Hurricane Lee Discussion Number 31
NWS National Hurricane Center Miami FL AL132023
1100 PM AST Tue Sep 12 2023
Geostationary satellite images show that Lee has a large eye about
40 n mi in diameter surrounded by very cold-topped central
convection. There are numerous convective banding features,
especially over the northern portion of the circulation. The
cirrus-level outflow pattern is fairly symmetric at this time,
suggesting that the vertical wind shear over the system is still
low. The intensity estimate is held at 100 kt for this advisory,
which is a blend of subjective and objective satellite estimates
from TAFB, SAB, and UW/CIMSS. The objective intensity estimates
are generally a little higher than the subjective values.
Lee continues to move on a generally northwestward heading, with a
motion estimate of 320/6 kt, on the southwestern side of a
mid-level anticyclone. Over the next couple of days, a 500-mb
trough moving through the eastern United States should induce a
northward turn with some increase in forward speed. Even though
the predicted track has the center of the hurricane passing well to
the west of Bermuda, Lee's very large wind field should result in
tropical storm conditions spreading over the island by late
Wednesday or early Thursday. In the 3 to 4 day time frame, the
model guidance suggests just a slight leftward bend in the track
while Lee interacts with the trough. There has been little change
to the NHC forecast track, which remains close to the corrected and
simple model consensus predictions. After 96 hours, Lee should
turn northeastward and east-northeastward in the mid-latitude
westerlies.
Gradual weakening is anticipated during the next few days days
while Lee moves over cooler waters and encounters high vertical
wind shear. However the system is likely to remain a large and
dangerous hurricane while it approaches the coast. If Lee moves
faster than forecast over the colder waters north of the Gulf
Stream, it will likely retain more of its strength when it reaches
land. Around 96 hours, simulated satellite imagery from the global
models show the appearance of an extratropical cyclone with
decreased convection and an asymmetric cloud pattern.
It should again be noted that the 34- and 50-kt wind speed
probabilities beyond 36 hours in the text product and graphics are
likely underestimating the risk of those winds occurring. This is
because the forecast wind field of Lee is considerably larger than
average compared to the wind field used to derive the wind speed
probability product.
KEY MESSAGES:
1. Dangerous surf and life-threatening rip currents will affect
portions of the northern Leeward Islands, the Virgin Islands, Puerto
Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas,
Bermuda, and most of the U.S East Coast through much of the week.
2. Tropical storm conditions, heavy rainfall, and high surf are
expected to impact Bermuda beginning Wednesday night or early
Thursday, and a Tropical Storm Warning has been issued for the
island.
3. It remains too soon to know what level of additional impacts Lee
might have along the northeastern U.S. coast and Atlantic Canada
late this week and this weekend. However, since wind and rainfall
hazards will extend well away from the center as Lee grows in size,
users should continue to monitor updates to Lee's forecast during
the next several days.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0300Z 25.3N 66.7W 100 KT 115 MPH
12H 13/1200Z 26.1N 67.2W 100 KT 115 MPH
24H 14/0000Z 27.7N 67.8W 95 KT 110 MPH
36H 14/1200Z 29.7N 68.2W 90 KT 105 MPH
48H 15/0000Z 32.1N 67.9W 80 KT 90 MPH
60H 15/1200Z 35.0N 67.1W 75 KT 85 MPH
72H 16/0000Z 38.0N 66.6W 75 KT 85 MPH
96H 17/0000Z 44.0N 66.4W 60 KT 70 MPH...POST-TROP/EXTRATROP
120H 18/0000Z 48.5N 62.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
$$
Forecaster Pasch
Hurricane Lee Discussion Number 32
NWS National Hurricane Center Miami FL AL132023
500 AM AST Wed Sep 13 2023
Lee's structure is very gradually declining in organization. The
hurricane has a ragged but somewhat elliptical 25-30 n mi wide eye,
but deep convection has become eroded a bit within the western
semicircle, possibly due to some moderate westerly shear. In
addition, a 0607 UTC AMSR-2 microwave pass showed that the eyewall
was open on the southwest side at that time. Subjective and
objective satellite estimates range from 90-105 kt, so Lee's
initial intensity remains 100 kt for now.
The hurricane is very slowly making its turn around a west-central
Atlantic mid-level high, with its motion now northwestward at
325/5 kt. The track guidance is tightly clustered during the next
2 days or so, showing Lee turning and accelerating toward the
north-northwest and north between the high and a shortwave trough
swinging across the Great Lakes region. Lee's core is forecast to
pass west of Bermuda in 36-48 hours, but tropical storm conditions
are likely to begin there late tonight or early Thursday due to the
hurricane's large wind field. On days 3 and 4, Lee is expected to
maintain a general northward track offshore the northeastern U.S.
However, the global models are suggesting that the hurricane
will interact with a remnant mid-level trough over the mid-Atlantic
states, causing Lee to possibly bend just west of due north while
it moves across the Gulf of Maine. Under the assumption that the
global models will have a better handle on this mid-latitude
pattern as compared to the regional hurricane models, the NHC track
forecast is close to a consensus of the GFS and ECMWF models (GFEX)
on days 3, 4, and 5, and therefore ends up being a bit west and
then north of the previous prediction on those days.
A number of factors--including Lee's broad structure, increasing
shear, and potential upwelling of cooler waters--are likely to lead
to a very gradual decrease in the hurricane's maximum winds during
the next 3 days or so. In addition, Lee is likely to begin
extratropical transition in 2-3 days, with that process expected to
be complete just before the cyclone's center reaches the coast of
Maine, New Brunswick, or Nova Scotia in about 4 days. That said,
Lee's expected post-tropical transition will not diminish potential
wind, rain, and coastal flooding impacts in New England and Atlantic
Canada due to the system's broad wind field.
It should again be noted that the 34- and 50-kt wind speed
probabilities beyond 36 hours in the text and graphical products are
likely underestimating the risk of those winds occurring. This is
because the forecast wind field of Lee is considerably larger than
average compared to the wind field used to derive the wind speed
probability product.
KEY MESSAGES:
1. Dangerous surf and life-threatening rip currents will affect
portions of the northern Leeward Islands, the Virgin Islands, Puerto
Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas,
Bermuda, and most of the U.S East Coast through much of the week.
2. Tropical storm conditions, heavy rainfall, and high surf are
expected to impact Bermuda beginning late tonight or early Thursday,
and a Tropical Storm Warning is in effect for the island.
3. There is an increasing risk of wind, coastal flooding, and rain
impacts from Lee in portions of New England and Atlantic Canada
beginning on Friday and continuing through the weekend. Watches may
be required for portions of these areas later today or tonight.
Due to Lee's large size, hazards will extend well away from the
center, and there will be little to no significance on exactly where
the center reaches the coast.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0900Z 25.7N 67.1W 100 KT 115 MPH
12H 13/1800Z 26.6N 67.6W 95 KT 110 MPH
24H 14/0600Z 28.4N 68.1W 90 KT 105 MPH
36H 14/1800Z 30.5N 68.3W 85 KT 100 MPH
48H 15/0600Z 33.0N 68.0W 80 KT 90 MPH
60H 15/1800Z 36.1N 67.4W 75 KT 85 MPH
72H 16/0600Z 39.6N 67.3W 70 KT 80 MPH
96H 17/0600Z 45.2N 67.3W 50 KT 60 MPH...POST-TROP/INLAND
120H 18/0600Z 51.0N 61.4W 35 KT 40 MPH...POST-TROP/INLAND
$$
Forecaster Berg
Hurricane Lee Discussion Number 33
NWS National Hurricane Center Miami FL AL132023
1100 AM AST Wed Sep 13 2023
Lee continues to exhibit concentric eyewalls, but there are some dry
slots between those features. An SSMIS microwave image around 10Z
showed that both eyewalls were open, however, recent infrared
satellite images indicate that the inner eyewall appears to be
becoming better organized during the past few hours. The initial
wind speed is held at 100 kt, but this is near the high end of the
latest satellite intensity estimates. The Air Force Hurricane
Hunters are scheduled to investigate Lee this afternoon, and the
data they collect should provide a better assessment of the
hurricane's intensity and structure.
Satellite images suggest that Lee seems to be beginning its
northward turn on the western side of a subtropical ridge situated
over the central Atlantic. The latest initial motion estimate is
345/6 kt. Lee should gradually increase in forward speed while
moving northward on the west side of the ridge during the next
couple of days, taking the core of the system to the west of Bermuda
Thursday and Thursday night. The combination of a shortwave trough
and a building ridge extending into Atlantic Canada could cause Lee
to turn slightly to the left Friday night and Saturday, which will
likely bring Lee close to southeastern New England before it reaches
Maine and Atlantic Canada later in the weekend. Confidence is
increasing in the forecast track, and the model spread is mostly
along-track, associated with the system's forward speed/timing.
Overall, little change was made to the previous NHC track forecast,
and it remains very near the various consensus models.
Lee is expected to gradually weaken as it moves into an environment
of increasing vertical wind shear, slightly drier air, and over
progressively cooler waters during the next few days. However, the
large size of the system suggests that the weakening process should
be slow. In addition, Lee is expected to grow in size as it gains
latitude during the next few days. The NHC intensity forecast is
largely the same as the previous one and fairly close to the HCCA
and IVCN models. Regardless of the details, there is high
confidence that Lee will be a large hurricane near the coast of New
England Friday night and Saturday.
It should again be noted that the 34- and 50-kt wind speed
probabilities beyond 36 hours in the text and graphical products are
likely underestimating the risk of those winds occurring. This is
because the forecast wind field of Lee is considerably larger than
average compared to the wind field used to derive the wind speed
probability product.
KEY MESSAGES:
1. Dangerous surf and life-threatening rip currents will affect
portions of the northern Leeward Islands, the Virgin Islands, Puerto
Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas,
Bermuda, the U.S East Coast, and Atlantic Canada into the weekend.
2. Tropical storm conditions, heavy rainfall, and high surf are
expected to impact Bermuda beginning early Thursday, and a Tropical
Storm Warning is in effect for the island.
3. There is an increasing risk of wind, coastal flooding, and rain
impacts from Lee in portions of New England and Atlantic Canada
beginning on Friday and continuing through the weekend. Watches
will likely required for portions of these areas later today or
tonight. Due to Lee's large size, hazards will extend well away
from the center, and there will be little to no significance on
exactly where the center reaches the coast.
FORECAST POSITIONS AND MAX WINDS
INIT 13/1500Z 26.4N 67.2W 100 KT 115 MPH
12H 14/0000Z 27.6N 67.7W 95 KT 110 MPH
24H 14/1200Z 29.6N 68.2W 90 KT 105 MPH
36H 15/0000Z 31.8N 68.2W 85 KT 100 MPH
48H 15/1200Z 34.6N 67.6W 80 KT 90 MPH
60H 16/0000Z 37.9N 67.1W 75 KT 85 MPH
72H 16/1200Z 41.1N 67.2W 70 KT 80 MPH
96H 17/1200Z 46.1N 66.6W 50 KT 60 MPH...POST-TROP/INLAND
120H 18/1200Z 52.1N 56.4W 35 KT 40 MPH...POST-TROP/INLAND
$$
Forecaster Cangialosi
Hurricane Lee Discussion Number 34
NWS National Hurricane Center Miami FL AL132023
500 PM AST Wed Sep 13 2023
The Air Force Hurricane Hunters investigated Lee earlier this
afternoon and found that the hurricane has lost some strength. The
initial intensity is lowered to 90 kt based on the aircraft data.
Although the core winds have decreased some, the wind field has
become quite expansive, with the hurricane-force winds now extending
roughly 100 n mi away from the center. The satellite appearance of
Lee has been relatively steady state through the day and there is
still evidence of concentric eyewalls.
Lee's forward speed is beginning to increase, and it is now moving
north-northwestward at 9 kt. A progressively faster motion to the
north on the west side of a subtropical ridge is forecast during the
next couple of days, taking the core of the system to the west of
Bermuda Thursday and Thursday night. The combination of a shortwave
trough over the Mid-Atlantic States and a building ridge extending
into Atlantic Canada should cause Lee to turn slightly to the left
Friday night and Saturday, which will likely bring Lee close to
southeastern New England before it moves near or over Maine and
Atlantic Canada later in the weekend. The GFS and ECMWF models
have converged, and are now near the previous NHC track forecast.
The new NHC track forecast is again just an update of the previous
one and near the various consensus models.
The environment ahead of Lee is expected to gradually become less
conducive for the hurricane as it moves into a region of higher
wind shear, drier air, and over progressively cooler SSTs. These
conditions favor weakening, but since the system is so large the
weakening process should be slow. The NHC intensity forecast is a
little lower than the previous one, in part due to the initial lower
wind speed, and remains near the HCCA and IVCN guidance.
Regardless of the details, there is high confidence that Lee will be
a large hurricane near the coast of New England Friday night and
Saturday.
It should again be noted that the 34- and 50-kt wind speed
probabilities beyond 36 hours in the text and graphical products are
likely underestimating the risk of those winds occurring. This is
because the forecast wind field of Lee is considerably larger than
average compared to the wind field used to derive the wind speed
probability product.
KEY MESSAGES:
1. Tropical storm conditions, heavy rainfall, and high surf are
expected to impact Bermuda beginning early Thursday, and a Tropical
Storm Warning is in effect for the island.
2. Hurricane conditions, heavy rainfall, and coastal flooding are
possible in portions of eastern Maine on Saturday, and a Hurricane
Watch has been issued for that area.
3. There is the potential for life-threatening storm surge flooding
in portions of southeastern Massachusetts, including Cape Cod and
Nantucket, late Friday and Saturday, where a Storm Surge Watch has
been issued.
4. Tropical storm conditions are possible over a large portion of
coastal New England, including Cape Cod, Nantucket, Martha's
Vineyard, and Block Island, where a Tropical Storm Watch has been
issued.
FORECAST POSITIONS AND MAX WINDS
INIT 13/2100Z 27.4N 67.6W 90 KT 105 MPH
12H 14/0600Z 28.7N 68.1W 90 KT 105 MPH
24H 14/1800Z 30.9N 68.2W 85 KT 100 MPH
36H 15/0600Z 33.4N 67.8W 80 KT 90 MPH
48H 15/1800Z 36.4N 67.2W 75 KT 85 MPH
60H 16/0600Z 39.7N 66.9W 70 KT 80 MPH
72H 16/1800Z 42.6N 66.9W 65 KT 75 MPH
96H 17/1800Z 47.7N 63.8W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 18/1800Z 52.3N 52.1W 35 KT 40 MPH...POST-TROP/EXTRATROP
$$
Forecaster Cangialosi
Hurricane Lee Discussion Number 35
NWS National Hurricane Center Miami FL AL132023
1100 PM AST Wed Sep 13 2023
Both NOAA and Air Force Reserve Unit Hurricane Hunter aircraft have
been investigating Lee this evening. They found that the central
pressure has not changed much since earlier today, and that the
hurricane still had concentric eyewalls, but these were partially
open over portions of the western quadrant. The Air Force
plane measured 700 mb flight-level winds as high as 105 kt and
the NOAA plane found winds as high as 107 kt at a flight level of
8000 ft. Tail Doppler radar velocities from the NOAA plane were
near 100 kt at elevations of 0.5 km. These observations support
maintaining the intensity at 90 kt for this advisory. Satellite
imagery also suggests that the eyewall is not fully closed but
there is fairly intense inner-core convection.
There has been a (likely temporary) decrease in forward speed and
the initial motion is just west of due north or 350/8 kt. The
steering scenario for the hurricane is essentially unchanged from
the previous few advisories. A 500-mb trough moving into the
northeastern U.S. and a mid-level ridge near eastern Atlantic
Canada should cause Lee to move generally northward at a faster
forward speed during the next couple of days. A slight bend to the
left is likely around 48 hours while the tropical cyclone interacts
with the trough. This will likely bring the center of Lee close to
southeastern New England late Friday before it moves near or over
Maine and Atlantic Canada later in the weekend. The official track
forecast is similar to the previous one and closely follows both the
simple and corrected dynamical consensus guidance.
Over the next couple of days, Lee will encounter significantly
increasing vertical wind shear and somewhat drier mid- to low-level
air. Sea surface temperatures along the projected track decrease
sharply north of around 40N latitude. These conditions should cause
weakening, but since the hurricane has such a large circulation, the
weakening will likely be slow. The NHC intensity forecast is near
or above the highest available model guidance. Notwithstanding,
there is still high confidence that Lee will be a large and
dangerous cyclone when it moves near or over land on Saturday.
It should again be noted that the 34- and 50-kt wind speed
probabilities beyond 36 hours in the text and graphical products are
likely underestimating the risk of those winds occurring. This is
because the forecast wind field of Lee is considerably larger than
average compared to the wind field used to derive the wind speed
probability product.
KEY MESSAGES:
1. Tropical storm conditions, heavy rainfall, and high surf are
expected to impact Bermuda beginning early Thursday, and a Tropical
Storm Warning is in effect for the island.
2. Hurricane conditions and coastal flooding are possible in
portions of eastern Maine, southern New Brunswick, and western Nova
Scotia on Saturday, and a Hurricane Watch has been issued for that
area. Heavy rainfall in these areas may produce localized urban
and small stream flooding from Friday night into Saturday night.
3. There is the potential for life-threatening storm surge flooding
in portions of southeastern Massachusetts, including Cape Cod and
Nantucket, late Friday and Saturday, where a Storm Surge Watch has
been issued.
4. Tropical storm conditions are possible over a large portion of
coastal New England, including Cape Cod, Nantucket, Martha's
Vineyard, Block Island, and portions of Atlantic Canada, where a
Tropical Storm Watch has been issued.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0300Z 28.0N 67.7W 90 KT 105 MPH
12H 14/1200Z 29.6N 68.1W 90 KT 105 MPH
24H 15/0000Z 31.9N 68.0W 85 KT 100 MPH
36H 15/1200Z 34.8N 67.2W 80 KT 90 MPH
48H 16/0000Z 37.7N 66.5W 75 KT 85 MPH
60H 16/1200Z 41.0N 66.7W 65 KT 75 MPH
72H 17/0000Z 44.0N 66.3W 60 KT 70 MPH
96H 18/0000Z 49.4N 60.9W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 19/0000Z 53.7N 50.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
$$
Forecaster Pasch
Hurricane Lee Discussion Number 36
NWS National Hurricane Center Miami FL AL132023
500 AM AST Thu Sep 14 2023
Lee's satellite presentation has been a little deceiving early this
morning, as earlier reconnaissance flight-level and dropsonde
surface wind data indicated that the hurricane's center was located
about 15-20 n mi to the west of the satellite eye feature. On the
last couple of passes of the Air Force Reserve C-130 through the
center, the highest 700-mb wind measured was 95 kt, and peak SFMR
readings from both the Air Force and NOAA were 70-75 kt. Accounting
for some undersampling, Lee's initial intensity is reduced slightly
to 85 kt.
The initial motion remains 350/8 kt. A faster northward motion,
with some wobbles, is expected during the next 2-3 days as Lee
moves between a mid-tropospheric high over the west-central Atlantic
and a deep-layer trough over the eastern United States. As noted
in earlier forecasts, a slight bend to the west toward the Gulf
of Maine is likely in 48-60 hours when Lee interacts with the tail
end of the trough over the Mid-Atlantic states. A turn toward the
north-northeast and then northeast is forecast on days 3 and 4,
bringing Lee's center across Atlantic Canada. The NHC track
forecast is nearly on top of the previous forecast, largely due to
consistent and tightly clustered model guidance.
The latest shear analyses suggest that moderate southwesterly shear
has begun to affect Lee, and this is confirmed by the offset of
the aircraft fixes relative to the satellite eye feature. The
shear is forecast to increase further in 24-36 hours, which will
cause Lee to ingest drier and more stable air into its circulation.
In addition, sea surface temperatures along Lee's future path drop
off significantly after 36 hours. Therefore, continued gradual
weakening is forecast, and the NHC intensity forecast is at or
slightly above the intensity consensus aids for much of the
forecast period. Extratropical transition is likely to begin on
Friday as Lee interacts with a frontal boundary moving off the east
coast of the United States, and a good chunk of the guidance
suggests the transition could be complete by 60 hours. In order to
maintain continuity with the previous forecast, Lee is now shown to
be a fully post-tropical cyclone by 72 hours. Regardless of its
designation, Lee will remain a large and dangerous cyclone while it
approaches eastern New England and Atlantic Canada into the weekend.
KEY MESSAGES:
1. Tropical storm conditions, heavy rainfall, and high surf are
beginning to impact Bermuda, and a Tropical Storm Warning is in
effect for the island.
2. Hurricane conditions and coastal flooding are possible in
portions of eastern Maine, southern New Brunswick, and western Nova
Scotia on Saturday, and a Hurricane Watch is in effect for that
area. Heavy rainfall in these areas may produce localized urban
and small stream flooding from Friday night into Saturday night.
Tropical storm conditions are possible elsewhere across New England
and Atlantic Canada within the Tropical Storm Watch areas.
3. There is the potential for life-threatening storm surge flooding
in portions of southeastern Massachusetts, including Cape Cod and
Nantucket, late Friday and Saturday, where a Storm Surge Watch is
in effect.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0900Z 29.1N 68.1W 85 KT 100 MPH
12H 14/1800Z 30.7N 68.2W 80 KT 90 MPH
24H 15/0600Z 33.3N 67.7W 80 KT 90 MPH
36H 15/1800Z 36.3N 66.9W 75 KT 85 MPH
48H 16/0600Z 39.5N 66.6W 70 KT 80 MPH
60H 16/1800Z 42.5N 66.7W 60 KT 70 MPH
72H 17/0600Z 45.2N 65.4W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 18/0600Z 50.2N 58.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 19/0600Z 54.6N 45.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
$$
Forecaster Berg
Hurricane Lee Discussion Number 37
NWS National Hurricane Center Miami FL AL132023
1100 AM AST Thu Sep 14 2023
The satellite presentation of Lee has degraded over the past day or
so. An eye is no longer apparent but deep convection continues to
wrap around the eastern and northern portions of the circulation.
Deep convection has waned over the southwestern portions of the
cyclone, likely due to an increase in southwesterly vertical wind
shear and dry air entrainment. An Air Force Reserve reconnaissance
aircraft that has been investigating Lee this morning has measured
peak 700-mb flight-level winds of 96 kt, and the NOAA P-3 aircraft
has found peak 8000 ft flight-level winds of 100 kt. However, peak
SFMR winds from both aircraft have been around 70 kt. Using a blend
of the flight-level and SFMR data, the initial wind speed has been
lowered to 80 kt, but this could be a little generous.
Lee is moving northward at a slightly faster forward speed of 12 kt.
A faster northward to north-northeastward motion is expected during
the next day or so around the western side of a mid-level ridge over
the central Atlantic. A slight bend to the north-northwest toward
the Gulf of Maine is likely late Friday or early Saturday as the
southern extent of mid-latitude trough moves off the Mid-Atlantic
coast. After that time, Lee is forecast to turn northeastward over
Atlantic Canada. The dynamical model guidance is tightly clustered
and only minor adjustments were made to the previous official
forecast. The NHC track is close to a blend of the typically
reliable GFS and ECMWF models.
Southwesterly vertical wind shear is expected to increase over Lee
during the next 24 to 36 hours, and this is likely to lead to
gradual weakening during that time. Sea surface temperatures will
decrease significantly just after 36 hours when Lee moves north of
the Gulf Stream. The global model guidance suggests that Lee will
begin extratropical transition Friday night and this is likely to be
completed within 48 hours, if not a little sooner. The NHC
intensity forecast is a blend of the HFIP corrected consensus and
and the IVCN consensus model. It can't be stressed enough, that
regardless of Lee's designation, it will remain a large and
dangerous cyclone while it approaches eastern New England and
Atlantic Canada.
KEY MESSAGES:
1. Tropical storm conditions, heavy rainfall, and high surf will
continue to impact Bermuda through Friday morning, and a Tropical
Storm Warning is in effect for the island.
2. Hurricane conditions and coastal flooding are possible in
portions of eastern Maine, southern New Brunswick, and western Nova
Scotia on Saturday, and a Hurricane Watch is in effect for that
area. Tropical storm conditions are expected on Cape Cod, Martha's
Vineyard, and Nantucket where a Tropical Storm Warning is now in
effect. Tropical storm conditions are possible elsewhere across New
England and Atlantic Canada within the Tropical Storm Watch areas.
3. Heavy rainfall from Lee may produce localized urban and small
stream flooding across eastern New England and into portions of New
Brunswick and Nova Scotia from Friday night into Saturday night.
4. There is the potential for life-threatening storm surge flooding
in portions of southeastern Massachusetts, including Cape Cod and
Nantucket, late Friday and Saturday, where a Storm Surge Watch is in
effect.
FORECAST POSITIONS AND MAX WINDS
INIT 14/1500Z 30.4N 68.3W 80 KT 90 MPH
12H 15/0000Z 32.2N 68.0W 75 KT 85 MPH
24H 15/1200Z 35.0N 67.2W 70 KT 80 MPH
36H 16/0000Z 38.2N 66.6W 70 KT 80 MPH
48H 16/1200Z 41.5N 66.5W 65 KT 75 MPH
60H 17/0000Z 44.0N 66.1W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 17/1200Z 47.0N 63.6W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 18/1200Z 52.6N 52.2W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 19/1200Z...DISSIPATED
$$
Forecaster Brown
Hurricane Lee Discussion Number 38
NWS National Hurricane Center Miami FL AL132023
500 PM AST Thu Sep 14 2023
There has been little overall change to the satellite presentation
of Lee since the previous advisory. Deep convection continues to
develop near the center, but it is primarily confined to the
northern portion of the circulation. Southwesterly shear and dry
air entrainment is disrupting the convective banding over the
southern portion of the storm. The initial intensity was lowered
to 75 kt on the 1800 UTC intermediate advisory, and was based
on data from the Air Force Reserve reconnaissance aircraft that was
in the storm through midday. The initial wind speed remains at
that value for this advisory. The next reconnaissance mission is
scheduled to investigate Lee this evening. The early aircraft data
along with a couple of fortuitous ASCAT overpasses showed that the
wind field of Lee has continued to expand. The 50-kt wind radii
extend outward up to 170 n mi over the eastern semicircle of the
storm. NOAA buoy 41048 located about 75 miles (120 km) west of the
center of Lee has recently reported a peak one-minute sustained wind
of 58 kt and a gust to 76 kt and wave heights of around 30 ft.
Bermuda, located more than 220 miles east-northeast of the center
has also reported sustained tropical-storm force winds today.
Lee is moving northward at about 13 kt, which is slightly faster
than before. Lee should continue to pick up some forward speed as
it moves northward around the western side of a mid-level ridge
over the central Atlantic during the next 12-24 hours. After that
time a slight bend to the north-northwest is likely late Friday or
early Saturday, and this motion should bring the center of Lee near
or over southwestern Nova Scotia late Saturday. After that time,
Lee is forecast to turn northeastward over Atlantic Canada. The
track guidance is still in good agreement, and no significant
changes to the previous official forecast were required.
Increasing southwesterly vertical wind shear and dry air entrainment
could cause some additional weakening, but baroclinic forcing
during the early stages of Lee's extratropical transition may help
to maintain the cyclone's intensity through Friday. By Friday
night Lee will be moving over significantly cooler sea surface
temperatures, and gradual weakening is expected after that time.
Lee is forecast to complete its transition into an extratropical
cyclone when it nears Atlantic Canada. Regardless of Lee's
designation when it approaches New England and Atlantic Canada, it
will remain a very large and dangerous cyclone through landfall.
KEY MESSAGES:
1. Tropical storm conditions, heavy rainfall, and high surf will
continue to impact Bermuda through Friday morning, and a Tropical
Storm Warning is in effect for the island.
2. Hurricane conditions and coastal flooding are possible in
portions of eastern Maine, southern New Brunswick, and western Nova
Scotia on Saturday, and a Hurricane Watch is in effect for that
area. Tropical storm conditions and coastal flooding are expected
to begin in southern New England on Friday afternoon, and spread
northward along the coast of New England through Saturday where
Tropical Storm warnings are in effect.
3. Heavy rainfall from Lee may produce localized urban and small
stream flooding across eastern New England and into portions of New
Brunswick and Nova Scotia from Friday night into Saturday night.
FORECAST POSITIONS AND MAX WINDS
INIT 14/2100Z 31.7N 68.3W 75 KT 85 MPH
12H 15/0600Z 33.8N 67.9W 75 KT 85 MPH
24H 15/1800Z 37.0N 66.9W 75 KT 85 MPH
36H 16/0600Z 40.3N 66.6W 70 KT 80 MPH
48H 16/1800Z 43.3N 66.4W 60 KT 70 MPH...POST-TROP/EXTRATROP
60H 17/0600Z 46.0N 65.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 17/1800Z 48.6N 61.4W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 18/1800Z 53.7N 48.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 19/1800Z...DISSIPATED
$$
Forecaster Brown