Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Major Hurricane Florence ****Life-threatening conditions expected****
Decision Support Briefing # 11a As of: Noon Wednesday Sept 12, 2018
Prepared by: Steven Pfaff, WCM
What has changed? Slower arrival of TS Force Winds Updated images for the latest advisory
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Situational Overview
Life-threatening storm surge is likely. A Storm Surge Warning remains in effect.
The time for preparations is becoming limited. Continue to preparations for strong winds, storm surge, and flooding rain. Follow any advice issued by local officials.
Damaging hurricane force winds are likely, especially along portions of the coast. Strong winds could also spread well inland. A Hurricane Warning remains in effect.
Life-threatening flooding is likely given excessive rainfall and subsequent flash flooding. A Flash Flood Watch is now in effect.
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Main Points
Hazard Impacts Location Timing
Wind High to Extreme wind impacts are possible
northeast SC and southeast NC
Increasing Thursday and persisting into Friday and
Saturday morning
Storm Surge/ Inundation
High to Extreme storm surge impacts are likely
All coastal areas and tidally connected
creeks, rivers, bays, and waterways
Thursday into Friday night
Flooding Rain Extreme Flooding Rain impacts are likely
northeast SC, and especially southeast
NC
Developing Thursday and continuing into the
weekend
Tornado A few tornadoes are likely southeast NC Thursday into Friday
Marine Extreme maritime and surf
conditions along with rip currents, large breakers, and very large/steep
seas expected
Surf zone and adjacent Atlantic
waters Through Saturday
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Potential Impacts Wind: Limited Confidence – track dependent
Surge/Inundation: Increasing Confidence – track dependent
Tornado: Increasing Confidence – track dependent
Marine: Very confident – regardless of track
Inland Flooding: Increasing Confidence – track dependent
None Elevated Moderate High Extreme
None Elevated Moderate High Extreme
None Elevated Moderate High Extreme
None Elevated Moderate High Extreme
None Elevated Moderate High Extreme
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Storm Surge Warning Area
- Surge estimated based on latest track - The water has the potential to reach the
following heights above ground level if peak surge occurs at the time of high tide
Note from NHC: The deepest water will occur along the immediate coast in areas of onshore wind, where the surge will be accompanied by large and destructive waves. Surge related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances.
● Cape Fear
● Cape Lookout
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Hurricane Florence Storm Surge Threat and Potential Impacts
In Extreme Surge threat areas we need to prepare for the possibility of devastating impacts such as: • Inundation affecting homes near
tidal creeks and waterways farther inland than what people are accustomed to
• Surge combined with battering waves causing severe damage to many structures along the barrier islands
• A large amount of sand deposition onto barrier islands and blocked roadways
• The formation of new inlets • Wash-outs or severely flooded
coastal roads • Extreme beach erosion with
significant loss of dunes • Damage to marinas, docks, and
piers • Aids to navigation may be off station
or missing, making navigation after the storm hazardous
• Delivery of drinking water and sewer services may be lost in coastal communities
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Hurricane Florence Wind Threat and Potential Impacts
In Extreme Wind threat prepare for the possibility of devastating impacts such as: • Structural damage to buildings and
complete destruction of mobile homes • Widespread tree damage and downed
power lines • Debris and power lines down on
roadways creating impassable conditions
• Widespread and long duration power outages
• Major communication disruptions or complete loss
• Vessels breaking free from moorings
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Most Likely Arrival Time of Tropical Storm Force Winds
Most likely TS arrival times for the southeast NC coast will be mid-day Thu and for the northeast SC coast Thu evening
Tropical storm force winds would spread farther inland during the day Thursday late afternoon and evening for inland areas of southeast NC and Thursday evening into early Friday morning inland areas of northeast SC.
Slower arrival times of TS force winds given a slower track
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Flooding Rain Threat Areas and Potential Impacts
In Extreme flood threat areas prepare for the possibility of devastating impacts such as: • Extreme flooding that may prompt
additional numerous evacuations, or result in numerous rescues
• Rapid rises in rivers and streams that overflow their banks in many places with deep flowing water
• Flood waters entering structures, and cutting off people or communities with roads becoming flooded or damaged
• Road scours or complete failures along with the potential for sinkholes
• Low-lying bridge closures with some weakened or washed away
• Hazardous materials or pollution in any flood waters
• Issues with the delivery of drinking water and sewer services
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Hurricane Florence Potential Rainfall Amounts
Since the track is slower and the storm will reside in the area for a longer period of time rainfall amounts are expected to be extreme
20-30” rainfall amounts with isolated higher amounts are possible in the axis of heaviest rain
Life-threatening flash flooding expected
Amounts will be influenced by the storm’s eventual track
Significant river flooding is expected as a result of excessive rainfall across area hydrologic basins
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Hurricane Florence Tornado Threat
There is a slight risk for tornadoes, especially from coastal portions of southeast NC into eastern NC, especially Thursday afternoon through Friday morning. The risk could continue through Friday as well.
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Latest Information: Hurricane Florence OVERVIEW:
Florence is a dangerous major hurricane and additional strengthening is possible
The storm will continue on a NW direction today and Thu, then forward speed is expected to slow down considerably Friday into the weekend
NHC Advisory #52: 5 AM Wednesday Sept 12, 2018
Max Winds: 130 MPH (Cat. 4)
Location: 485 mi. SE of Cape Fear 520 mi. ESE of Myrtle Beach
Movement: NW at 15 MPH
Pressure: 943 MB (27.85 inches)
Hurricane Florence – GOES East Band-02 1142 AM Wednesday Sept 12, 2018
Florence
● Cape Fear
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Official NHC Track Information
Florence will approach the coast as a major hurricane 120 MPH (Cat 3)
45 MPH (TS)
Life-threatening surge, wind, and rain impacts are likely
The storm will increase in size and have far reaching impacts, regardless of where the center of the storm moves
A much slower track has led to greater uncertainty as to where the storm goes Friday through Sunday
140 MPH (Cat 4)
100 MPH (Cat 2)
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Key Points
Time is becoming limited for preparations. Continue to prepare for a potential land-falling major hurricane
Stay informed and listen for instructions from local officials.
Please visit the following websites for information about protective actions:
https://www.weather.gov/safety/hurricane-plan or
https://www.ready.gov/hurricanes
As the storm nears the coast as a major hurricane it will slow in forward speed, creating unique forecast challenges and producing a long period of impacts
This is a life-threatening, and multi-hazard situation, ranging from the potential for deadly extremely hazardous maritime conditions, storm surge, high winds, and extreme flooding
Weather Forecast Office Presentation Created 9/12/2018 12:15 PM Wilmington, NC Follow us on Twitter Follow us on Facebook
Contact and Next Briefing Information
Disclaimer: The information contained within this briefing is time-sensitive, do not use after 4 PM Wed Sept. 12, 2018
Briefing Webpage: http://weather.gov/ilm/briefing
Web: http://weather.gov/ilm
E-mail: [email protected]
Facebook: NWSWilmingtonNC
Twitter: @NWSWilmingtonNC
Next Briefing When: By 6 PM on Wed Sept. 12, 2018
