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WFO MHX Coastal Flood Program

WFO MHX Coastal Flood Program. What is Coastal Flooding?. NATIONAL WEATHER SERVICE INSTRUCTION 10-320

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WFO MHX Coastal Flood Program

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  1. WFO MHX Coastal Flood Program

  2. What is Coastal Flooding? NATIONAL WEATHER SERVICE INSTRUCTION 10-320 “Coastal flooding is the inundation of people, buildings, and coastal structures on land at locations that, under normal conditions, are above the level of high tide. This flooding may impact the immediate oceanfront, gulfs, bays, back bays, sounds, tidal portions of river mouths and inland tidal waterways.” Coastal flooding is categorized into Minor, Moderate, or Major/Severe

  3. Coastal Flood Categories MINOR — nuisance coastal flooding of locations adjacent to the shore. Minor beach erosion can occur. Minor coastal flooding is not expected to close roads or do any major structural damage to homes and other buildings. MODERATE — more substantial coastal flooding, threatening life and property. Some roads may become impassable due to flooding. Moderate beach erosion will occur along with damage to some homes, businesses, and other facilities. MAJOR/SEVERE — a serious threat to both life and property. Numerous roads will likely become flooded. Many homes and businesses along the coast will receive major damage. People should review safety precautions and prepare to evacuate if necessary. Major beach erosion is also expected.

  4. Coastal Flood Watches, Warnings and Advisories • For water levels expected to rise 4 feet (moderate flooding threshold) or more above normal, Coastal Flood Watches and Warnings will be issued. • A Watch is issued 12 to 48 hours in advance of the coastal flooding. • A Warning is issued when coastal flooding is expected within 12 to 24 hours. • A Coastal Flood Advisory will be issued for minor events, generally 2 - 4 feet above normal.

  5. Coastal Flood Warning URGENT - IMMEDIATE BROADCAST REQUESTED COASTAL HAZARD MESSAGE NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC 419 PM EST TUE JAN 17 2006 NCZ103-180730- /O.UPG.KMHX.CF.A.0001.060118T0300Z-060118T2200Z/ /O.NEW.KMHX.CF.W.0001.060117T2119Z-060118T2100Z/ OUTER BANKS DARE- 419 PM EST TUE JAN 17 2006 ...COASTAL FLOOD WARNING IN EFFECT UNTIL 4 PM EST WEDNESDAY... THE NATIONAL WEATHER SERVICE IN NEWPORT/MOREHEAD CITY HAS ISSUED A COASTAL FLOOD WARNING...WHICH IS IN EFFECT UNTIL 4 PM EST WEDNESDAY. A STRONG COLD FRONT WILL APPROACH FROM THE WEST OVERNIGHT AND MOVE OFFSHORE EARLY WEDNESDAY. SOUTH WINDS ARE EXPECTED TO INCREASE TO 40 TO 50 MPH ALONG THE COAST TONIGHT...BECOMING SOUTHWEST EARLY WEDNESDAY...AND WEST BY AFTERNOON. THESE STRONG WINDS WILL INCREASE WATER LEVELS OVER THE NORTHERN PORTION OF THE PAMLICO SOUND. MODERATE FLOODING...WITH WATER LEVELS UP TO 4 FEET ABOVE NORMAL...WILL BE POSSIBLE OVER ROANOKE ISLAND...AND THE SOUND SIDE OF THE OUTER BANKS FROM SOUTHERN SHORES TO RODANTHE. AT THE PRESENT TIME IT APPEARS THE HIGHEST WATER LEVELS WILL OCCUR LATE TONIGHT AND WEDNESDAY MORNING. A COASTAL FLOOD WARNING MEANS THAT FLOODING IS OCCURRING OR IMMINENT. COASTAL RESIDENTS IN THE WARNED AREA SHOULD BE ALERT FOR RISING WATER...AND TAKE APPROPRIATE ACTION TO PROTECT LIFE AND PROPERTY.

  6. Coastal Flood Forecasting Techniques and Tools

  7. Soundside Coastal Flooding wind vs surge matrix(small tidal influence)

  8. Pamlico County • Northeast, East and Southeast Winds • Flooding across entire eastern half of county. • Roads flooded adjacent to Neuse Rivers and Pamlico Sound in: • Hobucken • Oriental • Vandemere • Whortonville

  9. Pamlico County • Northeast, east, and southeast winds will raise water levels. NE to E are the greatest impacts. Nearly the entire eastern section of the county and most roads flood as water levels begin to rise. • All of the county east of a line from Oriental to Stonewall to Hollyville (Cash Corner) has an elevation of less than 10 ft MSL. Alliance, Bayboro, and Arapahoe all have no flooding problems. • Hobucken – 4 ft surge cuts off road of escape across inland waterway and a 2 ft tide covers some sections of the road from Lowland. • Oriental – floods with NE to SE winds. Minor 3.5’, significant 5 ft. • Vandemere – Floods with beginning at 4 ft surge with east winds. Minor 3.5 ft, significant 5 ft. • Stonewall – minor 5 ft, significant 8 ft.

  10. Pamlico County (storm surge height vs coastal flood categories)

  11. Soundside Slosh Effect • Occurs when strong winds rapidly shift direction. • Typically occurs with tight compact circulations associated with tropical storms. • With strong easterly winds, water initially produces very high water rises on western side of sound with flooding of mainland counties. • Rapid wind shift to west water will quickly slosh to eastern side of sound and flood sound-side OBX. • Soundside OBX flooding usually occurs 1-2 hrs after wind shift. • Hurricane Emily produced water levels 9 ft above normal on soundside OBX as it hooked out to sea near Hatteras.

  12. South of Oregon Inlet • West and Northwest winds will push water from Pamlico Sound into the county • Slosh affects lead to rapid sound side flooding • Sound side areas from Hatteras Village to Rodanthe • Salvo • Frisco • Hatteras Village Outer Banks Dare Rodanthe Frisco Hatteras Village Buxton

  13. Oceanside Coastal Flooding wind vs surge matrix

  14. Northern Outer Banks Oceanside Flooding Kitty Hawk – especially MP 3-4 South Nags Head – MP 16-18 Rodanthe

  15. Rodanthe • Rodanthe S-Curves Rodanthe

  16. Hatteras Village - Frisco • 2003 Isabel Breach Frisco Hatteras Village

  17. Extratropical Surge Guidancewww.weather.gov/mdl/etsurge/

  18. Storm Surge Guidance

  19. MDL ET Surge Graph Key • MLLW, MSL, MHHW, and MAT. These stand for the Mean Lower Low Water, Mean Sea Level, Mean Higher High Water, and Maximum Astronomical Tide. The thought is that there is probably flooding if the total water level crosses MAT. • Red observation line. If there is no red line, then either Tides Online does not have data for that station, or there has been a communications break down. • Green Tide line. This is the astronomical tide at every hour. • Gold storm surge curve, difference between astronomical tide and water level. • Blue curve, simply the observation - (tide + storm surge). • Black forecast curve. This is what we are really interested in, which is the total water level created by adding the 5 day average anomaly to the predicted tide, and the predicted storm surge.

  20. Experimental Extratropical Storm Surge Forecast http://www.opc.ncep.noaa.gov

  21. SLOSH Tropical Storm Surge Guidance

  22. ADCIRCAdvanced Circulation Model

  23. Water Level Monitoring • NOS Tide Gauges • River Gauges/APHS/Hydroview • NC ST RTRM (Neuse River) • Staff Gauges • WebCams • Storm Surge Inundation Mapping

  24. National Ocean Service Tide Gauges

  25. NOS Gauge - Duck NC

  26. River Gages/AHPS

  27. River Gauge AHPS - Washington

  28. NC State Neuse River Network

  29. NCST Neuse River Monitoring Cherry Point

  30. NCDOT Ferry Staff Gauges

  31. Cherry Branch – Neuse River

  32. Webcams

  33. Web Cam – S curves

  34. Webcam – Oriental (slide show)

  35. Inundation Mappingwww.hurricanetrack.com

  36. WFO MHX Coastal Flood Program • Thanks for listening! • Any questions? • Brian.Cullen@noaa.gov

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