late Thursday or early Friday. Thus far, only Hatteras Island has received mandatory evacuation orders, though tourists on neighboring Ocracoke Islands were asked to leave yesterday. A hurricane warning is in effect from Bogue Inlet, North Carolina to the border with Virginia. Hurricane watches are in effect north of the border to Cape Henlopen, Delaware. In Massachusetts, hurricane watches are in effect from Westport to Plymouth, including Martha's Vineyard and Nantucket. The current forecast track continues to keep Earl just offshore—about 60 miles off Cape Hatteras, which is about 20 miles closer than yesterday’s forecast. Further north, a westward shift in the forecast track should now bring Earl about 35 miles from Cape Cod and just 20 miles east of Nantucket. While Earl is expected to maintain hurricane status as it passes New England, it will probably do so at Category 1 or Category 2 strength. It should be noted that the current track keeps onshore properties along the entire coast to the left-hand—and therefore weaker—side of the storm. Given the storm’s significant forward speed, which counteracts the storm’s winds on the left, the wind field is expected to become quite asymmetric. There is still considerable uncertainty associated with the forecast, however, and even a slight wobble to the west could have a significant impact on loss potential. Earl is a large system; on the right-hand side, hurricane force winds currently extend up to 90 miles from the center and tropical storm force winds extend outward up to 230 miles. That extent is smaller on the left-hand side due to the aforementioned asymmetry. The considerable forward speed will also mean that exposed properties should have only brief exposure to Earl’s winds. A slower moving storm could significantly exacerbate damage. North Carolina has a solid history of building code adoption and enforcement. Wind design requirements in coastal regions, including Cape Hatteras' Dare County, are among the most stringent in the country. The extent of any damage caused by Earl will therefore be quite sensitive to just how close the storm tracks to the coast. However, North Carolina is also very vulnerable to storm surge. Large breaking waves of 15 feet or higher are expected along the North Carolina’s Outer Banks, and a storm surge of 2 to 4 feet is possible north of Cape Lookout. This is due to coincide with high tide, which is scheduled to occur at about 2 am on Friday morning. The combination of surge and waves is likely to result in significant erosion and overwash. Storm surge will also be pushed into the lower Chesapeake Bay, raising water levels there by as much as 3 to 5 feet above ground level. Fortunately, low tide along Cape Cod is due at about 2:30 am on Saturday, which coincides with Earl’s closest approach there. Hurricane Earl is currently located about 410 miles south of Cape Hatteras and moving at a forward speed of 18 mph. At 8 am, satellite images show that the eye of Earl has turned to the north. Whether this is a shift in the track as seen in the forecast, or simply a temporary wobble, remains to be seen. The forecast track has Earl making a sustained turn to the north later today, followed by a slow turn to the northeast once the storm moves past Cape Hatteras. By then, Earl should begin to pick up speed and should make its closest approach to Cape Cod and the Islands in the early morning hours on Saturday. Meanwhile, Tropical Storm Gaston became the 7th named storm of the suddenly busy 2010 Atlantic hurricane season on Wednesday. Gaston is currently located 1550 miles east of Lesser Antilles and is moving to the west at 9 mph. Sustained winds are currently estimated at 40 mph and gradual strengthening is forecast during the next 48 hours. The current forecast from the NHC has Gaston achieving hurricane strength on Saturday as it continues a course for the Lesser Antilles. The AIR tropical cyclone team is monitoring both storms closely. Additional information on Hurricane Earl will be made available later today. Information on Gaston will be provided as warranted by events.

Pre-Landfall 4 | Downloads
Posting Date: September 2, 2010, 8:45:00 AM