ATL: ARLENE - Post-Tropical - Discussion

[weathaguyry]

Something like this reminds me of sitting of sitting on the beach, tracking some of the June storms, yet it's only April and well, I'm not going to the beach in 55 degrees and rain

[hurricanes1234]

Arlene the undying


Very peculiar yet fascinating storm!

[JaxGator]

Wow, we have Arlene (so it begins). An impressive storm for this time of year, but by no means in this case is it relative for an active season or whatever the outcome. It's also another good opportunity on seeing a Tropical Cyclone form via atmospheric forces and not so much warm sst's.

[Alyono]

So are we thinking this could tell us anything about the season or is it just a fluke? The only thing that gives me pause is the fact that we already had 90L at the end of March, and wasn't there another one recently? Or was that what became Arlene?

it's a medicane that formed in the Atlantic. No impact on what happens later on

Any chance this could indicate a more active subtropics? Both 1992 and 2003 had a fair number of storms there relative to the total season numbers.

not sure about that. This is basically a medicane, unrelated to later developments

[tatertawt24]

So are we thinking this could tell us anything about the season or is it just a fluke? The only thing that gives me pause is the fact that we already had 90L at the end of March, and wasn't there another one recently? Or was that what became Arlene?

If Arlene had formed from a wave that moved off the coast of Africa then THAT would be significant. Forming from a non-tropical low in the subtropics over cool water means nothing as far as the tropical season.

Ah, that makes a lot of sense. Thanks.

It seems that there's a lot about these off-season subtropic storms that we don't know. The way this is doing whatever it isn't supposed to despite the cool waters is very Epsilon-esque.

[cycloneye]

Tropical Storm Arlene Discussion Number 8
NWS National Hurricane Center Miami FL AL012017
500 AM AST Fri Apr 21 2017

Arlene has maintained a small area of deep convection surrounding
the center of the cyclone, with some of the cloud tops as cold as
-50 deg C. However, satellite trends over the past couple of hours
indicate that the areal coverage of the convection has decreased
significantly since the 0600 UTC satellite intensity estimates, an
indication that Arlene is beginning to lose its tropical
characteristics as the cyclone interacts with a frontal zone and
also moves over cooler water. Dvorak current intensity estimates
remain at 45 kt, and that is the intensity used for this advisory.

The initial motion estimate is now 270/27 kt. Arlene has
accelerated westward during the past 6 hours as the cyclone moves
around the northern periphery of a larger deep-layer extratropical
low that has remained nearly stationary near 36N 48W. The small
cyclone or its remnants are expected to move in a cyclonic loop
around this low for the next couple of days.

Arlene is gradually running out of space within the narrow warm
sector of the aforementioned occluded low pressure system, and
merger with one or more frontal zones is likely during the next 12
hours. The new official intensity forecast continues the trend of
the previous advisory, which shows Arlene degenerating to a
post-tropical cyclone by 12 hours, and dissipating by 24 hours when
the system is expected to be absorbed into the larger baroclinic
low.

Tropical storms in April are rare and Arlene is only the second
one observed in this month during the satellite era. It should be
noted, however, that this type of storm was practically impossible
to detect prior to the weather satellite era.

FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 40.0N 48.0W 45 KT 50 MPH
12H 21/1800Z 39.5N 50.4W 40 KT 45 MPH...POST-TROPICAL
24H 22/0600Z...DISSIPATED

$$
Forecaster Stewart

[Kazmit]

Post-tropical for the 11am update, but not much weakening so far.

Extratropical Storm ARLENE
As of 12:00 UTC Apr 21, 2017:

Location: 39.9°N 49.3°W
Maximum Winds: 45 kt Gusts: 55 kt
Minimum Central Pressure: 995 mb
Environmental Pressure: 1010 mb
Radius of Circulation: 400 NM
Radius of Maximum Wind: 40 NM
Eye Diameter: N/A

[cycloneye]

Last advisory.

Post-Tropical Cyclone Arlene Discussion Number 9
NWS National Hurricane Center Miami FL AL012017
1100 AM AST Fri Apr 21 2017

Arlene has become embedded within the circulation of a large
extratropical cyclone, and lost most of its deep convection while
surrounded by cold air. The post-tropical cyclone will move toward
the southwest and south at about 20 kt until dissipation later
today.

This is the last advisory on Arlene. Additional information on this
system can be found in High Seas Forecasts issued by the National
Weather Service...under AWIPS header NFDHSFAT1 and WMO header FZNT01
KWBC.


FORECAST POSITIONS AND MAX WINDS

INIT 21/1500Z 39.3N 49.9W 45 KT 50 MPH...POST-TROPICAL
12H 22/0000Z 37.5N 51.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
24H 22/1200Z...DISSIPATED

$$
Forecaster Avila

[Yellow Evan]

Looks on the brink of getting absorbed.

[Hammy]

The final track (including remnant phase) will be interesting to see whenever the report comes out.