Irene Briefing from NC State EMC

Hurricane Irene Briefing August 26-28, 2011 Eastern North Carolina Threat Assessment Hurricane Irene National Weather Service Newport/Morehead City, NC Date/Time Created: 8/26/11 500 AM

Overview Based on the current track…

• Hurricane Irene Currently a Category 2 Storm, but forecast to make landfall along Carteret County as a Category 3 on Saturday Afternoon.

• Hurricane Warning for entire area • Flood Watch for entire area (Fri Aft-Sun morning)

Latest Irene Information

8/26/11 SUMMARY OF 500 AM EDT INFORMATION -----------------------------------------------------------------------LOCATION...29.3N 77.2W ABOUT 420 MI SSW OF CAPE HATTERAS NORTH CAROLINA MAXIMUM SUSTAINED WINDS...110 MPH PRESENT MOVEMENT...N OR 360 DEGREES AT 14 MPH

MINIMUM CENTRAL PRESSURE...942 MB...27.82 INCHES

Irene Enhanced IR Satellite Imagery

Satellite image from 345 AM EDT Friday August 26th.

NHC Official Forecast Track

11 PM EDT 25 August - Advisory #23

HURRICANE IRENE MODEL TRACKS

Various model track guidance for Irene Remain clustered on a NC landfall with only a few outliers remaining completely off the coast. There was s very slight east trend in model guidance but not significant at this time.

These tracks should not be used for decision making. These model tracks are shown only to demonstrate the uncertainty associated with the forecast. In addition, these tracks only show the center of the storm. Irene is a . large and dangerous storm. Significant effects will be felt well away from the storm.

Hurricane Force Wind Probability This graphic shows probabilities of sustained (1-minute average) surface wind speeds equal to or exceeding 64 kt...74 mph (hurricane force).

Even lower probabilities represent a significant threat.

Probabilistic Storm Surge The exceedance graphics represents a composite of storm surge values from the NWS SLOSH model for various storm strengths, sizes, and and tracks. It can be used to assess the threat based on confidence level of forecast. The height of surge displayed for a 20% exceedance graphic represents 80% of the most likely solutions combined.

It does not include tide anomalies which must be factored in manually.

To access all Exceedance Graphics visit this website: http://www.weather.gov/mdl /psurge/active.php?Ty=e20 &Th=20&Z=z6

As the storm track becomes more certain, we can begin using a higher percentage exceedance graphic, 20% in this case. This is showing the potential for 7 to 9 feet of pure surge over the western Pamlico Sound basin. Adding an adjustment for tide and potential run off from heavy rains we can adjust this number up to get a higher inundation level on land of up to 9 to 11 feet above ground.

Coastal Flooding Southeast Coast • The highest inundation water levels from storm surge will be along the lower and western Pamlico Sound.

Inundation of 8 to 11 Feet from Storm Surge is possible along the Neuse and Pamlico Rivers and it tributaries. • Storm Surge will produce a range of significant erosion, overwash, and inundation along the coasts of Onslow and Carteret Counties. We expect 5 to 10 feet of water levels above ground on land along the immediate coast and 10 to 15 foot breaking waves on top of that.

Coastal Flooding Outer Banks and Northern Sounds • The highest inundation water levels from storm surge will be along the lower and western Pamlico Sound.

Inundation of 8 to 11 Feet from Storm Surge is possible along the Neuse and Pamlico Rivers and it tributaries. • Storm Surge will produce a range of significant erosion, overwash, and inundation along the Outer Banks including Ocracoke. We expect 5 to 7 feet of water levels above ground on land along the immediate coast and 10 to 15 foot breaking waves on top of that.

Inland Flooding • Rainfall 6-8” over Coastal Plains (W Hwy 17), 8-12” east.

Locally higher amounts possible.

• Significant rain starts this afternoon and lasts through early Sunday Morning.

Heaviest rain Saturday.

• Tributaries to the Pamlico and Albemarle Sound will likely see freshwater backup and flooding.

• Minor to moderate inland river flooding possible.

Major Points for Consideration •Irene is a Category 3 (Three) hurricane and is expected to be a large and dangerous hurricane as it impacts the North Carolina coast on Saturday. Because Irene has such a large and intense circulation, significant impacts are expected well away from the center of circulation and people should not focus only on the track of the center and the area of landfall. Significant effects will be felt well ahead of landfall beginning Saturday Morning.

•Residents of Eastern North Carolina should rush preparedness activities to completion today.

•Confidence of significant impacts is increasing due to model consistency and consensus.

Even if the track varies from the official forecast, the storm will be intense enough and close enough to produce significant impacts across Eastern North Carolina.

•Significant storm surge will produce life threatening coastal flooding. The storm surge combined with heavy rainfall and high astronomical tides will lead to significant coastal road flooding and possible closures, especially along Highway 12 along the Outer Banks and Downeast Carteret County.

•Initial swells from Irene will continue to build with breakers of 15 feet or higher expected

by Saturday. This will produce a high threat of dangerous rip currents along all beaches.

John Cole john.cole@noaa.gov Rich Bandy richard.bandy@noaa.gov For updates call the forecaster on Duty (252) 223-5122 x5

References NWS Newport/Morehead City http://www.erh.noaa.gov/mhx/ National Hurricane Center http://www.nhc.noaa.gov Rainfall Forecasts (QPF) http://www.hpc.ncep.noaa.gov/qpf/qpf2.shtml NWS Newport/ Morehead City Facebook http://www.facebook.com/pages/US-National-Weather-Service-NewportMorehead-CityNC/234322003272452?sk=wall