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Hurricane Irene Weakens on its Approach to North Carolina

By: Dr. Jeff Masters, 7:58 AM GMT on August 27, 2011

As of 300AM EDT, Hurricane Irene was located at 33.7N, 76.5W, 60 miles south of Cape Lookout. It was moving north-northeast at 14 mph with maximum sustained winds of 90 mph, making it a Category 1 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 952 mb.

Hurricane warnings are in effect for the US Atlantic coast from the Little River inlet in North Carolina to Sagamore Beach, Massachusetts. Tornado watches are also in effect for the North Carolina/Virginia/Maryland coast. Figure 1 shows the hurricane, tropical storm, and tornado watches and warnings for Irene. Remember, a hurricane warning means hurricane conditions are expected, and tropical storm force winds (greater than 34 mph) will occur within 36 hours. Tropical storm warning means that tropical storm force winds are expected in the next 36 hours, but hurricane conditions are not. A tropical storm watch means tropical storm force winds are possible within 48 hours.

To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. People living in New York City can find their evacuation zone here or use this map. FEMA has information on preparing for hurricanes. FEMA also has a blog describing their response to Irene.

Figure 1 Map of watches and warnings taken at 225AM EDT, August 27, 2011

Satellite Views
Figure 2 shows that Irene is a large storm, with outflow reaching from South Carolina to Long Island, NY. Irene's eye is not visible.

Figure 2 IR satellite view of Irene taken at 226AM EDT, August 27, 2011

Track Forecast

Irene is forecast to make landfall on the North Carolina coast Saturday morning as a category 1 storm with sustained winds around 90 mph. I believe that Irene's center of circulation will make landfall somewhere between Cape Lookout and Okracoke on the Outer Banks around 9-10 am. Irene should then move roughly north, along the mid-Atlantic coastline before making landfall in western Long Island. However, it is important to not focus solely on the track forecast. Irene is a large storm with a large windfield and equally large areas of storms and showers. It's impact will be felt over a wide swath of the northeastern US.

Figure 3 Official track forecast of Irene at 11PM EDT, Aug. 26.

Irene and Flooding
Six to ten inches of rain are possible along Irene's track from North Carolina north into New England, with 15 inches possible in isolated areas. Radar estimates indicate at least 5 inches have already fallen near Morehead City, NC. As a result, flooding is very likely. The Hydrometeorological Prediction Center (HPC) has issued their Significant River Flood Outlook for the next five days shown in figure 4. HPC thinks that river flooding from the Delmarva peninsula to northwestern Maine is likely, while river flooding in much of the rest of the northeastern US is possible.

Figure 4 Significant River Flood Outlook issued by HPC.


Tropical storm forces winds are occuring at Cape Lookout now, with hurricane force winds expected on the North Carolina coast later today. Use this Wundermap to keep track of how the winds are behaving around the North Carolina coastline. Within the hurricane warning area in North Carolina, storm surge is expected to be 6-11 feet above ground. This is our storm surge forecast map. To see how high the tides are running, NOAA has an excellent page collecting all of the relevant tide gauges.

People living on the the east coast of the US from the Carolinas to Cape Cod should continue monitoring Irene and be in the process of finishing their hurricane preparations. If you have not started preparing for this storm, start immediately. If an evacuation order is given, please follow it, unless it is unsafe to do so. Irene will be a large storm, impacting areas far from the storm center track.


If you're curious about power outages, here are some maps: Dominion Power Outage Map (NC/VA), Progress Energy Outage Map (NC/SC), and NOVEC Outage Map (Northern Virginia).

Dr. Masters will have a new blog entry this morning, and there will be another blog this afternoon. I'll be back with another blog entry late tonight.

Stay safe,

Dr. Rob Carver


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