Florence

sdanseo

Gaoth Laidir wrote: »

18Z SHIPS LGEM forecast has it decreasing steadily before landfall at about 78 hours. Somewhere Cat 3/2.

TIME (HR) | 0 | 6 | 12 | 18 | 24 | 36 | 48 | 60 | 72 | 84 | 96 | 108 | 120
V (KT) NO LAND | 120 | 127 | 129 | 132 | 132 | 133 | 133 | 131 | 125 | 116 | 110 | 102 | 106
V (KT) LAND | 120 | 127 | 129 | 132 | 132 | 133 | 133 | 131 | 125 | 80 | 44 | 32 | 28
V (KT) LGEM | 120 | 129 | 133 | 135 | 136 | 136 | 134 | 125 | 116 | 74 | 41 | 31 | 28
LAND (KM) | 930 | 888 | 864 | 894 | 905 | 962 | 622 | 321 | 77 | -92 | -160 | -228 | -295

Still very much a Cat 4 with the eye 40nm from shore.
Much of the storm and its effects over land by then.

igCorcaigh

As an aside:

Perhaps the media focus on the Saffir-Simpson scale of cat this cat that should not be the focus as much as the flooding possibility regarding impacts of hurricanes? Storm surge can be like a tsunami.

Anyway OT, and more of an issue for our American friends. Apologies.

Gaoth Laidir

I saw a comment somewhere that if Florence does stall like Harvey, the rainfall totals will not be as high as we're not dealing with Gulf of Mexico moisture.

igCorcaigh

Gaoth Laidir wrote: »

I saw a comment somewhere that if Florence does stall like Harvey, the rainfall totals will not be as high as we're not dealing with Gulf of Mexico moisture.

Ah right. Well thankfully that.

dfx-

Have many strong hurricanes hit NC/SC full force like this one is modelled to? There's a few that threatened it but then weakened off

sdanseo

dfx- wrote: »

Have many strong hurricanes hit NC/SC full force like this one is modelled to? There's a few that threatened it but then weakened off

Hugo, 1989

Sandy in 2012 was only (only!) Cat 3 at peak and caused $60+ bn in damage, a bit further north in NY and NJ including writing off my second cousin's house in Queens. Had to be razed and rebuilt.

igCorcaigh

sdanseo wrote: »

Hugo, 1989

Sandy in 2012 was only (only!) Cat 3 at peak and caused $60+ bn in damage, a bit further north in NY and NJ including writing off my second cousin's house in Queens. Had to be razed and rebuilt.

That's right. Decades. They may not be so prepared now

Meteorite58

dfx- wrote: »

Have many strong hurricanes hit NC/SC full force like this one is modelled to? There's a few that threatened it but then weakened off

Quote: Brian L Kahn

'Only three Category 4 hurricanes have made landfall in the Carolinas in recorded history. Florence could be #4'

Itssoeasy

dfx- wrote: »

Have many strong hurricanes hit NC/SC full force like this one is modelled to? There's a few that threatened it but then weakened off

There was one in 1999 that hit the same area and there one in 1954 I think.

Kermit.de.frog

Latest obs expected within the next hour and then...bedtime.

Meteorite58

https://twitter.com/NASA_SPoRT/status/1039259038452789248

pad199207

I don’t want to google it. What does someone mean by saying that ‘the Hurricane is stacked’ ?

sdanseo

pad199207 wrote: »

I don’t want to google it. What does someone mean by saying that ‘the Hurricane is stacked’ ?

Very little lateral windsheer pulling the vertical layers of the hurricane apart (all stacked on top of each other).

igCorcaigh

sdanseo wrote: »

Very little lateral windsheer pulling the vertical layers of the hurricane apart (all stacked on top of each other).

So it just spins?

Shear is winds against each other, is it?
So, without shear, it goes like a spinning top or an ice skater, no friction?

Meteorite58

GFS throwing out some crazy pressure readings on the 18Z. Has Florence pirouette around the coast as it powers up before moving inland and then the remnants running up the E coast and back out to sea.

Meteorite58

NASA Sat Pic from earlier today, for the purpose of scale. Track not definite yet.

Meteorite58

Meteorite58 wrote: »

GFS throwing out some crazy pressure readings on the 18Z. Has Florence pirouette around the coast as it powers up before moving inland and then the remnants running up the E coast and back out to sea.

Yep, the GFS is back snorting the white stuff. Had some insane sub 900 mb predictions for Irma before it made its Florida landfall last year.

Kermit.de.frog

Very latest aviation recon showing a little weaker than the headline surface speed at 133 MPH. That pass was over the weaker side though so might be higher surface winds recorded on the next pass in the next hour or so.... Central pressure remains 939hpa.

Updates on the current flight here...

https://www.tropicaltidbits.com/recon/

Kermit.de.frog

Looks like the next NHC update will be pretty much the same - maybe weakened a little based on latest obs. It has not intensified in the last few hours but it could be undergoing some eye wall replacement or something.

Kermit.de.frog

Florence is going through an eye wall replacement cycle which has resulted in temporary weakening but it will spruce up again very quickly once it's done. You can see the really tall cloud tops building again.




There is also a hint of some shear in the southeast corner with the upper cloud bands not fanning out from there at the moment.

Kermit.de.frog

...

Gaoth Laidir

There is certainly some asymmetry between the lower levels (37 GHz) and upper levels (85-92 GHz) overnight, supported by an increase in ERC probability.The latest NHC discussion has it as an admittedly generous 120 knots, and aircraft recon has it lower than that. It should restrengthen, though, but the 00Z SHIPS LGEM has it weakening again slightly before landfall (112 kts). This is based on the 120-kt initial value which, if it's too high, will make the rest of the forecast tonight too, so hopefully it will actually turn out to be lower than that.





http://tropic.ssec.wisc.edu/real-time/archerOnline/cyclones/2018_06L/web/summaryTableERC.html

Gaoth Laidir

The 06Z SHIPS LGEM has it at a slightly lower 105 kts at landfall (72 hrs). Around 25 knots of easterly shear affecting it at that point.

http://hurricanes.ral.ucar.edu/realtime/plots/northatlantic/2018/al062018/stext/18091106AL0618_ships.txt

Rhineshark

igCorcaigh wrote: »

So it just spins?

Shear is winds against each other, is it?
So, without shear, it goes like a spinning top or an ice skater, no friction?

That's pretty much how I understand it. The most relevent shear for hurricane formation is vertical shear as the hurricane itself reaches up into the atmosphere so the difference in wind speeds between the lower (850mb) and upper atmosphere (200mb). A 10 knot shear is 10knots difference. The greater the shear, the more it pulls the hurricane out of shape, weaken and can eventually collapse it. I think Florence's lack of shear as it closes in on land is rather unusual but I'm not sure on that.

star gazer

Hurricane watches issued.
Storm surge estimates also up.
wind speed same as last as is pressure.
NHC

ZCZC MIATCPAT1 ALL
TTAA00 KNHC DDHHMM

BULLETIN
Hurricane Florence Advisory Number 48
NWS National Hurricane Center Miami FL AL062018
500 AM AST Tue Sep 11 2018

...HURRICANE AND STORM SURGE WATCHES ISSUED FOR PORTIONS OF THE
COASTS OF NORTH AND SOUTH CAROLINA...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION

---

LOCATION...26.4N 64.1W
ABOUT 410 MI...660 KM S OF BERMUDA
ABOUT 975 MI...1570 KM ESE OF CAPE FEAR NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...944 MB...27.88 INCHES


WATCHES AND WARNINGS

---

CHANGES WITH THIS ADVISORY:

A Storm Surge Watch has been issued for the east coast of the
United States from Edisto Beach, South Carolina northward to
the North Carolina-Virginia border, including the Pamlico and
Albemarle Sounds.

A Hurricane Watch has been issued for the east coast of the United
States from Edisto Beach, South Carolina, northward to the
North Carolina-Virginia border, including the Pamlico and Albemarle
Sounds.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Watch is in effect for...
* Edisto Beach South Carolina to the North Carolina-Virginia border
* Albemarle and Pamlico Sounds, including the Neuse and Pamlico
Rivers

A Hurricane Watch is in effect for...
* Edisto Beach South Carolina to the North Carolina-Virginia border
* Albemarle and Pamlico Sounds

Interests elsewhere in the southeastern and mid-Atlantic states
should monitor the progress of Florence. Additional watches may be
required later today.

A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.
For a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov.

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.


DISCUSSION AND OUTLOOK

---

At 500 AM AST (0900 UTC), the center of Hurricane Florence was
located near latitude 26.4 North, longitude 64.1 West. Florence is
moving toward the west-northwest near 15 mph (24 km/h). A west-
northwestward to northwestward motion with a slight increase in
forward speed are expected during the next couple of days. On the
forecast track, the center of Florence will move over the
southwestern Atlantic Ocean between Bermuda and the Bahamas through
Wednesday, and approach the coast of North Carolina or South
Carolina on Thursday.

Maximum sustained winds are near 140 mph (220 km/h) with higher
gusts. Florence is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some strengthening is expected during the
next day or so, and Florence is expected to be an extremely
dangerous major hurricane through Thursday night.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 150 miles
(240 km).

The estimated minimum central pressure is 944 mb (27.88 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...

Edisto Beach to Murrells Inlet...2-4 ft
Murrells Inlet to Cape Fear...4-6 ft
Cape Fear to Cape Lookout including The Neuse and Pamlico
River...6-12 ft
Cape Lookout to Ocracoke Inlet...5-8 ft
Ocracoke Inlet to North Carolina/Virginia Border...3-5 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 total rainfall
accumulations of 15 to 20 inches with isolated maxima to 30 inches
near Florence's track over portions of North Carolina, Virginia, and
northern South Carolina through Saturday. This rainfall may produce
life-threatening flash flooding.

WIND: Hurricane conditions are possible within the watch area by
late Thursday or Thursday night, with tropical storm conditions
possible by Thursday morning.

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


NEXT ADVISORY

---

Next complete advisory at 1100 AM AST.

$$
Forecaster Brown

NNNN

star gazer

The track since last night is a little further North into the North Carolina coast. An eyewall replacement cycle is likely underway according to the NHC and indications from imagery. Once a new eyewall is in place the conditions are good for maintaining the strength of Florence for the next two days with even a bit more strengthening forecast. There is still a degree of uncertainty about the track three days out from expected landfall but the range of possiblities is narrowing all the time. There'll be intermediate advisories issued by the NHC now that the watches have started. Storm surge of up to three and a half meters in the most exposed areas with rainfall acumulations of 375mm to 500mm with isolated 750mm. The Hurricane will lose it's wind speed over land but it doesn't move very far for a couple of days so that increases the rainfall accumulations and inland flooding risks.

Kermit.de.frog

Eyewall replacement looks just about done. Central surface pressure on downward trend again according to latest recon so looks like intensification is underway.

daphne

Fantastic images here: https://www.nhc.noaa.gov/satellite.php

Cantona's Collars

Thought this was good.

star gazer

Florence has lower sustained max wind speed of 215 km/h 130mph (low Cat 4) with the eyewall replacement cycle temporarily weakening it but the forecast is still for strengthening to just below Category 5 level in the next 36 hours.

The hazards of Florence and Hurricanes in general
https://twitter.com/TropicalTidbits/status/1039538252296925184


Full storm surge forecast (48 hours) may take a little more time as landfall is forecast to be around Friday morning
https://twitter.com/NHC_Surge/status/1039466573952692224