ATL: DEBBY - Post-Tropical

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Re: ATL: INVEST 97L - Discussion

#21 Postby CyclonicFury » Mon Aug 06, 2018 10:01 am

650
ABNT20 KNHC 061138
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Mon Aug 6 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

A non-tropical low pressure system centered about 1200 miles
west-southwest of the Azores is interacting with an upper-level low.
Although the system is producing disorganized showers and
thunderstorms to the east and northeast of the center, environmental
conditions are expected to be only marginally conducive for the low
to acquire subtropical or tropical characteristics while it moves
north or north-northeastward over the next day or so. The low is
forecast to move over cooler waters by Tuesday night, and
development is not expected after that time. Additional information
on this system can be found in High Seas Forecasts issued by the
National Weather Service.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...low...20 percent.

&&
High Seas Forecasts issued by the National Weather Service can be
found under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and
on the Web at https://ocean.weather.gov/shtml/NFDHSFAT1.shtml.

$$
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Re: ATL: INVEST 97L - Discussion

#22 Postby Sciencerocks » Mon Aug 06, 2018 12:52 pm

Image

Looks good to me.
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Re: ATL: INVEST 97L - Discussion

#23 Postby CyclonicFury » Mon Aug 06, 2018 12:57 pm

30/30
470
ABNT20 KNHC 061740
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Mon Aug 6 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

A non-tropical low pressure system centered about 1100 miles
west-southwest of the Azores is interacting with an upper-level low.
Although the associated shower and thunderstorm activity has
increased during the past 24 hours, environmental conditions are
expected to be only marginally conducive for additional development
while the system moves north or north-northeastward over the next
day or so. The low is forecast to move over cooler waters Tuesday
night, and development is not expected after that time. Additional
information on this system can be found in High Seas Forecasts
issued by the National Weather Service.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...low...30 percent.

&&
High Seas Forecasts issued by the National Weather Service can be
found under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and
on the Web at https://ocean.weather.gov/shtml/NFDHSFAT1.shtml.

$$
Forecaster Brown
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Re: ATL: INVEST 97L - Discussion

#24 Postby CyclonicFury » Mon Aug 06, 2018 12:58 pm

Sciencerocks wrote:Image

Looks good to me.

Looks better than a 30/30, should be at least a 50/50 IMO. Often times NHC keeps chances with these subtropics systems too low.
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Re: ATL: INVEST 97L - Discussion

#25 Postby cycloneye » Mon Aug 06, 2018 6:47 pm

A non-tropical low pressure system centered a little more than 1000
miles west-southwest of the Azores is interacting with an upper-
level low, and most of its associated shower activity remains
disorganized. Environmental conditions could favor some development
during the next day or so, but after that time, the low will
encounter increasing cooler waters and development is not
anticipated. The low is already moving toward the north-northeast,
and this motion should continue for the next several days over the
open North Atlantic. Additional information on this system can be
found in High Seas Forecasts issued by the National Weather Service.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...low...30 percent.
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Re: ATL: INVEST 97L - Discussion

#26 Postby NDG » Mon Aug 06, 2018 9:26 pm

97L is looking good tonight, the pesky ULL is finally giving it some breathing room, time for an upgrade if the convection persists through the night.
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Re: ATL: INVEST 97L - Discussion

#27 Postby AJC3 » Mon Aug 06, 2018 10:25 pm

NDG wrote:97L is looking good tonight, the pesky ULL is finally giving it some breathing room, time for an upgrade if the convection persists through the night.


The satellite evolution of this thing is pretty fascinating. Near 97L (A), which had been completely exposed late this afternoon, there was a small upper level low (B) to its NW moving away from 97L's exposed center. Just NW of the small upper low, there was (and is) a very small low level vortex (C) that's started tooting some convection. It appears as if the small upper low is weakening/dissipating, and 97L is trying to tuck underneath the area of (now) central convection. I suspect that small LL vortex will deform/shear out as it gets entrained into the circulation of 97L.

Image
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Re: ATL: INVEST 97L - Discussion

#28 Postby Extratropical94 » Tue Aug 07, 2018 3:31 am

Up to 50/50:

Satellite data indicate that thunderstorm activity during the past
several hours has increased and become better organized in
association with a well-defined, non-tropical low pressure system
centered about 950 miles west-southwest of the Azores. Environmental
conditions are expected to be somewhat conducive for the system to
acquire subtropical or tropical characteristics later today. By
Wednesday, however, the low will encounter increasingly cooler
waters, which will hinder development while the system moves toward
the north-northeast over the open North Atlantic. Additional
information on this system can be found in High Seas Forecasts
issued by the National Weather Service.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.
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Re: ATL: INVEST 97L - Discussion

#29 Postby cycloneye » Tue Aug 07, 2018 6:34 am

Up to 60%/60%

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Tue Aug 7 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. Early visible satellite images indicate that the shower activity
associated with a non-tropical low pressure system located a little
more than 900 miles west-southwest of the Azores continues to
show some signs of organization. Although the shower activity has
decreased somewhat during the past few hours, this system could
still acquire subtropical or tropical characteristics later today.
By Wednesday, however, the low will encounter increasingly cooler
waters, which will hinder development while the system moves toward
the north-northeast over the open North Atlantic. Additional
information on this system can be found in High Seas Forecasts
issued by the National Weather Service.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...medium...60 percent.

High Seas Forecasts issued by the National Weather Service can be
found under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and
on the Web at https://ocean.weather.gov/shtml/NFDHSFAT1.shtml.

Forecaster Avila
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Re: ATL: INVEST 97L - Discussion

#30 Postby cycloneye » Tue Aug 07, 2018 7:16 am

@BigJoeBastardi
Seasons 4th named storm I think gets christened today right in middle of our highest ace% average area, out in the middle of nowhere. Could impact UK/Ireland in longer range
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Re: ATL: DEBBY - Subtropical Storm - Discussion

#31 Postby CyclonicFury » Tue Aug 07, 2018 10:00 am

Now SS Debby
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Re: ATL: DEBBY - SubTropical Storm

#32 Postby cycloneye » Tue Aug 07, 2018 11:49 am

@EricBlake12
Fun new scatterometer features on @Weathernerds - you can see the pass near #Debby this morning. Check it out! https://www.weathernerds.org/satellite/floaters/




https://twitter.com/EricBlake12/status/1026872252313346048
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Re: ATL: DEBBY - SubTropical Storm

#33 Postby weathaguyry » Tue Aug 07, 2018 12:41 pm

Has that classic subtropical look with thinner clouds in the middle and heavier convection around it like a donut, pretty cool to look at considering there's nothing else interesting in the basin
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Re: ATL: DEBBY - SubTropical Storm

#34 Postby CyclonicFury » Tue Aug 07, 2018 3:53 pm

716
WTNT44 KNHC 072032
TCDAT4

Subtropical Storm Debby Discussion Number 2
NWS National Hurricane Center Miami FL AL042018
500 PM AST Tue Aug 07 2018

Debby's cloud pattern consists of a cyclonically curved convective
band wrapping around a large but somewhat vigorous circulation. TAFB
provided a subtropical classification of ST2.5, while an earlier
ship located to the east of the center reported 35 kt. These data is
used to assign the current intensity of the subtropical cyclone.
Although transition to a tropical cyclone is still possible during
the next 24 hours, no significant strengthening is anticipated since
Debby will soon be moving over cool waters and become fully embedded
within a larger mid-latitude trough in a day or so. Debby is
forecast to dissipate in about 48 hours or earlier.

The best estimate of the initial motion is toward the north or 355
degrees at 13 kt. The subtropical storm should continue on this
general track with a decrease in forward speed for the next 24
hours or so and then turn to the northeast ahead of the trough,
which will eventually absorb Debby.

FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 39.7N 49.2W 35 KT 40 MPH
12H 08/0600Z 41.0N 49.5W 35 KT 40 MPH
24H 08/1800Z 42.3N 48.5W 35 KT 40 MPH
36H 09/0600Z 44.0N 46.0W 30 KT 35 MPH
48H 09/1800Z...DISSIPATED

$$
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Re: ATL: DEBBY - SubTropical Storm

#35 Postby euro6208 » Tue Aug 07, 2018 4:58 pm

The only basin in the world to recognize such systems regularly and is good at it. I know of a few in the WPAC this year that were likely *Subtropical*.
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Re: ATL: DEBBY - SubTropical Storm

#36 Postby cycloneye » Tue Aug 07, 2018 9:44 pm

Subtropical Storm Debby Discussion Number 3
NWS National Hurricane Center Miami FL AL042018
1100 PM AST Tue Aug 07 2018

A little bit of deep convection has developed near the center of
Debby, but the overall cloud pattern still resembles more of a
subtropical cyclone. Most of the convection is in a ragged band
well to the northeast of the center. The initial intensity is held
at 35 kt based on a subtropical ST2.5 classification from TAFB.
The global models are in good agreement that the system will open
up into a trough on the southern side of a large low pressure
system within 48 hours.

The initial motion estimate is a slightly slower 360/11 kt. Debby
is likely to turn northeastward in the flow on the eastern side of
a mid-level trough. The official forecast is somewhat faster than
the latest model consensus to maintain some continuity with the
previous NHC track.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 40.3N 49.1W 35 KT 40 MPH
12H 08/1200Z 41.2N 48.9W 35 KT 40 MPH
24H 09/0000Z 42.5N 47.5W 35 KT 40 MPH
36H 09/1200Z 43.9N 44.7W 30 KT 35 MPH
48H 10/0000Z...DISSIPATED

$$
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Re: ATL: DEBBY - SubTropical Storm

#37 Postby NDG » Tue Aug 07, 2018 10:34 pm

Not bad on latest ASCAT.

Image
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Re: ATL: DEBBY - Tropical Storm

#38 Postby AJC3 » Wed Aug 08, 2018 3:52 am

BULLETIN
Tropical Storm Debby Advisory Number 4
NWS National Hurricane Center Miami FL AL042018
500 AM AST Wed Aug 08 2018

...DEBBY STRENGTHENS SLIGHTLY WHILE MAKING THE TRANSITION TO A
TROPICAL STORM OVER THE FAR NORTH ATLANTIC...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...40.8N 48.8W
ABOUT 1175 MI...1890 KM WNW OF THE AZORES
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NNE OR 15 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


Tropical Storm Debby Discussion Number 4
NWS National Hurricane Center Miami FL AL042018
500 AM AST Wed Aug 08 2018

Over the past several hours, deep convection with cloud tops of -55
to -60 deg C has developed in the southeastern semicircle, with
some of the convective tops covering the previously exposed
low-level circulation center. In addition, outer banding
features have dissipated, and an elongated upper-level anticyclone
has developed over the cyclone. These convective- and synoptic-scale
features indicate that Debby has made the transition from a
subtropical to a tropical cyclone. The initial intensity of 40 kt
is based on a blend of UW-CIMSS ADT and SATCON intensity estimates
of 39 kt and 42 kt, respectively. Furthermore, the 34-kt wind radii
and radius of maximum winds (RMW) were decreased significantly on
this advisory based on ASCAT wind data.

The initial motion estimate is now 015/08 kt. Debby has made the
forecast turn toward the north-northeast, and a further turn toward
the northeast is expected later today as the cyclone moves around
the northwestern periphery of a deep-layer ridge and ahead of an
approaching mid-level trough. The latest model guidance remains in
good agreement on this developing track scenario, and the new NHC
forecast track is similar to the previous advisory, and lies close
to a blend of the track consensus models HCCA and FSSE.

Debby will be moving along a tight sea-surface temperature (SST)
gradient for the next 24-36 hours or so, with the northwestern half
the circulation being over sub-25C SSTs and the southeastern
semicircle being over warmer waters where convection could continue
to develop. Given the relatively low vertical wind shear regime
that the cyclone will be moving through, along with the possibility
of deep convection persisting near the center, the intensity
forecast calls for little change in strength today, followed by
only slight weakening tonight and early Thursday. By Thursday night
or early Friday, SSTs beneath the cyclone are expected to decrease
to near 20 deg C and the shear is forecast to increase to more than
20 kt, an unfavorable combination that should result in Debby
dissipating over the far north Atlantic by 48 hours.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 40.8N 48.8W 40 KT 45 MPH
12H 08/1800Z 41.8N 48.2W 40 KT 45 MPH
24H 09/0600Z 43.2N 46.1W 35 KT 40 MPH
36H 09/1800Z 44.5N 43.4W 30 KT 35 MPH
48H 10/0600Z...DISSIPATED
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Re: ATL: DEBBY - SubTropical Storm

#39 Postby NotoSans » Wed Aug 08, 2018 4:12 am

euro6208 wrote:The only basin in the world to recognize such systems regularly and is good at it. I know of a few in the WPAC this year that were likely *Subtropical*.

The MFR also classifies subtropical storms.
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Re: ATL: DEBBY - Tropical Storm

#40 Postby NDG » Wed Aug 08, 2018 6:50 am

No question that Debby has now transitioned into a fully tropical system this morning.

Image
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