ATL: FLORENCE - Post-Tropical - Discussion

[plasticup]

TropTidbits say the machine is now a 115 knot C4...

That's from the Best Track data. So, that's official.

[RL3AO]

I'm curious to see the weakening trend when it starts. Sometimes these storms come down as quick as the go up.

[DioBrando]

TropTidbits say the machine is now a 115 knot C4...

That's from the Best Track data. So, that's official.

oofy

[txwatcher91]

I'm curious to see the weakening trend when it starts. Sometimes these storms come down as quick as the go up.

IMO the most recent visible and IR frames show the eye has contracted some and isn't as symmetrical as it was earlier today. Either a sign of shear effecting it or an EWRC starting. Too early to tell which yet but most models seem to show some decent weakening next 48 hours.

[Emmett_Brown]

Definitely gaining some latitude this afternoon.

[1900hurricane]

Where did you get that dvorak floater? Been missing all the enhanced IR products ever since the Atlantic was blacked out on ssd.noaa.gov. They really need to restore those products for GOES-EAST. I love the RBTOP loops from that site in particular.

I got it from the CSU RAMMB TC Real-Time page.

[cycloneye]

Hurricane Florence Discussion Number 26
NWS National Hurricane Center Miami FL AL062018
500 PM AST Wed Sep 05 2018

Florence has continued to intensify during the day, with colder
cloud tops completely encircling a clearer eye. Both subjective and
objective Dvorak estimates have unanimously increased to T6.0/115
kt, and on this basis, the initial intensity is raised to 115 kt,
making Florence a category 4 hurricane.

Florence appears to be right along the southern edge of a zone of
stronger vertical shear and continues to defy the intensity
guidance, which has consistently been predicting weakening. That
said, the last few satellite images indicate that the eye may be
becoming slightly disrupted by the shear. Since the shear is
anticipated to increase during the next day or so, gradual weakening
is shown in the short-term official forecast, which lies along the
upper end of the guidance through 48 hours. Beyond 48 hours,
vertical shear is anticipated to weaken, which would allow Florence
to intensify and potentially regain major hurricane status. However,
Florence will need to thread the needle between areas of stronger
shear for this to happen, and there is significant uncertainty in
the intensity forecast. The new official intensity forecast is
little changed from before except to adjust upward to account for
the higher initial intensity.

The initial motion estimate remains northwestward, or 305/11 kt.
Strong upper-level ridging is forecast to strengthen north of
Florence over the next few days, forcing the hurricane to turn
toward the west-northwest through about 48 hours. Track guidance is
good agreement during this period, and the official forecast is
essentially an update to the previous one. Beyond day 2, a break
forms in the ridge, which results in a weakening of the steering
currents, a slowdown in Florence's forward speed, and a turn back
toward the northwest. The new official forecast is shifted south a
bit on days 3-5 to account for recent model trends and is closest to
the TVCN consensus.

It should be noted that there is considerable model ensemble spread
and run-to-run variability for Florence's track beyond day 5. Given
the large uncertainty at these time ranges, it is far too soon to
speculate what, if any, impacts Florence may have on the U.S. East
Coast next week. Regardless of Florence's eventual track, large
swells emanating from the hurricane will reach Bermuda beginning on
Friday, resulting in life-threatening surf and rip currents on the
island. Swells from Florence could also reach the U.S. East Coast by
early next week.

FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 22.7N 46.6W 115 KT 130 MPH
12H 06/0600Z 23.5N 48.1W 110 KT 125 MPH
24H 06/1800Z 24.5N 49.7W 105 KT 120 MPH
36H 07/0600Z 25.2N 51.3W 100 KT 115 MPH
48H 07/1800Z 25.5N 52.9W 95 KT 110 MPH
72H 08/1800Z 26.0N 55.3W 100 KT 115 MPH
96H 09/1800Z 27.0N 57.4W 105 KT 120 MPH
120H 10/1800Z 29.0N 60.0W 105 KT 120 MPH

$$
Forecaster Berg/Rhome

[cycloneye]

BULLETIN
Hurricane Florence Advisory Number 26
NWS National Hurricane Center Miami FL AL062018
500 PM AST Wed Sep 05 2018

...FLORENCE STRENGTHENS INTO A CATEGORY 4 HURRICANE...

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...22.7N 46.6W
ABOUT 1110 MI...1790 KM ENE OF THE NORTHERN LEEWARD ISLANDS
ABOUT 1295 MI...2080 KM ESE OF BERMUDA
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...953 MB...28.15 INCHES

[plasticup]

To get a sense of how remarkable this was day, compare the first and last visible images of Florence:

0920z:


2020z:


Incredible.

[LarryWx]

The 12Z EPS has an accurate 12Z initialization. However, the 5PM location of 22.7N, 46.6W is north of the mean by ~0.5 degrees or 35 statute miles and is near the northernmost members. Flo has moved NW since 12Z vs the WNW of the 12Z EPS mean. If Flo continues to track on the N edge of the members all other things being equal, that would be encouraging for a better chance for a safe recurve next week. I’d prefer she track on the northern edge over the middle and certainly over the southern edge. But that’s about as much as I can say about that as there is way too much uncertainty regardless of how it is now tracking with regard to the 12Z EPS.

[MacTavish]

Definitely looks to have taken a bend to the right over the last few hours.

[Hurricane Andrew]

I will briefly pop back on to add a note that now sticks in my heart after last season.

Climatology, historical patterns, etc, can mean absolutely squat to a tropical cyclone. It does what it dies; just because it hasn't happened before, or is rare, doesn't mean it won't happen. Irma taught many of us that on a personal level last fall.

[supercane4867]

I will briefly pop back on to add a note that now sticks in my heart after last season.

Climatology, historical patterns, etc, can mean absolutely squat to a tropical cyclone. It does what it dies; just because it hasn't happened before, or is rare, doesn't mean it won't happen. Irma taught many of us that on a personal level last fall.

Also don't forget last year's Ophelia, It wasn't supposed to intensify into a major over 25C SSTs. But it just happened.

[LarryWx]

I will briefly pop back on to add a note that now sticks in my heart after last season.

Climatology, historical patterns, etc, can mean absolutely squat to a tropical cyclone. It does what it dies; just because it hasn't happened before, or is rare, doesn't mean it won't happen. Irma taught many of us that on a personal level last fall.

Some people use climo/history the wrong way. It is a very useful tool but rather than provide 100% certainties they provide guidance as to tendencies/probabilities. History may not repeat itself exactly but it will often rhyme.

I'll give an extreme hypothetical example to make a point about the usefulness of climo: no TS+ has moved from N of 34N, 50W, to the CONUS in records back to 1851. Based on this fact, alone, if there is a TS+ at, say 40N, 50W, I'll bet very, very heavily against it later hitting the CONUS not knowing anything else about the TS+ and just using climo. It may not be a 100% chance it will be right in this case, but I'd go with 99%+ in something like this. Climo is also useful in much less extreme scenarios in setting odds or trying to make a prediction.

[pcbjr]

I will briefly pop back on to add a note that now sticks in my heart after last season.

Climatology, historical patterns, etc, can mean absolutely squat to a tropical cyclone. It does what it dies; just because it hasn't happened before, or is rare, doesn't mean it won't happen. Irma taught many of us that on a personal level last fall.

Some people use climo/history the wrong way. It is a very useful tool but rather than provide 100% certainties they provide guidance as to tendencies/probabilities. History may not repeat itself exactly but it will often rhyme.

I'll give an extreme hypothetical example to make a point about the usefulness of climo: no TS+ has moved from N of 34N, 50W, to the CONUS in records back to 1851. Based on this fact, alone, if there is a TS+ at, say 40N, 50W, I'll bet very, very heavily against it later hitting the CONUS not knowing anything else about the TS+ and just using climo. It may not be a 100% chance it will be right in this case, but I'd go with 99%+ in something like this. Climo is also useful in much less extreme scenarios in setting odds or trying to make a prediction.

Larry,
I'll go with this ... they always, always show up, where you least want them ... if you live there ...

[LarryWx]

I will briefly pop back on to add a note that now sticks in my heart after last season.

Climatology, historical patterns, etc, can mean absolutely squat to a tropical cyclone. It does what it dies; just because it hasn't happened before, or is rare, doesn't mean it won't happen. Irma taught many of us that on a personal level last fall.

Some people use climo/history the wrong way. It is a very useful tool but rather than provide 100% certainties they provide guidance as to tendencies/probabilities. History may not repeat itself exactly but it will often rhyme.

I'll give an extreme hypothetical example to make a point about the usefulness of climo: no TS+ has moved from N of 34N, 50W, to the CONUS in records back to 1851. Based on this fact, alone, if there is a TS+ at, say 40N, 50W, I'll bet very, very heavily against it later hitting the CONUS not knowing anything else about the TS+ and just using climo. It may not be a 100% chance it will be right in this case, but I'd go with 99%+ in something like this. Climo is also useful in much less extreme scenarios in setting odds or trying to make a prediction.

Larry,
I'll go with this ... they always, always show up, where you least want them ... if you live there ...

Or they will always go to where Jim Cantore is reporting from, climo supported or not!

[Hurricane Andrew]

I will briefly pop back on to add a note that now sticks in my heart after last season.

Climatology, historical patterns, etc, can mean absolutely squat to a tropical cyclone. It does what it dies; just because it hasn't happened before, or is rare, doesn't mean it won't happen. Irma taught many of us that on a personal level last fall.

Some people use climo/history the wrong way. It is a very useful tool but rather than provide 100% certainties they provide guidance as to tendencies/probabilities. History may not repeat itself exactly but it will often rhyme.

I'll give an extreme hypothetical example to make a point about the usefulness of climo: no TS+ has moved from N of 34N, 50W, to the CONUS in records back to 1851. Based on this fact, alone, if there is a TS+ at, say 40N, 50W, I'll bet very, very heavily against it later hitting the CONUS not knowing anything else about the TS+ and just using climo. It may not be a 100% chance it will be right in this case, but I'd go with 99%+ in something like this. Climo is also useful in much less extreme scenarios in setting odds or trying to make a prediction.

Oh, for sure! I'm not saying to throw out climo, don't get me wrong. I just remember some people (not necessarily here) who said that "X" and "Y" were all but impossible due to climo, etc, and that's a dangerous line of thinking.

[GCANE]

Doesn't look to be weakening anytime soon.
Off-the-scale rain rate.

[GeneratorPower]

Some people use climo/history the wrong way. It is a very useful tool but rather than provide 100% certainties they provide guidance as to tendencies/probabilities. History may not repeat itself exactly but it will often rhyme.

I'll give an extreme hypothetical example to make a point about the usefulness of climo: no TS+ has moved from N of 34N, 50W, to the CONUS in records back to 1851. Based on this fact, alone, if there is a TS+ at, say 40N, 50W, I'll bet very, very heavily against it later hitting the CONUS not knowing anything else about the TS+ and just using climo. It may not be a 100% chance it will be right in this case, but I'd go with 99%+ in something like this. Climo is also useful in much less extreme scenarios in setting odds or trying to make a prediction.

Larry,
I'll go with this ... they always, always show up, where you least want them ... if you live there ...

Or they will always go to where Jim Cantore is reporting from, climo supported or not!

The center will always pass 10-20 miles from Mark Sudduth’s location. Draw your own conclusions.

[Ntxw]

Raw T's have dropped a bit from earlier today with the warming cloud tops. Still a solid major.