ATL: LESLIE - Advisories

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ATL: LESLIE - Advisories

#1 Postby cycloneye » Sun Sep 23, 2018 9:45 am

All the advisories at link.

https://www.nhc.noaa.gov/archive/2018/LESLIE.shtml?

Subtropical Storm Leslie Discussion Number 1
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Sun Sep 23 2018

The development of a subtropical storm that NHC and the global
models have been advertising for the past several days has
materialized, and based on satellite intensity classification from
TAFB and earlier ASCAT data, advisories on Subtropical Storm Leslie
have been initiated.

Leslie is still embedded within an upper-level low and strong winds
are removed from the center. However, there is a chance as usual
that the subtropical cyclone could develop additional convection
near the center, and the transition to a tropical system during the
next day or so is not out of the question. Global models do
indicate that a new low is going to form north of Leslie, and that
the subtropical cyclone will become absorbed by the new larger low.
This is the scenario depicted by NHC at this time.

Leslie is embedded within very light steering currents, and most
likely the cyclone will be meandering today and tomorrow. After
that time, with the development of the new low to the north, Leslie
will likely move east until it becomes absorbed.

FORECAST POSITIONS AND MAX WINDS

INIT 23/1500Z 33.0N 46.5W 35 KT 40 MPH
12H 24/0000Z 33.2N 47.2W 40 KT 45 MPH
24H 24/1200Z 33.0N 47.5W 40 KT 45 MPH
36H 25/0000Z 33.0N 46.5W 40 KT 45 MPH
48H 25/1200Z 33.0N 45.0W 40 KT 45 MPH
72H 26/1200Z...ABSORBED BY LARGER LOW

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#2 Postby cycloneye » Sun Sep 23, 2018 3:37 pm

BULLETIN
Subtropical Storm Leslie Advisory Number 2
NWS National Hurricane Center Miami FL AL132018
500 PM AST Sun Sep 23 2018

...SUBTROPICAL STORM LESLIE EXPECTED TO DISSIPATE IN A COUPLE OF
DAYS...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...33.5N 47.2W
ABOUT 1170 MI...1885 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES



Subtropical Storm Leslie Discussion Number 2
NWS National Hurricane Center Miami FL AL132018
500 PM AST Sun Sep 23 2018

Leslie's cloud pattern has not become any better organized, nor do
we have any data to support a wind increase. The initial intensity
is then kept at 35 kt. The evolution of Leslie is very complex and
difficult to forecast. There is a possibility that Leslie will be
absorbed by a larger low that is forecast to form nearby, or that
Leslie could maintain its identity while rotating around the low. At
this time NHC will maintain continuity and forecasts Leslie to be
absorbed by the large low by 72 hours. No significant change in
intensity or structure is anticipated until then.

Leslie continues to be embedded within very light steering currents,
and most likely the cyclone will merely meander today and
tomorrow. After that time, with the development of the new low to
the north, Leslie will likely be steered eastward until it is
absorbed. The track forecast is highly uncertain given the complex
flow pattern surrounding the subtropical cyclone.


FORECAST POSITIONS AND MAX WINDS

INIT 23/2100Z 33.5N 47.2W 35 KT 40 MPH
12H 24/0600Z 33.4N 47.8W 40 KT 45 MPH
24H 24/1800Z 33.2N 48.0W 40 KT 45 MPH
36H 25/0600Z 33.2N 46.5W 40 KT 45 MPH
48H 25/1800Z 33.0N 44.0W 45 KT 50 MPH
72H 26/1800Z...DISSIPATED

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#3 Postby cycloneye » Sun Sep 23, 2018 9:45 pm

BULLETIN
Subtropical Storm Leslie Advisory Number 3
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Sun Sep 23 2018

...SUBTROPICAL STORM LESLIE MOVING SLOWLY SOUTHWESTWARD...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...33.3N 48.5W
ABOUT 1245 MI...2005 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...SW OR 230 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES



Subtropical Storm Leslie Discussion Number 3
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Sun Sep 23 2018

There has been little change in the organization of the subtropical
cyclone over the past several hours. Patches of deep convection
continue to develop over the southeastern portion of the circulation
but there is a lack of convective banding elsewhere. The initial
intensity remains 35 kt, which is based on a partial ASCAT pass that
detected 25-30 kt winds over the northwestern portion of the storm
this evening. Leslie is not forecast to strengthen over the next
day or so due to dry air and moderate vertical shear. By 48 hours,
some increase in wind is predicted as Leslie interacts with an
approaching baroclinic zone.

Leslie jogged west-southwestward for a few hours this evening, but
has since turned southwestward and slowed down. The system is
forecast to move little over the next 24 hours, then begin a faster
eastward motion on Monday night and Tuesday as a mid-latitude trough
and associated cold front digs southeastward over the central
Atlantic. The global models indicate that the front will overtake
Leslie in about 48 hours, and the NHC forecast calls for the system
to become an extratropical low at that time. The evolution of the
system becomes even more complex after that, as the GFS shows Leslie
being absorbed by a new non-tropical low pressure area to the north,
while some of other global models maintain post-tropical Leslie as
the primary low pressure area. For now, the NHC forecast maintains
continuity with the previous advisories and calls for the system to
merge with the larger front/low by 72 h, but there is a high level
of uncertainty in the exact evolution and structure of the system.
Regardless of the details of the evolution, a large non-tropical
low pressure area with gale- to storm-force winds is expected to be
over the east-central Atlantic later this week.


FORECAST POSITIONS AND MAX WINDS

INIT 24/0300Z 33.3N 48.5W 35 KT 40 MPH
12H 24/1200Z 33.1N 48.5W 35 KT 40 MPH
24H 25/0000Z 33.1N 47.8W 35 KT 40 MPH
36H 25/1200Z 32.9N 46.0W 35 KT 40 MPH
48H 26/0000Z 33.1N 43.2W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 27/0000Z...MERGED WITH FRONT AND LARGER LOW

$$
Forecaster Brown
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Re: ATL: LESLIE - Advisories

#4 Postby cycloneye » Mon Sep 24, 2018 4:50 am

Subtropical Storm Leslie Discussion Number 4
NWS National Hurricane Center Miami FL AL132018
500 AM AST Mon Sep 24 2018

Leslie has changed little overnight. The large subtropical cyclone
continues to produce patches of deep convection, mostly to the south
and east of the center. The initial intensity is again held at 35
kt, which is near the upper end of the satellite intensity
estimates.

The subtropical storm is moving southward at 5 kt. The steering
currents around Leslie are expected to collapse later today and
little overall motion is forecast during the next 12-18 hours.
After that time, a cold front is expected to approach the system,
and that should cause Leslie to move eastward tonight and Tuesday.
The front is expected to merge with Leslie by Tuesday night, causing
it to become extratropical. While little change in intensity is
expected during the next day or so, due to dry air and moderate
shear, some strengthening as an extratropical low is likely due to
baroclinic forcing. In fact, after becoming extratropical, the
models show Leslie merging with another frontal low to its north,
leading to the formation of a powerful slow-moving non-tropical low
with gale- or storm-force winds over the central Atlantic later this
week.

FORECAST POSITIONS AND MAX WINDS

INIT 24/0900Z 32.6N 48.6W 35 KT 40 MPH
12H 24/1800Z 32.6N 48.3W 35 KT 40 MPH
24H 25/0600Z 32.6N 46.9W 35 KT 40 MPH
36H 25/1800Z 32.5N 44.8W 35 KT 40 MPH
48H 26/0600Z 32.7N 42.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 27/0600Z...MERGED WITH FRONTAL SYSTEM

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#5 Postby cycloneye » Mon Sep 24, 2018 9:41 am

Subtropical Storm Leslie Discussion Number 5
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Mon Sep 24 2018

Conventional satellite imagery shows little change in Leslie's
cloud pattern during the past several hours with the exception of a
few new isolated thunderstorms developing near the surface center.
Accordingly, the initial intensity for this advisory is kept at 35
kt. The statistical intensity guidance and the large-scale models
show Leslie commencing a strengthening trend in 24 hours as a
mid-latitude baroclinic system digs southeastward toward the
cyclone. Some of the models also indicate that Leslie, after
completing an extratropical transition in around 48 hours, will
deepen and generate a large area of gale force winds, particularly
in the northwest quadrant. The NHC intensity forecast reflects this
scenario and is just below the IVCN intensity consensus.

The initial motion is estimated to be an eastward drift, or 090/4 kt
within the increasing mid-level westerly steering flow. A turn to
the east-northeast is forecast as an approaching mid-latitude
trough and associated cold front approaches from the northwest over
the central Atlantic. The deterministic guidance indicate that the
aforementioned baroclinic system will overtake Leslie near the 48
hour period, and influence a transition to a non-tropical low
pressure system. Subsequently, the GFS and the European models
still show extratropical Leslie as the primary system and deepening
with time. For now, the official forecast will indicate a merging
scenario, but succeeding advisories may include extratropical low
forecast points through day 5.

FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 32.5N 48.0W 35 KT 40 MPH
12H 25/0000Z 32.5N 47.2W 35 KT 40 MPH
24H 25/1200Z 32.4N 45.5W 40 KT 45 MPH
36H 26/0000Z 32.3N 42.8W 45 KT 50 MPH
48H 26/1200Z 33.6N 39.9W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 27/1200Z...MERGED WITH FRONT AND LARGER LOW

$$
Forecaster Roberts
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Re: ATL: LESLIE - Advisories

#6 Postby cycloneye » Mon Sep 24, 2018 3:40 pm

BULLETIN
Subtropical Storm Leslie Advisory Number 6
NWS National Hurricane Center Miami FL AL132018
500 PM AST Mon Sep 24 2018

...LESLIE A LITTLE LESS ORGANIZED...
...EXPECTED TO BECOME AN EXTRATROPICAL LOW WEDNESDAY...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...33.0N 47.2W
ABOUT 1185 MI...1905 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...E OR 90 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES


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


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Subtropical Storm Leslie was
located near latitude 33.0 North, longitude 47.2 West. The storm is
moving toward the east near 7 mph (11 km/h), and this general motion
is expected to continue through Tuesday night. A turn toward the
east-northeast with an increase in forward speed is forecast on
Wednesday followed by a north-northeastward turn by Thursday
morning.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Little change in strength is forecast through Tuesday morning.
Leslie is forecast to strengthen by mid-week while transitioning
into an extratropical cyclone.

Winds of 40 mph extend outward up to 205 miles (335 km) from the
center.

The estimated minimum central pressure is 1004 mb (29.65 inches).


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


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Roberts



Subtropical Storm Leslie Discussion Number 6
NWS National Hurricane Center Miami FL AL132018
500 PM AST Mon Sep 24 2018

Leslie's cloud pattern has become rather ragged and less organized
this afternoon. Visible satellite imagery indicates that the
surface circulation has become elongated, from north to south, with
multiple cloud swirls rotating within the larger gyre. The initial
intensity is held at 35 kt for this advisory and could be generous,
based on the earlier partial ASCAT-A wind retrievals. The
intensity forecast philosophy remains the same. Leslie is expected
to interact with the incoming baroclinic zone approaching from the
northwest and begin intensifying as it completes a
post-tropical/extratropical transition by mid period. The official
forecast is based on the IVCN multi-model intensity consensus
through 36 hours, and a blend of the global models after Leslie
becomes an extratropical low.

Based on a centroid position of the aforementioned multiple surface
swirls, Leslie continues to move in an eastward fashion, or 090/6
kt. Leslie should turn toward the east-northeast in 36 hours in
response to an approaching mid-latitude trough and associated cold
front from the northwest over the central Atlantic. The large-scale
models are in good agreement with Leslie completing an extratropical
transition at that time. Afterward, the post-tropical cyclone is
forecast to become cut off from the mid- to upper-tropospheric
westerly steering flow and move cyclonically toward the end of the
week between the building Bermuda high to the west and mid-level
ridging over the east Atlantic. The NHC forecast now shows Leslie
as a strengthening extratropical low through day 5, in agreement
with GFS, Canadian, and European models. Subsequently, the wind
radii forecast has also been adjusted based on a compromise of the
aforementioned large-scale models.

FORECAST POSITIONS AND MAX WINDS

INIT 24/2100Z 33.0N 47.2W 35 KT 40 MPH
12H 25/0600Z 32.9N 46.2W 35 KT 40 MPH
24H 25/1800Z 32.6N 44.0W 45 KT 50 MPH
36H 26/0600Z 33.4N 41.3W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 26/1800Z 35.4N 39.9W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 27/1800Z 36.9N 42.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 28/1800Z 36.7N 46.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 29/1800Z 36.2N 48.5W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: LESLIE - Advisories

#7 Postby cycloneye » Mon Sep 24, 2018 9:37 pm

BULLETIN
Subtropical Depression Leslie Advisory Number 7
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Mon Sep 24 2018

...LESLIE EXPECTED TO BECOME A POWERFUL POST-TROPICAL CYCLONE
BEGINNING TUESDAY...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...33.1N 47.1W
ABOUT 1175 MI...1895 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...E OR 90 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES




Subtropical Depression Leslie Discussion Number 7
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Mon Sep 24 2018

Leslie's appearance in satellite imagery hasn't changed much this
evening. Deep convection is mainly occuring in bands well displaced
to the southeast of the cyclone's center, and recent ASCAT data
indicated that the maximum winds have decreased to near 30 kt, with
the highest wind occuring in those bands.

All indications are that Leslie will undergo a complicated
transition over the next several days. Little change is expected
with Leslie until it becomes post-tropical in about 24 hours. After
that time, all of the global models suggest that Leslie will quickly
strengthen as a result of substantial baroclinic forcing, likely
reaching a peak intensity sometime between 48 and 72 h. At the same
time, the cyclone will likely undergo a classic transition from
frontal low to warm seclusion while the wind field rapidly expands,
with 34-kt (gale-force) winds reaching several hundred miles from
the cyclone's center. By 96 h, the models indicate that Leslie will
once again become cut-off from the mid-latitude flow, and could
begin to re-acquire subtropical or tropical characteristics. While
each of the global models handles the exact details of this complex
evolution a little differently, confidence is increasing that Leslie
will become a powerful extratropical cyclone over the central
Atlantic over the next few of days. The NHC intensity forecast has
been increased between 36 and 96 h, and is near a average of the
global and regional dynamical model tracker output.

The depression is currently moving slowly eastward with an initial
motion of 090/3 kt. The guidance is in good agreement that Leslie
will accelerate eastward as it becomes more embedded within an
approaching frontal zone. A northward turn is expected by mid-week,
followed by a bend back toward the west by the end of the week as
Leslie strengthens, occludes, and eventually cuts off from the
mid-latitude flow to the north. The NHC track forecast has not been
significantly changed, and is near the GFEX and HCCA consensus aids
at most forecast hours. However, it should be noted that spread in
the guidance is high, especially by the end of the forecast period,
so confidence in the track forecast at that time is low.

FORECAST POSITIONS AND MAX WINDS

INIT 25/0300Z 33.1N 47.1W 30 KT 35 MPH
12H 25/1200Z 32.9N 45.6W 30 KT 35 MPH
24H 26/0000Z 33.1N 43.2W 40 KT 45 MPH...POST-TROPICAL
36H 26/1200Z 34.5N 41.1W 55 KT 65 MPH...POST-TROP/EXTRATROP
48H 27/0000Z 36.2N 40.9W 60 KT 70 MPH...POST-TROP/EXTRATROP
72H 28/0000Z 36.9N 43.8W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 29/0000Z 36.5N 47.3W 55 KT 65 MPH...POST-TROP/EXTRATROP
120H 30/0000Z 36.5N 49.0W 50 KT 60 MPH...SUBTROPICAL STORM

$$
Forecaster Zelinsky
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Re: ATL: LESLIE - Advisories

#8 Postby cycloneye » Tue Sep 25, 2018 4:57 am

Subtropical Depression Leslie Discussion Number 8
NWS National Hurricane Center Miami FL AL132018
500 AM AST Tue Sep 25 2018

No significant changes have occurred with Leslie overnight. Deep
convection is generally confined to the eastern half of the
circulation as dry air continues to wrap into the western portion
of the cyclone. Satellite images indicate that the circulation has
become stretched from north to south, likely due to the approach of
a cold front that is currently located a few hundred miles to the
northwest of Leslie. The initial intensity is held at 30 kt based
on the earlier ASCAT data.

The cold front is expected to merge with Leslie by tonight, causing
extratropical transition. While transitioning, Leslie is forecast
to strengthen for a couple of days due to significant baroclinic
forcing, and the NHC intensity forecast takes the peak winds just
below hurricane force at 36 and 48 hours. Later in the week, the
extratropical system is expected to cut off and gradually lose its
frontal features. Although this will likely cause some weakening,
it should also allow the system to regain subtropical
characteristics. The NHC intensity forecast is fairly similar to
the previous one and near the IVCN consensus model. This forecast
is also in fairly good agreement with the GFS and ECMWF models,
which are usually reliable intensity models for large subtropical
systems like Leslie. Based on the latest guidance, Leslie is now
expected to transition back to a subtropical cyclone in 96 hours.

Leslie has jogged to the southeast during the past several hours,
but an eastward to northeastward motion is expected during the next
day or so as Leslie makes its extratropical transition. After that
time, a turn to the north is expected followed by a slow westward
motion when Leslie cuts off from the mid-latitude flow. The models
are in fairly good agreement on this looping motion, and the NHC
track forecast follows the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 25/0900Z 31.9N 46.2W 30 KT 35 MPH
12H 25/1800Z 32.1N 44.8W 40 KT 45 MPH
24H 26/0600Z 32.7N 41.9W 50 KT 60 MPH...POST-TROP/EXTRATROP
36H 26/1800Z 34.5N 40.5W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 27/0600Z 36.1N 41.1W 60 KT 70 MPH...POST-TROP/EXTRATROP
72H 28/0600Z 36.0N 45.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
96H 29/0600Z 35.3N 48.2W 55 KT 65 MPH...SUBTROPICAL STORM
120H 30/0600Z 35.0N 50.0W 50 KT 60 MPH

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#9 Postby cycloneye » Tue Sep 25, 2018 9:59 am

Post-Tropical Cyclone Leslie Discussion Number 9
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Tue Sep 25 2018

Leslie has become a post-tropical cyclone. Conventional and
microwave satellite imagery show that Leslie's surface circulation
has become elongated along an intruding baroclinic zone indicated
by a recent 1158 UTC ASCAT-A pass. Any deep convection appears to
be developing due to dynamic forcing. A rather large stratocumulus
cloud shield and associated cooler, stable air is quickly advecting
into the area as well. The initial intensity is maintained at 30 kt
for this last advisory.

Leslie is forecast to strengthen during the next couple of days due
to baroclinic processes. The official forecast, based on the GFS and
European global models, and the SHIPS statistical intensity
guidance, shows an increase of the sustained winds to hurricane
force in 2 days, around the same period that the shear drops below
10 kt. The non-tropical low is then forecast to move south of the
strong upper-level westerlies and detach from the frontal boundary.
According to the global models and the Florida State Cyclone Phase
forecast, Leslie should make a transition from a frontal system to
an asymmetric shallow warm-core seclusion. Beyond day 3, guidance
suggests that Leslie will acquire subtropical characteristics and a
more symmetric, deepening warm-core low while meandering in weaker
steering currents. The intensity forecast follows this scenario and
is based on the aforementioned global and statistical models.

Leslie is now moving eastward at a slightly faster forward motion,
about 10 kt. A turn to the north is expected in 36 hours followed
by a slower westward motion as Leslie slips south of the
mid-latitude westerlies. Through the remaining portion of the
forecast, Leslie should move at a slower speed generally westward
as a ridge builds to the north. NHC forecast is nudged toward the
TVCN consensus through 48 hours, then follows more closely to the
GFEX (GFS/ECMWF) consensus model.

This is the last advisory issued by the National Hurricane Center on
Leslie. Additional information on this system can be found in High
Seas Forecasts issued by the National Weather Service, under AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and available on the Web
at https://ocean.weather.gov/shtml/NFDHSFAT1.shtml.

FORECAST POSITIONS AND MAX WINDS

INIT 25/1500Z 31.6N 44.4W 30 KT 35 MPH...POST-TROPICAL
12H 26/0000Z 32.1N 42.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
24H 26/1200Z 33.6N 40.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
36H 27/0000Z 35.6N 39.9W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 27/1200Z 36.1N 41.7W 65 KT 75 MPH...POST-TROP/EXTRATROP
72H 28/1200Z 35.5N 45.3W 60 KT 70 MPH...SUBTROPICAL STORM
96H 29/1200Z 34.6N 48.1W 55 KT 65 MPH...SUBTROPICAL STORM
120H 30/1200Z 34.4N 49.6W 50 KT 60 MPH...SUBTROPICAL STORM

$$
Forecaster Roberts
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Re: ATL: LESLIE - Advisories

#10 Postby cycloneye » Fri Sep 28, 2018 3:47 pm

BULLETIN
Subtropical Storm Leslie Advisory Number 10
NWS National Hurricane Center Miami FL AL132018
500 PM AST Fri Sep 28 2018

...POST-TROPICAL CYCLONE LESLIE REGAINS SUBTROPICAL STORM STATUS...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...36.1N 48.1W
ABOUT 1170 MI...1880 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...W OR 260 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES


Subtropical Storm Leslie Discussion Number 10
NWS National Hurricane Center Miami FL AL132018
500 PM AST Fri Sep 28 2018

Central convection associated with Post-Tropical Storm Leslie has
gradually increased during the last couple of days and is now
organized into a group of bands that wraps most of the way around
the center. In addition, scatterometer data show that the cyclone
has lost much of its large baroclinic wind field, and that the
radius of maximum winds has contracted from 120-180 n mi yesterday
to 90 n mi or less today. While the storm has also developed a warm
core and shed some of its baroclinic characteristics, it is embedded
in a large deep-layer low pressure system, and thus it is designated
subtropical instead of tropical. The initial intensity is set at 45
kt based on the scatterometer data.

Leslie has been moving generally westward for the the past few
days. The large-scale models forecast a general southwesterly
motion for the next 3-4 days as the cyclone is steered by a segment
of the subtropical ridge to its west and another large deep-layer
low forming to its east over the eastern Atlantic, with a decrease
in forward speed near the end of the forecast period as the ridge
to the west weakens. The forecast guidance is tightly clustered
through 120 h, and the forecast track is near the center of the
guidance envelope and the consensus models.

The forecast track takes the center of Leslie over increasing sea
surface temperatures during the next several days, although the
temperatures may not be as warm as those indicated in the SHIPS
model. The global models suggest that little change in strength
will occur during the first 48-72 h as Leslie gradually develops
the upper-level outflow pattern of a tropical cyclone and
transitions to a tropical storm. After that time, they are in good
agreement that the cyclone will strengthen. Based on this, the
intensity forecast shows only modest intensification during the
first 48 h, followed by strengthening to a probably conservative
60 kt. The forecast also calls for transition to a tropical storm
between 48-72 h, with the caveat that this could occur earlier.


FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 36.1N 48.1W 45 KT 50 MPH
12H 29/0600Z 35.4N 49.6W 45 KT 50 MPH
24H 29/1800Z 34.4N 51.2W 45 KT 50 MPH
36H 30/0600Z 33.8N 52.2W 50 KT 60 MPH
48H 30/1800Z 33.2N 53.1W 50 KT 60 MPH
72H 01/1800Z 32.5N 54.5W 55 KT 65 MPH...TROPICAL STORM
96H 02/1800Z 31.0N 56.0W 60 KT 70 MPH
120H 03/1800Z 31.0N 57.0W 60 KT 70 MPH

$$
Forecaster Beven
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Re: ATL: LESLIE - Advisories

#11 Postby cycloneye » Fri Sep 28, 2018 9:53 pm

Subtropical Storm Leslie Discussion Number 11
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Fri Sep 28 2018

Convective banding has been consolidating to the south of Leslie's
center since the afternoon, but recent scatterometer data indicate
that the maximum winds have decreased to 40 kt and the area of
gale-force winds has decreased in size. The convective structure
suggests that Leslie may be taking on some tropical characteristics,
but since wave vapor imagery still shows the cyclone embedded within
a complex deep-layer low, Leslie is still being designated as
subtropical.

Leslie is moving west-southwestward, or 255 degrees at 10 kt.
Leslie is entrenched between several mid-tropospheric highs located
to its east and west, and these features are expected to push
Leslie slowly southwestward for the next 3 days. The track
guidance is tightly clustered during this period, and the NHC
forecast is very similar to the previous one. After day 3, Leslie
is likely to meander on days 4 and 5 in weak steering, and the
updated official forecast has been adjusted southward and eastward
at the end of the forecast period to account for the latest model
solutions.

Global model fields indicate that Leslie has migrated to the
northwest of its parent upper-level low, which is putting it under
a regime of moderate north-northeasterly shear. For the next 48
hours, this shear is expected to continue, and phase-space diagrams
suggest that Leslie will be straddling the line between shallow and
deep warm core. As a result, only modest strengthening is
anticipated during this period, and the official forecast maintains
Leslie as a subtropical storm through 48 hours. However, the
transition to a tropical storm could occur any time during the next
day or two. After 48 hours, Leslie should definitely be deep warm
core, and more significant strengthening is expected, with the
cyclone forecast to reach hurricane intensity by day 4. This
scenario is shown by the various intensity models, and the NHC
intensity forecast is very close to the HFIP Corrected Consensus
aid and the Florida State Superensemble. If the statistical-
dynamical models are correct, Leslie could be stronger by the end of
the forecast period than is indicated in the NHC forecast.

Large swells generated by Leslie when it was a stronger
extratropical low have already reached Bermuda, will soon reach the
Lesser and Greater Antilles, and should reach portions of the east
coast of the United States later this weekend. These swells could
cause life-threatening surf and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0300Z 35.7N 49.4W 40 KT 45 MPH
12H 29/1200Z 34.9N 50.8W 45 KT 50 MPH
24H 30/0000Z 34.0N 52.0W 45 KT 50 MPH
36H 30/1200Z 33.5N 53.0W 50 KT 60 MPH
48H 01/0000Z 33.1N 53.9W 50 KT 60 MPH
72H 02/0000Z 32.2N 55.4W 60 KT 70 MPH...TROPICAL CYCLONE
96H 03/0000Z 30.5N 56.0W 65 KT 75 MPH
120H 04/0000Z 31.5N 56.5W 70 KT 80 MPH

$$
Forecaster Berg
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Re: ATL: LESLIE - Advisories

#12 Postby cycloneye » Sat Sep 29, 2018 4:57 am

Subtropical Storm Leslie Discussion Number 12
NWS National Hurricane Center Miami FL AL132018
500 AM AST Sat Sep 29 2018

The deep convection has become more concentrated near the center
during the past several hours indicating that Leslie is gradually
acquiring some tropical characteristics, but the cyclone is still
too attached to a complex deep-layer low. On this basis, Leslie is
still considered a subtropical storm in this advisory with an
initial intensity of 40 kt. Global models indicate that the
subtropical cyclone will continue to be embedded within strong
northerly shear during the next 2 days or so. After that time, the
shear is forecast to relax and with a warm ocean along the cyclone's
path, Leslie is forecast to become fully tropical and reach
hurricane status by the end of the forecast period. SHIPS model and
its derivatives strengthen Leslie significantly, but the NHC
forecast is a little less aggressive, and it follows the intensity
consensus.

Leslie has been moving toward the southwest or 230 degrees at 6 kt,
steered by the flow around the western side of the large deep-layer
low in which Leslie is embedded. Since this steering pattern is
not expected to change, Leslie will probably continue on the same
general track for the next 3 to 4 days. After that time, the large
low weakens and the cyclone will become steered slowly northward by
the flow ahead of an approaching mid-latitude trough. Nevertheless,
Leslie is forecast to meander over the north-central Atlantic for
several more days. This is the solution provided by most of the
global models, and the NHC forecast follows very closely the
multi-model consensus aids and the corrected consensus HCCA.

Large swells previously generated by Leslie when it was a stronger
extratropical low have already reached Bermuda, and will soon reach
the Lesser and Greater Antilles. These swells are expected to reach
portions of the east coast of the United States by Sunday. These
swells could cause life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 35.2N 50.3W 40 KT 45 MPH
12H 29/1800Z 34.4N 51.3W 45 KT 50 MPH
24H 30/0600Z 33.8N 52.2W 45 KT 50 MPH
36H 30/1800Z 33.5N 53.3W 50 KT 60 MPH
48H 01/0600Z 33.2N 54.0W 50 KT 60 MPH...TROPICAL CYCLONE
72H 02/0600Z 32.3N 55.0W 60 KT 70 MPH
96H 03/0600Z 31.0N 55.5W 65 KT 75 MPH
120H 04/0600Z 32.0N 56.0W 70 KT 80 MPH

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#13 Postby cycloneye » Sat Sep 29, 2018 9:48 am

Subtropical Storm Leslie Discussion Number 13
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Sat Sep 29 2018

Leslie's cloud pattern has taken on a more tropical appearance
since last night. However, the cyclone is still co-located with an
upper-level low, so its status as a subtropical cyclone is
maintained for this advisory. The initial intensity remains 40 kt,
based on a subtropical classification of 35-40 kt from TAFB.

The global models forecast that Leslie will separate from the
upper-level low over the course of the next day or so, which should
complete its transition to a tropical cyclone. While this could
result in a short-term increase in shear over Leslie, by early next
week the cyclone will likely be located within a fairly low shear
environment. However, Leslie is expected to move very slowly by that
time, and ocean upwelling could limit or prevent further
strengthening. There is a large amount of spread in the intensity
guidance by day 5, but it is worth noting that the models most
capable of properly representing the effect of ocean cooling on
intensity, COAMPS-TC, HWRF, and HMON, all keep Leslie below
hurricane strength for the next 5 days. The HWRF in particular
forecasts nearly 5 deg C of ocean cooling beneath the cyclone. The
NHC intensity forecast is generally a little lower than the previous
advisory, but is still near the IVCN and HCCA consensus aids at all
forecast hours. If Leslie moves more than expected, it would not be
surprising if it strengthened more than currently forecast.

Little change was made to the official track forecast. Leslie is
still expected to move slowly southwestward for the next couple of
days, before coming to a near halt early next week. By the
middle of the week, an approaching mid-latitude trough could steer
Leslie toward the north or northeast and allow the cyclone to start
gaining speed, however, there is a lot of spread among the global
models as to how quickly this will occur, and confidence in this
portion of the forecast is fairly low.

Large swells generated by Leslie when it was a strong extratropical
low will affect Bermuda, the east coast of the United States, and
most of the Greater and Lesser Antilles through the weekend. These
swells could cause life-threatening surf and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 34.4N 50.8W 40 KT 45 MPH
12H 30/0000Z 33.8N 51.7W 45 KT 50 MPH
24H 30/1200Z 33.3N 52.7W 45 KT 50 MPH
36H 01/0000Z 33.1N 53.5W 50 KT 60 MPH...TROPICAL CYCLONE
48H 01/1200Z 32.8N 54.0W 50 KT 60 MPH
72H 02/1200Z 31.6N 55.0W 55 KT 65 MPH
96H 03/1200Z 31.0N 55.5W 60 KT 70 MPH
120H 04/1200Z 33.0N 55.0W 65 KT 75 MPH

$$
Forecaster Zelinsky
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Re: ATL: LESLIE - Advisories

#14 Postby cycloneye » Sun Sep 30, 2018 5:21 am

Tropical Storm Leslie Discussion Number 16
NWS National Hurricane Center Miami FL AL132018
500 AM AST Sun Sep 30 2018

Convection associated with the tropical storm has become more
fragmented over the past 12 hours or so, and now consists of several
broken bands primarily over the southeastern portion of the
circulation. Satellite intensity estimates have not changed much
since the previous advisory, and the initial intensity is held at
45 kt, which is in agreement with earlier ASCAT data and a recent
UW/CIMSS SATCON estimate of 42 kt. The recent warming of the clouds
tops may be associated with cooler waters caused by upwelling
beneath the large, slow-moving tropical storm. Leslie, however is
forecast to move southwestward toward somewhat warmer waters and a
more favorable upper-level environment during the next 2 to 3 days.
This conditions should allow for gradual strengthening, and the NHC
forecast follows the intensity guidance by bringing Leslie to
hurricane strength in about 72 hours. Later in the period, Leslie
is likely to move back over some of the cooler upwelled waters along
its previous track, which could result in gradual weakening.

Recent satellite fixes show that Leslie is moving west-
southwestward or 240 degrees at 4 kt. The tropical storm is caught
between a pair of mid-level ridges and a slow southwestward to
south-southwestward motion is expected over the next 2 to 3 days.
Around mid-week, a shortwave trough moving off the coast of the
northeastern United States is expected to help lift Leslie slowly
northward at days 4 and 5, but the models have trended toward a
somewhat slower solution. Despite the storm's expected slow motion,
the spread in the track guidance becomes fairly large by days 4 and
5, and it appears that Leslie is likely to meander over the Central
Atlantic for quite some time.

Large swells generated by Leslie when it was a strong extratropical
low will affect Bermuda, the east coast of the United States, and
most of the Greater and Lesser Antilles through at least the early
part of this week. These swells could cause life-threatening surf
and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 33.8N 52.5W 45 KT 50 MPH
12H 30/1800Z 33.4N 53.2W 45 KT 50 MPH
24H 01/0600Z 32.9N 53.8W 50 KT 60 MPH
36H 01/1800Z 32.5N 54.2W 55 KT 65 MPH
48H 02/0600Z 31.9N 54.5W 55 KT 65 MPH
72H 03/0600Z 30.7N 54.7W 65 KT 75 MPH
96H 04/0600Z 32.4N 54.1W 65 KT 75 MPH
120H 05/0600Z 35.5N 53.0W 60 KT 70 MPH

$$
Forecaster Brown
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Re: ATL: LESLIE - Advisories

#15 Postby cycloneye » Sun Sep 30, 2018 3:53 pm

Tropical Storm Leslie Discussion Number 18
NWS National Hurricane Center Miami FL AL132018
500 PM AST Sun Sep 30 2018

Leslie has generally changed little in organization today. The
tropical storm continues to produce deep convection in a band to
the southeast of the center, but there is a minimal amount of
shower activity elsewhere. This asymmetric cloud pattern is due to
about 25 kt of northwesterly wind shear. The initial intensity is
again held at 45 kt, but some of the satellite estimates suggest
that this could be a little generous. The global models show the
upper-level pattern becoming more favorable over Leslie in about a
day, which combined with warmer SSTs should allow Leslie to
gradually strengthen during the next 2 to 3 days. After that time,
the storm is expected to move northeastward back over its previous
track and cooler waters partly caused by its own upwelling. These
conditions should end the strengthening trend and induce some
weakening. The NHC intensity forecast is largely an update of the
previous one and in line with the IVCN, FSSE, and HCCA consensus
models.

Leslie is drifting to the southwest, with the latest initial motion
estimate being 240/4 kt. The storm is forecast to remain in very
weak steering currents, and Leslie will likely drift southward to
southwestward during the next few days on the east side of a
mid-level ridge. Thereafter, a developing trough to the southwest of
Leslie should cause the system to move northeastward at a slightly
faster pace. The models continue to shift back and forth each
cycle, which is not surprising given the weak steering. This
forecast is adjusted a little to the left of the previous one to
come into better agreement with the latest models. The bottom line
is that Leslie is forecast to meander over the central Atlantic for
the next several days.

Large swells generated by Leslie when it was a strong extratropical
low will continue to affect the east coast of the United States and
most of the Greater and Lesser Antilles for another day or two.
These swells could cause life-threatening surf and rip currents.
Although the swells will diminish some by mid-week, they will likely
remain hazardous for the same locations through the forecast period
due to Leslie's slow motion.

FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 33.5N 53.2W 45 KT 50 MPH
12H 01/0600Z 33.3N 53.7W 50 KT 60 MPH
24H 01/1800Z 32.9N 54.3W 55 KT 65 MPH
36H 02/0600Z 32.1N 55.0W 60 KT 70 MPH
48H 02/1800Z 31.3N 55.3W 65 KT 75 MPH
72H 03/1800Z 31.0N 54.7W 65 KT 75 MPH
96H 04/1800Z 33.5N 53.5W 60 KT 70 MPH
120H 05/1800Z 36.5N 52.0W 60 KT 70 MPH

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#16 Postby cycloneye » Mon Oct 01, 2018 9:34 am

Tropical Storm Leslie Discussion Number 21
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Mon Oct 01 2018

Leslie is gradually becoming better organized. A large band of
deep convection exists on the west side of the circulation and some
fragmented bands are beginning to form on the east side. Overall,
Leslie appears more symmetric than it has been during the past
couple of days due to a decrease in wind shear. Despite the
improved appearance, the satellite intensity estimates are largely
unchanged, so the initial intensity is held at 50 kt, near the high
end of the estimates.

Since Leslie is forecast to be in a low wind shear environment
and expected to move over slightly higher SSTs during the next
couple of days, slow strengthening is predicted. Most of
the models show Leslie becoming a hurricane in 24 to 36 hours, and
the NHC forecast follows suit. By late in the week and this
weekend, Leslie is expected to move north-northeastward back over
its previous track, where it has upwelled cooler waters. These less
conducive oceanic conditions should cause a slow decay.

Leslie continues to drift to the southwest on the east side of a
mid-level high, and a continued slow south to southwest motion
is expected during the next couple of days. Thereafter, a
developing shortwave trough to the west of Leslie should cause it to
move north-northeastward but only at a slightly faster pace. The
NHC track forecast is nudged to the left of the previous one to come
into better agreement with the latest guidance. Regardless of the
details of the forecast track, there is high confidence that Leslie
will meander for quite a while over the central Atlantic.

Large swells generated by Leslie will continue to affect portions
of the southeastern coast of the United States, Bermuda, the
Bahamas, and most of the Greater and Lesser Antilles through
tonight. These swells could cause life-threatening surf and rip
currents. Although the swells will diminish slightly by Tuesday,
they are expected to increase again over the Bahamas and most of the
Greater and Lesser Antilles late Wednesday and Thursday.

FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 33.2N 54.3W 50 KT 60 MPH
12H 02/0000Z 32.7N 54.9W 55 KT 65 MPH
24H 02/1200Z 31.6N 55.6W 65 KT 75 MPH
36H 03/0000Z 30.7N 55.9W 70 KT 80 MPH
48H 03/1200Z 30.4N 56.0W 70 KT 80 MPH
72H 04/1200Z 32.5N 55.3W 65 KT 75 MPH
96H 05/1200Z 35.7N 54.4W 60 KT 70 MPH
120H 06/1200Z 37.4N 52.0W 60 KT 70 MPH

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#17 Postby cycloneye » Mon Oct 01, 2018 3:38 pm

Tropical Storm Leslie Discussion Number 22
NWS National Hurricane Center Miami FL AL132018
500 PM AST Mon Oct 01 2018

The cloud pattern of Leslie has improved throughout the day, and
the system now has a ragged eye with multiple mesovorticies within
it. In addition, the associated convection has become more
symmetric this afternoon, but the cloud tops are not very cold south
of the center. Even though the system looks better organized, the
satellite intensity estimates are again unchanged. Accordingly, the
initial intensity is held at 50 kt near the high end of the
satellite estimates.

Leslie will likely strengthen gradually during the next day or
so as it heads toward slightly warmer SSTs and remains in relatively
low wind shear conditions. Most of the models show Leslie
becoming a hurricane on Tuesday, and the NHC forecast follows that
guidance. Leslie is expected to move north-northeastward back over
its own upwelled cool waters late this week and this weekend,
which should promote a gradual weakening trend. The NHC intensity
forecast is identical to the previous one and in line with the HCCA
and IVCN models.

Leslie continues to drift to the southwest on the east side of a
mid-level high. There has been no change to the track forecast
philosophy. Leslie is expected to continue to move slowly southward
to southwestward in weak steering currents during the next couple of
days. Thereafter, a developing shortwave trough to the west of
Leslie should cause it to move north-northeastward to northeastward
at a slightly faster pace. The guidance has shifted south and west
this cycle, and the NHC track forecast has been adjusted in those
directions. Regardless of the details of the forecast track, there
is high confidence that Leslie will meander for quite a while over
the central Atlantic.

Large swells generated by Leslie will continue to affect portions
of the southeastern coast of the United States, Bermuda, the
Bahamas, and most of the Greater and Lesser Antilles through
tonight. These swells could cause life-threatening surf and rip
currents. Although the swells will diminish slightly by Tuesday,
they are expected to increase again over the Bahamas and most of the
Greater and Lesser Antilles late Wednesday and Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 32.8N 54.6W 50 KT 60 MPH
12H 02/0600Z 31.9N 55.4W 55 KT 65 MPH
24H 02/1800Z 30.9N 55.9W 65 KT 75 MPH
36H 03/0600Z 30.2N 56.2W 70 KT 80 MPH
48H 03/1800Z 30.0N 56.4W 70 KT 80 MPH
72H 04/1800Z 33.3N 55.8W 65 KT 75 MPH
96H 05/1800Z 36.4N 55.0W 60 KT 70 MPH
120H 06/1800Z 37.2N 52.8W 60 KT 70 MPH

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#18 Postby cycloneye » Mon Oct 01, 2018 9:53 pm

Tropical Storm Leslie Discussion Number 23
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Mon Oct 01 2018

Satellite imagery shows that the convective organization of Leslie
has changed little during the past several hours. The eye-like
feature, however, has become a little more distinct and symmetric.
The subjective and objective intensity estimates haven't changed
though, and the initial intensity remains at 50 kt for this
advisory.

The initial motion is estimated to be a southwestward drift, or
220/4 kt. Leslie is forecast to continue drifting generally
southwestward through the 36-hour period in relatively weak
mid-tropospheric steering flow produced by a ridge extending
eastward from the southeast United States to near Bermuda.
Afterwards, an amplifying mid-latitude shortwave trough approaching
the cyclone from the Canadian Maritimes should induce a
north-northeastward to northeastward motion at an increasing forward
speed. The NHC forecast is adjusted just to the left of the
previous forecast track beyond 36 hours to align more with the TVCN
consensus guidance.

The intensity forecast philosophy remains basically the same, this
evening. Strengthening is still expected during the next 36 hours
and Leslie is likely to become a hurricane Tuesday tonight, as
indicated by the statistical and multi-model intensity guidance.
Near the 72-hour period, Leslie should begin a gradual weakening
trend as the cyclone moves back over cooler oceanic temperatures
and some invading drier mid-level air, associated with the
aforementioned shortwave trough which stabilizes the surrounding
environment. The official intensity forecast is an update of the
previous one and is close to the IVCN and NOAA-HCCA consensus aids.
The forecast wind radii have been adjusted based on the RVCN
(GFS/ECMWF/HWRF) multi-model consensus.

Large swells generated by Leslie will continue to affect portions of
the southeastern coast of the United States, Bermuda, and the
Bahamas. These swells could cause life-threatening surf and
rip currents. Although the swells are forecast to abate temporarily
in the Bahamas Tuesday, they are expected to increase again
Wednesday and Thursday and propagate farther southward into the
Greater and Lesser Antilles. Please consult products from your
local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 32.4N 55.0W 50 KT 60 MPH
12H 02/1200Z 31.3N 55.7W 55 KT 65 MPH
24H 03/0000Z 30.2N 56.3W 65 KT 75 MPH
36H 03/1200Z 29.9N 56.6W 70 KT 80 MPH
48H 04/0000Z 30.6N 56.4W 70 KT 80 MPH
72H 05/0000Z 34.4N 55.9W 65 KT 75 MPH
96H 06/0000Z 37.0N 55.0W 60 KT 70 MPH
120H 07/0000Z 37.3N 52.5W 55 KT 65 MPH

$$
Forecaster Roberts
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Re: ATL: LESLIE - Advisories

#19 Postby cycloneye » Tue Oct 02, 2018 4:57 am

Tropical Storm Leslie Discussion Number 24
NWS National Hurricane Center Miami FL AL132018
500 AM AST Tue Oct 02 2018

Infrared and passive microwave satellite imagery indicate that
convection has increased and become better organized around the
well-defined low-level circulation center. In fact, recent
microwave images showed that Leslie has developed a closed, 20- to
25-nmi wide low-level eye. Based on the presence of the distinct
low-level eye feature and a Dvorak intensity estimate of T3.5/55 kt
from SAB, the cyclone's intensity has been increased to 55 kt.

The initial motion is southwestward or 220 degrees at a faster
forward speed of 6 kt. For the next 24 h or so, Leslie is forecast
to move slowly southwestward to south-southwestward, trapped between
a deep-layer ridge to the west and a mid- to upper-level low to the
east. After possibly becoming stationary near the 36-h period, a
ridge to the southeast and east of Leslie is forecast to become
highly amplified, forcing the cyclone northward into the higher
latitudes through 72 h. On days 4 and 5, an approaching mid-latitude
shortwave trough well to the north of Leslie is forecast to nudge
the cyclone eastward, but only slowly at forward speeds of less than
10 kt. The new NHC forecast track has again been adjusted to the
left of the previous advisory track in the 36- to 72-h period, and
is similar to but slightly east of the various consensus models.

Leslie's outflow pattern has become a little more symmetrical during
the past 6 h, and further improvement is expected through 72 hours.
In addition, lightning data and satellite imagery during the past
few hours indicate that convection has been developing in the dry
slot to the north and east of the main convective band, suggesting
the mid-level environment is finally beginning to moisten. This dry
intrusion has been hindering the development of deep eyewall
convection and, thus, the lack of intensification of the cyclone.
However, given the strong instability that is forecast to develop in
the inner-core region region due to very cold air aloft moving over
relatively warm waters of near 26C beneath the cyclone, along with
increasing outflow and mid-level moisture, slow but steady
strengthening seems reasonable for the next 48 hours or so. By 72 h
and beyond, gradual weakening is expected as Leslie moves back over
cooler oceanic temperatures and dry mid-level air from the
mid-latitudes associated with the aforementioned shortwave trough
once again gets entrained into the cyclone's circulation. The
official intensity forecast is just an update of the previous
advisory, and is similar to the weaker IVCN consensus model.

Large swells generated by Leslie will continue to affect portions of
the southeastern coast of the United States, Bermuda, and the
Bahamas. These swells could cause life-threatening surf and
rip currents. Although the swells are forecast to abate temporarily
in the Bahamas later today, they are expected to increase again on
Wednesday and Thursday, and propagate farther southward into the
Greater and Lesser Antilles. Please consult products from your
local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 31.6N 55.6W 55 KT 65 MPH
12H 02/1800Z 30.6N 56.1W 60 KT 70 MPH
24H 03/0600Z 29.9N 56.5W 65 KT 75 MPH
36H 03/1800Z 30.2N 56.6W 70 KT 80 MPH
48H 04/0600Z 31.3N 56.4W 70 KT 80 MPH
72H 05/0600Z 35.0N 56.3W 65 KT 75 MPH
96H 06/0600Z 37.1N 54.8W 60 KT 70 MPH
120H 07/0600Z 37.1N 51.9W 55 KT 65 MPH

$$
Forecaster Stewart
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Re: ATL: LESLIE - Advisories

#20 Postby cycloneye » Tue Oct 02, 2018 9:37 am

Tropical Storm Leslie Discussion Number 25
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Tue Oct 02 2018

Leslie has generally changed little during the past several hours.
The storm continues to have a ragged banded eye feature with
multiple mesovortices within it. Deep convection is most organized
in a curved band that currently wraps from the northeast to
southwest quadrant of the storm. The initial intensity is held at
55 kt, which is near the high end of the satellite estimates.
Although the storm has not strengthened much during the past day or
so, it still has an opportunity to intensify while it moves over
slightly higher SSTs and remains in favorable atmospheric conditions
during the next day or two. Beyond a couple of days, slow weakening
seems likely as Leslie heads over SSTs cooler than 26 deg C and into
a slightly drier environment. The NHC intensity forecast is the
same as the previous one, and it is in good agreement with the HCCA
and IVCN consensus aids. This intensity forecast lies between the
aggressive statistical-dynamical models and the lower HMON and
COAMPS-TC models that keep Leslie below hurricane strength.

The tropical storm continues to lose latitude, with the latest
initial motion estimate being 215/7. A continued slow south to
south-southwest motion is forecast during the next 24 hours as the
system moves in the flow on the east side of a mid-level high.
After that time, the combination of a shortwave trough to the west
and an amplifying mid-level ridge to the southeast should cause
Leslie to move northward to north-northeastward late this week. By
the weekend, the models suggest that Leslie should turn eastward
when it moves in the mid-latitude westerlies. The NHC track
forecast is nudged to the west to come into better agreement with
the latest models.

Large swells generated by Leslie are expected to increase tomorrow
and Thursday across the southeastern coast of the United States,
Bermuda, the Bahamas, and the Greater and Lesser Antilles. These
swells will also begin to increase near the coasts of New England
and Atlantic Canada by the end of the week. Please consult products
from your local weather office as these conditions could cause
life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 30.9N 56.1W 55 KT 65 MPH
12H 03/0000Z 30.1N 56.4W 60 KT 70 MPH
24H 03/1200Z 29.8N 56.6W 65 KT 75 MPH
36H 04/0000Z 30.5N 56.7W 70 KT 80 MPH
48H 04/1200Z 31.9N 56.5W 70 KT 80 MPH
72H 05/1200Z 35.9N 56.3W 60 KT 70 MPH
96H 06/1200Z 37.6N 54.2W 60 KT 70 MPH
120H 07/1200Z 37.3N 50.5W 55 KT 65 MPH

$$
Forecaster Cangialosi
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