ATL: LESLIE - Advisories

[cycloneye]

BULLETIN
Hurricane Leslie Advisory Number 21
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Mon Oct 07 2024

...LESLIE SLIGHTLY WEAKER AS IT CONTINUES MOVING NORTHWESTWARD...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...16.4N 41.2W
ABOUT 1120 MI...1805 KM W OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES



Hurricane Leslie Discussion Number 21
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Mon Oct 07 2024

Leslie appears slightly less organized based on infrared and visible
satellite imagery. However, an SSMIS microwave pass from a few
hours ago indicated that there was still a feature resembling an eye
on the 91-GHz imagery. Subjective Dvorak estimates from TAFB and
SAB are T-4.5/77 kt. The objective estimates from UW-CIMSS range
from 65 to 84 kt. The initial intensity is nudged down slightly to
75 kt, based on the degraded satellite presentation noted on
conventional satellite imagery.

Leslie is moving northwestward, or 315/11 kt. Leslie is expected to
move around the southwestern periphery of a subtropical ridge to the
northeast of the cyclone and turn gradually north-northwestward to
northward toward the end of the week. The NHC track forecast was
nudged only slightly to the right of the previous official forecast
during the first 72 h of the forecast and is close to the various
track consensus aids.

Leslie will remain over warm ocean water through the 5-day forecast
period, and it will remain in an environment of relatively low
vertical wind shear for another 48 h. However, dry air in the
lower and middle troposphere should prevent any strengthening. In
fact, the bulk of the intensity guidance shows weakening, and the
NHC forecast follows suit. Due to Leslie's small size, its core
seems to be vulnerable to the dry air, despite the low shear. Only
minor changes are made to the official intensity forecast, which
lies near the lower end of the intensity guidance. Beyond 48 h,
Leslie is forecast to run into strong northerly wind shear as the
cyclone interacts with an upper-level trough. This shear will
cause continued weakening. Simulated satellite imagery is showing
Leslie losing its convection beyond day 4, and the NHC forecast
shows the tropical cyclone becoming post-tropical in 4 to 5 days.


FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 16.4N 41.2W 75 KT 85 MPH
12H 08/0000Z 17.5N 42.5W 65 KT 75 MPH
24H 08/1200Z 19.0N 44.2W 60 KT 70 MPH
36H 09/0000Z 20.5N 45.9W 55 KT 65 MPH
48H 09/1200Z 21.6N 47.2W 55 KT 65 MPH
60H 10/0000Z 22.4N 48.3W 50 KT 60 MPH
72H 10/1200Z 23.1N 49.1W 45 KT 50 MPH
96H 11/1200Z 24.7N 50.0W 40 KT 45 MPH
120H 12/1200Z 27.0N 48.9W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Hagen

[cycloneye]

Hurricane Leslie Discussion Number 22
NWS National Hurricane Center Miami FL AL132024
500 PM AST Mon Oct 07 2024

Leslie's convective organization continues to become a little less
organized this afternoon, although deep convection has persisted
over the center with cloud tops near -80C. A recent AMSR2 microwave
pass shows that the inner core has deteriorated from imagery earlier
today. Subjective and objective Dvorak estimates range from 60 to 75
kt. Using a blend of these estimates, the initial intensity for this
advisory is set to 70 kt.

The system is moving northwestward, or 315/12 kt. The hurricane is
rounding the edge of a subtropical ridge over the central/east
Atlantic. The system should continue to move northwestward with a
gradual turn more north-northwestward then northward by the end of
the forecast period. The NHC track forecast is slightly faster than
the previous forecast and was adjusted slightly to the right towards
the latest consensus aids.

Leslie will remain in a marginal environment for the next day or
two, with warm sea surface temperatures and low to moderate wind
shear. However, the system is entering a much drier air mass. Beyond
48 h, shear will also increase as the mid-levels will continue to be
dry. Intensity guidance is in fairly good agreement with gradual
then steady weakening throughout the forecast period. The NHC
intensity forecast follows these weakening trends and lies near the
model consensus. Model simulated satellite imagery depicts that by
day 4, the shear and drier air will cause Leslie to lose convection
and the system is forecast to become a post-tropical remnant low at
that time.


FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 17.4N 42.1W 70 KT 80 MPH
12H 08/0600Z 18.6N 43.5W 65 KT 75 MPH
24H 08/1800Z 20.2N 45.3W 60 KT 70 MPH
36H 09/0600Z 21.5N 46.8W 55 KT 65 MPH
48H 09/1800Z 22.6N 47.8W 55 KT 65 MPH
60H 10/0600Z 23.3N 48.5W 50 KT 60 MPH
72H 10/1800Z 24.2N 49.3W 45 KT 50 MPH
96H 11/1800Z 26.3N 49.0W 40 KT 45 MPH...POST-TROP/REMNT LOW
120H 12/1800Z 30.0N 46.5W 35 KT 40 MPH...POST-TROP/REMNT LOW

$$
Forecaster Kelly

[cycloneye]

Hurricane Leslie Discussion Number 23
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Mon Oct 07 2024

Deep convection has continued to pulse this evening in Leslie,
with the larger cirrus shield taking on an amorphous shape. Under
the cirrus canopy, the last few SSMIS microwave passes suggest that
the hurricane's structure continues to degrade, with the tighter
inner-core seen yesterday at this time no longer observed. The
subjective Dvorak estimates this evening were T4.0/65 kt from SAB
and T4.5 from TAFB. However, the objective intensity estimates have
decreased further, with the most recent DMINT down to 61 kt. Thus,
the initial intensity was lowered slightly to 65 kt this advisory.
The wind radii were adjusted a bit outward thanks to a helpful
ASCAT-B pass earlier this evening.

Leslie has maintained its northwestward motion, currently estimated
at 310/12 kt. There is not a lot of new information to provide for
the track reasoning this cycle, with Leslie rounding the western
side of a subtropical ridge to its northeast. The hurricane should
maintain its northwestward motion over the next day or two, followed
by a turn northward towards the end of this week once it reaches the
western edge of this synoptic steering feature. The track guidance
this cycle is just a notch left of the prior forecast, and the NHC
track has been nudged in that direction, but is still quite close to
the prior track forecast.

Leslie is currently battling a fairly marginal environment with
mid-level southerly shear of 20-25 kt continuing to undercut the
seemingly more favorable 200 mb upper-level flow. A ribbon of very
dry environmental air that can be seen on GOES-16 water vapor
imagery, which is likely being imported near Leslie's center,
contributing to its degraded inner-core structure seen on microwave
imagery. This shear is expected to persist, before quickly shifting
out of the north and increasing above 40 kt after 48 h. Intensity
guidance remains insistent that Leslie will weaken slowly at first,
and then more dramatically after this shear increases. The GFS,
ECMWF, and HAFS-A/B runs show Leslie quickly becoming devoid of
convection after 72 h due to this shear, and the NHC forecast
continues to show Leslie becoming a post-tropical cyclone in 96 h.


FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 18.4N 43.5W 65 KT 75 MPH
12H 08/1200Z 19.6N 44.9W 60 KT 70 MPH
24H 09/0000Z 21.0N 46.5W 55 KT 65 MPH
36H 09/1200Z 22.2N 47.7W 55 KT 65 MPH
48H 10/0000Z 23.0N 48.6W 55 KT 65 MPH
60H 10/1200Z 23.8N 49.5W 50 KT 60 MPH
72H 11/0000Z 25.0N 50.0W 40 KT 45 MPH
96H 12/0000Z 28.0N 48.5W 35 KT 40 MPH...POST-TROPICAL
120H 13/0000Z 32.0N 43.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin

NNNN

[cycloneye]

Tropical Storm Leslie Discussion Number 24
NWS National Hurricane Center Miami FL AL132024
500 AM AST Tue Oct 08 2024

This morning's satellite presentation consists of a shrinking cold
cloud top (-73C) irregular-shaped central dense overcast and curved
banding features in the south and north portion of the cyclone. A
recent METOP-B scatterometer pass revealed a somewhat distorted
asymmetric circulation located near the southeastern edge of the
convective mass. A blend of the AiDT/DPRINT/DMINT objective
estimates and a recent UW-CIMSS SATCON analysis yield an initial
intensity of 60 kt for this advisory.

A mid-tropospheric tongue of dry, stable air is penetrating Leslie's
deteriorating convective inner core from the southwest while
mid-level southwesterly flow undercuts the diffluence aloft. The
statistical SHIPS intensity guidance shows a significant increase
in the shear magnitude by mid-period. This and the
ongoing inhibiting thermodynamic surrounding environment should
cause Leslie to lose its organized convection in 72 hrs, if not
sooner, and become a post-tropical cyclone. Further weakening is
expected throughout the period, and the official forecast indicates
that the cyclone will degenerate into a remnant low this weekend.

The initial motion is estimated to be northwestward, or 310/11 kt.
The forecast track philosophy has not changed for this advisory, and
Leslie should continue to move in the mid-level peripheral flow of
a subtropical ridge to its northeast through the end of the week.
A turn toward the north is expected around the 72 hr period as it
rounds the southwestern portion of the above mentioned ridge. Only
small adjustments were made to the NHC forecast just to agree a
little more with the skilled consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 18.8N 44.2W 60 KT 70 MPH
12H 08/1800Z 19.8N 45.5W 60 KT 70 MPH
24H 09/0600Z 21.1N 47.1W 55 KT 65 MPH
36H 09/1800Z 22.1N 48.2W 55 KT 65 MPH
48H 10/0600Z 22.9N 49.2W 55 KT 65 MPH
60H 10/1800Z 23.8N 49.8W 50 KT 60 MPH
72H 11/0600Z 25.0N 49.8W 40 KT 45 MPH...POST-TROPICAL
96H 12/0600Z 28.7N 46.8W 35 KT 40 MPH...POST-TROPICAL
120H 13/0600Z 32.4N 39.6W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Roberts

[cycloneye]

BULLETIN
Tropical Storm Leslie Advisory Number 25
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Tue Oct 08 2024

...LESLIE CONTINUES MOVING NORTHWESTWARD OVER THE CENTRAL
ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.4N 45.6W
ABOUT 1435 MI...2305 KM WNW OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.36 INCHES


Tropical Storm Leslie Discussion Number 25
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Tue Oct 08 2024

Satellite images show Leslie has made a bit of a comeback this
morning, with convection trying to wrap around the center. Microwave
passes also display that Leslie still has some inner-core features
including a partial eyewall. Overall, Dvorak estimates are about
the same as earlier, so the initial wind speed will stay 60 kt.

Plentiful dry air in the mid-levels of the atmosphere has been
preventing sustained deep convection near Leslie, despite
low-to-moderate shear. Leslie does have a short window where the
shear diminishes later today and tomorrow, though Leslie will also
be contending with less instability near the wake of Kirk. While
some of the guidance is showing re-strengthening, the above factors
generally argue for little significant change during the next day or
so. The new forecast is nudged higher than the previous one, but
lies below the model consensus through 36 hours. After that time,
the storm should encounter strong northerly flow of over 50 kt,
which is forecast to cause Leslie to quickly decouple and degenerate
into a remnant low by this weekend.

The initial motion is estimated to be northwestward, or 310/11 kt.
There are no significant track changes to report as Leslie is being
steered around the southwest to northwest sides of the subtropical
ridge, causing the storm's motion to change to the north late
tomorrow and then recurve to the northeast later this week. Only
cosmetic changes were made to the last NHC forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 08/1500Z 19.4N 45.6W 60 KT 70 MPH
12H 09/0000Z 20.5N 46.7W 60 KT 70 MPH
24H 09/1200Z 21.7N 47.9W 60 KT 70 MPH
36H 10/0000Z 22.6N 48.7W 60 KT 70 MPH
48H 10/1200Z 23.4N 49.4W 55 KT 65 MPH
60H 11/0000Z 24.6N 49.8W 50 KT 60 MPH
72H 11/1200Z 26.3N 48.9W 40 KT 45 MPH...POST-TROPICAL
96H 12/1200Z 30.7N 43.7W 35 KT 40 MPH...POST-TROPICAL
120H 13/1200Z 34.0N 36.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Blake

[cycloneye]

BULLETIN
Hurricane Leslie Advisory Number 26
NWS National Hurricane Center Miami FL AL132024
500 PM AST Tue Oct 08 2024

...LESLIE STRENGTHENS BACK INTO A HURRICANE...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...20.0N 46.4W
ABOUT 1490 MI...2400 KM WNW OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...992 MB...29.30 INCHES


Hurricane Leslie Discussion Number 26
NWS National Hurricane Center Miami FL AL132024
500 PM AST Tue Oct 08 2024

Leslie appears to have made a bit of a comeback today. A couple of
fortuitous microwave images from the past few hours show a closed
eyewall. The latest subjective Dvorak classifications from TAFB and
SAB range from 55-77 kt, and recent objective estimates range from
65-74 kt. The microwave passes, the objective intensity estimates,
and the TAFB current intensity number all suggest that Leslie is a
hurricane. Therefore, the initial intensity is bumped back up to
65 kt.

The initial motion estimate is northwestward, or 305/12. A gradual
turn to the north is expected in a day or two as Leslie rounds the
southwestern and western side of a subtropical ridge. After that,
as Leslie gains latitude late this week, the cyclone will
increasingly come under the influence of the mid-latitude
westerlies, causing a turn toward the northeast. Very minor changes
have been made to the official track forecast, which lies near the
various consensus guidance.

Leslie is forecast to remain in an environment of very weak vertical
wind shear for another 24-36 h. Given the closed eyewall observed
on recent microwave images, Leslie may be able to prevent dry
environmental air from entraining into its inner-core during that
time. Leslie will be traveling over Kirk's cold wake over the next
day or so, which will limit the instability. The hurricane should
remain fairly steady during this time, and the NHC forecast is near
the high end of the intensity guidance during the first 24 h. By 36
h, models show Leslie running into a wall of strong northerly wind
shear, which is forecast to cause Leslie to decouple and degenerate
to a post-tropical cyclone by this weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 20.0N 46.4W 65 KT 75 MPH
12H 09/0600Z 21.0N 47.5W 70 KT 80 MPH
24H 09/1800Z 22.1N 48.6W 70 KT 80 MPH
36H 10/0600Z 23.0N 49.4W 65 KT 75 MPH
48H 10/1800Z 24.0N 50.1W 55 KT 65 MPH
60H 11/0600Z 25.5N 49.8W 50 KT 60 MPH
72H 11/1800Z 27.4N 48.3W 40 KT 45 MPH...POST-TROPICAL
96H 12/1800Z 31.5N 42.3W 35 KT 40 MPH...POST-TROPICAL
120H 13/1800Z 34.6N 34.2W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Hagen

[cycloneye]

BULLETIN
Hurricane Leslie Advisory Number 27
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Tue Oct 08 2024

...LESLIE A LITTLE STRONGER AND COULD INTENSIFY MORE OVER THE NEXT
DAY OR SO...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...20.7N 47.0W
ABOUT 1060 MI...1710 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...987 MB...29.15 INCHES



Hurricane Leslie Discussion Number 27
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Tue Oct 08 2024

This evening, Leslie's structure has improved further as deep
convection can be seen wrapping around the center on GOES-16
infrared imagery. An earlier ISS-COWVR microwave pass at 2021 UTC
also showed a small inner-core eyewall feature. Subjective Dvorak
fixes from TAFB and SAB were both T4.0/65-kt, but objective
estimates from ADT and SATCON have jumped up to 79 and 74 kt
respectively, and thus the initial intensity is raised to 70 kt, in
between the subjective and objective estimates.

One thing that hasn't changed is Leslie's current motion, still off
to the northwest at 310/10 kt. Over the next couple of days, Leslie
will be approaching the westward extent of the subtropical ridge
that has been its primary steering mechanism, resulting in a gradual
slow down and turn northward by the end of this week. Leslie is then
expected to be captured by an approaching long-wave trough, leading
to a northeastward motion by the end of the forecast period. The NHC
track continues to be in good agreement with the track guidance, and
is just a touch west compared to the prior forecast.

Leslie's intensity prospects in the short-term have undergone a
reversal from yesterday. The shear that had been affecting the
hurricane has subsided, and SHIPS guidance now shows deep-layer
shear reaming under 10 kt for at least the next 24 hours. Even
though Leslie has been traveling over a cooler ocean left behind
from Kirk last week, the sea-surface temperatures still appear to be
warm enough (27-28 C) to promote intensification, as evidence of its
continued deep convective bursts which have helped reform its inner
core. The intensity guidance has responded to these changes by now
showing more intensification. In fact, the raw 18 UTC HAFS-A/B runs
now show intensification up to 80-85 kt in 36 hours. In addition,
the latest ECMWF run, not usually known for being at the upper-end
of the intensity guidance, shows significant deepening in the
short-term, with a forecast pressure down to 969 mb by early
Thursday morning. Based on these signals, the intensity guidance was
raised upward significantly in the short term, and now shows Leslie
peaking as an 80 kt hurricane in 24-36 hours. After that time, a
large upper-level anticyclone approaching from the northwest
(partially related to outflow from both AL93 and Milton) should lead
to an abrupt increase in northerly shear. Thus, rapid weakening is
still anticipated beyond that time, and Leslie still appears likely
to become a post-tropical cyclone in about 3 days, as its convection
is stripped away by the shear. The intensity forecast is on the
upper-end of the guidance over the first 36 h, but falls back to the
guidance mean by the end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT 09/0300Z 20.7N 47.0W 70 KT 80 MPH
12H 09/1200Z 21.7N 48.0W 75 KT 85 MPH
24H 10/0000Z 22.7N 49.0W 80 KT 90 MPH
36H 10/1200Z 23.6N 49.7W 80 KT 90 MPH
48H 11/0000Z 24.8N 49.9W 60 KT 70 MPH
60H 11/1200Z 26.6N 49.1W 45 KT 50 MPH
72H 12/0000Z 29.0N 47.0W 40 KT 45 MPH...POST-TROPICAL
96H 13/0000Z 33.0N 39.5W 35 KT 40 MPH...POST-TROPICAL
120H 14/0000Z 35.1N 32.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin

[cycloneye]

Hurricane Leslie Discussion Number 28
NWS National Hurricane Center Miami FL AL132024
500 AM AST Wed Oct 09 2024

Conventional satellite imagery shows that Leslie's cloud pattern has
changed little during the past few hours. Earlier SSMIS and AMSU-B
microwaves overpasses, however, indicated that Leslie's structure
has become vertically tilted southeast to northwest, indicative of
the previously mentioned mid-level southerly shear component. A
blend of the Dvorak satellite intensity estimates from TAFB and
SAB and a 0610 UTC UW-CIMSS 72 kt SATCON analysis yield an
initial intensity at 70 kt.

Although the undercutting shear is expected to persist, slight
intensity fluctuations are possible today and tonight while Leslie
moves through a marginally conducive thermodynamic environment and
over warm oceanic surface temperatures. Afterward, the global
models show an upper-tropospheric anticyclone developing over the SW
Atlantic, between Milton and Leslie. This feature is expected to
spread moderate northerly shear over the central subtropical
Atlantic inhibiting ventilation aloft over the north portion of the
cyclone. Consequently, weakening is expected, and Leslie is
forecast to quickly lose its associated convection and become a
post-tropical cyclone in 3 days.

Leslie's initial motion is estimated to be northwestward, 310/9 kt,
and this general motion is expected to continue during the next
couple of days. By mid-period, the cyclone is forecast to slow in
forward speed and turn toward the north while rounding the
southwestern periphery of a subtropical ridge to the northeast.
Afterward, Leslie should accelerate and turn toward the northeast in
response to a major shortwave trough approaching the cyclone from
the northeast. The NHC forecast is close to the previous one and is
based on a compromise of the TVCN and HCCA consensus models.

Leslie's wind radii were adjusted based on 2354 UTC METOP-B and 0049
UTC METOP-C scatterometer passes.


FORECAST POSITIONS AND MAX WINDS

INIT 09/0900Z 21.2N 47.8W 70 KT 80 MPH
12H 09/1800Z 22.0N 48.6W 75 KT 85 MPH
24H 10/0600Z 23.0N 49.5W 75 KT 85 MPH
36H 10/1800Z 23.9N 50.0W 65 KT 75 MPH
48H 11/0600Z 25.4N 50.0W 55 KT 65 MPH
60H 11/1800Z 27.6N 48.8W 45 KT 50 MPH
72H 12/0600Z 30.0N 46.1W 40 KT 45 MPH...POST-TROPICAL
96H 13/0600Z 34.3N 36.8W 35 KT 40 MPH...POST-TROPICAL
120H 14/0600Z 35.4N 28.9W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Roberts

[cycloneye]

Hurricane Leslie Discussion Number 29
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Wed Oct 09 2024

Visible, infrared and some recent microwave images suggest that the
center of the small tropical cyclone continues to be located
underneath the middle of the central dense overcast. In fact, some
of the recent frames have hinted at a ragged eye feature. The TAFB
and SAB subjective Dvorak estimates are a consensus T-4.5/77 kt.
The initial intensity is increased to 75 kt, in best agreement with
the Dvorak estimates.

Leslie's initial motion is estimated to be northwestward, or 305/9
kt. A gradual turn to the north is expected in about 36 h as
Leslie rounds the southwestern and western periphery of a
subtropical ridge to the east. Afterward, Leslie should accelerate
toward the northeast in response to a strong trough approaching the
cyclone from the northwest. The NHC forecast is nearly identical
to the previous one and lies near the TVCN and HCCA consensus
models.

Leslie is forecast to remain in a favorable environment for another
12-18 h. The intensity forecast has been increased to an 85-kt
peak at hour 12 and 24, and it is possible that it could strengthen
a bit more than that, as suggested by the HAFS-B model. By hour
24, Leslie is expected to run into a wall of strong northerly
shear caused by a strengthening upper-level anticyclone in between
Milton and Leslie. The shear is expected to cause Leslie to
rapidly weaken during the 24 to 48 h period. While it is possible
that Leslie could lose most of its convection in 2 to 3 days, the
latest GFS and ECMWF simulated satellite imagery show periodic
bursts of convection continuing into Day 4. However, Leslie is
likely to merge with a front and become extratropical in 3 to 4
days, and a transition to an extratropical cyclone is
forecast at the end of that period.


FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 21.7N 48.4W 75 KT 85 MPH
12H 10/0000Z 22.5N 49.2W 85 KT 100 MPH
24H 10/1200Z 23.4N 49.9W 85 KT 100 MPH
36H 11/0000Z 24.6N 50.2W 70 KT 80 MPH
48H 11/1200Z 26.4N 49.6W 50 KT 60 MPH
60H 12/0000Z 28.7N 47.7W 45 KT 50 MPH
72H 12/1200Z 31.1N 44.2W 45 KT 50 MPH...POST-TROPICAL
96H 13/1200Z 34.5N 35.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 14/1200Z 35.9N 26.7W 30 KT 35 MPH...POST-TROP/EXTRATROP

$$
Forecaster Hagen

[cycloneye]

BULLETIN
Hurricane Leslie Advisory Number 30
NWS National Hurricane Center Miami FL AL132024
500 PM AST Wed Oct 09 2024

...LESLIE A LITTLE STRONGER BUT WILL REACH STRONGER UPPER-LEVEL
WINDS ON THURSDAY...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...22.2N 49.0W
ABOUT 955 MI...1535 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...982 MB...29.00 INCHES

Hurricane Leslie Discussion Number 30
NWS National Hurricane Center Miami FL AL132024
500 PM AST Wed Oct 09 2024

Leslie continues to take advantage of the little time it has left
under favorable environmental conditions. Although an eye is not
currently seen on visible or infrared imagery, a 1611 UTC AMSR2
image shows that an eye exists on microwave imagery, and it is
located underneath the middle of the central dense overcast.
Subjective Dvorak numbers from TAFB and SAB are a unanimous T-4.5/77
kt, whereas recent objective intensity estimates from UW-CIMSS have
been averaging in the 78-85 kt range for the past several hours.
The initial intensity is bumped up to 80 kt, using a blend of the
subjective and objective estimates.

Leslie's initial motion estimate is northwestward, or 310/8 kt.
There has been no change to the track forecast reasoning. Leslie is
expected to turn northward in 24-36 h as it rounds the southwestern
and western periphery of a subtropical ridge to the east.
Afterward, Leslie should accelerate toward the northeast in response
to a strong trough approaching the cyclone from the northwest. The
guidance is a bit farther west this cycle, and the new NHC forecast
has shifted west of the previous one.

Saildrone data from the last several hours indicates that Leslie is
over sea-surface temperatures approximately 1 to 2 degrees warmer
than other data sources are indicating, and this could be the main
reason why Leslie has strengthened a bit more than anticipated over
the past 12 to 24 h. A bit more strengthening is forecast during
the next 12 h while the vertical wind shear remains relatively
low. In about 12 to 18 h, Leslie is expected to run into a wall of
strong northerly shear caused by a strengthening upper-level
anticyclone in between Milton and Leslie. The shear is expected to
cause Leslie to rapidly weaken during the 24 to 48 h period. While
it is possible that Leslie could lose most of its convection in 2 to
3 days, the latest GFS and ECMWF simulated satellite imagery now
show several periodic bursts of convection continuing into Day 4.
Leslie might also merge with a front and become extratropical in 3
to 4 days. Regardless, Leslie will be traveling over much colder
water by that time, and the official forecast calls for Leslie to
become post-tropical in 3 to 4 days.


FORECAST POSITIONS AND MAX WINDS

INIT 09/2100Z 22.2N 49.0W 80 KT 90 MPH
12H 10/0600Z 22.9N 49.7W 85 KT 100 MPH
24H 10/1800Z 23.8N 50.4W 80 KT 90 MPH
36H 11/0600Z 25.3N 50.5W 60 KT 70 MPH
48H 11/1800Z 27.2N 49.4W 50 KT 60 MPH
60H 12/0600Z 29.7N 47.0W 45 KT 50 MPH
72H 12/1800Z 31.9N 43.2W 45 KT 50 MPH
96H 13/1800Z 35.4N 33.4W 45 KT 50 MPH...POST-TROPICAL
120H 14/1800Z 36.5N 25.2W 30 KT 35 MPH...POST-TROPICAL

$$
Forecaster Hagen

[cycloneye]

BULLETIN
Hurricane Leslie Advisory Number 31
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Wed Oct 09 2024

...LESLIE NOW A CATEGORY 2 HURRICANE AND COULD MAKE A RUN AT MAJOR
HURRICANE INTENSITY...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.6N 49.3W
ABOUT 945 MI...1515 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...972 MB...28.71 INCHES



Hurricane Leslie Discussion Number 31
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Wed Oct 09 2024

Since the previous advisory, a small eye feature has started
appearing on geostationary infrared imagery with Leslie, surrounded
by a ring of very cold (below -70 C) cloud top temperatures. This
structure is also supported by an earlier SAR-RCM2 pass that showed
a tight inner core with a radius of maximum wind that had contracted
from yesterday. 00 UTC subjective Dvorak estimates from TAFB and SAB
were T5.0/90-kt and T5.5/102-kt, respectively. Objective intensity
estimates were somewhat lower, between 79-86 kt, and blending the
data results in a 90 kt intensity this cycle. A Saildrone (SD-1036)
appears to be near the path of Leslie, and is currently reporting
sustained tropical-storm-force winds that are quickly increasing
about 50 n mi northwest of the center.

As noted previously, another saildrone (SD-1040) indicated that
sea-surface temperatures near Leslie are warmer than expected, near
29 C. At the same time, the hurricane is in a very narrow region of
low vertical wind shear that should persist for another 6-12 h.
While the interpolated intensity guidance is a bit lower, the raw
model output of all four of the hurricane-regional models (HAFS-A/B,
HMON, HWRF) show Leslie briefly becoming a major hurricane in 12 h.
Because the raw model output from these intensity aids has been
outperforming the interpolated guidance over the past day, the NHC
intensity forecast will now show a 100 kt peak tomorrow morning.
However, this peak is likely to be short-lived, as strong
upper-level northerly flow, via outflow from Milton and Invest 93L,
will soon overtake the hurricane, likely leading to rapid weakening.
Those same hurricane-regional models show Leslie weakening below
hurricane intensity in 36 h, and that rapid weakening continues to
be reflected in the latest intensity forecast. While sheared puffs
of deep convection may continue for a subsequent day or two,
eventually Leslie is likely to lose the necessary convective
organization to be classified as a tropical cyclone. The NHC
forecast continues to show Leslie becoming post-tropical by the end
of the weekend, though this could occur sooner than forecast given
the proximity of very dry environmental air and high shear affecting
the system.

Leslie continues to move northwestward, estimated at 315/7 kt this
evening. The track forecast is more straightforward, with Leslie
rounding the western edge of a subtropical ridge to its east,
resulting in a gradual turn northward and then northeastward over
the forecast period. With that said, there has been a notable
westward and poleward shift in the guidance this cycle, and the NHC
track forecast was moved in that direction, but not as far as the
latest TVCN and HCCA consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 10/0300Z 22.6N 49.3W 90 KT 105 MPH
12H 10/1200Z 23.3N 49.9W 100 KT 115 MPH
24H 11/0000Z 24.4N 50.4W 80 KT 90 MPH
36H 11/1200Z 26.0N 50.1W 55 KT 65 MPH
48H 12/0000Z 28.4N 48.4W 45 KT 50 MPH
60H 12/1200Z 30.7N 45.5W 45 KT 50 MPH
72H 13/0000Z 33.0N 41.6W 45 KT 50 MPH
96H 14/0000Z 36.0N 31.0W 40 KT 45 MPH...POST-TROPICAL
120H 15/0000Z 37.1N 21.9W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin

[cycloneye]

Hurricane Leslie Discussion Number 32
NWS National Hurricane Center Miami FL AL132024
500 AM AST Thu Oct 10 2024

The satellite presentation of Leslie has degraded since the previous
advisory. Based on geostationary satellite imagery, the eye feature
has filled, deep convection have shifted to the southern side of the
circulation, and the outflow appears to be impinged in the northwest
quadrant. Subjective and objective Dvorak intensity estimates have
plateaued, with final-T numbers coming down. The initial intensity
is held at a possibly generous 90 kt, in agreement with the latest
TAFB and SAB estimates.

The window for intensification seems to have closed. Vertical wind
shear appears to be strengthening significantly over Leslie. Global
models insist the strong upper-level winds will strip away deep
convection and force in the surrounding dry mid-level humidities
into the circulation quickly. Given the relatively small size of
the hurricane, rapid weakening is expected over the next few days.
Leslie is now forecast to become a post-tropical cyclone by Sunday
and open into a trough by early next week.

Leslie is moving northwestward at about 5 kt. This motion should
continue through today as Leslie moves around the southwestern
periphery of a subtropical ridge over the eastern Atlantic. On
Friday, the hurricane should speed up and turn to the north and
north-northeast, followed by a turn northeastward and
east-northeastward as it accelerates further over the weekend.
There have been only minor changes to the latest NHC track forecast,
which lies essentially on top of the previous prediction and between
the various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 10/0900Z 22.9N 49.8W 90 KT 105 MPH
12H 10/1800Z 23.6N 50.4W 85 KT 100 MPH
24H 11/0600Z 24.9N 50.5W 70 KT 80 MPH
36H 11/1800Z 27.0N 49.6W 50 KT 60 MPH
48H 12/0600Z 29.5N 47.2W 45 KT 50 MPH
60H 12/1800Z 32.0N 43.7W 40 KT 45 MPH
72H 13/0600Z 34.2N 38.7W 40 KT 45 MPH...POST-TROPICAL
96H 14/0600Z 36.5N 28.1W 35 KT 40 MPH...POST-TROPICAL
120H 15/0600Z...DISSIPATED

$$
Forecaster Bucci

[cycloneye]

Hurricane Leslie Discussion Number 33
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Thu Oct 10 2024

The satellite presentation of Leslie has degraded since the previous
advisory. Strong northerly wind shear has been pushing most of the
convection to the south side of the low-level center. The most
recent GOES-16 images suggest that the low-level center is likely
just barely underneath the northern edge of the central dense
overcast. The latest subjective current intensity values from TAFB
and SAB are still 90 kt due to continuity constraints, but the
latest ADT and AiDT intensity estimates from UW-CIMSS have decreased
down to 72 kt. The intensity is set to 80 kt, as a blend of all the
estimates.

Leslie has already entered the strong northerly shear zone that has
been advertised in previous discussions, and the guidance indicates
that the shear will continue to increase to over 40 kt over the next
12 to 24 h. Shear that strong, combined with the dry environment
that Leslie is embedded within, is likely to lead to steady to rapid
weakening. The NHC forecast calls for Leslie to weaken by 35 kt
over the next 36 h, in good agreement with the HCCA corrected
consensus, HAFS models, and the intensity consensus. After that,
the models hold on to Leslie, and there is quite a bit of
uncertainty in the timing of when Leslie will become post-tropical.
GFS and ECMWF simulated satellite imagery indicate that puffs of
convection could continue through the weekend. The cyclone is also
likely to interact with an approaching frontal system by Sunday.
The NHC forecast continues to call for Leslie to become
post-tropical by day 3.

The initial motion is estimated to be west-northwestward, or 300/6
kt. Model guidance is in excellent agreement that a northward turn
will happen very soon as Leslie moves around the southwestern
periphery of a subtropical ridge over the eastern Atlantic. On
Friday and Friday night, the hurricane should speed up and turn to
the northeast, followed by an east-northeastward turn as it
accelerates further over the weekend. The latest NHC track forecast
is slightly west of the previous one during the first 48 hours of
the forecast, and nearly identical to the previous forecast
thereafter. The official forecast is in best agreement with the
TVCA consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 10/1500Z 23.2N 50.4W 80 KT 90 MPH
12H 11/0000Z 24.0N 50.9W 70 KT 80 MPH
24H 11/1200Z 25.7N 50.6W 55 KT 65 MPH
36H 12/0000Z 28.1N 48.9W 45 KT 50 MPH
48H 12/1200Z 30.8N 45.9W 45 KT 50 MPH
60H 13/0000Z 33.3N 41.0W 45 KT 50 MPH
72H 13/1200Z 35.2N 35.6W 45 KT 50 MPH...POST-TROPICAL
96H 14/1200Z 36.6N 25.9W 35 KT 40 MPH...POST-TROPICAL
120H 15/1200Z...DISSIPATED

$$
Forecaster Hagen

[cycloneye]

Tropical Storm Leslie Discussion Number 34
NWS National Hurricane Center Miami FL AL132024
500 PM AST Thu Oct 10 2024

The center of Leslie has been exposed for the past 6 h, thanks to
strong northerly wind shear. The center has continued to move
farther away from the convection as the afternoon has progressed.
The initial intensity is brought down to 60 kt, which agrees with a
blend of the various objective intensity estimates from UW-CIMSS.

Leslie continues to plow through a zone of strong northerly shear,
and the SHIPS guidance and model fields indicate Leslie will
continue to experience 40 kt of northerly to northeasterly shear for
another 12 to 24 h. In addition, Leslie is forecast to continue
moving through a relatively dry environment. Rapid weakening is
expected to continue over the next 12 to 24 h, and the latest NHC
intensity forecast is lower than the previous one due to the weaker
initial intensity. If Leslie survives as a tropical cyclone for
another two days, which is not guaranteed, it will approach a
frontal zone in 2 to 3 days and could take on some frontal
characteristics. While all of the models show Leslie dissipating
by 4 to 5 days, there is significant uncertainty on whether Leslie
will become extratropical or just dissipate.

Leslie is moving northwestward, or 315/7 kt. Model guidance is in
good agreement that a northward turn will happen very soon as
Leslie moves around the southwestern periphery of a subtropical
ridge over the eastern Atlantic. On Friday and Friday night, the
hurricane should speed up and turn to the northeast, followed by an
east-northeastward turn as it accelerates further over the weekend.
There is a bit of along-track spread in the guidance after 48 h, as
some of the models show Leslie accelerating faster toward the
east-northeast. Only minor changes are made to the previous NHC
track to account for the models being slightly farther west during
the first 36 h of the forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 23.9N 50.9W 60 KT 70 MPH
12H 11/0600Z 24.9N 51.1W 45 KT 50 MPH
24H 11/1800Z 27.0N 50.1W 40 KT 45 MPH
36H 12/0600Z 29.6N 47.6W 40 KT 45 MPH
48H 12/1800Z 32.5N 43.3W 40 KT 45 MPH
60H 13/0600Z 34.8N 38.2W 40 KT 45 MPH...POST-TROPICAL
72H 13/1800Z 36.1N 32.8W 40 KT 45 MPH...POST-TROPICAL
96H 14/1800Z 36.0N 23.5W 30 KT 35 MPH...POST-TROPICAL
120H 15/1800Z...DISSIPATED

$$
Forecaster Hagen

[cycloneye]

Tropical Storm Leslie Discussion Number 35
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Thu Oct 10 2024

Leslie's center continues to be well exposed to the north of the
convection, as northerly wind shear continues to impact the system.
A recent scatterometer pass depicted winds of 50-55 kt. Satellite
intensity estimates from TAFB, SAB and UW-CIMSS have come down this
cycle and range from 45-55 kt which is in good agreement with the
scatterometer pass. Therefore, the initial intensity for this
advisory is lowered to 55 kt.

The storm is within a rather hostile environment with strong
northerly shear displacing the convection from the center, and this
shear is expected to persist over the next few days. Leslie is also
dealing with very dry mid-levels as is depicted on GOES-16 water
vapor imagery and the drier airmass continues along the forecast
track. Models differ on the type of post-tropical system Leslie will
eventually become, with the possibilities being either a remnant low
or an extra-tropical low. The NHC forecast calls for the system to
become a remnant low in 48 h with model simulated satellite
depicting Leslie will fail to produce organized deep convection
within the harsh environment. However, if the system is able to
continue to produce convection for the next 36- 48 h, Leslie will
approach a frontal zone and take on some frontal characteristics and
become extratropical at that time. Either way, by day 4, the
post-tropical low is forecast to dissipate into a open trough.

Leslie is moving north-northwestward, or 345/8 kt. Models are in
fairly good agreement that a turn to the north will occur early
Friday as the storm rounds the edge of the subtropical ridge located
over the eastern Atlantic. The system will then turn northeastward
with an increase in forward speed through the weekend. There was a
slight left shift in the latest forecast guidance, as well as some
along track spread. The latest NHC forecast was nudged left and is a
little faster than the previous, near the simple consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 24.4N 51.2W 55 KT 65 MPH
12H 11/1200Z 25.9N 50.7W 45 KT 50 MPH
24H 12/0000Z 28.4N 49.0W 40 KT 45 MPH
36H 12/1200Z 31.5N 45.4W 35 KT 40 MPH
48H 13/0000Z 34.6N 40.0W 35 KT 40 MPH...POST-TROPICAL
60H 13/1200Z 36.6N 34.2W 35 KT 40 MPH...POST-TROPICAL
72H 14/0000Z 37.1N 29.3W 30 KT 35 MPH...POST-TROPICAL
96H 15/0000Z...DISSIPATED

$$
Forecaster Kelly

[cycloneye]

Tropical Storm Leslie Discussion Number 36
NWS National Hurricane Center Miami FL AL132024
500 AM AST Fri Oct 11 2024

Leslie remains a sheared tropical storm this morning. Based on
geostationary satellite imagery, the low-level circulation is still
exposed and limited bursts of deep convection in the southern
semicircle are moving southwestward away from the center.
Subjective and objective Dvorak estimates continue to trend downward
and the initial intensity is lowered to 50 kt to represent a blend
of the final-T and CI numbers (T3.0/3.5) from TAFB and SAB.

The storm should continue to weaken during the next couple of days.
Model guidance agrees that the vertical wind shear will remain
moderate-to-strong, the mid-level humidities will gradually become
drier, and the sea surface temperatures will cool along the forecast
track. Leslie should lose its organized deep convection by Sunday,
if not sooner, based on simulated satellite imagery. There is still
the possibility the storm will take on some extratropical
characteristics in 48-72 h as well. For now, the NHC intensity
forecast still shows Leslie becoming a post-tropical cyclone over
the weekend and dissipating early next week.

Leslie is rounding the western edge of a subtropical ridge and has
turned northward at 9 kt. A turn to the north-northeast is
expected later today, followed by an acceleration to the northeast
and east-northeast over the weekend. The latest track forecast is
essentially the same as the previous prediction.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 25.5N 50.8W 50 KT 60 MPH
12H 11/1800Z 27.1N 50.0W 45 KT 50 MPH
24H 12/0600Z 30.0N 47.3W 40 KT 45 MPH
36H 12/1800Z 33.1N 42.8W 35 KT 40 MPH
48H 13/0600Z 35.6N 37.2W 35 KT 40 MPH...POST-TROPICAL
60H 13/1800Z 36.8N 31.8W 35 KT 40 MPH...POST-TROPICAL
72H 14/0600Z 37.5N 26.7W 30 KT 35 MPH...POST-TROPICAL
96H 15/0600Z...DISSIPATED

$$
Forecaster Bucci

[cycloneye]

Tropical Storm Leslie Discussion Number 37
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Fri Oct 11 2024

Leslie remains a sheared tropical storm. The low-level center is
exposed about 70 n mi outside of the northern edge of the convective
area, which has been shrinking and weakening over the past several
hours. As a result, subjective Dvorak estimates from TAFB and SAB
are both down to 45 kt. A pair of recently arriving ASCAT passes
still show an area of 40-44 kt winds in the eastern semicircle. The
initial intensity is set to 45 kt, which agrees well with the
subjective Dvorak estimates and the ASCAT data.

Leslie is likely currently experiencing more than 30 kt of
north-northeasterly vertical wind shear. The cyclone will be moving
toward an upper-level ridge axis over the next 12 to 24 h, which
will cause the deep-layer shear to decrease. However, Leslie will
reach sea-surface temperatures colder than 26C in about 24 h, and it
is forecast to remain in a relatively dry low- to mid-level
troposphere. Some slight additional weakening is forecast today,
followed by little change in strength for the next couple of days.
The intensity forecast is near the middle of the intensity model
guidance envelope. The GFS and ECMWF simulated satellite imagery
agree that the cyclone will lose its convection by 48 h, but
phase-space diagrams suggest that Leslie could potentially become
extratropical before that time, by 36 h. The NHC forecast continues
to show Leslie becoming post-tropical over the weekend, in agreement
with the aforementioned guidance. Leslie is still expected to
dissipate by day 4, as shown by the global models.

Leslie has been moving toward the north-northeast, or 015/9 kt, as
the cyclone rounds the western periphery of a subtropical ridge. A
strong frontal trough will approach Leslie from the west tonight
into Saturday, causing Leslie to accelerate toward the northeast.
Leslie's interaction with this frontal system could cause the
cyclone to lose its tropical characteristics by Saturday night. On
Sunday, the cyclone is expected to turn more towards the east within
the mid-latitude westerly flow. No significant changes were made to
the first 48 h of the official track forecast, with a slight
southward adjustment at the 72 h point. The NHC track forecast is
very near the TVCA consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 26.4N 50.5W 45 KT 50 MPH
12H 12/0000Z 28.4N 48.9W 40 KT 45 MPH
24H 12/1200Z 31.7N 45.1W 40 KT 45 MPH
36H 13/0000Z 34.6N 39.9W 40 KT 45 MPH...POST-TROPICAL
48H 13/1200Z 36.2N 34.4W 40 KT 45 MPH...POST-TROPICAL
60H 14/0000Z 36.8N 29.3W 35 KT 40 MPH...POST-TROPICAL
72H 14/1200Z 36.4N 24.6W 30 KT 35 MPH...POST-TROPICAL
96H 15/1200Z...DISSIPATED

$$
Forecaster Hagen

[cycloneye]

Tropical Storm Leslie Discussion Number 38
NWS National Hurricane Center Miami FL AL132024
500 PM AST Fri Oct 11 2024

Leslie continues to be a sheared tropical cyclone, struggling to
produce convection. The center of the system continues to be exposed
at it is accelerating to the northeast within an unfavorable
environment. The subjective and objective Dvorak estimates have come
down some between 30-45 kt with the final CI value from TAFB,
T3.0/45 kt. This is in good agreement with the satellite derived
winds from the scatterometer pass earlier today. Thus, will keep the
intensity steady at 45 kt with this advisory.

The storm will remain in a hostile environment with strong vertical
wind shear and dry air inhibiting convection over the system for the
next day or so. In about 18-24 h the shear is forecast to decrease
for a short-period of time, and model simulated satellite suggest
that Leslie will be able to regain some convection near the center
again, which will prolong the post-tropical transition. However, by
36 hours the shear will increase and Leslie will be crossing into
cooler sea surface temperatures. This will all be occuring as a
frontal boundary approaches Leslie,and the system will begin to
acquire some extratropical characteristics, eventually becoming post
tropical at that time. The NHC intensity forecast calls for the
system to remain steady with some gradual weakening as the system
becomes post-tropical in 36 h.

Leslie has been accelerating towards the northeast, or 035/15 kt,
between the flow of an approaching trough to the west and the
subtropical ridge to the east. Leslie will continue to move
northeastward then east-northeastward with an increase in forward
speed through the weekend. The NHC forecast was nudged slightly
poleward in the near term, with a slightly faster rate of forward
motion, and lies near the simple consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 11/2100Z 27.6N 49.4W 45 KT 50 MPH
12H 12/0600Z 30.0N 47.1W 45 KT 50 MPH
24H 12/1800Z 33.5N 42.3W 45 KT 50 MPH
36H 13/0600Z 36.0N 36.5W 40 KT 45 MPH...POST-TROPICAL
48H 13/1800Z 37.2N 30.0W 40 KT 45 MPH...POST-TROPICAL
60H 14/0600Z 36.7N 25.6W 35 KT 40 MPH...POST-TROPICAL
72H 14/1800Z 36.0N 21.1W 30 KT 35 MPH...POST-TROPICAL
96H 15/1800Z...DISSIPATED

$$
Forecaster Kelly

[cycloneye]

Tropical Storm Leslie Discussion Number 39
NWS National Hurricane Center Miami FL AL132024
1100 PM AST Fri Oct 11 2024

Convection associated with Leslie has been increasing during the
past several hours as the cyclone moves into an area of temporarily
decreased shear. A recent ASCAT overpass showed winds of 40-45 kt in
the southeastern quadrant, and based on these data the initial
intensity is held at 45 kt. The scatterometer data also suggest
that the circulation is becoming somewhat distorted due to the rapid
northeastward motion.

The initial motion is now 035/19 kt. The cyclone is accelerating
northeastward as it moves into the mid-latitude southwesterly flow
to the east of a deep-layer trough over the northwestern Atlantic.
This general motion should continue for 24 h or so. After that,
Leslie or its remnants should turn eastward and east-southeastward
on the southwestern side of another deep-layer trough located over
the northeastern Atlantic, with this motion continuing until the
system dissipates. There are no significant changes in the track
guidance since the previous advisory, and the new forecast track is
similar to the previous track.

Shear over Leslie should remain relatively low for the next 12-18
h, allowing the current convection to continue and the system to
maintain tropical cyclone status during that time. The global
models have come into good agreement that Leslie will merge with a
frontal system to become extratropical between 24-36 h, and thus the
intensity forecast status has been adjusted accordingly. The
extratropical cyclone should subsequently weaken and be absorbed
into the larger system over the eastern Atlantic by 96 h. It should
be noted that while the models show a closed low pressure area
through 72 h, the circulation could degenerate into an open trough
before then due to the fast forward speed.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 29.3N 47.9W 45 KT 50 MPH
12H 12/1200Z 31.8N 45.0W 45 KT 50 MPH
24H 13/0000Z 34.8N 39.5W 45 KT 50 MPH
36H 13/1200Z 36.7N 33.6W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 14/0000Z 37.1N 28.3W 35 KT 40 MPH...POST-TROP/EXTRATROP
60H 14/1200Z 36.0N 23.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
72H 15/0000Z 35.3N 19.2W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 16/0000Z...DISSIPATED

$$
Forecaster Beven

[cycloneye]

Tropical Storm Leslie Discussion Number 40
NWS National Hurricane Center Miami FL AL132024
500 AM AST Sat Oct 12 2024

Leslie has held steady through the night. The storm has maintained
a small burst of deep convection near the low-level center, with
cold cloud top temperatures of less than -80 degrees C. While the
satellite intensity estimates have trended downward, the initial
intensity is held at 45 kt in deference to the earlier scatterometer
data.

The storm is accelerating to the northeast at 21 kt in the flow
ahead of an approaching deep-layer trough over the northwestern
Atlantic. On Sunday, Leslie should turn east-northeastward to
eastward and continue this motion through the remainder of the
forecast period. Model guidance has shifted northward with a slight
increase in forward speed this advisory cycle. The latest NHC
forecast has been nudged northward and now lies between the previous
prediction and on the southern side of the tightly clustered
guidance envelope. Leslie, or its remnants, is now expected to move
near or over the Azores late Sunday through early Monday.

Leslie has a few more hours in a marginal environmental. Later
today, deep-layer vertical wind shear is forecast to steadily
increase and the storm is passing over the 26 degree C isotherm
towards cooler waters. Global models suggest Leslie will lose its
deep convection and merge with a frontal system in about a day. The
official forecast now reflects the timing of this transition. It
should be noted that while the models show a closed low pressure
area through 72 h, the circulation could degenerate into an open
trough before then due to the fast forward speed.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0900Z 31.3N 45.9W 45 KT 50 MPH
12H 12/1800Z 33.8N 42.3W 45 KT 50 MPH
24H 13/0600Z 36.5N 36.6W 40 KT 45 MPH...POST-TROP/EXTRATROP
36H 13/1800Z 37.6N 31.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 14/0600Z 37.7N 25.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
60H 14/1800Z 37.1N 21.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
72H 15/0600Z 37.1N 16.4W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 16/0600Z...DISSIPATED

$$
Forecaster Bucci