2023 Hurricane Season Discussion

General Weather Discussions and Analysis
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tireman4
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000
WTNT44 KNHC 130854
TCDAT4

Hurricane Margot Discussion Number 24
NWS National Hurricane Center Miami FL AL142023
900 AM GMT Wed Sep 13 2023

The eye of Margot has been obscured by clouds to varying degrees
overnight, but has begun to warm in the latest infrared satellite
images this morning. Recent AMSR2 microwave images reveal the
hurricane has a compact inner core, with a concentric outer ring of
convection that is broken to the northwest. Earlier scatterometer
data indicated a secondary wind maximum exists within this outer
band. The vortex is slightly tilted with height, as the mid-level
89-GHz eye lies to the southwest of the 37-GHz center. The
intensity for this advisory remains 75 kt based on consensus T4.5
Dvorak classifications from TAFB and SAB.

Margot has begun to slow down while moving northward (350/10 kt)
within the flow between a deep-layer ridge over the eastern Atlantic
and a narrow upper trough to its west. A general northward motion
should continue over the next day or so before the track forecast
becomes very challenging. Margot is forecast to become caught in
weak steering currents, with the global models showing a blocking
ridge developing to the north of the cyclone by late week into the
weekend. There are significant differences between the GFS and ECMWF
with regards to the strength and position of this ridge, which has
large implications in the longer-range track of Margot. Based on the
overall shift in the guidance suite this cycle, the latest NHC
forecast shows little net motion between 36-72 h as Margot meanders
over the central Atlantic. This is a fairly large departure from the
previous advisory, but better represents the latest consensus track
solutions. At days 4-5, most models (except for the ECMWF) show the
ridge sliding eastward, but overall track forecast confidence is
very low and larger future adjustments could be necessary.

It is possible that Margot is at or near its peak intensity. The
deep-layer shear is forecast to increase during the next 24 h, and
thereafter the coupled atmosphere-ocean models indicate the slow
motion of the storm is likely to result in upwelling of cooler
waters. In addition, the surrounding environment is expected to
become drier and more subsident by this weekend. The NHC intensity
forecast has been lowered from the previous one and shows steady
weakening beyond 36 h, in good agreement with the latest HCCA and
IVCN aids. Although this forecast keeps Margot a tropical cyclone
through day 5, simulated satellite imagery from the global models
suggests these environmental factors could cause the system to lose
organized convection and become post-tropical early next week.


FORECAST POSITIONS AND MAX WINDS

INIT 13/0900Z 33.6N 40.0W 75 KT 85 MPH
12H 13/1800Z 34.5N 40.5W 75 KT 85 MPH
24H 14/0600Z 35.6N 40.5W 70 KT 80 MPH
36H 14/1800Z 36.5N 39.9W 70 KT 80 MPH
48H 15/0600Z 36.9N 39.5W 65 KT 75 MPH
60H 15/1800Z 36.7N 39.4W 60 KT 70 MPH
72H 16/0600Z 36.5N 39.7W 55 KT 65 MPH
96H 17/0600Z 36.5N 42.5W 45 KT 50 MPH
120H 18/0600Z 38.0N 43.0W 40 KT 45 MPH

$$
Forecaster Reinhart
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I’m sorry, but Lee is an ugly looking hurricane. I’m not at all impressed with its presentation. It almost looks subtropical.
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tireman4
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From Senor 57

More like 75 kts in NE quadrant. Could make an argument that there may be higher winds not sampled, so maybe 80 kts now. Not even a Cat 2. 100kts was too high, even for last evening. I can't see NHC dropping 2 categories from one advisory to another, so I bet they go 85-90 kts. Surprise me, NHC.
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tireman4
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193
WTNT43 KNHC 131438
TCDAT3

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
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tireman4
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000
WTNT44 KNHC 131456
TCDAT4

Hurricane Margot Discussion Number 25
NWS National Hurricane Center Miami FL AL142023
Issued by the NWS Weather Prediction Center College Park MD
300 PM GMT Wed Sep 13 2023

Margot continues to exhibit a double eyewall structure based on
a recent SAR pass over the storm, with a well-defined inner core.
GOES-16 IR data shows the inner-eye feature occasionally obscured by
clouds, but overall the organization of Margot has changed little
over the last several hours. The latest microwave data in
conjunction with the SAR pass suggests the initial intensity may be
just a tad stronger compared to continuity, and so it will be set at
80 kt for this advisory.

Margot is slowing down as it moves within the flow between a
deep-layer ridge over the eastern Atlantic and a narrow upper trough
to its west. A general north to north-northwest motion should
continue over the next day or so before the track forecast becomes
very challenging. Margot is expected to become caught in weak
steering currents, with the global models showing a blocking ridge
developing to the north of the cyclone by late week into the
weekend. There are significant differences between the GFS and ECMWF
with regards to the strength and position of this ridge, which has
large implications in the longer-range track of Margot. The overall
consensus of the guidance suggests that Margot could make a
clockwise loop as the ridge builds, and the latest NHC forecast
shows little net motion between 36-72 hrs as the cyclone meanders
over the central Atlantic. At days 4-5, most models (except for the
ECMWF) show the ridge sliding eastward, allowing for Margot to
gain latitude, and the overall track forecast confidence remains
low.

The deep-layer shear is forecast to increase during the next 24 to
36 hrs, and this coupled with a likelihood of the upwelling of
cooler waters should result in a weakening trend. Drier air
surrounding the storm will also be a factor in causing a weakening
cyclone going into the weekend. The NHC intensity forecast is close
to the previous forecast and shows gradual decrease in strength
through 72 hrs, and in good agreement with the consensus of the
intensity aids. Although this forecast keeps Margot a tropical
cyclone through day 5, simulated satellite imagery from the global
models suggests these environmental factors could cause the system
to lose organized convection and become post-tropical early next
week as the storm lingers west of the Azores.


FORECAST POSITIONS AND MAX WINDS

INIT 13/1500Z 34.1N 40.4W 80 KT 90 MPH
12H 14/0000Z 35.0N 40.7W 75 KT 85 MPH
24H 14/1200Z 36.0N 40.2W 75 KT 85 MPH
36H 15/0000Z 36.8N 39.5W 70 KT 80 MPH
48H 15/1200Z 36.9N 39.4W 65 KT 75 MPH
60H 16/0000Z 36.5N 39.4W 60 KT 70 MPH
72H 16/1200Z 36.3N 40.2W 50 KT 60 MPH
96H 17/1200Z 36.0N 42.5W 45 KT 50 MPH
120H 18/1200Z 38.0N 42.5W 45 KT 50 MPH

$$
Forecaster Orrison/Blake
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tireman4
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From 57..

It appears that with the ingestion of last evening's G-IV dropsonde data into the models, they've come into better agreement on a track to western Nova Scotia Saturday evening. Still will see TS wind all along the NE U.S. coast Saturday, though.
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tireman4
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From the Eyewall..

Lee was determined to be post-tropical, which means it’s now essentially a gigantic nor’easter instead of a tropically-derived hurricane. It means absolutely nothing other than a classification change. Impacts are identical to forecast.

Lee is flinging very heavy rain onshore in Maine right now, with a band of torrential rain between Fredericton, NB and Acadia National Park.

Meanwhile, wind gusts have been ticking up around the region, with Grand Manan as high as 123 km/hr (77 mph), Halifax as high as 117 km/hr (73 mph), Mt. Washington, NH to 74 mph, St. John, NB to 85 km/hr (53 mph), Nantucket to 55 mph, and Eastport, ME to 62 mph.

The high tide cycle ongoing right now, as well as the next one this evening will be the highest for these areas. Yarmouth, NS is seeing about a 0.6m (2 ft) surge, Halifax 0.7m, and St. John about 0.5m. These are generally in line with expectations, maybe a smidge under. Surge of up to 1.5m (5 ft) is possible in Nova Scotia. With Lee’s center still technically south of Nova Scotia, the highest surge is yet to come. In addition, some potent waves will be coming ashore in Nova Scotia as well, with a buoy near Lee’s center at 8 AM AST reporting 30 foot waves.

So I think the takeaway here right now: Worst is over for southern New England, and it was handled pretty well as expected. Maine, particularly Downeast are in the height of the storm now, and it will wind down this afternoon. Nova Scotia, New Brunswick, and PEI will be in the height of the storm shortly if not already, and it will wind down tonight.
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No concern to us at all but southern Florida might need to watch out for a storm here within 10 days or so.
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