EPAC: KENNETH - Post-Tropical - Discussion

[cycloneye]

Tropical Storm Kenneth Discussion Number 4
NWS National Hurricane Center Miami FL EP132023
200 AM PDT Wed Sep 20 2023

Deep convection has been increasing over the past several hours, but
the thunderstorm activity remains confined to the northwest quadrant
of Kenneth due to moderate easterly vertical wind shear. An ASCAT-C
pass caught the western half of the circulation and showed maximum
winds in the 30-35 kt range, but it is possible that stronger winds
exists east of the center. Therefore, the initial intensity is held
at 40 kt, which is a near the average of the latest satellite
intensity estimates that range from 30 to 45 kt.

Kenneth could strengthen a little during the next day or so as the
shear decreases. However, the opportunity for strengthening seems
to end on Thursday when the storm moves into a region of strong
southwesterly vertical wind shear. These hostile winds aloft
combined with dry air entrainment and progressively cooler SSTs
should cause Kenneth to weaken and degenerate into a remnant low in
a few days and dissipate shortly thereafter. The NHC intensity
forecast is slightly lower than the previous one, but still lies at
the high end of the guidance.

The storm is moving westward at 9 kt. A turn to the west-northwest
is expected later today as Kenneth nears the southwestern periphery
of a subtropical ridge. On Thursday, a turn to the northwest is
forecast as Kenneth moves in the flow between the ridge and a mid-
to upper-level trough to its northwest. The models have trended
left this cycle, and the NHC track forecast has been nudged in that
direction.


FORECAST POSITIONS AND MAX WINDS

INIT 20/0900Z 14.8N 122.5W 40 KT 45 MPH
12H 20/1800Z 15.4N 123.9W 45 KT 50 MPH
24H 21/0600Z 16.0N 125.4W 45 KT 50 MPH
36H 21/1800Z 16.8N 126.5W 40 KT 45 MPH
48H 22/0600Z 18.0N 127.2W 35 KT 40 MPH
60H 22/1800Z 19.4N 127.6W 30 KT 35 MPH
72H 23/0600Z 20.3N 128.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 24/0600Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

EP, 13, 2023092012, , BEST, 0, 150N, 1230W, 45, 1000, TS

[cycloneye]

Tropical Storm Kenneth Discussion Number 5
NWS National Hurricane Center Miami FL EP132023
800 AM PDT Wed Sep 20 2023

Kenneth's cloud pattern has become a little better organized since
yesterday evening. Conventional imagery and a recent AMSR2
microwave overpass show improved curved banding in the northern and
eastern semi-circles. Accordingly, the initial intensity is raised
to 45 kt for this advisory and is based on a blend of the
subjective Dvorak intensity estimates from TAFB and SAB.

Although not explicitly shown in the official intensity
forecast, there's a possibility that the storm could strengthen
a little more in the short term, but that small window of
opportunity appears to end tomorrow while deep-layer shear
increases along Kenneth's track. This inhibiting upper-level wind
pattern, along with decreasing oceanic surface temperatures and
an invading stable and dry lower boundary marine layer should
induce a weakening trend through dissipation in about 4 days.

Kenneth's anticipated turn toward the west-northwest has
occurred overnight, and the estimated motion is 290/9 kt around
the southwestern periphery of a subtropical high centered over
northwestern Mexico. On Thursday, the cyclone is forecast to
turn northwestward while moving between the above mentioned high
pressure and an approaching mid-tropospheric trough to its
northwest. The NHC track forecast is based primarily on the
HFIP HCCA corrected consensus and only a slight adjustment to the
right of the previous forecast was made beyond the 24-hour period.


FORECAST POSITIONS AND MAX WINDS

INIT 20/1500Z 15.2N 123.4W 45 KT 50 MPH
12H 21/0000Z 15.6N 124.6W 45 KT 50 MPH
24H 21/1200Z 16.2N 125.9W 45 KT 50 MPH
36H 22/0000Z 17.4N 126.7W 40 KT 45 MPH
48H 22/1200Z 18.9N 127.1W 35 KT 40 MPH
60H 23/0000Z 20.2N 127.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 23/1200Z 20.7N 127.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 24/1200Z...DISSIPATED

$$
Forecaster Roberts

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[Sciencerocks]

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[cycloneye]

Tropical Storm Kenneth Discussion Number 6
NWS National Hurricane Center Miami FL EP132023
200 PM PDT Wed Sep 20 2023

Kenneth's cloud pattern has not changed appreciably during the last
6 hours. The average of the latest TAFB and SAB Dvorak numbers is
45 kt. Most of the objective intensity estimates are a bit lower.
Based on the above data, the initial intensity is maintained at 45
kt for this advisory.

The center of Kenneth is estimated to be near the southern edge of
the central dense overcast. However, the current position is quite
uncertain. The initial motion is estimated at 290/9 kt. A turn to
the northwest and north-northwest is expected on Thursday between a
subtropical high centered over northwestern Mexico and a potent
mid- to upper-level trough to the northwest of Kenneth. The track
forecast has been adjusted a bit to the north of the previous NHC
track prediction, but not as far north as the latest consensus
models.

Kenneth is currently located in an environment that is favorable
enough for it to at least maintain its intensity over the next
12-24 hours. However, a more stable air mass is located just to
the north and northwest of the cyclone, as evidenced by scattered
low stratus clouds seen on GOES-18 satellite imagery, indicative of
a marine boundary layer. As Kenneth approaches the mid- to
upper-level trough over the next couple of days, strong
southwesterly wind shear will increasingly encroach on Kenneth.
Kenneth will also cross the 26C isotherm about the same time the
shear ramps up Thursday evening. Therefore, steady weakening is
forecast, and Kenneth should become a remnant low Friday night or
Saturday. The latest NHC intensity forecast is similar to the
previous one and is near the middle of the intensity consensus
aids.



FORECAST POSITIONS AND MAX WINDS

INIT 20/2100Z 15.7N 124.2W 45 KT 50 MPH
12H 21/0600Z 16.2N 125.3W 45 KT 50 MPH
24H 21/1800Z 17.3N 126.4W 45 KT 50 MPH
36H 22/0600Z 18.5N 126.9W 40 KT 45 MPH
48H 22/1800Z 20.0N 127.1W 30 KT 35 MPH
60H 23/0600Z 21.0N 127.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 23/1800Z 21.8N 127.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 24/1800Z...DISSIPATED

$$
Forecaster Hagen/Roberts

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[cycloneye]

Tropical Storm Kenneth Discussion Number 7
NWS National Hurricane Center Miami FL EP132023
800 PM PDT Wed Sep 20 2023

It appears that southerly mid-level shear has set in over Kenneth
during the day, and the surface center is now located on the
southern side of the ongoing convective mass. Dvorak final-T
numbers are a consensus 3.0 from TAFB and SAB, so the initial
intensity remains 45 kt.

The shear appears to have pulled Kenneth's center farther to the
north, and as a result, the storm has turned northwestward with an
initial motion of 310/10 kt. A turn toward the north-northwest and
north is expected over the next 36 hours as Kenneth moves around
the western periphery of the subtropical ridge. Partly because of
the required adjustment of the initial position, the track guidance
has shifted significantly to the north and east on this cycle. The
new NHC track forecast lies very close to the GFS, ECMWF, TVCE, and
HCCA aids, particularly during the first 36 hours of the forecast,
and is as much as 30-40 n mi to the right of the previous
prediction.

As is often the case, the mid-level shear affecting the cyclone was
not foreseen, as nearly all shear diagnostics show that the shear in
a deeper layer of the atmosphere is currently very low. That said,
even the deep-layer shear is forecast to increase to
moderate-to-strong levels in the next 12-24 hours. Simultaneously,
Kenneth will be moving over increasingly cooler waters that are less
than 26 degrees Celsius. Therefore, weakening is expected to begin
by 24 hours, and strong shear and a drier, more stable atmosphere
should cause Kenneth to degenerate into a remnant low by late
Friday. The remnant low could hang around for a few days, opening
up into a trough by Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0300Z 16.9N 125.2W 45 KT 50 MPH
12H 21/1200Z 17.6N 126.0W 45 KT 50 MPH
24H 22/0000Z 19.0N 126.8W 40 KT 45 MPH
36H 22/1200Z 20.7N 126.9W 35 KT 40 MPH
48H 23/0000Z 22.1N 126.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 23/1200Z 23.1N 126.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 24/0000Z 23.8N 127.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 25/0000Z...DISSIPATED

$$
Forecaster Berg

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[Sciencerocks]

[Sciencerocks]

Tropical Storm Kenneth Discussion Number 10
NWS National Hurricane Center Miami FL EP132023
200 PM PDT Thu Sep 21 2023

Kenneth is a sheared tropical cyclone. The small area of active
convection associated with the storm has been displaced over 90 n mi
from its exposed low-level center by southwesterly shear. This
deteriorating satellite presentation has caused the intensity
estimates to decrease today. Based on a blend of the latest
objective and subjective Dvorak estimates, the initial intensity is
lowered to 35 kt.

Recent satellite images indicate Kenneth has begun its northward
turn, and the initial motion is north-northwestward at 330/6 kt. A
generally northward motion should continue for the next couple of
days as the system moves within the flow between a mid-level trough
to the northwest and a mid-level ridge over central Mexico. There
were no major changes to the track guidance this cycle, and the
latest NHC forecast is similar to the previous prediction. While
simulated satellite imagery from the global models suggest Kenneth
could produce intermittent bursts of sheared convection during the
next day or so, the environmental conditions (stronger shear,
progressively cooler SSTs, and a drier and more stable airmass) are
not conducive for sustained convection going forward. Based on these
factors and recent satellite trends, this forecast shows additional
weakening with post-tropical/remnant low status in 24 h.


FORECAST POSITIONS AND MAX WINDS

INIT 21/2100Z 17.9N 125.7W 35 KT 40 MPH
12H 22/0600Z 19.2N 126.0W 35 KT 40 MPH
24H 22/1800Z 20.9N 125.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 23/0600Z 22.3N 125.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 23/1800Z 23.4N 125.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 24/0600Z...DISSIPATED

$$
Forecaster Reinhart

[Sciencerocks]

[cycloneye]

Tropical Storm Kenneth Discussion Number 11
NWS National Hurricane Center Miami FL EP132023
800 PM PDT Thu Sep 21 2023

Kenneth is barely clinging to tropical cyclone status. Satellite
imagery shows an exposed low-level center with a small burst of deep
convection displaced over 100 miles to its north. The intensity is
held at 35 kt, closest to the latest TAFB Dvorak estimate.

The tropical storm is still moving to the north-northwest at 6 kt.
Track guidance suggests Nigel should turn northward soon in the flow
around a high pressure system centered over central Mexico. The
latest official track forecast is similar to the previous advisory
prediction. Atmospheric and oceanic conditions are expected to
remain hostile and therefore, Nigel should gradually weaken. Global
model simulate satellite imagery indicates there could be occasional
bursts of convection near the center, but the system is still
forecast to become a post-tropical remnant low in a day or so.


FORECAST POSITIONS AND MAX WINDS

INIT 22/0300Z 18.5N 125.9W 35 KT 40 MPH
12H 22/1200Z 19.9N 126.0W 30 KT 35 MPH
24H 23/0000Z 21.5N 125.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 23/1200Z 22.6N 125.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 24/0000Z 23.6N 126.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 24/1200Z...DISSIPATED

$$
Forecaster Bucci

[Iceresistance]

Tropical Storm Kenneth Discussion Number 11
NWS National Hurricane Center Miami FL EP132023
800 PM PDT Thu Sep 21 2023

Kenneth is barely clinging to tropical cyclone status. Satellite
imagery shows an exposed low-level center with a small burst of deep
convection displaced over 100 miles to its north. The intensity is
held at 35 kt, closest to the latest TAFB Dvorak estimate.

The tropical storm is still moving to the north-northwest at 6 kt.
Track guidance suggests Nigel should turn northward soon in the flow
around a high pressure system centered over central Mexico. The
latest official track forecast is similar to the previous advisory
prediction. Atmospheric and oceanic conditions are expected to
remain hostile and therefore, Nigel should gradually weaken. Global
model simulate satellite imagery indicates there could be occasional
bursts of convection near the center, but the system is still
forecast to become a post-tropical remnant low in a day or so.


FORECAST POSITIONS AND MAX WINDS

INIT 22/0300Z 18.5N 125.9W 35 KT 40 MPH
12H 22/1200Z 19.9N 126.0W 30 KT 35 MPH
24H 23/0000Z 21.5N 125.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 23/1200Z 22.6N 125.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 24/0000Z 23.6N 126.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 24/1200Z...DISSIPATED

$$
Forecaster Bucci

How did they mess up Kenneth with Nigel?

[cycloneye]

Tropical Depression Kenneth Discussion Number 12
NWS National Hurricane Center Miami FL EP132023
200 AM PDT Fri Sep 22 2023

Kenneth is just barely enough to be classified as a tropical
cyclone. Satellite imagery shows that the low-level center
continues to be exposed with waning convection displaced to the
north of the system. A recent scatterometer pass indicated that the
system is producing winds around 25-30 kt. Based on the
scatterometer pass, the intensity is lowered to 30 kt for this
advisory, which is also in good agreement with the latest TAFB
Dvorak intensity estimate.

The tropical depression is moving to the north at 9 kt. The system
will continue to move northward during the next day or two, around
a high pressure ridge centered over central Mexico. Towards the end
of the period, the remnant low will begin to move westward in the
low-level flow. There was little change to the previous forecast
track for this advisory.

Kenneth is in a fairly hostile environment with strong vertical wind
shear and cool sea surface temperatures. The system should continue
to gradually weaken in these unfavorable conditions. Kenneth is
forecast to become a post-tropical remnant low later today.


FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 19.4N 126.0W 30 KT 35 MPH
12H 22/1800Z 20.8N 125.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 23/0600Z 22.3N 125.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 23/1800Z 23.2N 126.4W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 24/0600Z 23.5N 127.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 24/1800Z...DISSIPATED

$$
Forecaster Kelly

[cycloneye]

Bye.


Post-Tropical Cyclone Kenneth Discussion Number 13
NWS National Hurricane Center Miami FL EP132023
800 AM PDT Fri Sep 22 2023

Kenneth no longer has organized deep convection. First light visible
imagery shows that Kenneth's circulation is no longer well defined.
It is also located in an environment with high deep-layer shear, dry
air, and cool SSTs. For these reasons, Kenneth has become a
post-tropical remnant low. The 30-kt intensity estimate is based on
overnight ASCAT data, but it is possible the winds have decreased
further since then.

Kenneth is moving generally northward and should continue moving
northward while weakening until it dissipates. This is the last NHC
advisory. For additional information on the remnant low please see
High Seas Forecasts issued by the National Weather Service, under
AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at
ocean.weather.gov/shtml/NFDHSFEPI.php.

FORECAST POSITIONS AND MAX WINDS

INIT 22/1500Z 20.5N 125.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
12H 23/0000Z 21.8N 125.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 23/1200Z 22.8N 126.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 24/0000Z...DISSIPATED

$$
Forecaster D. Zelinsky/R. Zelinsky

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