ATL: FLORENCE - Post-Tropical - Discussion

[plasticup]

Hello Florence! Welcome to the party...I hope you like fish...unless the euro is right...

NWS National Hurricane Center Miami FL AL062018
500 AM AST Sat Sep 01 2018

...TROPICAL STORM FLORENCE FORMS JUST WEST OF THE CABO VERDE
ISLANDS.

It is exceedingly difficult and really quite rare for storms that genesis this far E to hit CONUS.

There is a lot of land in the Atlantic other than CONUS. Bermuda is the most likely to be affected by this storm.

[plasticup]

I am wondering why we don't see these Atlantic storms indicated on the map at the top of the screen. I see the Epac ones but none of the
Atlantic. Did something change?

It has to be a glitch on the map.Hopefully is fixed very soon.

I'm not sure, I was hoping the declaration of a TD would fix it.

TS upgrade didn't fix it either. Could it be that coordinates so far East aren't rendered on the map?

[cycloneye]

BULLETIN
Tropical Storm Florence Intermediate Advisory Number 8A
NWS National Hurricane Center Miami FL AL062018
800 AM AST Sat Sep 01 2018

...TROPICAL STORM FLORENCE MOVING AWAY FROM THE CABO VERDE
ISLANDS...
...TROPICAL STORM WARNINGS DISCONTINED FOR THOSE ISLANDS...


SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...14.6N 27.2W
ABOUT 185 MI...300 KM W OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

[tolakram]

It has to be a glitch on the map.Hopefully is fixed very soon.

I'm not sure, I was hoping the declaration of a TD would fix it.

TS upgrade didn't fix it either. Could it be that coordinates so far East aren't rendered on the map?

The site used to get the data is down for the Atlantic, the directory is missing from the NOAA site. We are also receiving a message from another tool that a product is no longer supported. Not sure if this is a temporary glitch or not.

[xtyphooncyclonex]

Would be very uncomfortable if Florence develops slower than forecast or unexpectedly weakens. The recurve window seems to be a short one.

Even if this strengthens, a westerly path would remain likely.

[tolakram]

Pretty impressive looking this morning.

SLIDER: http://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=full_disk&x=18996&y=7960&z=4&im=12&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&p%5B0%5D=1&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&s=rammb-slider

[ava_ati]

Pretty impressive looking this morning.

SLIDER: http://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=full_disk&x=18996&y=7960&z=4&im=12&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&p%5B0%5D=1&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&s=rammb-slider

I was ready to write the GFS strength off as being another pipe dream but that is already an impressive looking structure as a whole

[otowntiger]

Would be very uncomfortable if Florence develops slower than forecast or unexpectedly weakens. The recurve window seems to be a short one.

Even if this strengthens, a westerly path would remain likely.

Possible, but not likely. Re-curves are generally more likely in this part of the Atlantic than anything else.

[OuterBanker]

Hmm, interesting in the 5 am discuss.

"The European model, in particular, swung
significantly to the left, showing a weaker Florence not feeling the
break in the ridge quite as much. I'd like to see this trend
continue before making a significant change to the forecast, so for
now the updated NHC track prediction is only nudged westward. That
said, the models appear to be trending away from a definitive
recurvature scenario."

I'm wondering if they will work the west shift into their plot later today.

I thought this was pretty much a given fish.

[Hurricaneman]

Hmm, interesting in the 5 am discuss.

"The European model, in particular, swung
significantly to the left, showing a weaker Florence not feeling the
break in the ridge quite as much. I'd like to see this trend
continue before making a significant change to the forecast, so for
now the updated NHC track prediction is only nudged westward. That
said, the models appear to be trending away from a definitive
recurvature scenario."

I'm wondering if they will work the west shift into their plot later today.

I thought this was pretty much a given fish.

Certainly not a given and more a 50/50 chance it is a threat area southeast US to Bermuda

[cycloneye]

Tropical Storm Florence Discussion Number 9
NWS National Hurricane Center Miami FL AL062018
1100 AM AST Sat Sep 01 2018

Satellite images indicate that Florence's cloud pattern has improved
in organization with the low-level center embedded within the
convection, and a cyclonically curved band surrounding the system. A
blend of subjective and objective Dvorak numbers from TAFB, SAB, and
the UW-CIMMS yield an initial intensity of 40 kt.

My predecessor wrote a very clear explanation of the reasoning of
his track and intensity forecasts, and I do not think I can improve
on it. The environment continues to be mixed with favorable and
unfavorable conditions for Florence to strengthen. Currently,
the shear is low and favors strengthening, but the ocean along the
cyclone's forecast path is cooler. The latter condition should
inhibit significant intensification. After 3 days, the opposite is
anticipated -- the ocean will be warmer, but the shear will likely
be high. Only at the very long range could both factors become
favorable. The best option at this time is to show only a gradual
strengthening at the rate indicated by the intensity consensus aids.

Florence is still moving toward the west-northwest or 295 degrees
at 12 kt. No change in track is anticipated during the next 3 days
while Florence is located to the south of the subtropical ridge.
After that time, Florence will reach a break in the ridge causing
the cyclone to turn toward the northwest with a decrease in forward
speed. The confidence in the forecast is high during the next 3 days
when the track guidance envelope is tightly packed. Thereafter, the
confidence is not so high since the envelope widens and becomes
bounded by the easternmost HWRF and the westernmost ECMWF models.
Since the guidance envelope shifted a little bit westward, the NHC
forecast was also adjusted slightly in that direction, primarily
during the end of the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 14.8N 27.8W 40 KT 45 MPH
12H 02/0000Z 15.3N 29.7W 45 KT 50 MPH
24H 02/1200Z 16.1N 32.4W 50 KT 60 MPH
36H 03/0000Z 16.5N 35.0W 50 KT 60 MPH
48H 03/1200Z 17.0N 37.5W 55 KT 65 MPH
72H 04/1200Z 19.0N 42.5W 60 KT 70 MPH
96H 05/1200Z 21.0N 46.5W 60 KT 70 MPH
120H 06/1200Z 23.5N 50.0W 55 KT 65 MPH

$$
Forecaster Avila

[Ntxw]

Florence is a very well organized system. Will be around for awhile. It may be stable for a few days yielding 3-5 ACE units per the NHC forecast through 5 days, but will have opportunity to really get going once it hits warmer waters further northwest later on.

[ava_ati]

Hmm, interesting in the 5 am discuss.

"The European model, in particular, swung
significantly to the left, showing a weaker Florence not feeling the
break in the ridge quite as much. I'd like to see this trend
continue before making a significant change to the forecast, so for
now the updated NHC track prediction is only nudged westward. That
said, the models appear to be trending away from a definitive
recurvature scenario."

I'm wondering if they will work the west shift into their plot later today.

I thought this was pretty much a given fish.

Depended who you talked to I had to correct my local meteorologist whose tweet made it sound like it was definitely going to re-curve. If we were still in the same pattern back in July and August where we had troughs making it all the way to the Gulf coast I would agree but the pattern we are in now you just can't put your eggs into these tiny gaps of high pressure 5 - 10 days out.

With that said, I think the ECMWF is underestimating the strength compared to what we are already seeing on visible this morning. So I don't exactly buy what it is selling at this point either.

[WAcyclone]

Microwave eye feature evident on the latest AMSR2 pass:

[Kazmit]

Florence seems to be gaining quite a bit of latitude now.

[Shell Mound]

Microwave eye feature evident on the latest AMSR2 pass:

This system is well on its way to hurricane status. Like Beryl, it is a compact intensifier in an otherwise unfavourable thermodynamic (dry) environment. In the short term, Florence is well ahead of even the most aggressive model guidance, owing to very conducive anticyclonic flow (upper-level divergence and low-level convergence). Plus, the inflow from the ITCZ is helping the system fend off periodic dry-air intrusions (stratocumulus) from the north and west. The fact that convection is developing near the nascent core during diurnal minimum (in a rather dry environment) is disconcerting. Rapid intensification definitely seems to be occurring. Florence will have at least two more days of low vertical shear before it encounters the TUTT, and the thermodynamics are not going to change appreciably, so it could easily reach Cat-2 or stronger status for a brief period, and will likely become a hurricane later tonight.

[chaser1]

Florence seems to be gaining quite a bit of latitude now.

At first blush I'd agree. I also think it is gaining a bit of latitude however less then what I had first thought earlier today. I think it's formative organizational process has contributed to appear as if it made a significant "stair-step" toward the northwest. Overall though, I'm thinking that it's more or less tracking on a 285 degree course. Sure does help to have a better identified COC to track! Continued moderate deepening should ensure easier Sat. observational analysis (along with improved model output). That all said, I have to believe that its present rate of organization might be a cause for NHC to adjust their near term track a bit more northward in their 5:00pm package. No way do I see Florence at (or south) of NHC's current 9/2 - 0Z forecast position of 15.3 and 29.7.

[Shell Mound]

At this point, the most likely outcome is a possible track near or over Bermuda in the long range, with a subsequent threat to Atlantic Canada. The synoptic pattern looks to become more progressive over time, resulting in transient ridging rather than stationary or quasi-stationary blocking. This would tend to favour a track to seaward of the U.S. East Coast. This is not necessarily a "fishy" scenario, however, as Bermuda and Canada are in line. Conditions look to become more conducive to intensification once Florence passes through the TUTT zone and enters the subtropics, so Bermuda and Atlantic Canada could still be looking at a potential (major) hurricane threat. Those areas should pay especially close attention to Florence.

[Kazmit]

It's funny the similarities this storm shares with Hurricane Florence of 2006. Both formed within a few days of one another, and it looks like this Florence may affect Bermuda in the future, like 2006 Florence did.

[cycloneye]

Tropical Storm Florence Discussion Number 10
NWS National Hurricane Center Miami FL AL062018
500 PM AST Sat Sep 01 2018

The cloud pattern has continued to improve with a circular area of
convection near the center, and a cyclonically curved band
surrounding the system. The upper-level outflow is fair in all
quadrants. Although the cloud pattern is better organized, the
Dvorak T-numbers have not changed, and only support 40 kt at this
time.

Florence has a couple of more days embedded within a low-shear
environment which supports strengthening, but it is also currently
heading toward marginal SSTs. By the time the cyclone reaches
warmer waters again, the shear is forecast to be unfavorable. The
best option at this time is to show only a very modest strengthening
at the rate indicated by the intensity consensus aids.

Florence has been moving toward the west-northwest or 285 degrees
at 12 to 14 kt. No change in track is anticipated during the next 3
days while Florence is located to the south of the Atlantic
subtropical ridge. After that time, Florence will reach a break in
the ridge causing the cyclone to turn toward the northwest with a
decrease in forward speed. The latter portion of the forecast is
uncertain since the strength of the subtropical ridge to the north
has been fluctuating from run to run in each model. At this time,
the overall guidance has been shifting a little bit westward,
suggesting a stronger ridge. On this basis, the NHC forecast was
adjusted slightly in that direction at the end of the forecast
period.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 15.6N 29.0W 40 KT 45 MPH
12H 02/0600Z 16.2N 31.0W 45 KT 50 MPH
24H 02/1800Z 16.8N 33.7W 50 KT 60 MPH
36H 03/0600Z 17.5N 36.5W 55 KT 65 MPH
48H 03/1800Z 18.0N 39.0W 55 KT 65 MPH
72H 04/1800Z 19.5N 43.5W 55 KT 65 MPH
96H 05/1800Z 21.5N 48.0W 50 KT 60 MPH
120H 06/1800Z 23.5N 52.0W 50 KT 60 MPH

$$
Forecaster Avila