In light of the risk Florence poses to the U.S., we’re publicly releasing our morning briefings on our blog. Check back daily for more updates. We are also providing a small sampling of our tropical weather graphics as we continue to track Hurricane Florence in the Atlantic.
Praedictix Briefing: Thursday morning, September 13th, 2018
- Florence has weakened slightly over the past 12-24 hours and is now a Category 2 hurricane as the storm slowly approaches the East Coast. As of 9 AM EDT, Florence had winds of 110 mph and was moving to the northwest at 12 mph.
- Florence will continue to track to the northwest today with a decrease in forward speed, turning to the west-northwest tonight and Friday, and then west-southwest Friday night into Saturday. Right now landfall will be possible Friday along the southeast North Carolina coast.
- Even though Florence is slightly weaker this morning, dangerous impacts are still expected over the next several days across the Mid-Atlantic. As Florence slows down, this only prolongs the system across the region, increasing the potential of life-threatening storm surge and catastrophic flash flooding across parts of the Mid-Atlantic States and the Carolinas. Between 1963 and 2012, 88% of all tropical cyclone-related deaths in the United States were related to water – between storm surge (49%), rainfall flooding (27%), surf and deaths that have occurred just offshore (6% each) – so the flood and storm surge threat is not one to take lightly.
- It is also important to remember that significant impacts from Florence will occur far from the center of the storm, including further inland. If you are within the forecast cone, preparations should be made or rushed to completion.
- Numerous Storm Surge and Hurricane Watches and Warnings are in effect along and near the coast ahead of Florence.
- Florence isn’t the only system we are tracking. First, a tropical wave that has moved into the Gulf of Mexico has a 50% chance of becoming a tropical system by the time it reaches the western Gulf Coast Friday. Facilities across portions of northeastern Mexico, Texas, and Louisiana should continue to monitor this situation over the next few days.
- Tropical Storm Isaac is moving across the Lesser Antilles today. A westward track is expected to continue over the next several days with slow weakening. Tropical Storm Watches and Warnings are in effect.
- Super Typhoon Mangkhut could have impacts on southeastern Asia into the weekend.
Hurricane Florence As Of Thursday Morning. Outer rain bands with tropical-storm-force wind gusts are starting to impact the North Carolina Outer Banks this morning as Florence nears the East Coast. As of a 9 AM EDT special update from the National Hurricane Center, Florence was located 170 miles east-southeast of Wilmington, NC, or 215 miles east of Myrtle Beach, SC, and moving to the northwest at 12 mph. Florence had winds of 110 mph. Even though Florence is slightly weaker this morning, dangerous impacts are still expected over the next several days across the Mid-Atlantic.
Numerous mandatory evacuations continue to be in effect across the Mid-Atlantic ahead of Florence, with almost two million told to leave the area. State emergency management offices have more on how states are preparing for the storm and what areas are under evacuations:
South Carolina: https://www.scemd.org/
North Carolina: https://www.ncdps.gov/florence
Virginia: https://www.vaemergency.gov/
Georgia: http://www.gema.ga.gov/Pages/default.aspx
Forecast Track. Florence will continue to track in a northwest direction today with a decrease in forward speed. This system will then turn to the west-northwest tonight and Friday, and then west-southwest Friday night into Saturday with a fairly slow forward speed. Florence will approach the Mid-Atlantic coast today, then slowly move inland tonight or Friday. This system will continue to move across South Carolina this weekend, weakening while doing so. With Florence slowly approaching the coast and moving inland over the next couple days, a prolonged storm surge event is expected along the East Coast, with several high tide cycles potentially impacted. Several days of heavy rain will occur along and near the coast, with catastrophic flash flood possible as well.
Facilities along the East Coast – especially across the Carolinas and Mid-Atlantic – should make sure contingency/hurricane plans are rushed to completion as conditions will deteriorate throughout the day.
Local Weather Service Offices have issued statements on what to expect from Florence – you can find those here: https://www.nhc.noaa.gov/text/refresh/index_hls1+shtml/111230.shtml
Tropical Alerts. Due to the expected wind impacts of Florence on the Mid-Atlantic, Tropical Storm and Hurricane Watches and Warnings have been issued.
Across inland areas:
- Hurricane Warnings are in effect from Myrtle Beach (SC), Wilmington, Jacksonville, New Bern, Goldsboro, and Greenville (NC).
- Hurricane Watches are in effect for Charleston, SC.
- Tropical Storm Warnings are in effect for Norfolk (VA), as well as Fayetteville (NC) and Florence (SC).
- Tropical Storms Watches are in effect for Sumter, SC.
Across coastal areas:
A Hurricane Warning is in effect for…
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds
A Hurricane Watch is in effect for…
* Edisto Beach South Carolina to South Santee River South Carolina
A Tropical Storm Warning is in effect for…
* North of Duck North Carolina to Cape Charles Light Virginia
* Chesapeake Bay south of New Point Comfort
Warnings indicate that either hurricane-force winds (74+ mph) or tropical-storm-force winds (39-73 mph) are expected within 36 hours. Watches means those conditions are possible within 48 hours.
Potential Earliest Tropical Storm Force Wind. Tropical-storm-force winds will start to impact the eastern Mid-Atlantic throughout the day as Florence moves closer to the East Coast. The wide wind field associated with Florence means that stronger wind gusts could even be possible for areas like Washington D.C. this afternoon, and northern Florida into Friday.
Peak Wind Gust Through 7 PM Saturday. As Florence approaches the coast and eventually makes landfall, very dangerous hurricane-force winds are expected, especially near and along the coast. Winds will start to increase today as Florence approaches the coast, reaching their peak across coastal North Carolina tonight and coastal South Carolina and some areas further inland across North and South Carolina Friday. Near the coast wind gusts over 100 mph will be possible for areas like Wilmington, NC tonight. These winds will easily knock out power and down trees across the region.
Strong Wind Gusts Reach Inland. You can see how far inland strong wind gusts of approximately 60+ mph (indicated by the browns and pinks) reach with this graphic. These strong winds should remain out of the Raleigh, Charlotte, and Columbia areas, but greatly impact areas of eastern North Carolina and northeastern South Carolina.
Power Outage Potential. The Guikema Research Group at the University of Michigan is forecasting the potential power outage numbers across the region based off the National Hurricane Center official track and intensity forecast. Their model is estimating 3.5 million without power due to this system across North and South Carolina, with the greatest concentration of outage in and around the area where Florence approaches the coast makes landfall.
Storm Surge Potential. A destructive and life-threatening storm surge is expected as Florence approaches coastal areas of North and South Carolina. In some areas particularly along the North Carolina coast near Wilmington and up through inland rivers near Jacksonville, New Bern and Greenville the storm surge could reach 9-13 feet above normally dry land. With Florence slowing down and hovering around the coast, these high water levels could occur across several high tides. The deepest water will occur along the coast in areas of onshore winds, where large and destructive waves will accompany the surge.
Cape Fear NC to Cape Lookout NC, including the Neuse, Pamlico, Pungo, and Bay Rivers…9-13 ft
North Myrtle Beach SC to Cape Fear NC…6-9 ft
Cape Lookout NC to Ocracoke Inlet NC…6-9 ft
South Santee River SC to North Myrtle Beach SC…4-6 ft
Ocracoke Inlet NC to Salvo NC…4-6 ft
Salvo NC to North Carolina/Virginia Border…2-4 ft
Edisto Beach SC to South Santee River SC…2-4 ft
Storm Surge Concerns. Due to the life-threatening storm surge threat, Storm Surge Watches and Warnings are in effect across parts of coastal North and South Carolina:
A Storm Surge Warning is in effect for…
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds, including the Neuse and Pamlico Rivers
A Storm Surge Watch is in effect for…
* Edisto Beach South Carolina to South Santee River South Carolina
* North of Duck North Carolina to the North Carolina/Virginia border
Catastrophic Flooding Possible. The other major concern we have to worry about with Florence is heavy rain. As Florence slows down and takes its time moving inland, rain will dump across portions on the Mid-Atlantic, especially coastal areas of North Carolina and northeastern South Carolina. By the time Florence pushes out of the region, 20-40” of rain could fall in areas like Wilmington, New Bern, and Myrtle Beach. This heavy rain will lead to catastrophic flooding across the region and significant river flooding. Running down potential rainfall totals (via NHC):
- Coastal North Carolina into far northeastern South Carolina…20 to 30 inches, isolated 40 inches. This rainfall would produce catastrophic flash flooding and prolonged significant river flooding.
- Rest of South and North Carolina into southwest Virginia…6 to 12 inches, isolated 24 inches.
Flood Concerns. Numerous Flash Flood Watches have been issued across parts of North and South Carolina from through Saturday due to the heavy rain potential associated with Florence.
Tornado Watch Until 9 PM ET. Landfalling tropical systems also pose the potential of producing tornadoes. Due to the potential of a few tornadoes with the outer bands of Florence today, a Tornado Watch has been issued for parts of eastern North Carolina (including Jacksonville, Greenville, New Bern, and Hatteras) until 9 PM.
Watching The Gulf Of Mexico. We continue to watch an area of low pressure across the western Gulf of Mexico producing disorganized showers and storms. There is the potential it could still form into a tropical depression, but it does not have much time to do so as it will reach the western Gulf Coast tomorrow. Facilities across portions of northeastern Mexico, Texas, and Louisiana should continue to monitor this situation over the next few days. Whether or not this system forms into something tropical, heavy rain and gusty winds are possible. As of Thursday morning, this area has a 50% chance of forming into a tropical system in the next two days.
Tropical Storm Isaac. Isaac is approaching the Leeward Islands this morning with gusty tropical storm force winds. As of the 8 AM AST update from the National Hurricane Center, Isaac was situated 25 miles east of Dominica, or 80 miles south-southeast of Guadeloupe, moving west at 21 mph. Isaac had sustained winds of 45 mph. Isaac will continue west over the next several days, passing over the Lesser Antilles today and into the Caribbean. Isaac will continue to weaken, and potentially become a trough of low pressure this weekend. We will continue to monitor this system, though, as some models are indicating this could regenerate into a system in the western Caribbean next week. Due to the threat Isaac poses to the Lesser Antilles, the following watches and warnings have been issued:
A Tropical Storm Warning is in effect for…
* Martinique
* Dominica
* Guadeloupe
A Tropical Storm Watch is in effect for…
* Antigua
* Barbuda
* Montserrat
* St. Kitts and Nevis
* Saba and St. Eustatius
* St. Martin and St. Maarten
Other Tropical Activity. The tropics continue to be active as we are watching several other systems across the Atlantic and Pacific basins as well this morning:
- Hurricane Helene continues to move north across the eastern Atlantic. The storm is in the process of weakening but could impact the Azores this weekend as a tropical storm.
- Subtropical Storm Joyce is expected to gain tropical characteristics soon but is no immediate threat to land. The system will not strengthen much over the next several days. It’ll move in a southerly direction until Helene passes by and then quickly start moving off to the northeast. This system could impact the Azores early next week.
- Olivia has weakened to a tropical depression as it continues to move away from Hawaii, although heavy rain is still occurring across parts of the Hawaiian Islands. All Tropical Storm Watches and Warnings have expired, but Flash Flood Watches continue through ThursdayNight.
Tracking Mangkhut. Further out into the western Pacific, we continue to track Super Typhoon Mangkhut. As of the 6 PM local time update, Mangkhut was moving to the west at 12 mph with 165 mph winds. The system is expected to continue in a west to west-northwesterly direction over the next several days. This path would bring Mangkhut toward Southeast Asia into the weekend. Right now the system looks to pass south of Tawain, more impacting parts of the northern Philippines Friday and Saturday local time before the center passes south of Hong Kong Sunday.
D.J. Kayser, Meteorologist, Praedictix