ATL: FLORENCE - Post-Tropical - Discussion

[wx247]

Generally I am not a fan of wobble watching but as this approaches the coast and she slows down, the wobbles and forward speed will become extremely important. Thoughts and prayers are with everyone in the path. Hats off to the NHC as this is going to be a nailbiter in terms of impacts across the coastal areas.

[MGC]

The expansion of Florence's wind field is a major concern. As with Katrina, the wind field expansion resulted in massive surge. Florence could have a much larger eye at the conclusion of the current ERC....MGC

[GCANE]

I dunno, EWRC may not last long.

[FLpanhandle91]

I dunno, EWRC may not last long.

http://tropic.ssec.wisc.edu/real-time/mimtc/2018_06L/web/last24hrs.gif

Is it known for storms to replace only a portion of their eye wall? It appears as though Florence's north and west outerwall has almost completed its replacement and the eastern eye wall is well on its way.

[Shell Mound]

The potential stall just offshore, combined with increased shear, means that the heaviest rainfall will be concentrated on the eastern side of the circulation, that is, offshore. That would potentially decrease the total precipitation over eastern NC, depending on where Florence stalls, which would affect its proximity to the coastline. If Florence were to move SW into SC, GA, or N FL, it would start to accelerate after landfall, due to building ridging overhead. That would reduce the threat for inland flooding. The weakening and stalling would certainly reduce the threat for severe wind and (potentially) flooding, but storm surge is still going to be extreme, owing to the expansion of the wind field and the current intensity of the storm.

[tolakram]

A collection of COD views as Florence approaches. Lat Lon turned on but you can turn these off by selecting the globe in the upper left and changing options.

Floater:
https://weather.cod.edu/satrad/exper/?parms=meso-meso1-02-24-0-100-1&checked=latlon-map&colorbar=undefined


https://weather.cod.edu/satrad/exper/?parms=regional-southeast-02-24-1-100-1&checked=latlon-map&colorbar=undefined


https://weather.cod.edu/satrad/exper/?parms=subregional-Bermuda-02-24-1-100-1&checked=latlon-map&colorbar=undefined


https://weather.cod.edu/satrad/exper/?parms=subregional-Carolinas-02-24-1-100-1&checked=latlon-map&colorbar=undefined

[jlauderdal]

Looking at 12z soundings coming in this morning, h50 heights have risen to 593 dm from Newport NC to Wallops Island VA to Upton NY.
I don't think they were supposed to be this high this morning, Florence may put on its break even sooner before approaching N.C.
IMO.

This is my biggest concern. The ridge indeed being much stronger than the past model runs initialized.

the models even the euro have done poorly with the ridge which is disappointing considering the recon data and special balloon launches that have been going on for days, its not like this system is sitting out in the central Atlantic with nothing but satellite data and ship reports..,my theory is there is so much data being pumped into he models that they have trouble with the calculations, ensembles are supposed to help mitigate that issue with multiple scenarios but in reality that hasnt really happened with this hurricane

[Mouton]

FWIW, from weather service archives: On September 3, Hurricane Betsy skirted the Bahamas moving northwest at 10 miles an hour. On September 4, it slowed down, came
to a standstill, and then gradually performed another loop. Betsy reached its farthest north location in the Atlantic of 430
miles south of Cape Hatteras, N. C. at 8:00 AM EST. A large high pressure area over the Eastern United States effectively blocked
any further northward movement of the hurricane, and at 11:OO PM on September 5, Betsy began an unusual southward movement at
8 miles an hour. The center was then located at 27.6' North Letitude and 75.6' West Longitude or 125 miles northeast of Great
Abaco Island, Bahamas. Highest winds were 125 miles an hour. Gales extended 300 miles to the north and 150 miles to the south
of the center. The Bahamas were warned to expect hurricane force winds and tides of 10 feet or a little higher where the center
would move through the Bahamas on Monday.

Florence right now is at approx 71w and 29.6 N.

[NDG]

Recon clearly shows the secondary eyewall on the NW quadrant.

[Blown Away]

Looking at 12z soundings coming in this morning, h50 heights have risen to 593 dm from Newport NC to Wallops Island VA to Upton NY.
I don't think they were supposed to be this high this morning, Florence may put on its break even sooner before approaching N.C.
IMO.

This is my biggest concern. The ridge indeed being much stronger than the past model runs initialized.

the models even the euro have done poorly with the ridge which is disappointing considering the recon data and special balloon launches that have been going on for days, its not like this system is sitting out in the central Atlantic with nothing but satellite data and ship reports..,my theory is there is so much data being pumped into he models that they have trouble with the calculations, ensembles are supposed to help mitigate that issue with multiple scenarios but in reality that hasnt really happened with this hurricane

Clearly some of the Euro ensembles show Flo hitting the brakes well offshore and then go SW... Doesn't seem that unreasonable at this time especially when the NHC used the term "Exceptional" in describing the HP...

[Aric Dunn]

Classic double wind maximum. ERC well under way

[GCANE]

Just passed thru the core.
Flight level winds way down on this one.

946.5 mb

[GCANE]

Hurricane Florence From Space on September 12

[youtube]https://youtu.be/weoWlAs4Dr4[/youtube]

[dukeblue219]

Is that a noteworthy double wind maxima at the eyewall or just noise in the data?

[plasticup]

Just passed thru the core.
Flight level winds way down on this one.

946.5 mb

http://i68.tinypic.com/2j4dcgi.png

They didn't go through the (likely strongest) NE quadrant on this run though.

[Extratropical94]

Is that a noteworthy double wind maxima at the eyewall or just noise in the data?

It is significant enough to imply that an EWRC is happening.

[Visioen]

Looking at 12z soundings coming in this morning, h50 heights have risen to 593 dm from Newport NC to Wallops Island VA to Upton NY.
I don't think they were supposed to be this high this morning, Florence may put on its break even sooner before approaching N.C.
IMO.

This is my biggest concern. The ridge indeed being much stronger than the past model runs initialized.

the models even the euro have done poorly with the ridge which is disappointing considering the recon data and special balloon launches that have been going on for days, its not like this system is sitting out in the central Atlantic with nothing but satellite data and ship reports..,my theory is there is so much data being pumped into he models that they have trouble with the calculations, ensembles are supposed to help mitigate that issue with multiple scenarios but in reality that hasnt really happened with this hurricane

I believe it's because of the changing subsidence caused by the disturbance in the GOM.

[longhorn2004]

With the High over the Atlantic breakging down and the High over the midwest growing, and possibly stalling Florence just off shore, what steering mechanism will continue to try to push it west?

[NDG]

With the High over the Atlantic breakging down and the High over the midwest growing, and possibly stalling Florence just off shore, what steering mechanism will continue to try to push it west?

The midwest High will be moving towards the Great Lakes, that's the high that will could push it SW then W.

[GCANE]

Eye has closed back up


Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 12th day of the month at 13:32Z


A. Time of Center Fix: 12th day of the month at 13:12:20Z
B. Center Fix Coordinates: 29.64N 70.99W

F. Eye Character: Closed
G. Eye Shape & Diameter: Circular with a diameter of 26 nautical miles (30 statute miles)
H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 93kts (107.0mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 10 nautical miles (12 statute miles) to the WNW (303°) of center fix at 13:09:30Z
J. Maximum Flight Level Wind Inbound: From 39° at 93kts (From the NE at 107.0mph)
K. Location & Time of the Maximum Flight Level Wind Inbound: 31 nautical miles (36 statute miles) to the WNW (301°) of center fix at 13:03:00Z
L. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 82kts (94.4mph)
M. Location & Time of the Estimated Maximum Surface Wind Outbound: 13 nautical miles (15 statute miles) to the ESE (115°) of center fix at 13:17:00Z
N. Maximum Flight Level Wind Outbound: From 219° at 101kts (From the SW at 116.2mph)
O. Location & Time of the Maximum Flight Level Wind Outbound: 16 nautical miles (18 statute miles) to the ESE (118°) of center fix at 13:17:30Z
P. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 8°C (46°F) at a pressure alt. of 3,048m (10,000ft)
Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 15°C (59°F) at a pressure alt. of 3,055m (10,023ft)
R. Dewpoint Temp (collected at same location as temp inside eye): 10°C (50°F)

S. Fix Level: 700mb

Remarks Section:

Maximum Flight Level Wind: 125kts (~ 143.8mph) which was observed 24 nautical miles (28 statute miles) to the NE (46°) from the flight level center at 11:34:00Z
Maximum Flight Level Temp: 15°C (59°F) which was observed 7 nautical miles to the NW (309°) from the flight level center