ATL: GABRIELLE - Post-Tropical - Discussion

[northjaxpro]

She's getting the attention and rightfully so. This morning's satellite presentation of the cyclone I think is the best of her lifespan to this point. Shear is letting up appreciably now
and deeper convection is now getting closer to the center to establish the inner core. She is in a better environment with lighter shear and I think she will become the season's third hurricane of the season by tonight or early Monday. I think she will become eventually a solid Cat 2 tropical cyclone. Conditions look pretty good for her to intensify in the short term (at least the next 2-3 days).

[cycloneye]

Tropical Storm Gabrielle Discussion Number 22
NWS National Hurricane Center Miami FL AL082019
500 PM AST Sun Sep 08 2019

The convective structure of Gabrielle now consists of a very well
defined curved band that envelops the center, which is evident by
recent microwave data as well as satellite imagery. An earlier
scatterometer pass partially sampled the eastern semicircle of the
cyclone and indicated the tropical storm force winds had expanded to
90 n mi from the center in the northeastern quadrant. The latest
subjective Dvorak intensity estimate from TAFB has increased to 55
kt, which will the initial intensity for this advisory.

Gabrielle will continue to move over warm SSTs and in a moderately
favorable atmospheric environment for the next 24 hours. Based on
these factors and the improved structure of the cyclone today, some
slight strengthening is expected into tonight. Although not
implicitly shown in the forecast, it is possible that Gabrielle may
reach hurricane intensity sometime tonight or early tomorrow. By
tomorrow afternoon, the cyclone will move over cooler waters and
southwesterly shear will increase, which should cause a weakening
trend to begin. By 48 hours, Gabrielle is expected to merge with a
cold front and become an extratropical cyclone. The official
forecast is essentially an update of the previous one, and is near
the corrected consensus HCCA.

The anticipated recurvature has begun and the initial motion is now
350/14 kt. Gabrielle will turn to the northeast by Monday as the
system rounds the western periphery of a mid-level ridge centered
near the Azores. Once Gabrielle turns northeastward, it will become
embedded in the increasing southwesterly flow ahead of the
approaching mid-latitude trough, which will accelerate the cyclone's
forward motion. The official forecast was nudged a little west from
the previous advisory due to a slight westward shift in the
tightly clustered track guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 35.3N 49.4W 55 KT 65 MPH
12H 09/0600Z 37.3N 48.7W 60 KT 70 MPH
24H 09/1800Z 40.0N 46.3W 60 KT 70 MPH
36H 10/0600Z 42.5N 42.4W 55 KT 65 MPH
48H 10/1800Z 45.2N 37.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 11/1800Z 52.3N 21.9W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 12/1800Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

Tropical Storm Gabrielle Discussion Number 23
NWS National Hurricane Center Miami FL AL082019
1100 PM AST Sun Sep 08 2019

Gabrielle's cloud pattern has not become better organized since
earlier today. The central convection has become a little more
fragmented, and the center is estimated to be near the northern
side of the main area of convection. There is a well-defined
upper-level outflow jet over the southern portion of the
circulation. The initial intensity is held at 55 kt in agreement
with the latest Dvorak Current Intensity number from TAFB, although
this may be generous given a recent ASCAT overpass of the storm.
Gabrielle's window for additional strengthening should soon close,
since the cyclone will be over warm waters for less than 24 hours,
and the dynamical models indicate a significant increase in vertical
shear during the next day or so. Therefore, only a slight
short-term increase in strength seems likely. The official
intensity forecast is in fairly good agreement with the latest
corrected consensus guidance, HCCA. By 48 hours, the global models
depict the cyclone as embedded within a baroclinic zone over the
mid-latitudes of the Atlantic. Therefore, the official forecast
shows Gabrielle becoming extratropical by that time. By 96 hours,
the system should become absorbed by a large low pressure system at
high latitudes.

The initial motion is northward, or 360/13 kt. The track forecast
philosophy is basically unchanged. Over the next 1 to 2 days,
Gabrielle should turn northeastward and accelerate as it moves
around the northwestern periphery of a mid-level high centered near
the Azores. Later on, the cyclone should accelerate further within
the mid-latitude west-southwesterly flow. The official forecast is
very close to the previous NHC track, and close to the corrected
consensus prediction.

Based on the ASCAT data, the 34-kt wind radii over the southern
semicircle of the circulation were increased a bit.

FORECAST POSITIONS AND MAX WINDS

INIT 09/0300Z 36.5N 49.3W 55 KT 65 MPH
12H 09/1200Z 38.6N 47.8W 60 KT 70 MPH
24H 10/0000Z 41.1N 44.7W 55 KT 65 MPH
36H 10/1200Z 43.6N 40.4W 50 KT 60 MPH
48H 11/0000Z 46.5N 35.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 12/0000Z 54.5N 18.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 13/0000Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Tropical Storm Gabrielle Discussion Number 24
NWS National Hurricane Center Miami FL AL082019
500 AM AST Mon Sep 09 2019

Deep convection associated with Gabrielle has become somewhat
less organized overnight with the center located near the
northeastern portion of the coldest cloud tops. There is still
banding present over the southern and southwestern portions of the
circulation but it has become fragmented. Gabrielle has likely
peaked in intensity, and the latest satellite estimates and earlier
ASCAT data support an initial intensity of 50 kt for this advisory.
Little change in intensity is expected today while Gabrielle remains
over warm water and within a moderate shear environment. By
tonight, decreasing SSTs and increasing southerly shear should
begin to cause gradual weakening. Shortly after that time,
the global models indicate Gabrielle will become embedded within a
baroclinic zone and become extratropical. The extratropical low is
predicted to slowly weaken and be absorbed by a larger low pressure
system over the northeastern Atlantic in a little more than 3 days.

Gabrielle has turned north-northeastward with an initial motion
estimate of 015/14 kt. Gabrielle should turn northeastward today
and begin to accelerate ahead of a broad mid-level trough
approaching the central Atlantic. Once the cyclone is fully
embedded within the mid-latitude westerlies, an additional
acceleration toward the northeast is expected. There is good
agreement among the dynamical models, and the updated NHC track
forecast is similar to the previous advisory. The official forecast
track remains between the TVCA and HCCA consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT 09/0900Z 37.7N 48.5W 50 KT 60 MPH
12H 09/1800Z 39.7N 46.6W 50 KT 60 MPH
24H 10/0600Z 42.2N 42.9W 50 KT 60 MPH
36H 10/1800Z 44.8N 38.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 11/0600Z 48.1N 31.7W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 12/0600Z 55.8N 12.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 13/0600Z...DISSIPATED

$$
Forecaster Brown

[cycloneye]

BULLETIN
Tropical Storm Gabrielle Advisory Number 25...Corrected
NWS National Hurricane Center Miami FL AL082019
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Mon Sep 09 2019

Corrected headers

...GABRIELLE MOVING NORTHEASTWARD OVER THE NORTH ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...39.0N 47.3W
ABOUT 1095 MI...1765 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NE OR 35 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM AST (1500 UTC), the center of Tropical Storm Gabrielle
was located near latitude 39.0 North, longitude 47.3 West. Gabrielle
is moving toward the northeast near 18 mph (30 km/h), and this
general motion with an increase in forward speed is forecast over
the next few days.

Maximum sustained winds are near 50 mph (85 km/h) with higher
gusts. Little change in strength is expected today, but a weakening
trend is likely to begin Tuesday. Gabrielle is expected to become
an extratropical low by Tuesday night.

Tropical-storm-force winds extend outward up to 115 miles (185 km)
from the center.

The estimated minimum central pressure is 1000 mb (29.53 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Taylor/Blake



Tropical Storm Gabrielle Discussion Number 25
NWS National Hurricane Center Miami FL AL082019
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Mon Sep 09 2019

Satellite images indicate that deep convection has increased
overnight and become more symmetric around the center of Gabrielle.
Still, ASCAT data show maximum winds of only about 40 kt,
suggestive that this convective burst hasn't changed the intensity
much. The initial wind speed is set to 45 kt, near the TAFB
satellite estimate and a little above the ASCAT data to account for
undersampling.

Gabrielle has turned northeastward and picked up some speed.
The system is expected to move at an increasing pace in a similar
direction over the next few days as it is picked up by a
mid-latitude trough. Model guidance is tightly clustered around
the previous NHC prediction, and no significant changes were made
to the prior NHC track forecast.

The storm has about a day over marginally warm waters before it
crosses the north wall of the Gulf Stream into much colder waters.
Gabrielle is forecast to transition into an extratropical low by
Tuesday due to an increase in shear and baroclinicity from an
approaching cold front. The intensity forecast was reduced
slightly from the previous one and is in close agreement with a
blend of the GFS/ECMWF wind speed forecasts, which should best
handle this extratropical transition scenario.


FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 39.0N 47.3W 45 KT 50 MPH
12H 10/0000Z 40.9N 44.7W 45 KT 50 MPH
24H 10/1200Z 43.4N 40.2W 45 KT 50 MPH
36H 11/0000Z 46.4N 34.7W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 11/1200Z 50.1N 26.9W 35 KT 40 MPH...POST-TROP/EXTRATROP
72H 12/1200Z 57.5N 5.5W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 13/1200Z...DISSIPATED

$$
Forecaster Taylor/Blake

[Astromanía]

This looks great now, shame that it doesn´t have time left to be something stronger

[cycloneye]

Tropical Storm Gabrielle Discussion Number 26
NWS National Hurricane Center Miami FL AL082019
Issued by the NWS Weather Prediction Center College Park MD
500 PM AST Mon Sep 09 2019

Satellite imagery continues to show symmetric convection around the
center of Gabrielle despite some gradual warming in the cloud tops
seen in the latest GOES infrared imagery. The initial wind speed was
maintained at 45 kt, near the TAFB satellite estimate and a little
above the SAB estimate.

Gabrielle remains on a northeastward motion and is moving a bit
faster than the previous advisory, or 040/18 kt. The system is
expected to further increase in forward speed in a similar direction
over the next couple of days due to strengthening southwesterly flow
near a mid-latitude trough. Only a slight northward adjustment was
made to the prior NHC forecast since, overall, model guidance
remains tightly clustered with the track of Gabrielle.

The storm has less than a day over marginally warm waters
before it crosses the north wall of the Gulf Stream and into much
colder waters. Gabrielle should transition into an extratropical low
on Tuesday night as a result of an increase in shear and
low-level baroclinicity from an approaching cold front. The
intensity forecast is essentially unchanged from the previous
forecast and continues to use a blend of the GFS and ECMWF model
wind fields.


FORECAST POSITIONS AND MAX WINDS

INIT 09/2100Z 40.7N 45.4W 45 KT 50 MPH
12H 10/0600Z 42.6N 42.4W 45 KT 50 MPH
24H 10/1800Z 45.1N 37.7W 40 KT 45 MPH
36H 11/0600Z 48.2N 31.4W 35 KT 40 MPH...POST-TROP/EXTRATROP
48H 11/1800Z 52.0N 22.5W 30 KT 35 MPH...POST-TROP/EXTRATROP
72H 12/1800Z...DISSIPATED

$$
Forecaster Taylor/Blake

[cycloneye]

TCDAT3

Tropical Storm Gabrielle Discussion Number 27
NWS National Hurricane Center Miami FL AL082019
1100 PM AST Mon Sep 09 2019

Gabrielle's convection has waned considerably since the previous
advisory, and the cloud pattern now has a disheveled appearance that
is becoming more reminiscent of an extratropical low pressure
system. However, a recent 2246Z ASCAT-A scatterometer pass indicated
that the tropical storm has maintained a very robust surface wind
field, with peak winds still at 45 kt and a radius of maximum winds
of 45-50 nmi.

The initial motion estimate is 055/21 kt, based primarily on passive
microwave and scatterometer satellite fixes. Gabrielle is now well
embedded in the high-latitude westerlies, and an additional increase
in forward speed toward the northeast or east-northeast is expected
over the next 2 days. By 72 hours, Gabrielle is forecast to
dissipate near the northern British Isles.

Gabrielle is currently located over sub-25 deg C sea-surface
temperatures and within a strong vertical wind shear regime of near
30 kt. With much colder water and stronger southwesterly shear ahead
of the cyclone, extratropical transition now appears likely to occur
within the next 12 hours. The intensity forecast is similar to the
previous advisory, and is a blend of the statistical SHIPS intensity
models, and the GFS and ECMWF dynamical model wind fields.

FORECAST POSITIONS AND MAX WINDS

INIT 10/0300Z 42.1N 43.1W 45 KT 50 MPH
12H 10/1200Z 44.0N 39.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
24H 11/0000Z 46.6N 34.6W 40 KT 45 MPH...POST-TROP/EXTRATROP
36H 11/1200Z 50.1N 27.1W 35 KT 40 MPH...POST-TROP/EXTRATROP
48H 12/0000Z 54.0N 16.6W 30 KT 35 MPH...POST-TROP/EXTRATROP
72H 13/0000Z...DISSIPATED

$$
Forecaster Stewart

[cycloneye]

Tropical Storm Gabrielle Discussion Number 28
NWS National Hurricane Center Miami FL AL082019
500 AM AST Tue Sep 10 2019

Gabrielle's extratropical transition is well underway. Deep
convection is now confined to an area near and to the north of
the center, and a baroclinic zone is already impinging upon the
circulation. The initial wind speed has been maintained at
45 kt, which was in agreement with earlier scatterometer data. The
cyclone should become fully extratropical later this morning, and
the global models indicate that gradual weakening will occur after
that time. As a result, the NHC forecast shows steady weakening
after 12 hours, and calls for the system to dissipate in a little
more than 2 days as it approaches the northern British Isles.

Gabrielle has become embedded within the mid-latitude flow and is
now moving northeastward at 22 kt. The cyclone is forecast to
continue accelerating northeastward during the next day or so until
dissipation occurs. The updated NHC track forecast is similar to
the previous advisory and lies near the middle of the tightly
cluster model guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 10/0900Z 43.4N 40.2W 45 KT 50 MPH
12H 10/1800Z 45.2N 36.3W 45 KT 50 MPH...POST-TROP/EXTRATROP
24H 11/0600Z 48.3N 29.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
36H 11/1800Z 51.8N 21.3W 35 KT 40 MPH...POST-TROP/EXTRATROP
48H 12/0600Z 55.0N 11.0W 30 KT 35 MPH...POST-TROP/EXTRATROP
72H 13/0600Z...DISSIPATED

$$
Forecaster Brown

[TallyTracker]

...GABRIELLE BECOMES AN EXTRATROPICAL CYCLONE...
...THIS IS THE FINAL ADVISORY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...43.9N 37.8W
ABOUT 695 MI...1115 KM NW OF THE AZORES
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NE OR 55 DEGREES AT 29 MPH...46 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES

With Gabrielle’s demise, it looks like we enter a brief, much-needed lull in the tropics.