ATL: FLORENCE - Post-Tropical - Discussion

[PTPatrick]

Battering waves are key...if you are beach front with a 13 foot surge and battering waves you got problems. But often we underestimate the elevation we are at when we walk up off of a beach. We can easily overestimate too. In any case, my family flooded in Katrina but they are on a bayou with a thicket of pine trees between the waves and them. Houses on front beach were largely battered down to slabs... thiers stood strong, if not wet.

[jdjaguar]

1 or 2 story house?

2 story. Directly on the Pungo River/Pamlico Sound.

Please let her know that projected surge is 9-13 ft for her locale.

(NHC does err on the side of caution with these estimates, but 3 ft elevation is not gonna cut it)

She needs to leave immediately, and if she doesn't, make sure she has a way of knocking out the roof of her attic from the inside.

[meriland29]

The bursting of convection continues, but she is still weakening. Her winds are getting lower. Looks like no chance her winds will pick up again...which is at least 1 positive thing about her...

[artist]

Reminder, wave height is on top of surge height. 13 ft storm surge + even a 15 ft wave height = 28 ft of water coming at you. Standard one story building height is 10- 15 ft.

Not trying to be argumentative, while that may be true if you live right on the beach, its not entirely accurate for inland locales.

STORM SURGE: The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline. The water has the
potential to reach the following heights above ground if peak surge
occurs at the time of high tide...

That is correct, but it does not allow for waves on top of surge and tide.

Total Water Level = Storm Surge +
Tides +
Waves + Freshwater Input
https://www.nhc.noaa.gov/surge/surge_intro.pdf

[marionstorm]

Looks like she is struggling on radar. Huge dry slot

[kurthi]

Saw a tweet from earlier (few pages back) that said about 200 people remained on Okracoke Island. The town (all the homes) is roughly 0.75 - 1 mile behind the shoreline; max elevation is 3 feet. If this thing does drift just a bit north toward Morehead then this is definitely not a good situation. There is literally nowhere to run.

Here is a site with two Ocracoke webcams. One from Silver Lake harbor in the town's center, and the other from Teaches Hole on the ocean side. Prayers to the town and those who stayed.

https://ocracokeharborinn.com/webcams/

[dizzyfish]

Please let her know that projected surge is 9-13 ft for her locale.

(NHC does err on the side of caution with these estimates, but 3 ft elevation is not gonna cut it)

She needs to leave immediately, and if she doesn't, make sure she has a way of knocking out the roof of her attic from the inside.

I went over all of that with her last night. Her husband is with her so at least she isn't alone in this mess. Thank you!

Rail Dawg - stay safe!

[Noctilucent]

https://imgur.com/vYkrRPV

Link to the livestream: https://www.youtube.com/watch?v=deG4NxkouGM

[J_J99]

Looks like she is struggling on radar. Huge dry slot

https://weather.cod.edu/satrad/nexrad/i ... X-N0Q-1-48
Clearly has closed it off in the last few frames in the NW
EDIT: Sigh, site has gone down now.... BOO!

[ScottNAtlanta]

On microwave it looks like the eye is trying to close off again...this is not weakening currently

[Ken711]

NHC:

11:00 AM EDT Thu Sep 13
Location: 33.4°N 75.5°W
Moving: NW at 10 mph
Min pressure: 955 mb
Max sustained: 105 mph

[J_J99]

https://weather.cod.edu/satrad/nexrad/i ... X-N0Q-1-48
Back up again...

Closing up the dry slot to the NW and the eyewall on the radar appears to be intensifying.

[Ken711]

[jasons2k]

I went over all of that with her last night. Her husband is with her so at least she isn't alone in this mess. Thank you!

Rail Dawg - stay safe!

Just checked some maps. When this is over, they will wish they had left. That's all I can say about it.

[Cuda]

Pressure appears to be dropping in this pass. No stronger winds found, however.

Isn't their typically a lag between pressure drops and winds picking up?

[cycloneye]

BULLETIN
Hurricane Florence Advisory Number 57
NWS National Hurricane Center Miami FL AL062018
1100 AM EDT Thu Sep 13 2018

...HEAVY RAINBANDS WITH TROPICAL-STORM-FORCE WINDS SPREADING ACROSS
THE OUTER BANKS AND COASTAL SOUTHEASTERN NORTH CAROLINA...
...LIFE-THREATENING STORM SURGE AND RAINFALL EXPECTED...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...33.4N 75.5W
ABOUT 145 MI...230 KM ESE OF WILMINGTON NORTH CAROLINA
ABOUT 195 MI...315 KM E OF MYRTLE BEACH SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...955 MB...28.20 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

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

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

Interests elsewhere in the southeastern and mid-Atlantic states
should monitor the progress of Florence.

A Storm Surge Warning means there is a danger of life-threatening
inundation, from rising water moving inland from the coastline. For
a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov. This is a life-threatening situation. Persons
located within these areas should take all necessary actions to
protect life and property from rising water and the potential for
other dangerous conditions. Promptly follow evacuation and other
instructions from local officials.

A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline.

A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area, in this case within the next 12
to 24 hours. Preparations to protect life and property should be
nearing completion.

A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area.

For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), data from an Air Force Reserve Unit
Hurricane Hunter aircraft and NOAA Doppler weather radars from
indicate that Florence was located near latitude 33.4 North,
longitude 75.5 West. Florence is moving toward the northwest near
10 mph (17 km/h). This general motion, accompanied by a further
decrease in forward speed, is expected to continue through today. A
turn to the west-northwest and west at an even slower forward speed
is expected tonight and Friday, and a slow west-southwestward motion
is forecast Friday night and Saturday. On the forecast track, the
center of Florence will approach the coasts of North and South
Carolina later today, then move near or over the coast of southern
North Carolina and northeastern South Carolina in the hurricane
warning area tonight and Friday. A slow motion across portions of
eastern South Carolina is forecast Friday night through Saturday
night.

Data from the aircraft and Doppler weather radars indicate that
maximum sustained winds have decreased to near 105 mph (165 km/h)
with higher gusts. Little change in strength is expected before the
center reaches the coast, with weakening expected after the center
moves inland.

Florence is a large hurricane. Hurricane-force winds extend outward
up to 80 miles (130 km) from the center and tropical-storm-force
winds extend outward up to 195 miles (315 km). NOAA Buoy 41025,
located near Diamond Shoals, North Carolina, recently reported a
sustained wind of 54 mph (87 km/h).

The latest minimum central pressure based on data from the aircraft
is 955 mb (28.20 inches).


HAZARDS AFFECTING LAND
----------------------
STORM SURGE: The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline. The water has the
potential to reach the following heights above ground if peak surge
occurs at the time of high tide...

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

The deepest water will occur along the immediate coast in areas of
onshore winds, 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. For information specific to your area, please see
products issued by your local National Weather Service forecast
office.

RAINFALL: Florence is expected to produce heavy and excessive
rainfall in the following areas...

Coastal North Carolina into far northeastern South Carolina...20 to
30 inches, isolated 40 inches. This rainfall will produce
catastrophic flash flooding and prolonged significant river
flooding.

Remainder of South Carolina and North Carolina into southwest
Virginia...6 to 12 inches, isolated 24 inches.

WIND: Hurricane conditions are expected to reach the coast within
the hurricane warning area this evening or early Friday. Tropical
storm conditions are already moving onshore within the warning
area.

TORNADOES: A few tornadoes are possible in eastern North Carolina
through Friday.

SURF: Swells generated by Florence are affecting Bermuda, portions
of the U.S. East Coast, and the northwestern and central Bahamas.
These swells are likely to cause life-threatening surf and rip
current conditions. Please consult products from your local weather
office.


NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM EDT.
Next complete advisory at 500 PM EDT.

$$
Forecaster Stewart

[Steve]

https://weather.cod.edu/satrad/nexrad/index.php?type=MHX-N0Q-1-48
Back up again...

Closing up the dry slot to the NW and the eyewall on the radar appears to be intensifying.

It does. But there's a pretty significant dry slot around the closed off center to the SW/S/SE/E/NE/N. I hate conspiracy theories and their believers, but the magnitude of that dry slot is suspect. May or may not be natural causes.

[hurricaneCW]

The main narrative hasn't changed, the flooding will be catastrophic for a lot of places, just look at how slow this massive system is already moving and it will slow down even further tonight.

I wouldn't pay much attention to the max winds with this.

[jasons2k]

Pressure appears to be dropping in this pass. No stronger winds found, however.

Isn't their typically a lag between pressure drops and winds picking up?

Yes, there is. And when the storm is very large, the process takes even longer.

[Cuda]

https://weather.cod.edu/satrad/nexrad/index.php?type=MHX-N0Q-1-48
Back up again...

Closing up the dry slot to the NW and the eyewall on the radar appears to be intensifying.

It does. But there's a pretty significant dry slot around the closed off center to the SW/S/SE/E/NE/N. I hate conspiracy theories and their believers, but the magnitude of that dry slot is suspect. May or may not be natural causes.

Ok... I need you to elaborate. What beyond natural causes would be causing dry slots?