ATL: FIONA - Post-Tropical - Discussion

[Aric Dunn]

Convention building again around the center. will probably build quite a bit and collapse many more times with the SAL around but should strengthen somewhat.

[tarheelprogrammer]

This system looks like crap to put it kindly. Not sure how/why it would get an upgrade to TS but so far it seems to be struggling to even produce convection. Earl was an invest earlier this month and still looked better than this.

It looks fine. The convection has waned somewhat; hardly makes it "crap". It's still a well defined system, and it's only a 5kt difference between a TD and TS, your hyperbole on its "crappy" looks aside. If the NHC decides to wait, it will probably be due to the ASCAT pass.

It is fighting SAL and losing currently. It could find better conditions down the road but I doubt it. Atlantic is looking pretty hostile at the moment and doesn't look to change much in the models.

[hurricanes1234]

Uncle Sal wants to give this system a visit.

[TheStormExpert]

Looks pathetic like most tropical cyclones in the Atlantic so far this season.

[TheStormExpert]

 https://twitter.com/mjventrice/status/765915174662537217

[tolakram]

System looks pretty good to me, what image is showing it looking like crap? What evidence is there that the system is ingesting dry air?

It's certainly not ramping up quickly, but hardly falling apart.

Live visible, still not in range of the hither rez loops.
http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20NHE&lat=19&lon=-28&info=vis&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=ir1.pal&numframes=5

WV
http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20NHE&lat=19&lon=-28&info=wv&zoom=1&width=1024&height=768&type=Animation&quality=92&palette=wv2.pal&numframes=5

[wxman57]

Even though the NHC initialized the model guidance at 35kts, the recent ASCAT pass indicating no 35kt barbs combined with diminishing convection means it'll remain a TD this morning. If it does make it to TS strength it may not last very long as a TS. Euro ensembles are more westward than the GFS, but keep it below TS strength for the most part.

[chaser1]

As I see it, TD6 has a nicely established circulation. While there is significant dry air around it, I think that the moist feed to its south will allow it to strengthen a little and attain T.S. intensity sometime today or early tomm. While I don't quite think it will directly impact the Leeward Islands, as it approaches 55W, the water temps warm to 29C and I can see a plausible outcome being where a struggling storm, depression, or remnant low might reintensify north of the islands. I'm not ready to assume that the Carolina's or the Northeast U.S. is absolutely without concern here especially in light of a poleward (Northwest, NNW, or Northerly) moving system that might well mitigate some minimal southerly shear at that time. At such a time, water temps will have increased to about 31C. My concerns are the possibility of a CONUS 500mb ridge that could expand eastward in the wake of a progressive east coast trough that might just be pulling up and out around that time. Such a scenario might just be enough to capture any storm south of 40N and west of 60W. Overall, a struggling TD6 or Fiona would end up being the primary cause for any chance of the storm to potentially threaten Bermuda or any other point. Ironically without Uncle SAL making his untimely visit, Fiona would likely be strengthening fairly steadily and already moving in a decernable NW direction safely out to sea.

[TheStormExpert]

Still TD #6 @ 11am.

[cycloneye]

BULLETIN
TROPICAL DEPRESSION SIX ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016
1100 AM AST WED AUG 17 2016

...DEPRESSION EXPECTED TO BECOME A TROPICAL STORM LATER TODAY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...14.0N 36.4W
ABOUT 840 MI...1350 KM W OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES



TROPICAL DEPRESSION SIX DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016
1100 AM AST WED AUG 17 2016

The depression's overall cloud pattern and low-level wind field have
continued to improve, although cloud tops have warmed considerably
near the center since the previous advisory. An 1139Z ASCAT-B
overpass showed a well-defined low-level circulation center with a
tight radius of maximum winds of only 10-15 nmi. Although there were
a few vectors near tropical storm force, and satellite estimates at
1200Z were T2.5/35 kt from TAFB and SAB, the intensity is being
maintained at 30 kt for this advisory due to the sharp decrease in
deep convection near the center during the past few hours.

The modest northeasterly vertical wind shear across the cyclone is
forecast to weaken and veer to the southeast during the next 12
hours, and remain less than 10 kt for the next 36-48 hours, which
typically favors strengthening. Sea-surface temperatures just below
27C are marginal for intensification and the small cyclone will be
moving through dry mid-level air with humidity values dropping below
50 percent by 48 hours and beyond, conditions that are generally not
conducive for significant strengthening. But given the tight
inner-core wind field noted in recent ASCAT data, the cyclone is
expected to be able to mix out any dry air intrusions and slowly
strengthen for about the next 48 hours. By 72 hours and beyond,
however, increasing southwesterly to westerly wind shear is expected
to induce gradual weakening. The official intensity forecast is
similar to the previous advisory and closely follows the intensity
consensus model IVCN.

The initial motion estimate is 300 /13 kt, based primarily on
microwave and scatterometer fixes. The NHC model guidance is in
good agreement on the cyclone moving west-northwestward to
northwestward toward a weakness in the Bermuda-Azores ridge for the
next 48 hours or so. After that, however, there is significant
divergence in the models with the GFDL, GFS, and GFS-ensemble mean
models taking a stronger and more vertically deep cyclone more
toward the northwest, whereas the HWRF, UKMET, NAVGEM, and ECMWF
models show a weaker and shallower cyclone turning more westward
and moving along the southern periphery of the low-level ridge. As
a result, the forecast track depends heavily on the strength and
vertical structure of the cyclone. The new NHC forecast track is a
little to the south or left of the previous advisory, but not nearly
as far south as the ECMWF model due to expectations that the cyclone
will not weaken nearly as much as that model is indicating.

The forecast wind radii were decreased somewhat based on the smaller
wind field depicted in recent ASCAT data.

FORECAST POSITIONS AND MAX WINDS

INIT 17/1500Z 14.0N 36.4W 30 KT 35 MPH
12H 18/0000Z 14.9N 37.7W 35 KT 40 MPH
24H 18/1200Z 16.0N 39.3W 40 KT 45 MPH
36H 19/0000Z 17.0N 40.7W 45 KT 50 MPH
48H 19/1200Z 17.9N 42.3W 50 KT 60 MPH
72H 20/1200Z 19.6N 45.9W 45 KT 50 MPH
96H 21/1200Z 21.8N 49.8W 40 KT 45 MPH
120H 22/1200Z 23.9N 53.4W 35 KT 40 MPH

$$
Forecaster Stewart

[Florida1118]

Looks pathetic like most tropical cyclones in the Atlantic so far this season.

Oh the horrors. 2 hurricanes, that both impacted land, by Mid August, and a Tropical Depression, in an area we ALREADY knew wasn't going to be very favorable, is hardly pathetic. Quit having a pity party for once. It's a Tropical Depression, it's going to have to fight sometimes like we already knew it would. It'll be fine, and I'm sure it'll make a good run at becoming Fiona.

[Kazmit]

The cone is slowly moving more to the southwest...

[hurricanes1234]

According to this advisory it's expected to mix out the dry air and still strengthen.

[Kazmit]

12z guidance. More models now show a more WNW track than the initially predicted NW one.

[Florida1118]

"The depression's overall cloud pattern and low-level wind field have continued to improve"...hmm, the NHC seems to think its not a "pathetic" "crap" storm It's structure looks great, just needs some more convection and it'll be a fine looking storm.

[JaxGator]

Building more convection around the center. The storm looks fine to me and the cone has also shifted more south on the latest advisory.

[terstorm1012]

Structure looks pretty good, given the hostility it faces out there. Fiona at 5pm or 11pm I say.

[wxman57]

Building more convection around the center. The storm looks fine to me and the cone has also shifted more south on the latest advisory.

Note that the "cone' merely identifies track error (66.7 percentile) over the previous 5 years, it has nothing to do with the current levels of uncertainty with this (or any) potential storm. In this case, uncertainty would be a little higher than normal. The center could very easily track south/west of the current cone. In fact, ensemble guidance is centered on a track taking it to 20N/60W in 5-6 days - but as a TD or remnant low, not a TS. It will likely continue to struggle.

[LarryWx]

:uarrow:

I think that's because it runs into a wall of strong shear. And the Euro pretty much takes it to a latitude that even if it survives the shear it'll miss the GOM where conditions are favorable.

On the other hand, there have been a number of noteable past hurricanes which have reached a position of approx. 22N and 55W that did make landfall on the CONUS East Coast, some having significant impact.

There have been H's that were near 22N, 55W, that later hit the CONUS east coast but note that no MDR TC on record that moved at 315+ degrees between any two 6 hourly positions east of around 48W made it all of the way to the CONUS as a TC. So, I'm looking to see if there will be any NW movement of TD 6 anytime soon.

Edit: TD 6 has yet to move NW (315 degrees) and is now not forecasted to do so. However, the chance of a later Conus hit still has to be considered very low at this point, especially if it strengthens soon.

[Yellow Evan]

FYI, there's a low bias with ASCAT, especially with smaller systems.