EPAC: IVO - Post-Tropical - Discussion

[cycloneye]

Tropical Storm Ivo Discussion Number 14
NWS National Hurricane Center Miami FL EP092025
800 PM MST Sat Aug 09 2025

Convection associated with Ivo has continued to slowly decrease
during the past 6 hours, but the cyclone's overall appearance hasn't
changed drastically. The latest TAFB Dvorak Current Intensity
estimate is still 45 kt, which is similar to the most recent
UW-CIMSS SATCON, valid around 2210 UTC (43 kt). Therefore, no change
was made to the 45-kt intensity estimate for this advisory.

No noteworthy changes were made to any aspect of the NHC forecast.
Ivo is moving over cooler waters and into a more stable environment
and is therefore forecast to gradually weaken, as shown by all of
the intensity guidance. Simulated satellite imagery from the GFS,
ECMWF and HAFS models indicates Ivo will become post-tropical within
about 36 h. Ivo's motion is now west-northwestward, still at 6 kt.
All models continue to forecast that Ivo will gradually turn due
west in a day or two as it weakens and is steered by the low-level
flow. The model forecast agreement is very good with respect to all
aspects of Ivo's evolution during the next couple of days until it
dissipates early next week.


FORECAST POSITIONS AND MAX WINDS

INIT 10/0300Z 21.2N 114.1W 45 KT 50 MPH
12H 10/1200Z 21.7N 115.4W 40 KT 45 MPH
24H 11/0000Z 22.4N 117.3W 35 KT 40 MPH
36H 11/1200Z 22.8N 119.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 12/0000Z 23.0N 121.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 12/1200Z 23.1N 124.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 13/0000Z...DISSIPATED

$$
Forecaster D. Zelinsky

[cycloneye]

Tropical Storm Ivo Discussion Number 15
NWS National Hurricane Center Miami FL EP092025
200 AM MST Sun Aug 10 2025

Ivo is weakening while it passes over the cooler waters well to the
west of Baja California Sur, and its associated deep convection
is gradually decreasing in coverage and intensity. Data from an
excellent scatterometer overpass just before 0500 UTC showed that
the maximum winds have decreased to near 35 kt. Subjective Dvorak
analyses from TAFB and SAB, along with objective Dvorak values from
UW-CIMSS gave a similar intensity estimate, indicating that Ivo is
now at minimal tropical storm strength.

Center fixes indicate that the cyclone continues to move
west-northwestward, or at about 285/7 kt. A low- to mid-level
ridge is predicted to remain to the north of Ivo during the next
couple of days. The system is likely to turn more westward with a
slight increase in forward speed in a day or so as the increasingly
shallow circulation becomes steered by the low-level easterlies.
The official forecast track is very similar to the one from the
previous advisory.

Ivo is moving over cooler waters with gradually decreasing
environmental moisture. Therefore weakening should continue, and
the system will likely degenerate into a post-tropical remnant low
in 24 hours or so. The intensity forecast is similar to the
previous NHC forecast and near the high end of the model guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 10/0900Z 21.5N 114.9W 35 KT 40 MPH
12H 10/1800Z 22.0N 116.3W 30 KT 35 MPH
24H 11/0600Z 22.7N 118.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 11/1800Z 23.0N 120.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 12/0600Z 23.1N 122.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 12/1800Z 23.0N 125.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 13/0600Z...DISSIPATED

$$
Forecaster Pasch

[StormWeather]

Ivo still holding on just about

617
WTPZ44 KNHC 101435
TCDEP4

Tropical Storm Ivo Discussion Number 16
NWS National Hurricane Center Miami FL EP092025
800 AM PDT Sun Aug 10 2025

Ivo is maintaining a small cluster of deep convection, near and to
the south of the low-level center. Dvorak CI numbers of 2.5 from
TAFB and SAB and objective estimates from UW-CIMSS support holding
the initial intensity at 35 kt for this advisory. The cyclone is
moving over cooler waters and in a more stable environment,
while also contending with moderate northeasterly shear, and
weakening is therefore forecast during the next couple of days.
Ivo should lose all its convection and become a remnant low by 24
hours, and global models show dissipation into a surface trough in
60 hours.

The initial motion is a bit faster toward the west-northwest (290/9
kt). Low- to mid-level ridging to the north should keep Ivo on a
westward to west-northwestward trajectory at a fairly steady speed
during the next couple of days. The NHC forecast is well within
the tightly packed guidance envelope, and no significant changes
were made from the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 10/1500Z 21.9N 116.1W 35 KT 40 MPH
12H 11/0000Z 22.5N 117.5W 30 KT 35 MPH
24H 11/1200Z 23.0N 119.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 12/0000Z 23.2N 121.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 12/1200Z 23.2N 124.2W 15 KT 15 MPH...POST-TROP/REMNT LOW
60H 13/0000Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Still there.

Tropical Storm Ivo Discussion Number 17
NWS National Hurricane Center Miami FL EP092025
200 PM PDT Sun Aug 10 2025

Even over waters of 23-24 degrees Celsius, Ivo is managing to
maintain a persistent area of deep convection. A recent ASCAT pass
showed maximum winds of 30 kt. Accounting for the instrument's
sampling limitations, and combined with satellite estimates still
running around 35 kt, it is estimated that Ivo is hanging on to
tropical storm status. Sea surface temperatures drop by another 2-3
degrees along Ivo's forecast track, so weakening is expected to
resume tonight, and simulated satellite images from the GFS and
ECMWF show that deep convection could finally be gone by Monday
morning. Degeneration into a remnant low is forecast by 24 hours,
followed by dissipation into a trough in 60 hours.

Ivo is moving west-northwestward (285 deg) at 10 kt. This motion
should continue for the next 12 hours, followed by a slight bend to
the west in 24 hours as Ivo stays situated to the south of the low-
to mid-level ridge. The track models are tightly clustered, and
the new NHC forecast is mainly an update of the previous
prediction.

FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 22.1N 117.2W 35 KT 40 MPH
12H 11/0600Z 22.5N 118.6W 30 KT 35 MPH
24H 11/1800Z 22.8N 120.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 12/0600Z 22.9N 123.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 12/1800Z 22.9N 125.3W 15 KT 15 MPH...POST-TROP/REMNT LOW
60H 13/0600Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Down to TD.

Tropical Depression Ivo Discussion Number 18
NWS National Hurricane Center Miami FL EP092025
800 PM PDT Sun Aug 10 2025

Cool waters, dry air, and northeasterly vertical wind shear are
taking a toll on Ivo. Deep convection has been steadily declining
over the past several hours, and the system appears to be on its way
to becoming a remnant low. The initial intensity is lowered to 30
kt, making Ivo a tropical depression. Since the environment is
expected to become even more hostile, Ivo is forecast to continue
weakening. It is now forecast to become a remnant low early Monday
and dissipate entirely in a couple of days.

Ivo is moving toward the west-northwest at about 9 kt. A westward
to west-northwestward motion at about the same forward speed is
expected within the low-level flow until the system dissipates.
Little change was made to the previous track, and this one lies
near the middle of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 22.3N 117.9W 30 KT 35 MPH
12H 11/1200Z 22.6N 119.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 12/0000Z 22.8N 121.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 12/1200Z 22.8N 123.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 13/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[Yellow Evan]

May have been a hurricane at peak.

[cycloneye]

Tropical Depression Ivo Discussion Number 19
NWS National Hurricane Center Miami FL EP092025
200 AM PDT Mon Aug 11 2025

Ivo has become devoid of deep convection as it moves over
increasingly cooler waters and into a drier air mass. The current
intensity estimate is 30 kt which could be a bit generous based on
partial scatterometer overpasses.

The motion continues west-northwestward, or around 295/9 kt. Ivo
should remain embedded in low-level easterly flow for the next day
or two. The track forecast is similar to that from the previous
advisory and very close to the latest corrected consensus, HCCA,
solution.

Since the system is expected to traverse even cooler waters during
the next 36 hours or so, it is unlikely to regenerate significant
deep convection. Thus the cyclone will likely become a
post-tropical remnant low very soon. The global models depict
the system opening up into a trough within 48 hours and this is
reflected in the official forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 22.7N 118.7W 30 KT 35 MPH
12H 11/1800Z 23.0N 120.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 12/0600Z 23.0N 122.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 12/1800Z 23.0N 125.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 13/0600Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Post-Tropical Cyclone Ivo Discussion Number 20
NWS National Hurricane Center Miami FL EP092025
800 AM PDT Mon Aug 11 2025

The last bit of convection associated with Ivo dissipated about 15
hours ago, and it has therefore degenerated into a remnant low.
Maximum winds are estimated to be 25 kt, and further weakening is
forecast as the system moves over colder waters. Ivo is expected
to open up into a trough--and thus dissipate--in about 36 hours, as
depicted in global model fields. Until that time, a low-level
ridge to the north is expected to steer the remnant low westward at
about 10 kt, and no major changes were made to the official track
forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 23.2N 119.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
12H 12/0000Z 23.4N 121.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
24H 12/1200Z 23.5N 123.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 13/0000Z...DISSIPATED

$$
Forecaster Berg