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Category 2 Earl Passes the Outer Banks, Heads for Cape Cod

By: Dr. Jeff Masters, 5:11 AM GMT on September 03, 2010

Hi, Dr. Rob Carver with your evening blog update. Earl continues to weaken, as he is now a category 2 storm.

As of 11PM EDT, Earl is a Category 2 storm with sustained winds of 105 mph. From the advisory, Earl is located at 33.8 N, 74.4 W, 115 miles south-southeast of Cape Hatteras, NC and 570 miles south-southwest of Nantucket, MA. On average, Earl is currently moving north-northeast at 18 mph. Data from hurricane hunter flights show that Earl's pressure has risen, the minimum central pressure is now 951 mb. Satellite data (Fig. 1), WSR-88D radar data (Fig. 2) and the hurricane hunters describe Earl's eyewall as being open in the west, which is to be expected for a weakening storm.

Fig. 1 Estimated rainfall-rate of Earl taken at 11PM EDT 2 September 2010. Image courtesy of the Naval Research Lab

Fig. 2 Reflectivity image of Earl taken at midnight 3 September 2010. Doppler velocity scan showing the large-scale rotation of the storm.

Even though Earl's winds are declinling, he still covers a very large area. Hurricane force winds extend 70 miles from the storm center and tropical storm force winds can be found 205 miles away. 12 foot seas extend at least 220 nmi from the center in all directions and may reach out to 420 nmi in the southeast quadrant of the storm. The most recent estimate (930PM EDT) of Earl's integrated kinetic energy is 91 TJ, with a wind impact of 3.0 out of 6 and a storm surge impact of 4.7 out of 6.

Track/Intensity Forecast

NHC has not really altered their track forecast for this update. The track has been adjusted to the east by a small amount. After Earl is captured by the trough in the jet stream Thursday, he will complete his turn to the northeast and start moving more rapidly. At the same time, shear from the trough and cooler surface waters will furthur weaken Earl. This forecast weakening calls for Earl to be a category 1 storm when he passes Cape Cod on Friday and when he makes landfall in Nova Scotia Saturday.

Right now, it looks like Earl is staying out to sea as it passes the Outer Banks. It will pass by the mouth of the Chesapeake Bay Friday morning. Tropical-storm force winds will start in Nantucket, MA Friday afternoon, and hurricane-force winds will arrive by late Friday evening.

Winds Forecast
NHC puts out a very useful wind probability forecast. Cape Hatteras has a 99% chance of tropical-storm (TS) force winds, and according to our M ETAR history page, the winds only need to pick up slightly. Besides the Outer Banks, Nantucket, MA looks to be the place most likely effected by Earl, there is a 90% chance of TS force winds. With the eastward shift in Earl's track, the area of 30% chance of TS force winds doesn't go as far inland as it did Wednesday night.

Current Watches and Warnings
Hurricane warnings are valid for the coast from Bogue Inlet, NC to the NC/VA border and for eastern MA from Westport to Hull. Hurricane watches are in effect from the NC/VA border to Cape Henlopen, DE and for Nova Scotia from Medway Harbour to Digby. Tropical storm warnings and watches cover the Atlantic coast from Cape Fear to Nova Scotia.

For the latest information on watches and warnings for Earl in the US, visit our Tropical Alerts page. For people interested in watches and warnings for New Brunswick and Nova Scotia, visit Environment Canada's watches and warnings page.

The primary threats from Earl are going to be surf, wind, and storm surge. The wind threat is going to be greatest in eastern MA since the passage of Earl is expected to bring hurricane-force winds to Nantucket. Eastern Long Island will have the greatest winds outside of MA, with estimated winds of 30-40 mph, with gusts to 55 mph. This is expected to bring down trees and cause trouble for older mobile homes. Elsewhere between the Outer Banks and New England, expect weak tropical storm force winds (less than 35 mph).

For storm surge, 1-2 feet are expected along the NJ coast, with 3 feet possible in some locations. Eastern Long Island may have 2-4 feet surges along the Long Island Sound and Petonic and Gardines Bay. The Boston NWS office is not concerned about storm surge, but they note 20-25 foot seas are possible off Nantucket.

Since Earl is going to be moving quickly, flooding from rain should be confined to poor drainage areas and urban area street flooding.

For more localized info, check out NWS's Hurricane Local Statements or our severe weather page.

What to do
It's time to batten down the hatches. People living in New England have less than 18 hours to finish their preparations. Be sure to listen to local media for statements from emergency management agencies and the local NWS.

Next update
Dr. Jeff Masters will have an update Friday morning.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.