ATL: FLORENCE - Post-Tropical - Discussion

[shiny-pebble]

 https://twitter.com/webberweather/status/1038796027967561729




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[chris_fit]

Pressure around 983-984 from the recon.

Peak (10s) Flt. Lvl. Wind: 70 kts (80.6 mph)
SFMR Peak (10s) Sfc. Wind: 66 kts (76.0 mph)

What I think is more important (I think) is that the center is around 24.3 according to recon - might make a difference extrapolated 5 days out - It is still loosing latitude - this was forecast by just a fraction of the models. This is lower than any NHC forecast had Flo at.

[supercane4867]

Pressure is quite low for a low-end hurricane in the open Atlantic. Expect windspeed to catch up soon.

[psyclone]

Florence looks like a hurricane now with deep convection all around... and it looks like it's going to be a good sized storm. A period of rapid intensification is likely soon.

[Ken711]

Pressure around 983-984 from the recon.

Peak (10s) Flt. Lvl. Wind: 70 kts (80.6 mph)
SFMR Peak (10s) Sfc. Wind: 66 kts (76.0 mph)

What I think is more important (I think) is that the center is around 24.3 according to recon - might make a difference extrapolated 5 days out - It is still loosing latitude - this was forecast by just a fraction of the models. This is lower than any NHC forecast had Flo at.

Affecting a South and West shift with the model tracks?

[pgoss11]

Pressure around 983-984 from the recon.

Peak (10s) Flt. Lvl. Wind: 70 kts (80.6 mph)
SFMR Peak (10s) Sfc. Wind: 66 kts (76.0 mph)

What I think is more important (I think) is that the center is around 24.3 according to recon - might make a difference extrapolated 5 days out - It is still loosing latitude - this was forecast by just a fraction of the models. This is lower than any NHC forecast had Flo at.

I just wonder if the storm intensifies will it move more poleward and maybe the motion averages out. Not an expert just an opinion.

[toad strangler]

 https://twitter.com/TropicalTidbits/status/1038797401706975232

[toad strangler]

Florence looks like a hurricane now with deep convection all around... and it looks like it's going to be a good sized storm. A period of rapid intensification is likely soon.

 https://twitter.com/TropicalTidbits/status/1038797401706975232

[Ken711]

What is the projected wind field size of Florence as it approaches landfall as compared to Irma when it approached FL?

[toad strangler]

 https://twitter.com/TropicalTidbits/status/1038778260241506304

[J_J99]

What is the projected wind field size of Florence as it approaches landfall as compared to Irma when it approached FL?

Irma had 375-400 miles diameter of TS winds.... I dont think Flo will get that big but it has been taking its time intensifying and instead increasing its size.

[KWT]

Pressure is quite low for a low-end hurricane in the open Atlantic. Expect windspeed to catch up soon.

A little low but systems with some issues with dry air tend to have somewhat lower pressure, it will likely balance out now the system is convectively more active.

[Airboy]

D. Minimum Sea Level Pressure: 985mb (29.09 inHg)
E. Dropsonde Surface Wind at Center: From 135° at 7kts (From the SE at 8mph)
F. Eye Character: Open from the west to the southeast
G. Eye Shape & Diameter: Circular with a diameter of 20 nautical miles (23 statute miles)
H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 53kts (61.0mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 10 nautical miles (12 statute miles) to the WSW (239°) of center fix at 14:11:38Z
J. Maximum Flight Level Wind Inbound: From 311° at 65kts (From the NW at 74.8mph)

[SFLcane]

Per recon around 24.3 so indeed has continued to loose latitude.

[toad strangler]

Per recon around 24.3 so indeed has continued to loose latitude.

Looks like recon found W movement
...FLORENCE FORECAST TO RAPIDLY INTENSIFY INTO A MAJOR HURRICANE BY MONDAY...
11:00 AM AST Sun Sep 9
Location: 24.4°N 56.3°W
Moving: W at 6 mph
Min pressure: 984 mb
Max sustained: 75 mph

[cycloneye]

BULLETIN
Hurricane Florence Advisory Number 41
NWS National Hurricane Center Miami FL AL062018
1100 AM AST Sun Sep 09 2018

...FLORENCE FORECAST TO RAPIDLY INTENSIFY INTO A MAJOR HURRICANE BY
MONDAY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...24.4N 56.3W
ABOUT 750 MI...1210 KM SE OF BERMUDA
ABOUT 610 MI...985 KM NE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...984 MB...29.06 INCHES




Hurricane Florence Discussion Number 41
NWS National Hurricane Center Miami FL AL062018
1100 AM AST Sun Sep 09 2018

Satellite images indicate that Florence is strengthening. Deep
convection has intensified in the central dense overcast, with
hints of a ragged eye in the latest GOES-16 visible channel. The
NOAA Hurricane Hunters just flew through the eye, finding 70 kt
winds at flight-level and 66 kt from the SFMR. This data confirms
that Florence has become a hurricane again, and the initial wind
speed is set to 65 kt. The aircraft also found that the minimum
pressure has decreased to 984 mb.

Overnight microwave data and the Hurricane Hunter vortex message
show that a mostly complete eyewall has formed with Florence. In
combination with low vertical wind shear and progressively warmer
waters near 29C, this structure is a blueprint for rapid
intensification. Almost all of the intensity guidance is showing at
least one period of rapid strengthening during the next few days,
which is rather rare. The NHC wind speed forecast is raised in the
first couple of days following the guidance trend, then is very
similar to the previous one. All indications are that Florence will
be an extremely dangerous Category 4 hurricane while it moves over
the western Atlantic toward the southeastern United States.

Florence continues moving slowly westward, caught between a pair
of mid-level ridges over the Atlantic Ocean. A very strong ridge is
forecast to build over the northwestern Atlantic during the next few
days, which should steer Florence west-northwestward at a much
faster forward speed. By Wednesday, the hurricane should turn
northwestward, and slow down somewhat due to another ridge forming
over the Ohio Valley. It is interesting to note that while the
ensemble means from the ECMWF and UKMET are west of the NHC
forecast, the strongest members are on the right side of their
ensemble envelope. Thus, the new NHC track forecast is very similar
to the previous one, and continues to lie between the corrected
consensus and consensus aids. The Ohio Valley ridge is concerning
because Florence could stop moving pretty quickly around day 5,
potentially leading to a serious heavy rain episode and inland flood
hazard.

Key Messages:

1. There is an increasing risk of two life-threatening impacts from
Florence: storm surge at the coast and freshwater flooding from a
prolonged heavy rainfall event inland. While it is too soon to
determine the exact timing, location, and magnitude of these
impacts, interests at the coast and inland from South Carolina into
the mid-Atlantic region should closely monitor the progress of
Florence, ensure they have their hurricane plan in place, and follow
any advice given by local officials.

FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 24.4N 56.3W 65 KT 75 MPH
12H 10/0000Z 24.5N 57.4W 80 KT 90 MPH
24H 10/1200Z 24.9N 59.3W 95 KT 110 MPH
36H 11/0000Z 25.6N 61.7W 105 KT 120 MPH
48H 11/1200Z 26.4N 64.5W 120 KT 140 MPH
72H 12/1200Z 29.0N 70.8W 125 KT 145 MPH
96H 13/1200Z 32.2N 75.8W 120 KT 140 MPH
120H 14/1200Z 35.0N 78.5W 85 KT 100 MPH...INLAND

$$
Forecaster Blake

[KWT]

Florence looks like a hurricane now with deep convection all around... and it looks like it's going to be a good sized storm. A period of rapid intensification is likely soon.

Eye really is popping out at the moment when the convective burst eases at times. Certainly looking like we are in the first stages of RI though, suspect we will see Florence will be a much stronger system by tonight.

How low do people think we will go?

[KWT]

Per recon around 24.3 so indeed has continued to loose latitude.

Looks like recon found W movement
...FLORENCE FORECAST TO RAPIDLY INTENSIFY INTO A MAJOR HURRICANE BY MONDAY...
11:00 AM AST Sun Sep 9
Location: 24.4°N 56.3°W
Moving: W at 6 mph
Min pressure: 984 mb
Max sustained: 75 mph

Still loosing a little latitude based on that, but given the strengthening, you have to think that this is going to come to an end soon.

[weathaguyry]

I found it interesting that in the 11AM wind speed probabilities, NYC and Daytona Beach have the same chance of receiving TS winds.

[Hurricaneman]

By looking at how this is moving it seems maybe the models aren’t getting the initial motion right as the models are moving this from 275 to 280 while recon and satellite show 265 to 270 so maybe we have a flatter east to west ridge than modeled similar to what the NAM and NAVGEM is showing, so those even in Florida need to keep tabs on this and Georgia too