2023 Hurricane Season Discussion

General Weather Discussions and Analysis
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tireman4
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Eric Webb
@webberweather
The entire mid-latitude wave pattern over the western hemisphere is significantly amplifying and slowing in the medium range (likely in response to extratropical wave activity changes over the West Pacific).

This ultimately triggers a deeper trough + ridge couplet near #TD13/#Lee as it enters the western Atlantic next week, slowing the steering currents down + encouraging the storm to come further west/closer to the US East Coast & Atlantic Canada.

Moral of the story here: be real careful to assume that #TD13/#Lee is going to be a “fish storm.” Long ways to go
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Even the northeast Caribbean needs to monitor. Irma was forecast 3 days before impact to move north of the Caribbean.Models and forecasters have improved significantly since Irma, however
-- Derek Ortt (@DerekOrtt) September 5, 2023
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000
WTNT43 KNHC 052054
TCDAT3

Tropical Storm Lee Discussion Number 2
NWS National Hurricane Center Miami FL AL132023
500 PM AST Tue Sep 05 2023

1-min GOES-16 satellite imagery shows that the tropical cyclone has
been improving in structure throughout the day, with additional
curved banding features and a new burst of convection near the
center. A late-arriving ASCAT-C pass indicated maximum winds
supporting 35 kt, and the satellite presentation has notably
improved since that time. The initial wind speed is set to 40 kt
to match the satellite trends.

Lee is moving west-northwestward at about 14 kt. There are no
significant changes to the NHC track forecast with a mid-level ridge
over the central Atlantic likely to persist to the north of the
storm. This ridge should provide a steady steering current, with a
general west-northwestward course expected through the weekend with
some reduction in forward speed. The spread in the model guidance
remains low, and the official forecast is adjusted a bit to the
northeast closer to the model consensus. Still, it is too early to
determine exactly how close this system will be to the Leeward
Islands given the average track forecast error at those time ranges.

It is becoming a question of when and not if rapid intensification
(RI) occurs with Lee. A well-defined outflow pattern has developed
over the circulation, and there are some hints on a recent SSMI/S
microwave pass that parts of an inner core are forming. There's
still some notable northeasterly shear that could keep Lee in
check for the next day or two, so the NHC intensity forecast will
stay at a more moderate rate of intensification during that time.
All of the models decrease the shear by Friday, so RI is explicitly
forecast at that time frame while Lee is moving over extremely warm
waters. The new forecast is adjusted higher than the last advisory,
near the model consensus, but there's a notable contingent of
guidance higher than this forecast. There is increasing confidence
on Lee becoming a very powerful hurricane by this weekend.

KEY MESSAGES:

1. Lee is forecast to become a major hurricane by this weekend and
could bring impacts to the Leeward Islands by that time. While it
is too soon to determine the location and magnitude of these
possible impacts, interests in this area should monitor the
progress of Lee and further updates to the forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 13.2N 41.8W 40 KT 45 MPH
12H 06/0600Z 13.7N 43.7W 50 KT 60 MPH
24H 06/1800Z 14.4N 46.2W 60 KT 70 MPH
36H 07/0600Z 15.2N 48.5W 70 KT 80 MPH
48H 07/1800Z 16.2N 51.0W 80 KT 90 MPH
60H 08/0600Z 17.2N 53.6W 90 KT 105 MPH
72H 08/1800Z 18.3N 56.0W 110 KT 125 MPH
96H 09/1800Z 20.4N 60.5W 120 KT 140 MPH
120H 10/1800Z 22.2N 64.3W 125 KT 145 MPH

$$
Forecaster Blake
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tireman4
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We might be seeing the start of #Lee's rapid intensification phase, as convective bursts start to wrap around what appears to be a healthy mid-level eye (based on microwave imagery). pic.twitter.com/Ops1YmldLP
-- Andy Hazelton (@AndyHazelton) September 7, 2023
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000
WTNT43 KNHC 071459
TCDAT3

Hurricane Lee Discussion Number 9
NWS National Hurricane Center Miami FL AL132023
1100 AM AST Thu Sep 07 2023

Lee is rapidly intensifying. Early this morning, a well-defined
low-to mid-level eye was observed in microwave imagery, a signal
that is often a precursor rapid intensification (RI). Since then,
Lee has developed an eye in visible and infrared imagery, with
subjective Dvorak Data-T estimates quickly increasing to as high as
5.5 during the past hour or so. Satellite classifications supported
an intensity of around 80 kt at 1200 UTC, but given the significant
improvement in Lee's appearance since then, the advisory intensity
is set at 90 kt.

The track guidance remains in very good agreement on the forecast
for Lee through the weekend and confidence in the track forecast is
high. Lee should continue west-northwestward, gradually slowing its
forward speed, moving along the southern periphery of a subtropical
ridge over the central Atlantic. Confidence continues to increase
that Lee will pass north of the northern Leeward Islands, though
swells associated with Lee will affect the islands starting
tomorrow. By the end of the forecast, the uncertainty is a little
higher, with the hurricane models (HAFS, HWRF) generally being
farther south than the global models. Very small changes were made
to the NHC track forecast, which is between the HCCA and simple
consensus aids.

As stated above, RI is occuring, and will likely continue today. The
question doesn't appear to be if RI continues, but rather how
strong Lee will get, and how quickly will it get there. Many of the
models are calling for remarkable rates of intensification, beyond
rates normally seen with model forecasts. Both HAFS models forecast
Lee to exceed 150 kt within the next 2 days, and even HCCA brings
the hurricane above the category 5 threshold. The NHC intensity
forecast has been shifted significantly higher, but is actually
within the guidance envelope. It should be stressed that internal
dynamics (eyewall replacement cycles) will become a factor with the
maximum strength of Lee as it becomes a major hurricane. This
is almost certain to lead to fluctuations in intensity that are
beyond our ability to forecast at these lead times. Hurricane Hunter
aircraft are scheduled to investigate Lee beginning this evening and
overnight, which should provide extremely useful information about
Lee's intensity during the coming days.


KEY MESSAGES:

1. Lee is forecast to become a major hurricane later today, with
its core moving north of the northern Leeward Islands, the Virgin
Islands, and Puerto Rico this weekend and early next week. The
potential for tropical storm conditions to occur in the islands is
decreasing, but residents there should continue to monitor updates
on Lee.

2. Swells generated by Lee are expected to reach portions of the
Lesser Antilles on Friday, and the British and U.S. Virgin Islands,
Puerto Rico, Hispaniola, the Bahamas, and Bermuda this weekend.
These swells are likely to cause life-threatening surf and rip
current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 16.4N 50.0W 90 KT 105 MPH
12H 08/0000Z 17.1N 51.7W 115 KT 130 MPH
24H 08/1200Z 18.2N 54.0W 130 KT 150 MPH
36H 09/0000Z 19.2N 56.1W 140 KT 160 MPH
48H 09/1200Z 20.1N 58.1W 140 KT 160 MPH
60H 10/0000Z 20.9N 59.8W 135 KT 155 MPH
72H 10/1200Z 21.5N 61.2W 135 KT 155 MPH
96H 11/1200Z 22.6N 63.7W 125 KT 145 MPH
120H 12/1200Z 23.6N 66.0W 120 KT 140 MPH

$$
Forecaster D. Zelinsky
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tireman4
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Good Bye Franklin

Northeastern Atlantic (ex-Franklin):
Shower and thunderstorm activity associated with Post-Tropical
Cyclone Franklin, located a few hundred miles west-northwest of the
northwestern coast of Spain, have diminished this afternoon.
Environmental conditions are becoming increasing unfavorable, and
development is no longer expected, as the system meanders northwest
of Spain and Portugal. For additional information, including gale
warnings, see High Seas Forecasts issued by Meteo France.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...near 0 percent.
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We'll need to carefully monitor trends in the upper air pattern to see if the ridging N/NW of Hurricane #Lee contnues to trend stronger, which would encourage it to bend Wearly next week and increase the risk of a longer-term track close enough to bring impacts to the NE US coast
-- Yaakov Cantor (@yconsor) September 7, 2023
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From Mr. 57....

Came across a very good tropical models page from a Univ. of OK PHD student. Has a multi-model ensemble plot of Lee using the GFS, EC, CMC, and UKMET ensembles. Lots of other stuff, too.

Select "Cumulative Plots", "Total Density (no lines)" for the graphic that shows the probability of the center passing within 150km of a point using all 4 ensembles.

http://arctic.som.ou.edu/tburg/products ... m=AL132023
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Hurricane Lee
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Hurricane Lee
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URNT12 KWBC 081208
VORTEX DATA MESSAGE AL132023
A. 08/11:41:56Z
B. 17.88 deg N 054.05 deg W
C. NA
D. 941 mb
E. 165 deg 11 kt
F. CLOSED
G. E04/14/9
H. 121 kt
I. 349 deg 5 nm 11:40:37Z
J. 080 deg 134 kt
K. 353 deg 7 nm 11:40:07Z
L. 97 kt
M. 173 deg 9 nm 11:44:32Z
N. 254 deg 113 kt
O. 173 deg 8 nm 11:44:12Z
P. 15 C / 2450 m
Q. 26 C / 2445 m
R. 19 C / NA
S. 12345 / NA
T. 0.01 / 1 nm
U. NOAA3 0313A LEE OB 15
MAX FL WIND 134 KT 353 / 7 NM 11:40:07Z
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Mr 57 concerning Lee

Once Lee reaches the latitude of Cape Cod, it will be in the process of becoming ET. It's wind field will double in size, with TS winds raking the coast of Maine down to as far west as eastern Long Island. Max winds may only be 50-60 kts by then and 50 kts at final landfall. Even though the pressure will be quite low, the expansion of the wind field will reduce the pressure gradient and max sustained winds will drop. TS wind may extend out to 250 miles west of its center as it passes Cape Cod.
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Margot...

Tropical Storm Margot Discussion Number 16
NWS National Hurricane Center Miami FL AL142023
900 AM GMT Mon Sep 11 2023

This morning's satellite presentation consists of an isolated area
of deep convection near Margot's surface center and a curved band
displaced about 160 mi to the northeast beneath upper-level
southerly diffluent flow. This distinctive cloud pattern is a
result of very dry mid-tropospheric air intruding from the
southwest and wrapping around and into the northeast sector of the
cyclone. The Dvorak satellite intensity estimates from TAFB and
SAB haven't changed since last night, and the initial intensity is
held at 55 kt for this advisory.

The latest GFS and ECMWF sounding analyses show modest northwesterly
shear undercutting the diffluent southerly flow aloft while drying
and stabilizing the mid-level portion of the atmosphere. In fact,
the statistical-dynamic SHIPS indicates 40 to 50% relative humidity
in the surrounding environment. The deterministic and SHIPS models
still indicate, however, that the upper-level trough providing these
inhibiting conditions will lift northeastward soon, allowing
anticyclonic upper-tropospheric flow to develop over Margot. As a
result, the cyclone should strengthen, and the NHC intensity
forecast follows suit and indicates the cyclone becoming a hurricane
in less than 24 hours while intensifying further through mid-week.
Weakening is predicted beyond day 3 as the thermodynamic environment
in the mid-latitudes of the central Atlantic becomes even less
favorable. The official intensity forecast follows the HFIP HCCA
corrected consensus intensity model through 48 hours, then is based
on a blend of the HCCA, Decay SHIPS, and the IVCN intensity aids.

Margot's initial motion during the past 12 hours has been north, or
360/7 kt. A mid-tropospheric subtropical ridge extending from west
Africa to the eastern subtropical Atlantic should steer the cyclone
in a generally northward trajectory through an amplified weakness
over the central Atlantic over the next 72 hours. Through the
remaining period, Margot is expected to slow in forward speed, and
possibly meander, in response to high pressure building to the
north of the cyclone over the central north Atlantic. The NHC
forecast track is adjusted slightly to the right beyond 48 hours,
and lies between the previous forecast and the TVCA simple average
multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 25.3N 40.0W 55 KT 65 MPH
12H 11/1800Z 26.6N 39.9W 60 KT 70 MPH
24H 12/0600Z 28.6N 39.8W 70 KT 80 MPH
36H 12/1800Z 30.8N 40.1W 75 KT 85 MPH
48H 13/0600Z 32.7N 40.8W 75 KT 85 MPH
60H 13/1800Z 34.0N 41.7W 75 KT 85 MPH
72H 14/0600Z 35.0N 42.0W 75 KT 85 MPH
96H 15/0600Z 36.7N 41.0W 70 KT 80 MPH
120H 16/0600Z 37.1N 40.9W 60 KT 70 MPH

$$
Forecaster Roberts
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This FL wind data screams eyewall replacement cycle due to the double wind maxima. At this rate, the window of intensification is closing for #Lee & y’all can say the chances of rapid intensification are on the very edge of the table if not falling off. #tropicswx https://t.co/zt52sPVcIl pic.twitter.com/QPLQmnU90g
-- Vorti𝕏 (@VortixWx) September 11, 2023
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tireman4
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#Lee’s eyewall is partially open to the south side, likely due to some shear still hanging around. With this kind of structure, if things don’t improve, it would be rather hard to rapidly intensify. The most recent VDM also tells the same story. Shear is still hanging on. #tropicswx
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I know anything can happen but.... how is the GOM looking for any potential patterns for the rest of September?
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The pattern down the road spells good news for texas, I think we are very likely safe from anymore threats with the frequent troughing over the SE us, id say the eastern gulf has a more higher threat for getting hit, id say odds of texas getting hit are now less than 5%, so very unlikely anything comes this way
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Stratton20 wrote: Mon Sep 11, 2023 11:39 am The pattern down the road spells good news for texas, I think we are very likely safe from anymore threats with the frequent troughing over the SE us, id say the eastern gulf has a more higher threat for getting hit, id say odds of texas getting hit are now less than 5%, so very unlikely anything comes this way
I’m done with this years hurricane season. I’m trying to find out more about next years season, which as of right now, appears to be much more active in the Gulf.
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ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM

Hurricane Lee Discussion Number 25
NWS National Hurricane Center Miami FL AL132023
1100 AM AST Mon Sep 11 2023

Lee has been holding steady in strength this morning. The NOAA
Hurricane Hunters have been investigating Lee and found that the
minimum pressure was around 948 mb while a combination of the
measured flight-level and SFMR winds support holding the initial
intensity at 105 kt. The aircraft data have also shown a clear
indication of concentric eyewalls, which will likely cause
fluctuations, both up and down, in Lee's intensity over the next day
or two.

The major hurricane is moving slowly toward the northwest at about
7 kt. A continued slow motion between west-northwest and northwest
is expected during the next couple of days as Lee continues to be
steered by a mid-level high to its north-northeast. Around the
middle of the week, the ridge is expected to shift eastward as a
mid- to upper-level trough amplifies over the eastern U.S. This
pattern change should cause Lee to turn northward with an increase
in forward speed. The models have generally changed little this
cycle, and only small changes were made to the previous NHC track
forecast. Lee is likely to pass near, but to the west of Bermuda,
late Thursday and Friday and be situated offshore of the
mid-Atlantic states and New England by the end of the forecast
period.

As mentioned above, fluctuations in strength are likely in the
short term due to eyewall replacement cycles, but there is an
opportunity for some strengthening during that time since the
system is expected to remain over very warm waters and in
relatively low wind shear conditions. Beyond a couple of days,
however, progressively cooler waters and a notable increase in
shear should cause Lee to gradually weaken. Although the weakening
is forecast later in the week, Lee is expected to significantly
increase in size and hazards will extend well away from the center
of the storm by the end of the forecast period.


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. Lee could bring strong winds, rainfall, and high surf impacts to
Bermuda later this week. Interests there should monitor the latest
forecasts.

3. It remains too soon to know what level of additional impacts Lee
might have along the Northeast U.S. coast and Atlantic Canada late
this week and this weekend, however, wind and rainfall hazards will
likely extend well away from the center as Lee grows in size. Users
should continue to monitor updates to the forecast of Lee during the
next several days.


FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 23.5N 63.5W 105 KT 120 MPH
12H 12/0000Z 23.9N 64.4W 110 KT 125 MPH
24H 12/1200Z 24.4N 65.5W 115 KT 130 MPH
36H 13/0000Z 24.9N 66.5W 110 KT 125 MPH
48H 13/1200Z 25.7N 67.2W 100 KT 115 MPH
60H 14/0000Z 27.0N 67.7W 95 KT 110 MPH
72H 14/1200Z 28.8N 68.0W 90 KT 105 MPH
96H 15/1200Z 33.1N 67.6W 80 KT 90 MPH
120H 16/1200Z 38.9N 67.1W 70 KT 80 MPH

$$
Forecaster Cangialosi

NNNN
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