ATL: FLORENCE - Post-Tropical - Discussion

[GCANE]

Last three Archer satellite fixes show a consistent and increasing deviation south of forecast track.

Great map - Are you able to share link on where you get this this map for this and other storms?

http://tropic.ssec.wisc.edu/real-time/a ... ndex.shtml

[PavelGaborik10]

Shear is moving with the storm, doesn't seem to be hurting her either.

Now, these factors will likely prevent her from becoming a 5, or maybe even a strong 4, but the NHC's forecast seems to discount them as hindering a 145-150mph hurricane. And even a 3 of her size and magnitude could be devastating.

If you're hoping for dry air to prevent this thing from bombing out to a strong cat 4, or even a potential 5...you best hope it starts doing it's thing ASAP. This thing is exploding, at this rate I expect a cat 4 by this evening.

[txwatcher91]

Last three Archer satellite fixes show a consistent and increasing deviation south of forecast track.

http://i65.tinypic.com/2q8r1oi.png

Why would we use satellite estimates which are prone to error/deviation when we have the official NHC plot points that are much more accurate? The official NHC points are showing the gradual turn here.

[GCANE]

Eyewall just about perfect symmetry.
Cloud top temperatures at top of the scale

https://weather.msfc.nasa.gov/cgi-bin/b ... 0(Band%208)&time_drop=show

[otowntiger]

Shear is moving with the storm, doesn't seem to be hurting her either.

Now, these factors will likely prevent her from becoming a 5, or maybe even a strong 4, but the NHC's forecast seems to discount them as hindering a 145-150mph hurricane. And even a 3 of her size and magnitude could be devastating.

If you're hoping for dry air to prevent this thing from bombing out to a strong cat 4, or even a potential 5...you best hope it starts doing it's thing ASAP. This thing is exploding, at this rate I expect a cat 4 by this evening.

While its pretty clear this will likely be a very strong hurricane regardless, I think the point can be made that they can weaken as quickly as they strenghten. I"m not saying that will happen here but since the NHC still struggles with accurate intensity forecasts (although they are getting better) Flo could do her thing now and RI up to and beyond forcast but could have just the right amount of currently unforcast dry air and shear to take a lot of the wind out of her sails (no pun intended, lol!) prior to landfall. One can hope, but it certainly is not impossible by any means.

[otowntiger]

Eyewall just about perfect symmetry.
Cloud top temperatures at top of the scale

https://weather.msfc.nasa.gov/cgi-bin/b ... 0(Band%208)&time_drop=show

That loop shows a distinct lattitude gain, doesn't it? I know its may not be quite as much as forecast but I wonder if its negligible at this point?

[cycloneye]

Very impressive.

 https://twitter.com/NOAASatellites/status/1039139924304384001

[Yellow Evan]

Clear cut T5.5. OW eye with B ring.

[northjaxpro]

Hmmm.. This is very interesting indeed!

if this keeps going for another few hours. I wont say Im not surprised. lol

This would imply to me that stronger ridging is already in place.

[GCANE]

Eyewall just about perfect symmetry.
Cloud top temperatures at top of the scale

https://weather.msfc.nasa.gov/cgi-bin/b ... 0(Band%208)&time_drop=show

That loop shows a distinct lattitude gain, doesn't it? I know its may not be quite as much as forecast but I wonder if its negligible at this point?

I think it may be a bit deceiving.
Need to watch the date and time stamp closely.
Looks almost due west from 6:00Z to 12:45Z

[cycloneye]

 https://twitter.com/TheAstroNick/status/1039139901944602625

[Aric Dunn]

[img]http://i65.tinypic.com/2q8r1oi.png[/ig]

Hmmm.. This is very interesting indeed!

if this keeps going for another few hours. I wont say Im not surprised. lol

This would imply to me that stronger ridging is already in place.

Correct. the upper air mission just completed. the data should get into the 12z models.

then there is the issue of it continually passing south or well south of forecast points. all the models had a distinct wnw turn at 60W ..

it is at 60 west with no sign of a turn. just barely a drift north of west. still considered west for the last 3 hours.

[Mouton]

Storm has an interesting XTRAP trend moving from southerly over the past 6 hours. This flies in the face of the NW turn and to me indicates that Ridge is building west, not retreating to the North, North East or staying stationary. An earlier EURO had this storm doing a loop over NC and back over SE Ga which to me showed some belief by that run the ridge would become stronger or move west with the storm but staying out in front. While the most recent EURO shows a straight line path after land fall, what I am seeing does not equal what the models are all telling me.

This movement generally west continues another day and I will skeddalle from NE Florida to points west starting with Tallahassee regardless of the cone!

[Blinhart]

Eyewall just about perfect symmetry.
Cloud top temperatures at top of the scale

https://weather.msfc.nasa.gov/cgi-bin/b ... 0(Band%208)&time_drop=show

That loop shows a distinct lattitude gain, doesn't it? I know its may not be quite as much as forecast but I wonder if its negligible at this point?

That loops was over almost a whole day, and didn't even gain a whole degree of Latitude, so not much gain.

[Aric Dunn]

if this motion continues for the next 2 hours. we will likely see out first short term track adjustment to the west.. probably 1st of many..

[Shell Mound]

The sharp increase in southwesterly vertical wind shear shortly before landfall is related to the amplification and retrogression of the mid-level trough over the central subtropical North Atlantic. As this trough does so, it erodes and displaces the anticyclone over Florence, resulting in shear. The slowing movement of Florence as it nears the coastline will only enhance the strength of the storm-relative shear, and also result in upwelling of relatively cooler shelf waters as the storm leaves the Gulf Stream. Additionally, the shear vectors will certainly draw in some drier continental air; however, the absence of an approaching large-scale trough from the west mitigates this somewhat. Nevertheless, even if Florence were to strengthen to near-Cat-5 status over the thirty-six hours, the increase in shear and upwelling, owing to both the trough and the reduction in forward speed, will cause significant weakening in the intensity of Florence before landfall. The rate of weakening could well be faster than the initial intensification. I think a Cat-4 landfall is very unlikely, despite the NHC's forecast. Florence, while quite likely to reach Cat-4 status over the Gulf Stream, will probably be a Cat-2 or low-end Cat-3 at landfall. I would go with a peak of 130-135 knots over the Gulf Stream and a landfall intensity of 90-105 knots over eastern NC. This is more in line with climatology for major hurricanes at the latitude of eastern NC. Honestly, I think rain and storms surge are going to be the biggest threats. Wind, while threatening, will not differ significantly from that of climatology for Cat-2/Cat-3 systems at this latitude.

[jlauderdal]

if this motion continues for the next 2 hours. we will likely see out first short term track adjustment to the west.. probably 1st of many..

i am with you until we go down, i have been thinking further west since saturday..gfs is so biased towards the right its sad, lets see..today is the day of truth

[StormPyrate]

Second eyewall?
https://www.tropicaltidbits.com/sat/satlooper.php?region=meso1&product=ir

[Blinhart]

The sharp increase in southwesterly vertical wind shear shortly before landfall is related to the amplification and retrogression of the mid-level trough over the central subtropical North Atlantic. As this trough does so, it erodes and displaces the anticyclone over Florence, resulting in shear. The slowing movement of Florence as it nears the coastline will only enhance the strength of the storm-relative shear, and also result in upwelling of relatively cooler shelf waters as the storm leaves the Gulf Stream. Additionally, the shear vectors will certainly draw in some drier continental air; however, the absence of an approaching large-scale trough from the west mitigates this somewhat. Nevertheless, even if Florence were to strengthen to near-Cat-5 status over the thirty-six hours, the increase in shear and upwelling, owing to both the trough and the reduction in forward speed, will cause significant weakening in the intensity of Florence before landfall. The rate of weakening could well be faster than the initial intensification. I think a Cat-4 landfall is very unlikely, despite the NHC's forecast. Florence, while quite likely to reach Cat-4 status over the Gulf Stream, will probably be a Cat-2 or low-end Cat-3 at landfall. I would go with a peak of 130-135 knots over the Gulf Stream and a landfall intensity of 90-105 knots over eastern NC. This is more in line with climatology for major hurricanes at the latitude of eastern NC.

Florence has already proven you can not go with Climatology with her. There will not be much to cause her to weaken, there is nearly no wind shear forecasted for her in the future. She should be able to get well in the Cat 5 status, Landfall should be at the lowest Cat 4.

[BobHarlem]

Two RI hurricanes happening at once, Helene's shooting up quickly also (NHC put out a special update for that), Florence looks like it also. But no special update for it (yet).