EPAC: HENRIETTE - Post-Tropical - Discussion

[StormWeather]

Another possible basin crossover but coming from the Epac...

Last EPAC->WPAC system was Dora 2023.

[Kingarabian]

Loving the structure on it. Shrimp look + light easterly shear. Just needs deeper convection.

[Kingarabian]

Doubt a Hawaii threat since the islands are such a hard target. But the Euro gets this modestly close. Euro and GFS keeping this intact north of Hawaii. If this manages to get stronger than normal and become a Cat.4, this could pump the ridge and get closer to Hawaii.

[Kingarabian]

Needs a more pronounced WNW heading for this to be classic EPAC long tracker.

[cycloneye]

Tropical Storm Henriette Discussion Number 4
NWS National Hurricane Center Miami FL EP082025
500 PM HST Mon Aug 04 2025

Henriette has become slightly better organized this afternoon, with
curved banding becoming more defined and a brief burst of deep
convection developing over the low-level center. The latest
subjective Dvorak intensity estimates from TAFB and SAB are both
3.0/45 knots, while objective estimates from UW-CIMSS have ranged
from 39 to 43 knots during the past few hours and show an upward
trend. Based on these data, the initial intensity for this advisory
has been increased to 45 knots.

The cyclone is moving west-northwest, or 290 degrees, at 13 knots.
This general motion is expected to continue during the next couple
of days as Henriette moves along the southern edge of a subtropical
ridge to the north. Between 48 and 72 hours, a slight turn toward
the west is forecast as the ridge strengthens north of the cyclone.
Beyond 72 hours, a turn back toward the west-northwest or northwest
is anticipated as a weakness develops in the ridge north of Hawaii
due to an amplifying longwave trough near 160W. The official track
forecast remains near the center of the tightly clustered guidance
envelope and is very close to the previous advisory.

Henriette appears to have a brief window for further intensification
over the next day or so, as sea surface temperatures hover between
26 and 27C, mid-level moisture remains sufficient, and vertical wind
shear stays light. After 36 hours, the cyclone is expected to move
over progressively cooler waters, with mid-level moisture gradually
decreasing, and these conditions should lead to steady weakening.
The official forecast maintains Henriette as a tropical cyclone
through 120 hours, however, it would not be surprising if it
transitions into a post-tropical low prior to day 5. The intensity
forecast is most closely aligned with the SHIPS and ICON guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0300Z 15.4N 121.9W 45 KT 50 MPH
12H 05/1200Z 16.0N 123.7W 50 KT 60 MPH
24H 06/0000Z 16.9N 126.4W 55 KT 65 MPH
36H 06/1200Z 17.5N 129.2W 55 KT 65 MPH
48H 07/0000Z 18.0N 132.0W 50 KT 60 MPH
60H 07/1200Z 18.3N 135.0W 45 KT 50 MPH
72H 08/0000Z 18.6N 138.0W 40 KT 45 MPH
96H 09/0000Z 19.9N 143.5W 35 KT 40 MPH
120H 10/0000Z 22.0N 148.3W 35 KT 40 MPH

$$
Forecaster Jelsema (CPHC)

[StormWeather]

Doubt a Hawaii threat since the islands are such a hard target. But the Euro gets this modestly close. Euro and GFS keeping this intact north of Hawaii. If this manages to get stronger than normal and become a Cat.4, this could pump the ridge and get closer to Hawaii.

Well right now its not even forecast to become a hurricane, but the possibility remains (Otis taught us that forecasts don’t always go as planned)

[cycloneye]

Tropical Storm Henriette Discussion Number 5
NWS National Hurricane Center Miami FL EP082025
1100 PM HST Mon Aug 04 2025

The satellite presentation of Henriette has degraded some since the
previous advisory, with cloud tops warming and the curved band
structure becoming more fragmented. The latest subjective Dvorak
intensity estimates from TAFB and SAB are both 3.0/45 kt, while
objective estimates from UW-CIMSS have ranged from 37 to 46 kt
during the past several hours. Meanwhile, a timely 05/0545Z Metop-C
ASCAT pass showed several 40-45 kt wind barbs, assisting with
determining the initial intensity as well as the extent of the
tropical-storm-force wind radii. The initial intensity for this
advisory has been held at 45 kt.

The cyclone is moving west-northwest, or 290 degrees, at 13 knots.
This general motion is expected to continue during the next day or
so, as Henriette moves along the southern edge of a subtropical
ridge to the north. Between 36 and 72 hours, a slight turn toward
the west is forecast as the ridge strengthens north of the cyclone.
Beyond 72 hours, a turn back toward the west-northwest or northwest
is anticipated as an amplifying longwave trough northwest of Hawaii
erodes the western extent of the subtropical ridge steering the
cyclone. The official track forecast closely follows a blend of
the latest HCCA/TVCE/FSSE consensus guidance, and is very close to
the track from the previous advisory.

Henriette appears to have a brief window for further intensification
over the next 12 to 18 hours, as sea surface temperatures hover
between 26 and 26.5C, mid-level moisture remains sufficient, and
vertical wind shear stays light. Little change in strength is
expected then through 36 hours as the cyclone moves over slightly
cooler water but close to the 26C isotherm, while shear remains
light and the mid-levels remain moist. Beyond 36 hours, the cyclone
is expected to move over progressively cooler waters, with mid-level
moisture decreasing, and these conditions should lead to gradual
weakening. The official forecast maintains Henriette as a tropical
cyclone through 120 hours, however, it would not be surprising if it
transitions into a post-tropical low prior to day 5. The intensity
forecast is most closely aligned with the FSSE, which is near the
middle of the intensity guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0900Z 15.9N 123.1W 45 KT 50 MPH
12H 05/1800Z 16.5N 125.0W 50 KT 60 MPH
24H 06/0600Z 17.2N 127.7W 50 KT 60 MPH
36H 06/1800Z 17.8N 130.6W 50 KT 60 MPH
48H 07/0600Z 18.2N 133.5W 45 KT 50 MPH
60H 07/1800Z 18.5N 136.5W 45 KT 50 MPH
72H 08/0600Z 19.0N 139.6W 40 KT 45 MPH
96H 09/0600Z 20.3N 144.9W 35 KT 40 MPH
120H 10/0600Z 22.3N 149.8W 35 KT 40 MPH

$$
Forecaster Jelsema (CPHC)

[cycloneye]

Tropical Storm Henriette Discussion Number 6
NWS National Hurricane Center Miami FL EP082025
500 AM HST Tue Aug 05 2025

Henriette's cloud pattern has deteriorated a bit overnight. Modest
southeasterly shear, evidence of a slight southeast to northwest
tilt with height in a 0638 UTC GPM microwave image, and an
increasingly inhibiting thermodynamic environment continue to
impede strengthening. Based on a compromise of the Dvorak
intensity estimates from TAFB, SAB, and recent CIMSS SATCON
objective intensity analysis of 46 kt, the initial intensity
is held at 45 kt.

Little change in strength is expected during the next few days
due to the above mentioned adverse atmospheric conditions, and
Henriette traversing slightly cooler oceanic temperatures. Only
the HAFS-B hurricane model suggests an increase to 50 kt during the
24-36 hrs. Of course, a 5 kt increase isn't out of the question.
Beyond day 3, toward the end of the week, the thermodynamic
environment is expected to become even more stifling while
Henriette moves over the subtropical central Pacific waters.
Subsequently, gradual weakening is noted in the official forecast.
The NHC intensity forecast is near the previous one and is hedged
toward the IVCN intensity consensus, and is just above the
Decay-SHIPS statistical aid.

Henriette's initial motion is estimated to be west-northwestward,
or 290/13 kt. A general west-northwestward or westward motion is
expected through day 4 while a strong subtropical ridge remains
to the north of the cyclone. Toward the end of the period,
Henriette is forecast to gradually turn northwestward in response
to an amplifying mid- to upper-tropospheric trough approaching the
Hawaiian Islands from the central north Pacific. The track
forecast is essentially an update from the previous advisory and
lies between the HCCA corrected consensus model and the ECMWF
control.

Henriette's wind radii were adjusted based on a 0839 UTC Oceansat-3
Scatterometer overpass.


FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 16.4N 124.3W 45 KT 50 MPH
12H 06/0000Z 16.9N 126.3W 45 KT 50 MPH
24H 06/1200Z 17.5N 129.1W 45 KT 50 MPH
36H 07/0000Z 18.0N 132.0W 45 KT 50 MPH
48H 07/1200Z 18.4N 134.9W 45 KT 50 MPH
60H 08/0000Z 18.8N 137.9W 45 KT 50 MPH
72H 08/1200Z 19.3N 140.8W 40 KT 45 MPH
96H 09/1200Z 21.0N 146.1W 35 KT 40 MPH
120H 10/1200Z 23.4N 150.7W 35 KT 40 MPH

$$
Forecaster Roberts

[cycloneye]

Hayabusa, look at GFS as it moves this cyclone to the WPAC and is SE of Japan.

[Kingarabian]

Hayabusa, look at GFS as it moves this cyclone to the WPAC and is SE of Japan.

https://i.imgur.com/FcAwk9t.gif

Thats a crazy run lol

[StormWeather]

Hayabusa, look at GFS as it moves this cyclone to the WPAC and is SE of Japan.

https://i.imgur.com/FcAwk9t.gif

Thats a crazy run lol

Im all for it if it doesn’t strike land. By all means, let’s get the ACE up and running.

[cycloneye]

Tropical Storm Henriette Discussion Number 7
NWS National Hurricane Center Miami FL EP082025
1100 AM HST Tue Aug 05 2025

This morning's satellite presentation consists of a convective
curved band on the west side of the cyclone and a cluster of strong
thunderstorms with cold cloud tops of -70 Celsius just to the west
of Henriette's surface circulation center. The initial intensity is
held at 45 kt for this advisory and is based on a blend of the
TAFB and SAB subjective and CIMSS objective intensity estimates.

Little change in strength is expected during the next couple of
days, although 5-kt fluctuations are possible, while Henriette
moves over slightly cooler water and through an increasingly
inhibiting thermodynamic environment. Toward the end of the week,
the thermodynamic environment is expected to become even more
hostile while Henriette moves over the subtropical central
Pacific waters. Therefore, some weakening of the cyclone is
forecast through day 5. The official intensity forecast is based
on the IVCN intensity consensus model and the Decay-SHIPS
statistical aid.

Henriette's initial motion is estimated to be west-northwestward,
or 295/13 kt, and a west-northwestward or westward motion should
continue through day 4 while the cyclone is steered by a strong
mid-level ridge stretching across the subtropical Central Pacific.
Over the weekend, Henriette is expected to turn gradually
northwestward in response to an amplifying mid- to
upper-tropospheric trough approaching the Hawaiian Islands from the
Central North Pacific. The NHC track forecast is based on the
various consensus aids and is basically an update of the previous
advisory.


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 17.0N 125.6W 45 KT 50 MPH
12H 06/0600Z 17.4N 127.7W 45 KT 50 MPH
24H 06/1800Z 17.9N 130.4W 45 KT 50 MPH
36H 07/0600Z 18.4N 133.3W 40 KT 45 MPH
48H 07/1800Z 18.8N 136.3W 40 KT 45 MPH
60H 08/0600Z 19.4N 139.4W 40 KT 45 MPH
72H 08/1800Z 20.1N 142.2W 40 KT 45 MPH
96H 09/1800Z 22.3N 147.4W 35 KT 40 MPH
120H 10/1800Z 24.5N 152.0W 35 KT 40 MPH

$$
Forecaster Roberts

[cycloneye]

Tropical Storm Henriette Discussion Number 8
NWS National Hurricane Center Miami FL EP082025
500 PM HST Tue Aug 05 2025

The satellite presentation of Henriette had remained rather ragged
for several hours since the previous advisory, however, a new burst
of deep convection has now developed just to the west of the
low-level center of the cyclone. The latest subjective Dvorak
current intensity estimates from TAFB and SAB were 3.0/45 kt and
2.5/35 kt respectively. Meanwhile, the objective estimates from
UW-CIMSS have ranged from 34 to 47 kt during the past several hours.
Earlier today, a 05/1815Z Metop-C ASCAT pass showed several 45 knot
wind barbs to the north of the low level center and a 05/2133Z AMRS2
pass revealed a nice inner core structure of the cyclone. Based on
these data, the initial intensity for this advisory has been held at
45 kt.

The cyclone is moving west-northwest, or 290 degrees, at 14 kt. A
slight turn toward the west is expected tonight, with this motion
then continuing for the next several days as Henriette is steered by
a strengthening subtropical ridge to the north. By 72 hours, a turn
toward the west-northwest is anticipated as an amplifying longwave
trough northwest of Hawaii erodes the western extent of the
subtropical ridge steering the cyclone. The official track forecast
closely follows a blend of the latest consensus guidance, and is
very close to the previous advisory.

Henriette will remain in a low shear environment during the next
several days, while sea surface temperatures gradually cool to near
or slightly below 24C and the mid-level moisture decreases below 50
percent. Despite the cooling water and drying mid-levels, the large
circulation of the system and the well-established inner core should
keep Henriette rather resilient in the very low shear environment
during the next several days. The intensity forecast only calls for
slight weakening during this time followed by little change in
strength. By late in the forecast period, sea surface temperatures
will begin to increase, and if the cyclone manages to survive the
trip over the cooler water as suggested by the GFS and ECMWF models,
some re-intensification is possible and the official forecast
reflects this. The intensity forecast is near the middle of the
intensity guidance envelope and most closely aligned with the IVCN
intensity aid.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 17.6N 126.9W 45 KT 50 MPH
12H 06/1200Z 17.9N 129.1W 45 KT 50 MPH
24H 07/0000Z 18.3N 132.1W 45 KT 50 MPH
36H 07/1200Z 18.6N 135.1W 40 KT 45 MPH
48H 08/0000Z 19.0N 138.1W 40 KT 45 MPH
60H 08/1200Z 19.6N 141.0W 40 KT 45 MPH
72H 09/0000Z 20.5N 143.8W 40 KT 45 MPH
96H 10/0000Z 22.8N 148.9W 40 KT 45 MPH
120H 11/0000Z 25.1N 153.2W 45 KT 50 MPH

$$
Forecaster Jelsema (CPHC)

[cycloneye]

Tropical Storm Henriette Discussion Number 9
NWS National Hurricane Center Miami FL EP082025
1100 PM HST Tue Aug 05 2025

The satellite presentation of Henriette has changed little since the
previous advisory, with intermittent bursts of deep convection
continuing, primarily located over and west of the cyclone’s
low-level center. Recent subjective Dvorak intensity estimates from
TAFB and SAB were 3.0/45 kt and 2.5/35 kt, respectively, while
objective estimates from UW-CIMSS have ranged between 34 and 46 kt
over the past several hours. A timely 06/0525Z Metop-C ASCAT pass
revealed several 40–45 kt wind barbs north of the low-level center.
Based on these data, the initial intensity for this advisory remains
45 kt.

Henriette has recently turned toward the west, or 280 degrees, at 13
kt. This general motion is expected to persist over the next couple
of days as the cyclone is steered by a strengthening subtropical
ridge situated to the north. By around 72 hours, a gradual turn
toward the west-northwest or northwest is anticipated as an
amplifying longwave trough northwest of Hawaii begins to erode the
western periphery of the ridge. The official track forecast is
closely aligned with the latest multi-model consensus aids and
remains very similar to the previous advisory.

Henriette is forecast to remain in a low vertical wind shear
environment for the next several days. During this period, sea
surface temperatures are expected to gradually decrease to near or
slightly below 24C, while mid-level moisture drops below 50 percent.
Despite these marginal thermodynamic conditions, Henriette’s broad
circulation and well-established inner core should allow the system
to remain relatively resilient in the low shear environment. Only
slight weakening is forecast during the next few days, followed by
little change in strength. Toward the end of the forecast period,
sea surface temperatures are expected to rise again. If the system
manages to endure the cooler waters, as persistently suggested by
both the GFS and ECMWF models, some re-intensification is possible.
The official forecast reflects this potential and lies near the
middle of the intensity guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 17.8N 128.2W 45 KT 50 MPH
12H 06/1800Z 18.1N 130.4W 45 KT 50 MPH
24H 07/0600Z 18.4N 133.4W 40 KT 45 MPH
36H 07/1800Z 18.7N 136.4W 40 KT 45 MPH
48H 08/0600Z 19.2N 139.4W 40 KT 45 MPH
60H 08/1800Z 19.9N 142.3W 40 KT 45 MPH
72H 09/0600Z 20.9N 145.2W 40 KT 45 MPH
96H 10/0600Z 23.3N 149.9W 40 KT 45 MPH
120H 11/0600Z 26.1N 154.1W 50 KT 60 MPH

$$
Forecaster Jelsema (CPHC)

[Hayabusa]

Hayabusa, look at GFS as it moves this cyclone to the WPAC and is SE of Japan.

https://i.imgur.com/FcAwk9t.gif

Really interesting ENSO-neutral season...

[cycloneye]

BULLETIN
Tropical Storm Henriette Advisory Number 10
NWS National Hurricane Center Miami FL EP082025
500 AM HST Wed Aug 06 2025

...HENRIETTE CONTINUES HEADING WEST-NORTHWESTWARD...


SUMMARY OF 500 AM HST...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...18.1N 129.7W
ABOUT 1660 MI...2675 KM E OF HILO HAWAII
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES


Tropical Storm Henriette Discussion Number 10
NWS National Hurricane Center Miami FL EP082025
500 AM HST Wed Aug 06 2025

Henriette has changed very little this morning. It continues to
produce a relatively small area of deep convection, with cold cloud
tops present mostly to the north of its low-level center. The
initial intensity remains 45 kt for this advisory, based on
overnight ASCAT data and the lack of noticeable change in
Henriette's structure since that time.

Virtually no change was made to the NHC track forecast. Henriette
is moving westward to west-northwestward to the south of a deep
ridge centered over the northern east Pacific. In a few days, a
trough approaching from the west will turn Henriette toward the
northwest, taking the tropical cyclone north of Hawaii. The
various deterministic and global ensemble models are all in good
agreement on the forecast, so confidence in the track forecast is
fairly high.

The tropical storm is still forecast to slowly weaken during the
next few days while it moves over cool SSTs near 24C. However, once
Henriette moves north of Hawaii, it will move over warmer waters.
Upper-level difluent flow associated with a mid-latitude trough to
the northwest may also provide additional support for
intensification. As a result, most of the dynamical models forecast
strengthening to occur near the end of the forecast period, and the
NHC intensity forecast has been adjusted upward accordingly. Some of
the guidance is much higher, including both HAFS models, which show
Henriette developing a robust inner core by 120 h. Additional
adjustments to the intensity forecast at day 4 or 5 may be needed
with future advisories.

FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 18.1N 129.7W 45 KT 50 MPH
12H 07/0000Z 18.3N 132.0W 45 KT 50 MPH
24H 07/1200Z 18.6N 135.0W 40 KT 45 MPH
36H 08/0000Z 19.0N 138.0W 40 KT 45 MPH
48H 08/1200Z 19.6N 141.1W 40 KT 45 MPH
60H 09/0000Z 20.4N 144.0W 40 KT 45 MPH
72H 09/1200Z 21.5N 146.6W 40 KT 45 MPH
96H 10/1200Z 24.2N 151.3W 45 KT 50 MPH
120H 11/1200Z 27.5N 155.0W 60 KT 70 MPH

$$
Forecaster D. Zelinsky

[Cyclenall]

This is that storm that the Euro was showing days ago moving north of Hawaii yet was upping its game all the way to the Wpac, can't say I've ever seen that and would be insane.

[cycloneye]

This is that storm that the Euro was showing days ago moving north of Hawaii yet was upping its game all the way to the Wpac, can't say I've ever seen that and would be insane.

This is the one that yes crosses to WPAC and be a typhoon there.

[TallyTracker]

The 5th day trajectory makes it look like Henriette might be a rare CPAC recurve storm. I’m interested to see if that occurs or if it gets further west into the WPAC.

[cycloneye]

The 5th day trajectory makes it look like Henriette might be a rare CPAC recurve storm. I’m interested to see if that occurs or if it gets further west into the WPAC.

Looks like in the 12z GFS run it recurves without crossing the dateline.