ATL: LEE - Post-Tropical Low - Discussion

[cycloneye]

BULLETIN
Tropical Depression Fourteen Advisory Number 1
NWS National Hurricane Center Miami FL AL142017
1100 PM AST Thu Sep 14 2017

...TROPICAL DEPRESSION FORMS OVER THE EASTERN ATLANTIC...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...10.7N 25.4W
ABOUT 380 MI...610 KM SSW OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 22 MPH...35 KM/H
MINIMUM CENTRAL PRESSURE...1010 MB...29.83 INCHES

[HurricaneRyan]

Smells like a recurve

[La Breeze]

Smells like a recurve

Let's hope that it's a re-curve out at sea (a fish)!

[Sciencerocks]

Seems to have nice banding and has sustained convection. We'll have to wait until Tafb and Sab says 2.5t.

[cycloneye]

Tropical Depression Fourteen Discussion Number 4
NWS National Hurricane Center Miami FL AL142017
500 PM AST Fri Sep 15 2017

The depression has become less organized since earlier today with
the center now exposed to the north and northwest of the deep
convection due to northwesterly shear. Dvorak data T-numbers have
decreased, but an average of the current intensity numbers of
1.5 and 2.5 support maintaining an initial wind speed of 30 kt.
Although the depression is forecast to move over warm water,
moderate northwesterly shear and dry mid-level air to the north
of the cyclone is likely to prevent significant intensification.
However, most of the intensity guidance shows some strengthening and
the depression is forecast to become a tropical storm within the
next day or two. After that time, increasing westerly shear
produced by a mid- to upper-level trough over the central Atlantic
is expected to weaken the system, and the tropical cyclone is now
forecast to degenerate to a remnant low by day 5. The new NHC
intensity forecast has been adjusted downward to be in better
agreement with the various intensity consensus aids.

The depression has jogged a little northward this afternoon, but the
long-term motion is west-northwestward at about 10 kt. The
depression is expected to move westward to west-northwestward to
the south of a narrow ridge over the eastern Atlantic over the
weekend. By early next week, the ridge is forecast to weaken as a
deep-layer trough becomes established over the east-central
Atlantic. This should cause the cyclone to gain some latitude
later in the forecast period. The more northward initial position
has required a northward adjustment of the track forecast, but the
NHC track remains along the southern side of the guidance envelope,
in agreement with the typically reliable HFIP corrected consensus
model.


FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 12.6N 29.7W 30 KT 35 MPH
12H 16/0600Z 12.8N 30.8W 30 KT 35 MPH
24H 16/1800Z 12.9N 32.2W 35 KT 40 MPH
36H 17/0600Z 13.0N 33.4W 40 KT 45 MPH
48H 17/1800Z 13.2N 34.7W 40 KT 45 MPH
72H 18/1800Z 14.6N 38.4W 35 KT 40 MPH
96H 19/1800Z 16.5N 42.5W 30 KT 35 MPH
120H 20/1800Z 18.5N 46.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

[emeraldislenc]

With the trough becoming well established could this mean the Cape Verde season is winding down?

[bob rulz]

Climatologically speaking, we are nearing the end of the Cape Verde season. We've never seen them later than about September 25th iirc

[RL3AO]

Climatologically speaking, we are nearing the end of the Cape Verde season. We've never seen them later than about September 25th iirc

Africa is pretty dry right now, with the exception of one more active wave which the Euro wants to develop.

[emeraldislenc]

Thanks for all the responses it just seemed to me it might be winding down.

[CrazyC83]

Waves often move off Africa well through September and even into October, but they don't usually develop until they get near or past 50W once into late September.

[CyclonicFury]

Waves often move off Africa well through September and even into October, but they don't usually develop until they get near or past 50W once into late September.

I've always wondered this. Why is the Eastern MDR always so quiet in October? SSTs are still warm, SAL is not a problem, is shear the main issue? The MDR manages to produce more storms in July (when it's very dry and dusty out there, as well as cooler) than October. This doesn't make any sense to me.

[NotSparta]

Waves often move off Africa well through September and even into October, but they don't usually develop until they get near or past 50W once into late September.

I've always wondered this. Why is the Eastern MDR always so quiet in October? SSTs are still warm, SAL is not a problem, is shear the main issue? The MDR manages to produce more storms in July (when it's very dry and dusty out there, as well as cooler) than October. This doesn't make any sense to me.

I think it's shear, because the trough becomes more defined and shears a lot of disturbances in the MDR

[HenkL]

The Intertropical Convergence Zone (ITCZ) moves southward towards the equator, where there is no Coriolis force.

[CrazyC83]

16/0000 UTC 12.8N 30.2W T2.0/2.0 14L -- Atlantic

[CrazyC83]

https://manati.star.nesdis.noaa.gov/asc ... Bas124.png

https://manati.star.nesdis.noaa.gov/win ... 6_noaa.png

I see a bunch of 30 kt wind barbs and possibly a 35 kt barb in the partial ASCAT pass. I also see a 35 kt barb on the WindSat pass.

[galaxy401]

What is the longest a Tropical Depression went before being upgraded to a Tropical Storm?

[CrazyC83]

What is the longest a Tropical Depression went before being upgraded to a Tropical Storm?

TD15-E in the EPAC has gone 17 advisories without an upgrade, and in the Atlantic I am sure there have been many that have gone a long time too.

[galaxy401]

What is the longest a Tropical Depression went before being upgraded to a Tropical Storm?

TD15-E in the EPAC has gone 17 advisories without an upgrade, and in the Atlantic I am sure there have been many that have gone a long time too.

Oh I just realized I posted this on the wrong topic. Got the depressions mixed up.

[Hammy]

What is the longest a Tropical Depression went before being upgraded to a Tropical Storm?

http://tropicalatlantic.com/models/models.cgi?basin=al&year=1970&storm=15 though given satellite imagery I've seen I can see it being upped to a TS on reanalysis.

[Sciencerocks]

If the LLC is under the convection then this system looks really good this morning...