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Category 3 Irene Approaches The Carolina Coastline

By: Dr. Jeff Masters, 6:19 AM GMT on August 26, 2011

As of 200AM EDT, Hurricane Irene was located at 28.7N, 77.3W, 460 miles south-southwest of Cape Hatteras. It was moving north at 14 mph with maximum sustained winds of 115 mph, making it a Category 3 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 942 mb. Outside of the US, hurricane warnings are still in effect for Grand Bahama and the Abaco islands. In the US, hurricane warnings are in effect for the coast of North Carolina from the Little River inlet north to the Virginia border. Hurricane watches are in effect from the NC/Virginia border north to Sandy Hook, New Jersey. Figure 1 shows the hurricane and tropical storm watches and warnings for Irene. Remember, a hurricane warning means hurricane conditions are expected, and tropical storm force winds will occur within 36 hours. A hurricane watch means that hurricane conditions are possible and tropical storm force winds are expected within 48 hours.

To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. 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 1215AM EDT, August 26, 2011

Satellite Views
Figure 2 shows that Irene is a large storm, with outflow reaching from Florida to North Carolina. Irene's eye is visible in the infrared imagery.

Figure 2 IR satellite view of Irene taken at 100AM EDT, August 26, 2011

Track Forecast

Irene is forecast to make landfall on the North Carolina coast Saturday afternoon. It will likely be a Category 3 storm, with windspeeds around 115 mph. As Irene moves northwards through the mid-Atlantic region it will weaken considerably. On Sunday, Irene's center will pass through the Tri-State region of New Jersey, New York, and Connecticut, with impacts spread over a wider region due to Irene's size.

Figure 3 Official track forecast of Irene at 11PM EDT, Aug. 25.

Irene and Flooding
Six to ten inches of rain are possible along Irene's track from the Carolinas northward, with 15 inches possible in isolated areas. 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 in eastern Pennsylvania and New Jersey is likely, while flooding along the rest of the northeastern US is possible.

Figure 4 Significant River Flood Outlook issued by HPC.


Tropical storm forces winds will reach the southern North Carolina coast by late Friday, with hurricane force winds arriving Saturday. Within the hurricane warning area in North Carolina, storm surge is expected to be 5-10 feet above ground. This is our storm surge forecast map.

People living on the the east coast of the US from the Carolinas to Cape Cod should closely monitor 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. Irene will be a large storm, impacting areas far from the storm center track.

Dr. Masters will have a new blog entry this morning, and there will be another blog this afternoon. There will be a special online broadcast at 430PM with Shaun Tanner, Tim Roche, Dr. Masters, Angela Fritz and me. Please email any questions you have to broadcast@wunderground.com. We will be taking phone calls at 415-983-2634. I'll be back with another blog entry late tonight.

Thanks for reading,

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.