CPAC: TWELVE-E - Remnants - Discussion

[Sciencerocks]

[cycloneye]

Tropical Depression Twelve-E Discussion Number 2
NWS National Hurricane Center Miami FL EP122023
Issued by NWS Central Pacific Hurricane Center Honolulu HI
500 PM HST Fri Sep 15 2023

Tropical Depression 12E has a fully exposed low level center. Deep
convection is displaced about 60 nm to the east, in the face of 15
to 20 kt of westerly shear as analyzed by the UW-CIMSS shear
analysis. A blend of the satellite-based intensity estimates
suggests maintaining a 25 kt intensity for this advisory.

The low level center has been moving rather erratically today as it
decouples from the deep convection. A longer term initial motion
estimate is 255/8, but it should be noted this is less certain than
normal due to the wobbles seen today. 12E is expected to continue
moving toward the west-southwest in the low level trade wind flow
well south of a subtropical ridge. The official forecast has been
nudged a bit to the south, in deference to the recent trends in low
level motion after decoupling. Our forecast track is fairly close
to the middle of the guidance envelope for the expected duration of
the system.

Guidance suggests that over the next few days, the subtropical jet
will sag south over the central Pacific, with a gradual increase in
shear over the system. The low level center will be moving over
slightly warmer sea surface temperatures over the next couple of
days, which suggests that an intermittent bursts of deep convection
will be possible, but significant reintensification seems unlikely.
Simulated satellite imagery from the GFS and ECMWF also agree
with this idea. The depression is forecast to become a remnant low
in about 36 hours, leading to dissipation in a couple of days far
southeast of Hawaii.

FORECAST POSITIONS AND MAX WINDS

INIT 16/0300Z 14.6N 136.8W 25 KT 30 MPH
12H 16/1200Z 14.4N 137.8W 25 KT 30 MPH
24H 17/0000Z 14.1N 139.3W 25 KT 30 MPH
36H 17/1200Z 13.9N 141.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 18/0000Z 13.7N 142.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 18/1200Z...DISSIPATED

$$
Forecaster R Ballard

[xtyphooncyclonex]

It's September 15.

A new TD in the Atlantic is forecast to become a major hurricane, in addition to another hurricane and a TS that are currently active, and another AOI.

A new TD in the EPAC is forecast to dissipate in 3 days without ever being named. It's the only system that the NHC expects to exist within 7 days.

Question: What's the ENSO state of the year? El Nino or La Nina?

In all fairness, the EPAC has had quite a quality season. Two more hurricanes, five more hurricane days, two more majors, and close to six more major hurricane days than the Atlantic and the Atlantic is already above-normal to date. ACE is also 15-20 units higher, tho this could be surpassed. It's the most intense and active in terms of the said counts since 2018 despite only ten named storms.

[Teban54]

It's September 15.

A new TD in the Atlantic is forecast to become a major hurricane, in addition to another hurricane and a TS that are currently active, and another AOI.

A new TD in the EPAC is forecast to dissipate in 3 days without ever being named. It's the only system that the NHC expects to exist within 7 days.

Question: What's the ENSO state of the year? El Nino or La Nina?

In all fairness, the EPAC has had quite a quality season. Two more hurricanes, five more hurricane days, two more majors, and close to six more major hurricane days than the Atlantic and the Atlantic is already above-normal to date. ACE is also 15-20 units higher, tho this could be surpassed. It's the most intense and active in terms of the said counts since 2018 despite only ten named storms.

Oh that I agree, EPAC's quality this year is amazing with the likes of Dora, Hilary and Jova. Just that this particular day was hilarious.

[cycloneye]

Tropical Depression Twelve-E Discussion Number 3
NWS National Hurricane Center Miami FL EP122023
1100 PM HST Fri Sep 15 2023

The depression is producing short-lived bursts of deep convection
well to the east of its center this evening. Although this cloud
pattern lacks significant convective organization, it's been
sufficiently persistent to continue classifying the system as a
sheared tropical cyclone. The initial intensity is held at 25 kt,
consistent with the latest Dvorak satellite intensity estimates
from TAFB and SAB.

Despite marginally warm oceanic surface temperatures along the
depression's track, the cyclone is expected to continue struggling
with intrusions of dry and stable mid-level air from its surrounding
environment due to moderate westerly shear. Subsequently, the
depression is forecast to degenerate to a remnant low within the
next 24 hours or so. This forecast is similar to the previous
advisory and the latest GFS and ECMWF simulated satellite infrared
imagery. The global models indicate that the remnant low will
dissipate by Monday night far southeast of Hawaii, and the official
intensity forecast follows suit.

The depression's initial motion is estimated to be
west-southwestward, or 255/7 kt. This general motion south
of a strengthening low- to mid-tropospheric subtropical ridge should
continue through the depression's dissipation. The NHC forecast
track is nudged closer to the TVCE and HFIP HCCA consensus models
and is a little faster and to the south of the previous advisory.


FORECAST POSITIONS AND MAX WINDS

INIT 16/0900Z 14.5N 137.5W 25 KT 30 MPH
12H 16/1800Z 14.3N 138.5W 25 KT 30 MPH
24H 17/0600Z 13.9N 140.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 17/1800Z 13.5N 142.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 18/0600Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Depression Twelve-E Discussion Number 4
NWS National Hurricane Center Miami FL EP122023
500 AM HST Sat Sep 16 2023

The depression has generally changed little overnight and it remains
strongly sheared with deep convection confined to the eastern side
of the circulation. A partial ASCAT-C pass from a few hours ago
showed an area of 30 kt winds to the east of the center, and that is
the basis for the initial intensity.

The system is moving westward at 10 kt. A westward to
west-southwestward motion is expected in the low- to mid-level flow
during the next couple of days. The depression, or its remnant low,
is expected to move into the Central Pacific basin by tonight.

Strong shear and dry air will continue to affect the depression and
should ultimately cause the system to lose much of its deep
convection around the time it crosses into the Central Pacific, as
persistently forecast by the GFS and ECMWF models. Dissipation is
likely to occur in 36 to 48 hours.


FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 14.5N 138.6W 30 KT 35 MPH
12H 17/0000Z 14.2N 139.9W 30 KT 35 MPH
24H 17/1200Z 13.8N 141.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 18/0000Z 13.3N 143.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 18/1200Z...DISSIPATED

$$
Forecaster Cangialosi

[Sciencerocks]

[Sciencerocks]

[cycloneye]

Tropical Depression Twelve-E Discussion Number 5
NWS National Hurricane Center Miami FL EP122023
1100 AM HST Sat Sep 16 2023

The structure of the depression has degraded during the last
several hours. The low-level center is now completely exposed and
well removed to the west of a decaying area of deep convection.
The initial intensity is held at 30 kt, but this could be a little
generous.

The system is moving westward at 10 kt. A westward to
west-southwestward motion is expected in the low- to mid-level flow
during the next day or so. The depression, or its remnant low,
is expected to move into the Central Pacific basin this afternoon.

Strong shear and dry air will continue to affect the depression and
should ultimately cause the system to lose the remaining
convection by tonight, as persistently forecast by the GFS and
ECMWF models. Dissipation is likely to occur by 36 hours.

Future information on this system can be found in Public Advisories
issued by the Central Pacific Hurricane Center beginning at 500 PM
HST, under AWIPS header HFOTCPCP4, WMO header WTPA34 PHFO. Products
will continue to be available on the web at hurricanes.gov


FORECAST POSITIONS AND MAX WINDS

INIT 16/2100Z 14.2N 139.7W 30 KT 35 MPH
12H 17/0600Z 13.9N 141.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 17/1800Z 13.5N 142.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 18/0600Z...DISSIPATED

$$
Forecaster Cangialosi

[Sciencerocks]

[cycloneye]

BULLETIN
Post-Tropical Cyclone Twelve-E Advisory Number 6
NWS Central Pacific Hurricane Center Honolulu HI EP122023
500 PM HST Sat Sep 16 2023

...REMNANT LOW OF FORMER TROPICAL DEPRESSION 12E ENTERS THE CENTRAL
PACIFIC...
...THIS IS THE LAST ADVISORY...


SUMMARY OF 500 PM HST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...13.5N 140.7W
ABOUT 1045 MI...1680 KM ESE OF HILO HAWAII
ABOUT 1255 MI...2015 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 260 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM HST (0300 UTC), the center of Post-Tropical Cyclone
Twelve-E was located near latitude 13.5 North, longitude 140.7 West.
The post-tropical cyclone is moving toward the west near 14 mph (22
km/h) and this motion is expected to continue until dissipation.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
The remnant low should gradually weaken until dissipation, which is
expected in the next 24 hours.

The estimated minimum central pressure is 1008 mb (29.77 inches).


HAZARDS AFFECTING LAND
----------------------
None


NEXT ADVISORY
-------------
This is the last public advisory issued by the Central Pacific
Hurricane Center on this system unless regeneration occurs.
Additional information on this system can be found in High Seas
Forecasts issued by the National Weather Service under AWIPS header
HFOHSFNP and WMO Header FZPN40 PHFO.

$$
Forecaster R Ballard

[Sciencerocks]

Tropical storm of 35 knot strength