EPAC: HENRIETTE - Post-Tropical - Discussion

[cycloneye]

Hurricane Henriette Discussion Number 27
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 AM HST Sun Aug 10 2025

Henriette has put on quite the show today with a well-defined eye
emerging during the past few hours along with cooling temperatures
in the eyewall. Dvorak intensity estimates were up to 65 kt by
18Z, and with the further development on satellite since that time,
the initial wind speed is set to 70 kt for this advisory.

It remains to be seen how strong Henriette will get with an
improving environment along its path during the next day or so,
including decreasing shear, increasing SSTs and cooling upper-level
temperatures. Given that this rapid intensification period was not
well forecast, and a recent closed 37 GHz ring on AMSR2 data, I'm
inclined to go above the guidance in this situation and show near
rapid intensification for about 24 h until the environment becomes
more hostile. Henriette should lose all deep convection in about 3
days over cold waters and in very high shear.

The storm is moving northwestward at about 15 kt. A large ridge
over the north-central Pacific should cause a continued fast
northwestward track of Henriette for several days until its slows
down a bit near dissipation. The only minor change to the previous
forecast is a faster forward speed, probably a function of the
hurricane feeling stronger upper-level southeasterly flow during
the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 25.7N 152.5W 70 KT 80 MPH
12H 11/0600Z 27.3N 154.3W 80 KT 90 MPH
24H 11/1800Z 29.4N 156.9W 90 KT 105 MPH
36H 12/0600Z 31.5N 159.6W 85 KT 100 MPH
48H 12/1800Z 33.6N 162.3W 75 KT 85 MPH
60H 13/0600Z 35.5N 164.9W 60 KT 70 MPH
72H 13/1800Z 37.3N 167.3W 40 KT 45 MPH...POST-TROPICAL
96H 14/1800Z 41.0N 170.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 15/1800Z...DISSIPATED

$$
Forecaster Blake

[StormWeather]

Making a run towards major hurricane status

Literally! I think this would be historic if it were to become a MH north of Hawaii.

[ElectricStorm]

Could get to 100kts+ at this rate. Crazy things going on in the CPAC this year lol

[Kingarabian]

Dual feeder bands. I dont know what's its feeding on that high North lol.

[Hurricane2022]

[StormWeather]

https://i.imgur.com/jufukIB.jpeg

That definitely looks like a structure conducive for more intensification.

[cycloneye]

Up to 70kt at 00z Best Track.

EP, 08, 2025081100, , BEST, 0, 262N, 1532W, 70, 990, HU

[StormWeather]

Up to 70kt at 00z Best Track.

EP, 08, 2025081100, , BEST, 0, 262N, 1532W, 70, 990, HU

It’s already 70 kts according to the most recent discussion.

[cycloneye]

Hurricane Henriette Discussion Number 28
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
500 PM HST Sun Aug 10 2025

Henriette's appearance on satellite imagery is similar to 6 hours
ago. The hurricane has maintained a visible eye on geostationary
imagery since about 1800 UTC (9 hours ago). The east eyewall is a
bit thin, and some dry air may be attempting to entrain into the
circulation east of the center. The latest subjective Dvorak
estimates are a consensus 4.0/65 kt from JTWC, PHFO and SAB.
Objective DPRINT and SATCON values from UW-CIMSS have been running
in the 65-70 kt range for the past several hours. The initial
intensity is held at 70 kt for this advisory.

Henriette is currently over sea-surface temperatures (SSTs) of about
26C, and the SSTs along the cyclone's path should peak close to 27C
in 24-36 h. The hurricane will encounter its coldest upper-level
temperatures in about 18-24 h as it passes east of a large mid- to
upper-level trough. This means that despite environmental dry
air, Henriette will still have access to plenty of instability for
another day or so. The NHC forecast continues to call for
additional strengthening, and is at the high end of the guidance for
the first 36 h. After that time, vertical wind shear is expected to
increase and SSTs will decrease along Henriette's path as it gains
latitude, and the NHC forecast lies near the middle of the guidance
envelope from day 2 onward. The shear and colder water should cause
the cyclone to lose its convection and become post-tropical in 60 to
72 h, with the low dissipating in about 4 days.

The hurricane is moving northwestward at 14 kt in between a large
ridge to its northeast and the aforementioned trough to its
northwest. These features will continue steering Henriette rather
quickly toward the northwest for several days until dissipation.
Only very minor changes were made to the previous official forecast,
which lies near the various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 26.8N 153.8W 70 KT 80 MPH
12H 11/1200Z 28.4N 155.8W 80 KT 90 MPH
24H 12/0000Z 30.5N 158.4W 85 KT 100 MPH
36H 12/1200Z 32.6N 161.1W 80 KT 90 MPH
48H 13/0000Z 34.7N 163.8W 65 KT 75 MPH
60H 13/1200Z 36.6N 166.2W 50 KT 60 MPH
72H 14/0000Z 38.5N 168.2W 35 KT 40 MPH...POST-TROPICAL
96H 15/0000Z 42.1N 169.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 16/0000Z...DISSIPATED

$$
Forecaster Hagen

[Hurricane2022]

Here is the sunset over our pretty little baby!

[Yellow Evan]

Per a pair of microwave passes, likely completed an ERC earlier today.

Dry air will be a problem at this latitude and will probably hold this back from strengthening too much more.

[cycloneye]

Hurricane Henriette Discussion Number 29
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Sun Aug 10 2025

The satellite presentation of Henriette had degraded earlier this
evening, perhaps due to what appeared to be an eye wall replacement
cycle, while the cyclone was also passing over a tongue of slightly
cooler sea surface temperatures around 25.5C. Recent satellite
images however depict the eye becoming better defined and surrounded
by cooling cloud tops. The most recent subjective Dvorak current
intensity estimates were 4.0/65 kt from PHFO and SAB, and 4.5/77 kt
from JTWC. Meanwhile, the objective estimates from UW-CIMSS have
ranged between 65 and 76 kt during the past several hours. Taking a
blend of these estimates, the initial intensity has been held at 70
kt for this advisory.

Henriette is moving toward the northwest, or 315 degrees, at 15 kt.
This general motion is expected to continue during the next couple
of days as the cyclone is steered between a mid-level low to the
northwest of Hawaii and a building mid-level ridge far to the north
of the cyclone. A turn toward the north and a decrease in forward
speed is expected beyond 60 hours as the increasingly shallow system
is steered by a low to mid-level ridge to the east. The official
track forecast is near the middle of the guidance envelope and is
very close to the previous advisory.

Henriette will remain over sufficiently warm water for some
intensification during the next day or so, however, vertical wind
shear is forecast to increase considerably by about 36 hours. As a
result, the official forecast calls for some strengthening during
the next 24 hours, followed by slight weakening between 24 and 36
hours, and more rapid weakening thereafter. Henriette is expected
to weaken into a post-tropical low by 72 hours, with dissipation
expected by 120 hours. The intensity forecast is mostly unchanged
and is slightly higher than the intensity guidance in the near term,
then close to the middle of the intensity guidance envelope beyond
36 hours.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 27.6N 155.0W 70 KT 80 MPH
12H 11/1800Z 29.2N 157.1W 80 KT 90 MPH
24H 12/0600Z 31.4N 159.7W 85 KT 100 MPH
36H 12/1800Z 33.5N 162.3W 80 KT 90 MPH
48H 13/0600Z 35.5N 165.1W 55 KT 65 MPH
60H 13/1800Z 37.4N 167.6W 40 KT 45 MPH
72H 14/0600Z 39.6N 169.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 15/0600Z 42.6N 171.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 16/0600Z...DISSIPATED

$$
Forecaster Jelsema (CPHC)

[cycloneye]

Hurricane Henriette Discussion Number 30
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
500 AM HST Mon Aug 11 2025

Henriette has been going through some rapid structural changes
during the past several hours. A 1138 UTC GMI microwave pass
confirmed that an eyewall replacement was in the process of
occurring, with a ring of deep convection surrounding a small
remnant of the previous eyewall. Since that time, convection
appears to have redeveloped in the inner eyewall, and a small eye
is trying to form in conventional satellite imagery. Dvorak CI
numbers at 1200 UTC from PHFO, SAB, and JTWC ranged between 4.0/65
kt and 4.5/77 kt, while most of the objective numbers are between
70-80 kt. The initial intensity is raised to 75 kt as a blend of
all these numbers.

The hurricane is moving quickly toward the northwest, or 310/16 kt.
The forecast track is remarkably straight and steady during the next
48 hours or so, as Henriette is steered between a mid-level low
northwest of the Hawaiian Islands and a large ridge centered off the
coast of the Pacific Northwest United States. After 48 hours, the
cyclone is expected to turn toward the north-northwest and slow down
when it reaches the western periphery of the ridge. Confidence
remains high in the track forecast, and the new NHC prediction is
right on top of the previous one, lying close to the TVCE and HCCA
consensus aids.

Henriette probably has another 12-24 hours to take advantage of an
environment of sufficiently warm sea surface temperatures, low
shear, and upper-level divergence. The NHC forecast therefore
shows a little more strengthening in the short term. Although
ocean temperatures only become gradually cooler after that time,
the atmosphere quickly becomes less conducive with an increase in
shear and convergence aloft. Weakening is therefore indicated, at
a rate similar to the bulk of the guidance, and Henriette could
become post-tropical in about 60 hours when it loses its organized
deep convection. The post-tropical cyclone/remnant low is then
likely to dissipate by day 5 over the far northern Pacific.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 28.8N 156.5W 75 KT 85 MPH
12H 12/0000Z 30.4N 158.6W 80 KT 90 MPH
24H 12/1200Z 32.5N 161.1W 75 KT 85 MPH
36H 13/0000Z 34.5N 163.7W 70 KT 80 MPH
48H 13/1200Z 36.5N 166.4W 50 KT 60 MPH
60H 14/0000Z 38.5N 168.6W 40 KT 45 MPH...POST-TROPICAL
72H 14/1200Z 40.4N 169.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 15/1200Z 43.1N 171.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 16/1200Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Hurricane Henriette Discussion Number 31
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 AM HST Mon Aug 11 2025

Henriette now has a compact Central Dense Overcast, with a dimple
noted in visible satellite imagery where a small eye could be
attempting to form, surrounded by a long spiral band. Subjective
and objective satellite intensity estimates are relatively
unchanged from 6 hours ago, so the initial intensity is still
assumed to be around 75 kt.

The initial motion is also unchanged--northwestward, or 310/16 kt.
The track guidance is tightly packed for the next 48-60 hours, with
Henriette expected to continue moving northwestward between a
mid-level low northwest of the Hawaiian Islands and a large ridge
centered off the coast of the Pacific Northwest United States.
There is more significant spread after 60 hours, related to whether
or not Henriette gets picked up by a shortwave trough near the
Aleutian Islands (and turns eastward, as in the GFS) or gets left
behind and continues northward (as in the ECWMF). The new NHC
track forecast is a little east of the previous prediction at the
end of the forecast, leaning toward the new consensus aids.

Some intensification is still possible during the next 12 hours or
so while there remains some favorable divergence aloft, and the NHC
intensity forecast reflects that potential. By 24 hours,
upper-level convergence, increasing northerly to northwesterly
shear, and cooling sea surface temperatures are expected to induce
weakening. Henriette could lose its organized deep convection, and
thus become post-tropical, in about 60 hours, with the remnant low
likely dissipating by day 5 over the far northern Pacific.


FORECAST POSITIONS AND MAX WINDS

INIT 11/2100Z 29.8N 157.8W 75 KT 85 MPH
12H 12/0600Z 31.4N 159.8W 80 KT 90 MPH
24H 12/1800Z 33.3N 162.3W 75 KT 85 MPH
36H 13/0600Z 35.2N 164.9W 65 KT 75 MPH
48H 13/1800Z 37.3N 167.4W 45 KT 50 MPH
60H 14/0600Z 39.4N 169.4W 35 KT 40 MPH...POST-TROPICAL
72H 14/1800Z 41.4N 170.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 15/1800Z 43.8N 169.3W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 16/1800Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

BULLETIN
Hurricane Henriette Advisory Number 32
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
500 PM HST Mon Aug 11 2025

...COMPACT HURRICANE HENRIETTE CONTINUES NORTHWESTWARD WELL NORTH
OF HAWAII...


SUMMARY OF 500 PM HST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...30.8N 159.0W
ABOUT 660 MI...1060 KM N OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...987 MB...29.15 INCHES



Hurricane Henriette Discussion Number 32
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
500 PM HST Mon Aug 11 2025

Satellite images show that the structure of Henriette has degraded a
little over the past several hours. The eye feature seen earlier has
disappeared, and the convective pattern has lost some organization.
The initial intensity is nudged downward to 70 kt based on a
blend of the latest satellite intensity estimates. An ASCAT pass
shortly after 20Z confirmed that the wind field of Henriette is
very compact, with its tropical-storm-force winds extending no more
than 60 n mi from the center.

Henriette is likely to maintain its intensity through tonight, but
weakening should commence shortly thereafter. In fact, the weakening
trend on Tuesday and Wednesday is likely to be quite fast as the
small system will be moving over sharply cooler waters and into an
environment of strong shear. Most of the models show Henriette
becoming a post-tropical cyclone in 48 to 60 hours and dissipating
entirely in about 4 days, and that is reflected in the official
forecast.

The hurricane is moving northwestward at about 15 kt. This general
motion is expected to persist during the next couple of days as the
cyclone continues to be steered by the flow between a mid-level
ridge to its northeast and a mid- to upper-level low currently
situated northwest of Henriette. After that time, a turn to the
north-northwest is expected in the low-level flow. The models are
in good agreement, and little change was made to the previous track.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 30.8N 159.0W 70 KT 80 MPH
12H 12/1200Z 32.3N 160.9W 70 KT 80 MPH
24H 13/0000Z 34.2N 163.4W 65 KT 75 MPH
36H 13/1200Z 35.9N 165.8W 55 KT 65 MPH
48H 14/0000Z 38.0N 168.3W 45 KT 50 MPH
60H 14/1200Z 40.1N 170.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 15/0000Z 41.9N 170.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 16/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Hurricane Henriette Discussion Number 33
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Mon Aug 11 2025

Henriette's inner core has deteriorated during the past several
hours. Microwave overpasses from the Space Operations Command
(SpOC) WSF-M1 and an ISS TEMPEST-D CubeSat imager revealed a
collapsed, partial eyewall in the eastern half of the cyclone and
fragmented curved bands in the southwest and northeast quadrants.
Subjective intensity estimates from PGTW (17th OWS), PHFO, and SAB,
a 0710 UTC SATCON analysis of 64 kt and a blend of the UW-CIMSS
objective intensity techniques yield a lowered initial intensity of
65 kt.

Henriette is moving beneath a region of upper-level convergence
between an upper-tropospheric low to the northwest of the cyclone
and an upper-level anticyclone to the northeast. This inhibiting
dynamic contribution, along with increasing northerly shear and
progressively cooler oceanic surface temperatures, should cause
Henriette to weaken quickly through the remainder of the period.
The majority of the deterministic models predict that Henriette
should degenerate into a post-tropical cyclone by early Thursday
and open up into a trough over the central north Pacific by the
weekend. Accordingly, quick weakening is indicated in the NHC
forecast and resembles the previous one, and is very close to the
LGEM and just above the HCCA and IVCN consensus intensity models.

The initial motion is estimated to be northwestward, or 315/14 kt.
Henriette should continue moving in this general heading during the
next couple of days in the mid-level steering flow provided by a
subtropical ridge to Henriette's northeast and a mid- to
upper-level low located northwest of the cyclone. Afterward, a
weakened, vertically shallow Henriette should turn toward the
north-northwest then to the north while rounding the western
periphery of a low- to mid-level high to the east. The new track
forecast is essentially an update of the previous advisory and lies
close to the various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0900Z 31.7N 160.1W 65 KT 75 MPH
12H 12/1800Z 33.1N 161.9W 60 KT 70 MPH
24H 13/0600Z 35.0N 164.5W 55 KT 65 MPH
36H 13/1800Z 37.0N 166.9W 45 KT 50 MPH
48H 14/0600Z 39.2N 169.1W 35 KT 40 MPH...POST-TROPICAL
60H 14/1800Z 41.3N 169.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 15/0600Z 43.2N 169.4W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 16/0600Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Storm Henriette Discussion Number 34
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
500 AM HST Tue Aug 12 2025

The overall satellite presentation of Henriette has not changed
much overnight with deep convection over the small inner core of
the cyclone. Earlier microwave imagery showed that the eye had
become less distinct, and the latest subjective and objective
satellite intensity estimates have begun to decrease. A blend of
Dvorak Final-T and CI-numbers from the subjective estimates support
an initial intensity of 60 kt for this advisory.

Environmental conditions consisting of SSTs of 26-27 degrees C and
moderate vertical wind shear suggests that only gradual weakening
will occur today. However, the shear is forecast to increase
significantly overnight and on Wednesday which should result in a
faster rate of demise. Simulated satellite imagery from the
global models show the system decoupling in 24 to 36 hours, and the
updated forecast calls for Henriette to become post-tropical by
36 hours, but this could occur a little sooner. The latest NHC
intensity forecast is near the IVCN multi-model consensus aid, which
is a little above the HFIP corrected consensus that indicates an
even faster rate of weakening.

Henriette is moving northwestward or 315/15 kt, and this general
motion should continue for another 24 to 36 hours as the system is
steered between a mid-level ridge to its northeast and an
upper-level low to the west. As the cyclone weakens and is steered
more by the low-level low it is expected to decelerate and turn
north-northwestward and northward. The updated official track
forecast is essentially an update of the previous advisory and lies
close to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 12/1500Z 32.8N 161.6W 60 KT 70 MPH
12H 13/0000Z 34.3N 163.5W 55 KT 65 MPH
24H 13/1200Z 36.2N 166.0W 45 KT 50 MPH
36H 14/0000Z 38.3N 168.2W 35 KT 40 MPH...POST-TROPICAL
48H 14/1200Z 40.7N 169.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 15/0000Z 42.7N 169.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 15/1200Z...DISSIPATED

$$
Forecaster Brown/E. Adams

[cycloneye]

Tropical Storm Henriette Discussion Number 35
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 AM HST Tue Aug 12 2025


Henriette continues to weaken. Convection has become fragmented
over the past few hours with some shallow convection to the east of
the center. A microwave image from 1740 UTC showed the low-level
eyewall open to the west. Subjective and objective Dvorak estimates
have generally decreased this cycle and a blend of these data
supports an initial intensity of 55 kt for this advisory.

Atmospheric and oceanic conditions are becoming increasingly
hostile. Sea surface temperatures are expected to drop below 26
degrees C within a few hours. The ongoing moderate wind shear is
forecast to increase and likely force additional nearby dry air into
the storm's circulation. Global models suggest that Henriette will
lose all deep convection within 24 hours. The latest official
intensity forecast now shows the storm becoming a post-tropical
cyclone on Wednesday and a remnant low by Wednesday evening, and
this is in line with the latest consensus aids.

Henriette is moving northwestward or 315/15 kt. This general motion
should continue for the next day or so as the storm is steered
between a mid-level ridge to the northeast and an upper-level low to
the west. Thereafter, the system should be steered more by the
low-level flow as it weakens and is expected to decelerate and turn
north-northwestward and northward. Only minor adjustments have been
made to the latest NHC track forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 12/2100Z 34.1N 162.9W 55 KT 65 MPH
12H 13/0600Z 35.7N 164.9W 45 KT 50 MPH
24H 13/1800Z 37.7N 167.2W 35 KT 40 MPH...POST-TROPICAL
36H 14/0600Z 39.9N 169.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 14/1800Z 42.0N 169.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 15/0600Z 44.0N 169.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 15/1800Z...DISSIPATED

$$
Forecaster Bucci

[cycloneye]

Bye.

BULLETIN
Post-Tropical Cyclone Henriette Advisory Number 37
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Tue Aug 12 2025

...HENRIETTE NOW A POST-TROPICAL CYCLONE...
...THIS IS THE LAST ADVISORY...


SUMMARY OF 1100 PM HST...0900 UTC...INFORMATION
-----------------------------------------------
LOCATION...36.7N 165.6W
ABOUT 1160 MI...1865 KM NNW OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 20 MPH...31 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES

[StormWeather]

Goodbye Henriette, you had a good run.