ATL: LESLIE - Advisories

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Re: ATL: LESLIE - Advisories

#21 Postby cycloneye » Tue Oct 02, 2018 3:38 pm

Tropical Storm Leslie Discussion Number 26
NWS National Hurricane Center Miami FL AL132018
500 PM AST Tue Oct 02 2018

Leslie is almost a hurricane. Satellite images indicate that a ring
of deep convection now nearly surrounds Leslie's large ragged eye.
A pair of ASCAT passes from this morning showed maximum winds around
55 kt. Based on that data and a blend of the latest Dvorak
estimates, the initial intensity is increased to 60 kt. Leslie is
expected to remain over relatively warm water and in favorable
atmospheric conditions for another day or two, so continued gradual
strengthening is forecast during that time period. Based on the
improved organization this afternoon and the model guidance, Leslie
is forecast to reach hurricane strength tonight or early Wednesday.
After a couple of days, the system is expected to move over waters
cooler than 26 deg C, and those unfavorable oceanic conditions
combined with some increase in shear this weekend should cause a
slow weakening trend. The NHC intensity forecast remains
between the aggressive statistical-dynamical models and the lower
HMON and COAMPS-TC models, but this forecast is a tad higher than
the previous one.

The tropical storm is still losing latitude, with the latest initial
motion now estimated to be 205/8. This south-southwestward
motion is expected to slow down tonight, and Leslie will likely come
to a stall on Wednesday in very weak steering currents. 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 on Thursday and Friday. A turn to the
northeast and then east is forecast to occur by the weekend when the
storm moves within the mid-latitude westerlies. The NHC track
forecast is nudged to the south and west of the previous one to come
into better agreement with the latest guidance.

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.

The initial 34- and 50-kt wind radii have been modified based on
the aforementioned ASCAT data.

FORECAST POSITIONS AND MAX WINDS

INIT 02/2100Z 30.1N 56.4W 60 KT 70 MPH
12H 03/0600Z 29.7N 56.6W 65 KT 75 MPH
24H 03/1800Z 29.5N 56.8W 70 KT 80 MPH
36H 04/0600Z 30.7N 56.8W 75 KT 85 MPH
48H 04/1800Z 32.6N 56.7W 70 KT 80 MPH
72H 05/1800Z 36.3N 56.5W 65 KT 75 MPH
96H 06/1800Z 37.2N 54.2W 60 KT 70 MPH
120H 07/1800Z 37.0N 51.0W 55 KT 65 MPH

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#22 Postby cycloneye » Wed Oct 03, 2018 4:59 am

Hurricane Leslie Discussion Number 28
NWS National Hurricane Center Miami FL AL132018
500 AM AST Wed Oct 03 2018

Deep convection surrounding the center of Leslie has become better
organized overnight, with the development of a ragged eye in
infrared satellite images. A 0552 UTC AMSR2 microwave overpass
revealed a well-defined low-level eye with a ring of broken
convection surrounding it. T-numbers from both TAFB and SAB were
4.0 on the Dvorak scale, therefore the initial intensity has
been increased to 65 kt. This makes Leslie the sixth hurricane
of the 2018 Atlantic hurricane season.

The hurricane is forecast to remain within favorable environmental
conditions consisting of warm water and low vertical wind shear
over the next day or two. These conditions should allow for some
additional strengthening. After 48 hours, Leslie will be moving
over cooler waters, which should induce gradual weakening later
in the period.

Leslie has become nearly stationary overnight, and it appears that
the cyclone's equatorward motion has likely come to an end. A
shortwave trough to the northwest of the storm and a building ridge
to the east, are expected to allow Leslie to begin moving northward
by tonight. A northward motion is then expected to continue over
the next 2-3 days, but by the weekend Leslie is predicted to turn
eastward as a broad trough dips southward over the north Atlantic.
The dynamical model guidance is in relatively good agreement on this
scenario and the new NHC track forecast is essentially an update of
the previous advisory.

Large swells generated by Leslie are expected to increase over the
next couple of days 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 03/0900Z 29.6N 56.9W 65 KT 75 MPH
12H 03/1800Z 29.7N 57.0W 65 KT 75 MPH
24H 04/0600Z 30.8N 57.0W 70 KT 80 MPH
36H 04/1800Z 32.8N 57.1W 75 KT 85 MPH
48H 05/0600Z 35.0N 57.3W 70 KT 80 MPH
72H 06/0600Z 37.1N 56.7W 65 KT 75 MPH
96H 07/0600Z 37.0N 53.7W 60 KT 70 MPH
120H 08/0600Z 37.0N 50.5W 55 KT 65 MPH

$$
Forecaster Brown
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Re: ATL: LESLIE - Advisories

#23 Postby cycloneye » Wed Oct 03, 2018 3:37 pm

Hurricane Leslie Discussion Number 30
NWS National Hurricane Center Miami FL AL132018
500 PM AST Wed Oct 03 2018

The satellite presentation of Leslie has changed little over the
past six hours. Leslie continues to have a large ragged eye with
periodic intrusions of slightly drier air. The hurricane still has
well-defined outflow over the northern semicircle. The initial wind
speed is held at 70 kt based on the steady state appearance.

Now that Leslie that has begun its advertised northward turn, it is
passing over the cool wake that it presumably created during the
past day or so, therefore, little change in strength is expected
through this evening. However, some slight strengthening is
possible later tonight and Thursday after crossing the cool wake.
Gradual weakening then is expected to begin late Thursday when
the system reaches cooler waters farther to the north. The NHC
intensity forecast is an update of the previous one and near the
middle of the guidance envelope.

Satellite images indicate that Leslie is moving northward, and this
motion appears to be accelerating. This northward motion is
expected to continue through Friday as the hurricane moves in the
flow between a shortwave trough to the northwest and a mid-level
ridge to its southeast. After that time, an eastward motion is
forecast when a second trough approaches Leslie from the north. The
latest model guidance has shifted a little to the west in the short
term and is slightly slower and farther south at the latter forecast
points. The NHC official track forecast has been adjusted
accordingly to trend toward this guidance.

Large swells generated by Leslie are expected to continue during the
next few days 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 on Friday. 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 03/2100Z 29.9N 56.9W 70 KT 80 MPH
12H 04/0600Z 30.7N 57.0W 75 KT 85 MPH
24H 04/1800Z 32.7N 57.0W 75 KT 85 MPH
36H 05/0600Z 34.7N 57.4W 70 KT 80 MPH
48H 05/1800Z 36.1N 57.6W 65 KT 75 MPH
72H 06/1800Z 36.8N 56.4W 60 KT 70 MPH
96H 07/1800Z 36.7N 53.6W 55 KT 65 MPH
120H 08/1800Z 36.0N 49.5W 55 KT 65 MPH

$$
Forecaster Cangialosi/Onderlinde

NNNN
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Re: ATL: LESLIE - Advisories

#24 Postby cycloneye » Wed Oct 03, 2018 9:36 pm

Hurricane Leslie Discussion Number 31
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Wed Oct 03 2018

It is difficult to add more to the discussion about a cyclone that
has moved very little during the past few days and has not changed
significantly in structure either. Leslie's cloud pattern is
not very impressive with a large ragged-eye feature (if you can
call that an eye) surrounded by weaker convection than earlier
today. Although Dvorak numbers are lower tonight, we can still hold
the intensity at 70 kt in this advisory. Most likely, the convection
will reinvigorate tonight, but no important changes in intensity are
anticipated during the next 24 hours or so. A weakening trend is
expected thereafter as the cyclone reaches cooler waters.

Leslie has begun to move northward at about 7 kt, and most likely
the cyclone will continue on that track for the next two days. By
then, Leslie will encounter the mid-latitude westerlies and this
flow will force the cyclone to make a sharp turn to the east. Track
models are in remarkably good agreement with the initial northward
turn and with eastward turn. However, during the last portion of
the forecast models diverge, and the confidence in the track
forecast is not very high.

Large swells generated by Leslie are expected to continue during the
next few days 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 on Friday. 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 04/0300Z 30.6N 57.0W 70 KT 80 MPH
12H 04/1200Z 32.0N 57.0W 70 KT 80 MPH
24H 05/0000Z 34.2N 57.4W 70 KT 80 MPH
36H 05/1200Z 36.0N 57.8W 65 KT 75 MPH
48H 06/0000Z 37.0N 57.8W 65 KT 75 MPH
72H 07/0000Z 36.5N 56.0W 60 KT 70 MPH
96H 08/0000Z 36.5N 53.5W 55 KT 65 MPH
120H 09/0000Z 35.5N 50.0W 55 KT 65 MPH

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#25 Postby cycloneye » Thu Oct 04, 2018 5:23 am

Hurricane Leslie Discussion Number 32
NWS National Hurricane Center Miami FL AL132018
500 AM AST Thu Oct 04 2018

Leslie has shown no appreciable changes in its structure during the
past several hours, and it continues to be a little thin on
convection within its eyewall. Another more impressive band of
convection extends nearly more than 120 n mi northwest of the
center of the ragged eye. The initial intensity remains 70 kt for
this advisory, mainly based on a blend of Dvorak CI numbers from
TAFB and SAB and an earlier SATCON estimate. Leslie's center has
reached sea surface temperatures of 26 degrees Celsius, and these
marginal water temperatures are likely to cause a gradual decrease
in the cyclone's winds during the next several days. The new NHC
intensity forecast is mainly just an update to the previous
forecast, largely following the HCCA guidance and the ICON
intensity consensus.

Leslie continues to move northward, or 350/7 kt, between a
shortwave trough south of Nova Scotia and a mid-level ridge over
the central Atlantic. This northward motion should continue for
the next 36 hours before Leslie becomes trapped between two
mid-level highs and is isolated from the mid-latitude westerlies to
the north, thus causing its forward motion to nearly stall by 48
hours. By days 3 through 5, Leslie should feel enough influence
from the westerlies and an approaching cold front to cause it to
move a bit faster toward the east or east-southeast over the north
Atlantic. Like the intensity forecast, no major changes were
required to the official track forecast, which is merely an update
to the previous NHC prediction.

Large swells generated by Leslie are expected to continue during the
next few days 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 on Friday. 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 04/0900Z 31.4N 57.1W 70 KT 80 MPH
12H 04/1800Z 33.0N 57.3W 65 KT 75 MPH
24H 05/0600Z 35.1N 58.0W 65 KT 75 MPH
36H 05/1800Z 36.3N 58.3W 60 KT 70 MPH
48H 06/0600Z 36.8N 57.7W 60 KT 70 MPH
72H 07/0600Z 36.3N 54.6W 55 KT 65 MPH
96H 08/0600Z 35.5N 51.5W 50 KT 60 MPH
120H 09/0600Z 34.5N 48.0W 50 KT 60 MPH

$$
Forecaster Berg
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Re: ATL: LESLIE - Advisories

#26 Postby cycloneye » Thu Oct 04, 2018 9:44 am

Hurricane Leslie Discussion Number 33
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Thu Oct 04 2018

Leslie continues to have an inner area of convection near the
center, with a larger convective band present about 120 n mi from
the center and additional banding in the northwestern quadrant.
Since the last advisory, the central convection has become less
symmetric and the eye has become less defined. Based on this and
the latest satellite intensity estimates, the initial intensity is
nudged downward to 65 kt. While the vertical shear should remain
light through the forecast period, the forecast track takes the
center away from 26C sea surface temperatures and over 24-25C
temperatures, and this should cause a gradual weakening for the
next several days. Since there is little change in the guidance,
the new intensity forecast is again an update of the previous
forecast.

The initial motion is now 355/8. In the short term, Leslie will be
steered northward with some increase in speed between a mid-level
ridge over the central Atlantic and a mid- to upper-level trough
seen in water vapor imagery north of Bermuda. A decrease in
forward speed should occur from 24-36 h as the trough moves south
and a second ridge develops to the west of the tropical cyclone.
Beyond 48 h, Leslie is expected to move eastward to
east-southeastward at a faster forward speed along the southern edge
of the mid-latitude westerlies. The track guidance generally
agrees with this scenario, although some spread in both direction
and speed appears by 120 h. The new track forecast is similar to
the previous forecast and is mostly a blend of the TVCN and HCCA
consensus models.

Large swells generated by Leslie are expected to continue during the
next few days 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 on Friday. 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 04/1500Z 32.5N 57.2W 65 KT 75 MPH
12H 05/0000Z 34.1N 57.6W 65 KT 75 MPH
24H 05/1200Z 35.8N 58.1W 60 KT 70 MPH
36H 06/0000Z 36.6N 58.1W 60 KT 70 MPH
48H 06/1200Z 36.8N 56.8W 55 KT 65 MPH
72H 07/1200Z 36.0N 53.5W 50 KT 60 MPH
96H 08/1200Z 35.0N 50.5W 50 KT 60 MPH
120H 09/1200Z 33.5N 47.0W 50 KT 60 MPH

$$
Forecaster Beven
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Re: ATL: LESLIE - Advisories

#27 Postby cycloneye » Thu Oct 04, 2018 3:44 pm

Tropical Storm Leslie Discussion Number 34
NWS National Hurricane Center Miami FL AL132018
500 PM AST Thu Oct 04 2018

Leslie has changed little in convective structure today. Visible
imagery shows occasional appearances of an eye inside an area of
central convection, with a complex of outer bands wrapping around
this inner feature. Infrared imagery, though, suggests that the
convection is relatively shallow. Despite the lack of change in the
convective pattern, scatterometer data shows there have been
significant changes in the wind structure. The strongest winds are
now in a band about 90-100 n mi from the center, with the winds in
the inner core being notably weaker. This suggest the possibility
that Leslie is trying to undergo an eyewall replacement, albeit one
with a very large outer eyewall. Based on the scatterometer data
and slightly decreased satellite intensity estimates, the initial
intensity is reduced to 60 kt.

There is little change to the intensity forecast philosophy, the
intensity forecast guidance, or the intensity forecast. While the
vertical shear should remain light through the forecast period, the
forecast track takes the center away from 26C sea surface
temperatures and over 24-25C temperatures, and this should cause a
gradual weakening for the next several days. There are major
changes to the initial and forecast wind radii based on the
scatterometer data and the analyzed initial size.

The initial motion is 355/10. In the short term, Leslie will be
steered northward between a mid-level ridge over the central
Atlantic and a mid- to upper-level trough seen in water vapor
imagery north of Bermuda. A decrease in forward speed should occur
from 24-36 h as the trough moves south and a second ridge develops
to the west of the tropical cyclone. Beyond 36 h, Leslie is
expected to move eastward to east-southeastward at a faster forward
speed along the southern edge of the mid-latitude westerlies.
Overall, the new forecast track is close to the previous track
through 48 h, then a little north of the old track after that time.
However, there is an increased spread in the guidance in both the
track and the forward speed near the end of the forecast period, and
confidence is decreasing for this part of the forecast.

Large swells generated by Leslie are expected to continue during the
next few days 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 on Friday. 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 04/2100Z 33.3N 57.5W 60 KT 70 MPH
12H 05/0600Z 34.9N 58.0W 60 KT 70 MPH
24H 05/1800Z 36.1N 58.2W 60 KT 70 MPH
36H 06/0600Z 36.8N 57.5W 55 KT 65 MPH
48H 06/1800Z 36.7N 55.9W 55 KT 65 MPH
72H 07/1800Z 36.0N 52.5W 50 KT 60 MPH
96H 08/1800Z 34.5N 48.5W 50 KT 60 MPH
120H 09/1800Z 32.5N 44.5W 50 KT 60 MPH

$$
Forecaster Beven
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Re: ATL: LESLIE - Advisories

#28 Postby cycloneye » Thu Oct 04, 2018 9:41 pm

Tropical Storm Leslie Discussion Number 35
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Thu Oct 04 2018

Leslie lacks an inner core and now consists of a vigorous large
circulation with small outer bands of shallow to moderate
convection. Satellite intensity estimates have continued to yield a
lower intensity, and the winds have been reduced to 55 kt in this
advisory based on a recent ASCAT pass. The shear does not appear to
be a problem for Leslie, and the cyclone is forecast to be moving
over SSTs which appear to not be cool enough to result in
significant weakening. In fact, the average of the intensity
guidance suggests that Leslie basically will be a 50-kt cyclone
through the forecast period and so does the NHC forecast.

Leslie is moving northward or 350 degrees at 10 kt steered by the
southerly flow on the western edge of the subtropical ridge. In
about 24 to 36 hours, the storm will encounter the mid-latitude
westerlies, and this flow pattern will force Leslie to make a sharp
turn to the east and even to the east-southeast with no change in
forward speed. Track guidance is in extremely good agreement with
this solution for the next 3 to 4 days. After that time, the models
vary significantly in speed, but since the cyclone will be embedded
in the westerlies, the NHC forecast maintains the eastward
progression of Leslie as indicated in the previous forecast.

Large swells generated by Leslie are expected to continue during the
next few days 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 on Friday. 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 05/0300Z 34.9N 57.6W 55 KT 65 MPH
12H 05/1200Z 36.2N 58.0W 50 KT 60 MPH
24H 06/0000Z 37.2N 57.7W 50 KT 60 MPH
36H 06/1200Z 37.5N 56.5W 50 KT 60 MPH
48H 07/0000Z 37.5N 54.5W 50 KT 60 MPH
72H 08/0000Z 36.5N 50.0W 50 KT 60 MPH
96H 09/0000Z 34.5N 45.5W 50 KT 60 MPH
120H 10/0000Z 33.0N 42.5W 50 KT 60 MPH

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#29 Postby cycloneye » Fri Oct 05, 2018 4:47 am

Tropical Storm Leslie Discussion Number 36
NWS National Hurricane Center Miami FL AL132018
500 AM AST Fri Oct 05 2018

Leslie's structure has evolved somewhat just within the past 6
hours. Deep convection has redeveloped near the low-level center,
although it is displaced a bit to the north due to some southerly
shear. The cyclone's circulation remains quite large, and earlier
ASCAT data indicated that the radius of maximum winds is about
90-100 n mi away from the center. Since there is some inner-core
convection again, the initial intensity remains 55 kt based on the
ASCAT data.

Leslie has gained some speed and has turned toward the
north-northwest, now with an initial motion of 345/12 kt. A
general northward motion should continue for the next 12-24 hours,
but then Leslie will reach the mid-latitude westerlies and make an
abrupt turn toward the east by 36 hours. After that time, Leslie
is expected to make some significant eastward progress, although
the global models are showing several shortwave troughs in the
westerlies imparting a southeastward motion on Leslie by days 4 and
5. In fact, some of the models have shifted significantly
southward by the end of the forecast period, leaving the previous
official forecast near the northern edge of the guidance envelope.
Due to this shift, the new NHC track prediction has been adjusted
southward on days 3-5, although it does not yet show as much
southward motion as indicated by the normally reliable ECMWF, HCCA,
and TVCN multi-model consensus.

Leslie doesn't appear to have to contend with much shear during the
next 3 days or so, but with such a large wind field mixing the
ocean around it, marginal sea surface temperatures are likely to
keep the intensity steady. By days 3 and 4, an increase in shear
could cause some slight weakening. The models are in very good
agreement in showing little to any change in Leslie's intensity
during the next 5 days, and that is largely what is indicated in
the NHC forecast.

Large swells generated by Leslie are expected to continue during the
next few days across the southeastern coast of the United States,
Bermuda, the Bahamas, and the Greater and Lesser Antilles. These
swells will also increase near the coasts of New England and
Atlantic Canada later today. 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 05/0900Z 35.9N 58.3W 55 KT 65 MPH
12H 05/1800Z 36.9N 58.4W 50 KT 60 MPH
24H 06/0600Z 37.4N 57.6W 50 KT 60 MPH
36H 06/1800Z 37.4N 55.8W 50 KT 60 MPH
48H 07/0600Z 37.0N 53.7W 50 KT 60 MPH
72H 08/0600Z 35.7N 49.7W 45 KT 50 MPH
96H 09/0600Z 33.5N 45.5W 45 KT 50 MPH
120H 10/0600Z 31.5N 42.0W 50 KT 60 MPH

$$
Forecaster Berg
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Re: ATL: LESLIE - Advisories

#30 Postby cycloneye » Fri Oct 05, 2018 9:54 am

Tropical Storm Leslie Discussion Number 37
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Fri Oct 05 2018

The structure of Leslie has changed little since the last advisory,
with a cluster of convection just north of the low-level center and
a second cluster well to the southeast of the center. The initial
intensity is held at 55 kt based mainly on continuity from earlier
scatterometer data, but it is possible that this is a little
generous. It should be noted that overall, Leslie has lost some
organization since this time yesterday due to the disappearance of
the eye and an overall decrease in convective banding.

Leslie appears to be slowing its forward speed, with the initial
motion now 345/8. A turn to the north and a slower forward speed
are expected during the next 12 h, followed by a turn toward the
east-southeast by 36 h as Leslie encounters the southern edge of the
mid-latitude westerlies. A general motion toward the east-southeast
or southeast should then continue for the remainder of the forecast
period. As noted in the previous advisory, there has been a
southward shift in the guidance, and the new forecast track is again
shifted a little to the south of the previous track. However, it
lies to the north of the HCCA and TVCN consensus models.

The forecast track takes Leslie over cooler waters around days 2-3,
into increasing shear around days 3-4, and over warmer water with
decreasing shear around days 4-5. However, the structure of Leslie
is not currently conducive for rapid changes in intensity either up
or down. Thus, the intensity forecast follows the trend of the
previous forecast and the guidance in showing gradual weakening for
48-72 h, followed by slight intensification near 96-120 h.

Large swells generated by Leslie are expected to continue during the
next few days across the southeastern coast of the United States,
Bermuda, the Bahamas, and the Greater and Lesser Antilles. These
swells will also increase near the coasts of New England and
Atlantic Canada later today. 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 05/1500Z 36.2N 58.4W 55 KT 65 MPH
12H 06/0000Z 36.8N 58.1W 50 KT 60 MPH
24H 06/1200Z 37.1N 56.9W 50 KT 60 MPH
36H 07/0000Z 36.9N 54.9W 50 KT 60 MPH
48H 07/1200Z 36.5N 53.0W 45 KT 50 MPH
72H 08/1200Z 35.0N 49.5W 45 KT 50 MPH
96H 09/1200Z 33.0N 45.5W 50 KT 60 MPH
120H 10/1200Z 31.0N 42.5W 50 KT 60 MPH

$$
Forecaster Beven
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Re: ATL: LESLIE - Advisories

#31 Postby cycloneye » Fri Oct 05, 2018 3:43 pm

Tropical Storm Leslie Discussion Number 38
NWS National Hurricane Center Miami FL AL132018
500 PM AST Fri Oct 05 2018

Leslie is currently maintaining a small central convective feature
and an outer convective band in the southeastern semicircle. The
various satellite intensity estimates have decreased a little, so
the initial intensity is nudged downward to 50 kt. This is still a
little above the estimates from TAFB, SAB, and the CIMSS satellite
consensus. While no data was available from the inner core,
scatterometer overpasses this morning suggests that Leslie has
changed little in size since last night.

Leslie has now slowed its forward motion and is starting to turn
more eastward, with an initial motion of 030/3. A turn to the east
is expected during the next 24 h, followed by a turn toward the
east-southeast by 36 h as Leslie encounters the southern edge of the
mid-latitude westerlies. A general motion toward the east-southeast
or southeast should then continue for the remainder of the forecast
period. The latest guidance again shifted southward, and the new
forecast track, which is in best agreement with the TVCN consensus
model, is shifted to the south of the previous track

The forecast track again takes Leslie over cooler waters around day
2, into slightly stronger shear around day 3, and over warmer
water with decreasing shear around days 4-5. However, the structure
of Leslie is not currently conducive for rapid changes in intensity
either up or down. Thus, the intensity forecast, which has only
minor tweaks from the previous forecast, follows the trend of the
previous forecast and the guidance in showing gradual weakening near
48 h, followed by slight intensification near 96-120 h.

Large swells generated by Leslie are expected to continue during the
next few days across the eastern coast of the United States,
Bermuda, the Bahamas, the Greater and Lesser Antilles, and Atlantic
Canada. 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 05/2100Z 36.2N 58.1W 50 KT 60 MPH
12H 06/0600Z 36.7N 57.5W 50 KT 60 MPH
24H 06/1800Z 36.7N 55.8W 50 KT 60 MPH
36H 07/0600Z 36.4N 53.8W 50 KT 60 MPH
48H 07/1800Z 35.8N 51.7W 45 KT 50 MPH
72H 08/1800Z 34.0N 48.0W 45 KT 50 MPH
96H 09/1800Z 31.5N 44.5W 50 KT 60 MPH
120H 10/1800Z 30.0N 42.0W 55 KT 65 MPH

$$
Forecaster Beven
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Re: ATL: LESLIE - Advisories

#32 Postby cycloneye » Fri Oct 05, 2018 9:37 pm

Tropical Storm Leslie Discussion Number 39
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Fri Oct 05 2018

Leslie's cloud pattern consists of a small ring of shallow to
moderate convection embedded within a large and vigorous
circulation. Dvorak classifications allow me to keep the same
intensity, and in fact, ASCAT data just came in with a few 50-kt
wind vectors. So the initial intensity remains at 50 kt in this
advisory. Leslie will not encounter any hostile shear, but the
cyclone will move over a few patches of warm and cool waters. The
guidance shows some minor fluctuations in the cyclone intensity,
most likely due to the aforementioned SST variations along the
track, and this is reflected in the NHC forecast.

Leslie is moving toward the east-northeast or 075 degrees at 6 kt.
The cyclone is already embedded in the mid-latitude westerly flow,
which is being modulated by passing shortwaves. This flow pattern
is expected to persist and should steer Leslie eastward and
east-southeastward through the next 5 days. Although the track
guidance is not as clustered as in previous days, most of the models
agree with the eastward motion of the cyclone, but vary in speed. It
appears that stubborn Leslie will be with us for several more days.

Large swells generated by Leslie are expected to continue during the
next few days across the eastern coast of the United States,
Bermuda, the Bahamas, the Greater and Lesser Antilles, and Atlantic
Canada. 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 06/0300Z 36.6N 57.2W 50 KT 60 MPH
12H 06/1200Z 37.0N 56.0W 50 KT 60 MPH
24H 07/0000Z 37.0N 54.0W 50 KT 60 MPH
36H 07/1200Z 36.5N 51.7W 50 KT 60 MPH
48H 08/0000Z 36.0N 49.5W 45 KT 50 MPH
72H 09/0000Z 34.0N 45.0W 45 KT 50 MPH
96H 10/0000Z 31.0N 41.0W 50 KT 60 MPH
120H 11/0000Z 29.0N 38.0W 55 KT 65 MPH

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#33 Postby cycloneye » Sat Oct 06, 2018 5:08 am

Tropical Storm Leslie Discussion Number 40
NWS National Hurricane Center Miami FL AL132018
500 AM AST Sat Oct 06 2018

Leslie is producing a cluster of deep convection near its center of
circulation and a far-reaching band that curls around the eastern
side of the expansive circulation. The maximum winds are still
estimated to be 50 kt based on last evening's ASCAT pass. Leslie's
future intensity will largely be limited by a less-than-ideal
thermodynamic environment, with the center moving over water
temperatures of 24-25 degrees Celsius within its own cold wake
during the next 48 hours. Some weakening is anticipated during that
period, and the NHC forecast follows the intensity consensus and
HCCA guidance. After 48 hours, some restrengthening is possible
when Leslie reaches some warmer waters, although increasing
westerly shear is likely to temper the amount of intensification.

Leslie's current motion is northeastward, or 045/7 kt. The cyclone
is becoming increasingly embedded within the mid-latitude
westerlies, and these winds, with the assistance of a couple of
shortwave troughs, are expected to push Leslie toward the east and
southeast throughout the forecast period. The one notable model
anomaly is the ECMWF, which shows Leslie becoming more separated
from the mid-latitude flow and moving more slowly than shown in the
other models on days 3 through 5. Even with that model being an
outlier, the rest of the guidance has sped up a bit, pulling the
consensus aids eastward. This resulted in the new NHC track
forecast being a little faster than the previous one on days 4 and
5.

Large swells generated by Leslie are expected to continue during the
next few days across the eastern coast of the United States,
Bermuda, the Bahamas, the Greater and Lesser Antilles, and Atlantic
Canada. 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 06/0900Z 37.2N 56.4W 50 KT 60 MPH
12H 06/1800Z 37.3N 55.0W 50 KT 60 MPH
24H 07/0600Z 37.1N 52.6W 50 KT 60 MPH
36H 07/1800Z 36.5N 50.2W 45 KT 50 MPH
48H 08/0600Z 35.7N 47.8W 40 KT 45 MPH
72H 09/0600Z 33.4N 42.6W 45 KT 50 MPH
96H 10/0600Z 30.5N 37.5W 50 KT 60 MPH
120H 11/0600Z 28.5N 32.5W 50 KT 60 MPH

$$
Forecaster Berg
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Re: ATL: LESLIE - Advisories

#34 Postby cycloneye » Sat Oct 06, 2018 9:59 am

Tropical Storm Leslie Discussion Number 41
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Sat Oct 06 2018

The central convection associated with Leslie has become better
organized this morning, with conventional satellite imagery showing
a tightly curved band and recent microwave imagery showing a
mid-level eye. However, the microwave data also suggests the
mid-level eye is located to the southeast of the low-level center.
It is also not known whether there is an inner wind maximum
associated with this feature. Satellite intensity estimates are
mostly in the 45-55 kt range, so the initial intensity remains 50
kt.

The initial motion is now 080/8. Leslie is now in or near the
southern edge of the mid-latitude westerlies, and with the
assistance of a couple of shortwave troughs, these are expected to
push Leslie toward the east and southeast throughout the forecast
period. Despite general agreement on the synoptic pattern, there is
now a large spread in the guidance toward the end of the forecast
period. The ECMWF and UKMET show a more southward turn after 72 h,
taking Leslie well south of 30N. The GFS, on the other hand,
shows a more eastward motion to the point where by 96 h it is 950
n mi from the UKMET forecast position. The new forecast track
compromises between these extremes and lies near the TVCN consensus,
with the caveat that the part after 72 h is of low confidence.

Leslie should weaken some during the next 48 h or so as it crosses
an area of cooler sea surface temperatures. After that, the track
takes the center back over warmer water at the same time when there
may be an increase in shear. There is an increased uncertainty in
the intensity forecast caused by the track forecast uncertainties.
If Leslie moves closer to the GFS track, it will be over cooler
water and in stronger shear, while if it moves closer to the UKMET
solution it will be over warmer water and lighter shear. Due to to
the uncertainty, only minor adjustments are made to the previous
intensity forecast. Additional adjustments may be needed later
depending on changes in the track forecast.

Large swells generated by Leslie are expected to continue during the
next few days across the northeastern coast of the United States,
Bermuda, the Greater and Lesser Antilles, and Atlantic Canada.
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 06/1500Z 37.7N 55.8W 50 KT 60 MPH
12H 07/0000Z 37.6N 54.1W 50 KT 60 MPH
24H 07/1200Z 37.3N 51.5W 45 KT 50 MPH
36H 08/0000Z 36.6N 49.0W 45 KT 50 MPH
48H 08/1200Z 35.7N 46.5W 40 KT 45 MPH
72H 09/1200Z 33.0N 41.5W 45 KT 50 MPH
96H 10/1200Z 30.0N 37.0W 50 KT 60 MPH
120H 11/1200Z 29.0N 31.0W 50 KT 60 MPH

$$
Forecaster Beven
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Re: ATL: LESLIE - Advisories

#35 Postby cycloneye » Sat Oct 06, 2018 3:56 pm

Tropical Storm Leslie Discussion Number 42
NWS National Hurricane Center Miami FL AL132018
500 PM AST Sat Oct 06 2018

The central convection associated with Leslie is still well
organized and concentrated. A recent SSMIS image shows that
Leslie's inner core is better defined resembling an eyewall.
However, Dvorak estimates still support an initial intensity
intensity of 50 kt.

Leslie should weaken slightly during the next 24 to 36 h as the
cyclone crosses patches of cooler SSTs. After that time, the track
takes the center back over warmer waters, but the shear could
increase a little. Only minor adjustments are made to the previous
intensity forecast, and the NHC forecast follows very close the
model consensus which suggests slight strengthening by the end of
the forecast period.

Leslie continues to be embedded within the mid-latitude westerlies
and is moving toward the east or 100 degrees at 10 kt. These
westerlies are forecast to be modulated by the passage of short
waves, and the flow pattern will initially keep Leslie on east to
east-southeast track for most of the forecast period. By the end of
the period a turn to the northeast is anticipated. Models are not
in great agreement but they are consistently showing the eastward
progression of the cyclone. The NHC forecast is very close to the
models consensus, and is basically in the middle of the track
envelope.

Large swells generated by Leslie are expected to continue during the
next few days across the northeastern coast of the United States,
Bermuda, the Greater and Lesser Antilles, and Atlantic Canada.
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 06/2100Z 37.4N 54.5W 50 KT 60 MPH
12H 07/0600Z 37.1N 52.8W 45 KT 50 MPH
24H 07/1800Z 36.6N 50.4W 45 KT 50 MPH
36H 08/0600Z 35.8N 48.0W 45 KT 50 MPH
48H 08/1800Z 34.8N 45.4W 50 KT 60 MPH
72H 09/1800Z 31.5N 40.5W 55 KT 65 MPH
96H 10/1800Z 28.5N 35.5W 55 KT 65 MPH
120H 11/1800Z 28.5N 31.0W 55 KT 65 MPH

$$
Forecaster Beven/Avila
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Re: ATL: LESLIE - Advisories

#36 Postby cycloneye » Sat Oct 06, 2018 3:57 pm

Tropical Storm Leslie Discussion Number 42
NWS National Hurricane Center Miami FL AL132018
500 PM AST Sat Oct 06 2018

The central convection associated with Leslie is still well
organized and concentrated. A recent SSMIS image shows that
Leslie's inner core is better defined resembling an eyewall.
However, Dvorak estimates still support an initial intensity
intensity of 50 kt.

Leslie should weaken slightly during the next 24 to 36 h as the
cyclone crosses patches of cooler SSTs. After that time, the track
takes the center back over warmer waters, but the shear could
increase a little. Only minor adjustments are made to the previous
intensity forecast, and the NHC forecast follows very close the
model consensus which suggests slight strengthening by the end of
the forecast period.

Leslie continues to be embedded within the mid-latitude westerlies
and is moving toward the east or 100 degrees at 10 kt. These
westerlies are forecast to be modulated by the passage of short
waves, and the flow pattern will initially keep Leslie on east to
east-southeast track for most of the forecast period. By the end of
the period a turn to the northeast is anticipated. Models are not
in great agreement but they are consistently showing the eastward
progression of the cyclone. The NHC forecast is very close to the
models consensus, and is basically in the middle of the track
envelope.

Large swells generated by Leslie are expected to continue during the
next few days across the northeastern coast of the United States,
Bermuda, the Greater and Lesser Antilles, and Atlantic Canada.
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 06/2100Z 37.4N 54.5W 50 KT 60 MPH
12H 07/0600Z 37.1N 52.8W 45 KT 50 MPH
24H 07/1800Z 36.6N 50.4W 45 KT 50 MPH
36H 08/0600Z 35.8N 48.0W 45 KT 50 MPH
48H 08/1800Z 34.8N 45.4W 50 KT 60 MPH
72H 09/1800Z 31.5N 40.5W 55 KT 65 MPH
96H 10/1800Z 28.5N 35.5W 55 KT 65 MPH
120H 11/1800Z 28.5N 31.0W 55 KT 65 MPH

$$
Forecaster Beven/Avila
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Re: ATL: LESLIE - Advisories

#37 Postby cycloneye » Sun Oct 07, 2018 3:38 pm

Tropical Storm Leslie Discussion Number 46
NWS National Hurricane Center Miami FL AL132018
500 PM AST Sun Oct 07 2018

Late-arriving ASCAT data from shortly after 1200 UTC indicated that
Leslie is still producing winds of just below 45 kt, primarily in
the southwest and northeast quadrants of the tropical storm.
Assuming at least a little undersampling has occurred, this would
support an initial intensity of 45 or 50 kt, while an average of
more recent intensity estimates from SAB, TAFB, and the UW-CIMSS
is 50 kt. The initial value is therefore held at 50 kt.

Regardless of the exact initial intensity of Leslie, only slight
fluctuations are expected over the next 24 to 36 hours while Leslie
is over fairly cool SSTs, in part because it will be crossing its
own previous track multiple times. Beyond 48 h, the intensity
guidance is now in better agreement that some intensification
will occur, and Leslie is forecast to become a hurricane once again
by the end of the week. The NHC intensity forecast is a little
higher than the previous advisory by the end of the forecast
period, and is close to IVCN at all times.

Leslie is still moving east-southeastward with an initial speed of 9
kt, and this general motion will likely continue for at least the
next day or two while the tropical storm is steered by westerly flow
associated with a mid-latitude trough to its north. Most of the
global models still forecast that Leslie will separate from the
trough in a few days and turn southeastward, and there are still
large differences on exactly when that will occur. The deterministic
runs of the GFS and ECMWF have come into better agreement on the
future track of Leslie, but the ensembles of those models indicate
that the range of possible tracks hasn't actually decreased.
Confidence in the track forecast therefore remains quite low. In
general, the guidance suite has shifted to the south and west,
particularly between 36 and 96 h. The official track forecast has
been shifted in that direction to bring it closer to the track
consensus. However, it should be emphasized that confidence in the
track forecast remains low at this time.


FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 35.9N 49.9W 50 KT 60 MPH
12H 08/0600Z 35.4N 48.2W 50 KT 60 MPH
24H 08/1800Z 34.3N 45.7W 50 KT 60 MPH
36H 09/0600Z 32.8N 43.2W 55 KT 65 MPH
48H 09/1800Z 31.2N 41.3W 55 KT 65 MPH
72H 10/1800Z 28.2N 38.8W 60 KT 70 MPH
96H 11/1800Z 28.6N 33.0W 65 KT 75 MPH
120H 12/1800Z 30.5N 27.0W 60 KT 70 MPH

$$
Forecaster Zelinsky
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Re: ATL: LESLIE - Advisories

#38 Postby cycloneye » Sun Oct 07, 2018 9:42 pm

Tropical Storm Leslie Discussion Number 47
NWS National Hurricane Center Miami FL AL132018
1100 PM AST Sun Oct 07 2018

Leslie's cloud pattern consists of a large and vigorous circulation,
but the convection is shallow at this time. Dvorak numbers only
support an initial intensity of 45 kt. Some fluctuations in
intensity are expected over the next 24 to 36 hours, while Leslie
is over fairly cool SSTs. After that time, Leslie will encounter
warmer waters, and since the shear is low, some re-intensification
is anticipated. Leslie will likely become a hurricane once again
by the end of the week as indicated by the guidance.

Leslie is still moving east-southeastward at about 11 kt. Since
Leslie is embedded within the mid-latitude westerly flow, this
general motion will likely continue for the next 2 days or so.
This is consistent with most of the track guidance, which continue
to show a southeastward motion of the cyclone during that period.
Another shortwave trough in the westerlies will bypass the cyclone,
but will modify the steering flow, and Leslie should then turn to
the east-northeast. It should be emphasized that confidence in the
track forecast remains low.


FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 35.7N 49.1W 45 KT 50 MPH
12H 08/1200Z 35.2N 47.4W 45 KT 50 MPH
24H 09/0000Z 33.8N 45.0W 45 KT 50 MPH
36H 09/1200Z 32.0N 43.0W 50 KT 60 MPH
48H 10/0000Z 30.5N 41.5W 55 KT 65 MPH
72H 11/0000Z 28.5N 39.0W 60 KT 70 MPH
96H 12/0000Z 30.0N 33.0W 65 KT 75 MPH
120H 13/0000Z 32.0N 24.0W 60 KT 70 MPH

$$
Forecaster Avila
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Re: ATL: LESLIE - Advisories

#39 Postby cycloneye » Mon Oct 08, 2018 4:55 am

Tropical Storm Leslie Discussion Number 48
NWS National Hurricane Center Miami FL AL132018
500 AM AST Mon Oct 08 2018

There has not been a lot of change with Leslie overnight. Deep
convection is still organized in curved bands near and to the north
of the center, but there is some dry air entraining into the
western side of the circulation. A blend of the latest satellite
intensity estimates supports holding the initial intensity at 45 kt.

Leslie is over cool 24 deg C waters, but it will be headed over
slightly warmer waters during the next few days while remaining in
low wind shear conditions. Therefore, slow strengthening is
expected and most of the intensity models show Leslie reaching
hurricane strength once again within the next 3 to 4 days. By the
end of the period, cooler waters and an increase in shear could
cause some weakening. The NHC intensity forecast is a little higher
than the previous one, to trend toward the latest IVCN and HCCA
guidance.

Leslie is moving east-southeastward at 11 kt steered by the flow on
the south side of a broad mid- to upper-level trough over the north
Atlantic. An east-southeast to southeast motion is expected during
the next couple of days as the trough passes by to the north of
Leslie. After that time, another large-scale trough will approach
Leslie from the northwest and that should cause the storm to turn
east-northeastward at a faster pace in the 4 to 5 day time frame.
The models have come into a better agreement this cycle showing a
faster and more northward motion at the end of the period, and the
NHC forecast has been adjusted accordingly.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 35.2N 47.9W 45 KT 50 MPH
12H 08/1800Z 34.3N 46.2W 45 KT 50 MPH
24H 09/0600Z 32.9N 44.0W 50 KT 60 MPH
36H 09/1800Z 31.1N 42.4W 55 KT 65 MPH
48H 10/0600Z 29.6N 41.3W 60 KT 70 MPH
72H 11/0600Z 28.8N 38.3W 65 KT 75 MPH
96H 12/0600Z 31.2N 30.4W 70 KT 80 MPH
120H 13/0600Z 36.8N 20.0W 65 KT 75 MPH

$$
Forecaster Cangialosi
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Re: ATL: LESLIE - Advisories

#40 Postby cycloneye » Mon Oct 08, 2018 9:47 am

Tropical Storm Leslie Discussion Number 49
NWS National Hurricane Center Miami FL AL132018
1100 AM AST Mon Oct 08 2018

For the fourth (and hopefully final) time as a tropical or
subtropical cyclone, Leslie has crossed 48W. The convective pattern
of the tropical storm hasn't changed significantly over the past
several hours, though there is some evidence of a convective band
attempting to wrap around the western side of the storm. The
initial intensity is still 45 kt, based on a blend of the most
recent current intensity estimates from TAFB, SAB, and the UW-CIMSS
SATCON.

There has been little change in the intensity forecast. Just about
all of the typically reliable intensity models still call for
Leslie to gradually strengthen over the next 3 days, despite
marginal SSTs. All of the dynamical models call for Leslie to
become a hurricane once again by 72 h, but SHIPS and LGEM
are a little lower. The official intensity forecast remains near
the HCCA and IVCN consensus aids, and calls for Leslie to become a
hurricane by the end of the week.

Leslie has continued to move east-southeastward, now at 12 kt, and
the global models are in good agreement that this motion will
continue through today. After that time, most of the guidance
generally shows that Leslie will separate from a mid-latitude
trough, causing the tropical storm to turn toward the southeast or
south-southeast and slow down. A day or so after that, another
mid-latitude trough will approach from the west and cause Leslie to
accelerate toward the east-northeast. The timing of Leslie's
acceleration is still very uncertain, and the model spread beyond
72 h remains very high. Until the spread decreases, I don't feel
confident making a big change to the forecast, so the official track
forecast has only been slightly tweaked to bring it closer to HCCA
and TVCN.

FORECAST POSITIONS AND MAX WINDS

INIT 08/1500Z 34.6N 47.0W 45 KT 50 MPH
12H 09/0000Z 33.6N 45.2W 50 KT 60 MPH
24H 09/1200Z 32.0N 43.5W 50 KT 60 MPH
36H 10/0000Z 30.2N 42.2W 55 KT 65 MPH
48H 10/1200Z 29.1N 41.2W 60 KT 70 MPH
72H 11/1200Z 29.5N 37.0W 65 KT 75 MPH
96H 12/1200Z 33.0N 28.0W 70 KT 80 MPH
120H 13/1200Z 39.0N 18.0W 65 KT 75 MPH

$$
Forecaster Zelinsky
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