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Major Hurricane Florence: STORM MODE THREAD

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Tonight's burst of deep convection should rebuild a solid eyewall one last time prior to shelf water disrupting Flo's heat engine; I'm going out on a limb and will forecast Cat 4 for a few dropsondes tomorrow morning...and the unmodeled moderate shear appears to be relaxing as well.

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11 minutes ago, adiabatic13 said:

Tonight's burst of deep convection should rebuild a solid eyewall one last time prior to shelf water disrupting Flo's heat engine; I'm going out on a limb and will forecast Cat 4 for a few dropsondes tomorrow morning...and the unmodeled moderate shear appears to be relaxing as well.

120 mph at 5pm advisory 

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677 
WTNT41 KNHC 122042
TCDAT1

Hurricane Florence Discussion Number  54
NWS National Hurricane Center Miami FL       AL062018
500 PM EDT Wed Sep 12 2018

Data from an Air Force Reserve hurricane hunter aircraft along with
satellite imagery and various intensity estimates indicate that
Florence has weakened instead of strengthening. However, while the
hurricane hasn't strengthened in terms of peak winds, the inner-core
and outer wind fields have continued to expand, resulting in an
increase the cyclone's total energy, which will create a significant
storm surge event. The upper-level outflow remains impressive and is
still expanding except toward the south.

Florence is moving toward the northwest or 315/14 kt. The new 12Z
global and regional model runs have come into much better agreement
on Florence moving steadily northwestward around a strong ridge
located between Bermuda and the U.S. mid-Atlantic region for the
next 48 hours or so. By late on day 2, Florence is forecast to
approach the southern portion of the North Carolina coast, then slow
down considerably and turn westward within collapsing steering flow,
with a very slow westward motion near the coasts of North and South
Carolina continuing into Friday and Saturday. Corrected-consensus
models HCCA and FSSE remain very close to each other and are quite
similar to the simple consensus model TVCA. Therefore, only a slight
eastward shift was needed to the previous forecast track through 36
hours or so, mainly due to the more eastward initial position based
on the reconnaissance fixes. At 48 hours and beyond, no significant
changes were required to the previous advisory track, which still
shows Florence moving slowly westward across South Carolina and
western North Carolina on day 4, followed by a slow northward motion
up the Appalachian mountain chain on day 5.

A narrow window of opportunity remains during the next 24 hours or
so for Florence to strengthen a little when the hurricane passes
over the warmer SSTs and deeper warm water/higher upper-ocean heat
content associated with the Gulf Stream, and low vertical shear
conditions of 5-10 kt will aid in any strengthening process.
However, significant strengthening is not anticipated due to
Florence's large and expanding inner-core wind field. By 36 h
and beyond, decreasing ocean heat content along with the slowing
forward speed of Florence will likely produce cold upwelling beneath
the hurricane, inducing a gradual weakening trend. When Florence
moves over the shallow coastal shelf waters in 48-72 h, land
interaction and more significant upwelling are anticipated, which
should further enhance the weakening process. The NHC intensity
forecast remains near the higher statistical guidance through 48
hours, then follows the trend of the decay SHIPS model after that
time.

Although the maximum winds are expected to weaken a little more,
Florence is still expected to remain a dangerous major hurricane as
it approaches the coast. The threat to life from storm surge and
rainfall will not diminish, and these impacts will cover a large
area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along
portions of the coastlines of South Carolina and North Carolina, and
a Storm Surge Warning is in effect for a portion of this area.  All
interests in these areas should complete preparations and follow any
advice given by local officials.

2. Life-threatening, catastrophic flash flooding and prolonged
significant river flooding are likely over portions of the Carolinas
and the southern and central Appalachians late this week into early
next week, as Florence is expected to slow down as it approaches the
coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the
coasts of South Carolina and North Carolina, and a Hurricane Warning
is in effect. Strong winds could also spread inland into portions
of the Carolinas.

4. Large swells affecting Bermuda, portions of the U.S. East
Coast, and the northwestern and central Bahamas will continue this
week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 30.9N  72.5W  105 KT 120 MPH
 12H  13/0600Z 32.1N  74.1W  110 KT 125 MPH
 24H  13/1800Z 33.4N  75.9W  110 KT 125 MPH
 36H  14/0600Z 33.9N  77.1W  105 KT 120 MPH
 48H  14/1800Z 34.0N  77.9W  100 KT 115 MPH...NEAR THE COAST
 72H  15/1800Z 33.6N  79.2W   70 KT  80 MPH...NEAR THE COAST
 96H  16/1800Z 34.0N  81.7W   30 KT  35 MPH...INLAND
120H  17/1800Z 35.6N  83.4W   20 KT  25 MPH...POST-TROP/INLAND

$$
Forecaster Stewart

 

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22 minutes ago, PennyForYourThoughts said:

Water already rising in Oriental Nc.  

 

Keep in mind this is a naturally very low spot that is prone to water on the road. That SUV is parked just past a permanently posted High Water sign. The local river is up a foot in recent days.

Oriental.JPG

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9 minutes ago, f2tornado said:

Keep in mind this is a naturally very low spot that is prone to water on the road. That SUV is parked just past a permanently posted High Water sign. The local river is up a foot in recent days.

 

Yeah wind tides like that are not uncommon..the water level there is 100% dependent on the wind...Belhaven is already higher since they take more water on a south wind, if the wind stays up overnight this gauge wont get below this again for 3-4 days at least with a stall SW keeping the surge in on the SE wind.....

 

blhn7_hg.png.5d61117e9c7e212334ad6090254c45f2.png

 

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Have y’all noticed that Florence has been riding on the north side of things so far today? Was almost out of previous come of uncertainty earlier, and already starting to deviate north on the new cone. Storm has a mind of its own i swear.

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1 hour ago, adiabatic13 said:

Tonight's burst of deep convection should rebuild a solid eyewall one last time prior to shelf water disrupting Flo's heat engine; I'm going out on a limb and will forecast Cat 4 for a few dropsondes tomorrow morning...and the unmodeled moderate shear appears to be relaxing as well.

Isn't it always amazing how there always seems to be that unmodeled fly in the ointment with all types of storm systems....so many moving parts to take into account...surprises always abound.

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the 18Z NAM (yes I kn ow its the NAM) is an absolute nightmare taking the eye right on the coast around Wilmington around 39 hrs then paralleling the coast while slowly weakening all the way down to Charleston at 84 hrs.

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3 minutes ago, hazwoper said:

the 18Z NAM (yes I kn ow its the NAM) is an absolute nightmare taking the eye right on the coast around Wilmington around 39 hrs then paralleling the coast while slowly weakening all the way down to Charleston at 84 hrs.

6pm gfs takes inland NC the deepest of any recent runs. Doesn’t run down coast of SC. 

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9 minutes ago, Cooper08 said:

6pm gfs takes inland NC the deepest of any recent runs. Doesn’t run down coast of SC. 

Quickly loses its strength

It also doesn't stall for a long time

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37 minutes ago, Rd9108 said:

I have a hard time this storm is gonna restrengthen even a little. It looks terrible right now. 

 

Well considering the shear is weakening by the minute and the gulf stream is still in play I wouldnt count it out.  There is a window over night for it to get stronger.  Look at Harvey last year, it doesn't take a long time.

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I think the large circulation and expanded vortex / core structure goes against conventional reintensification. Deep convection and improvement of the core over the Gulf Stream could help to drop pressure again, but it would probably not be able to retighten the core gradient enough for a substantial increase in vortex wind speeds. Perhaps it maintains a steady state longer. However, this is inconsequential to the greatest shoreline threat. I am already bought into the massive surge threat Florence poses due to it having already been an intense hurricane, then developing a large wind field in the northern semicircle of the surface circulation and pushing fetch perpendicular to the Carolina shoreline.

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1 hour ago, Rd9108 said:

I have a hard time this storm is gonna restrengthen even a little. It looks terrible right now. 

I agree, looks like a mess right now. Must be a dry air intrusion. There is some deep convection firing though. It’s far from DOA

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13 minutes ago, NYCGreg said:

Yea, the eye is gone now.  It's not DOA, but I don't believe it will be close to a major hurricane by the time it even reaches land.

It won't really matter, the effects will be the same.

I don't know what kind of hurricane people were expecting at 32-35N, it's holding pretty well. The outflow to the north and northeast looks fantastic. 

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Looking like this will be somewhere between a Fran and Isabel intensity level coming in, but the larger size and fetch will mean a greater surge threat, in addition to the slower speed. The eye becoming less distinct and issues with shear/dry air mean to me that intensity is leveling off and may decrease as it comes near shore and especially as it slows and interacts with land. I’d guess Cat 2 somewhere when the eye wall makes it onshore. The surge though will still be a horrible issue given the slow forward speed and large size. 

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Recon just made their first pass through the core.  Even in the stronger northeast quad, the top flight level wind was only 101 kts and the top SFMR wind was only 79 kts.  The wind field has become large, but the core wind has really come down quite a bit.

Update:  Central pressure is 956 mb.

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36 minutes ago, NYCGreg said:

Yea, the eye is gone now.  It's not DOA, but I don't believe it will be close to a major hurricane by the time it even reaches land.

And you are basing this on what??  The eye is just covered by overcast and I believe it's reorganizing. I'm not saying it's to going to jump to a cat 5 or even a 4 but it still has to traverse across the gulf stream and many models show it holding its own or even strengthen a bit. 

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6 minutes ago, navvet8992 said:

343615353_ScreenShot2018-09-12at8_06_13PM.png.6e93670b4c1c1eb793235c46c2ae807d.png

It’s been doing this for hours today. Every track is updated slightly north and it still goes North. Because of this I’m thinking the SW curve is gonna start looking less and less impressive.

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48 minutes ago, SnoSki14 said:

It won't really matter, the effects will be the same.

I don't know what kind of hurricane people were expecting at 32-35N, it's holding pretty well. The outflow to the north and northeast looks fantastic. 

Truth. This is still a dangerous juggernaut but weenies let their passions get the best of them. 

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And you are basing this on what??  The eye is just covered by overcast and I believe it's reorganizing. I'm not saying it's to going to jump to a cat 5 or even a 4 but it still has to traverse across the gulf stream and many models show it holding its own or even strengthen a bit. 

The gulf stream affect tends to be greatly exaggerated throughout history. If I were a betting man I would bet continued weakening until landfall. I wonder why the models continue to mishandle the intensity in this final approach ?


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