EPAC: LORENA - Post-Tropical - Discussion

[StormWeather]

Radar has generally improved throughout the morning. Recon probably finds 75-85 knots.

I’m going to be bold and say they find 90-95 kts by the time they get there.

When was the last time we had duel majors in the Eastern Pacific?

[cycloneye]

BULLETIN
Hurricane Lorena Intermediate Advisory Number 7A
NWS National Hurricane Center Miami FL EP122025
1100 AM MST Wed Sep 03 2025

...AIR FORCE RECONNAISSANCE CURRENTLY INVESTIGATING LORENA...
...HEAVY RAINFALL AND LIFE-THREATENING FLASH FLOODING SPREADING
NORTHWARD ACROSS BAJA CALIFORNIA SUR...


SUMMARY OF 1100 AM MST...1800 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.5N 112.1W
ABOUT 145 MI...230 KM W OF CABO SAN LUCAS MEXICO
ABOUT 160 MI...255 KM S OF CABO SAN LAZARO MEXICO
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES

[Zonacane]

GFS has a firehose of rain for southern AZ,

[Zonacane]

Quite the convective burst rotating around the eye

[Travorum]

[cycloneye]

BULLETIN
Hurricane Lorena Advisory Number 8
NWS National Hurricane Center Miami FL EP122025
200 PM MST Wed Sep 03 2025

...AIR FORCE RECONNAISSANCE FINDS LORENA STILL A CATEGORY 1
HURRICANE...
...HEAVY RAINFALL AND LIFE-THREATENING FLASH FLOODING EXPECTED
ACROSS BAJA CALIFORNIA SUR...


SUMMARY OF 200 PM MST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...22.8N 112.4W
ABOUT 160 MI...255 KM W OF CABO SAN LUCAS MEXICO
ABOUT 140 MI...220 KM S OF CABO SAN LAZARO MEXICO
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES



Hurricane Lorena Discussion Number 8
NWS National Hurricane Center Miami FL EP122025
200 PM MST Wed Sep 03 2025

The Air Force Reserve reconnaissance aircraft that investigated
Lorena made two passes through the center, measuring maximum 700-mb
flight-level winds of 79 kt in the NE quadrant and a center
dropsonde pressure of 985 mb with 7 kt of wind. The intensity is
held at 70 kt based on the reconnaissance data. The data also
confirmed that Lorena is rather small in size, with the aircraft
data indicating a similar extent of the wind field as to what was
previous estimated.

Lorena could still intensify for another 6-12 hours while it remains
over warm water and in low wind shear conditions. By 18 hours, the
hurricane is expected to cross the 26C sea-surface temperature
isotherm while southwesterly wind shear also begins to significantly
increase. These conditions are expected to lead to rapid weakening
beginning by Thursday afternoon. Only minor adjustments were made
to the official intensity forecast. The official forecast is at the
high end of the intensity guidance through 24 hours, and then lies
closer to the middle of the guidance envelope thereafter.

The track guidance hasn't changed too much, but the TVCE, GFEX, and
other consensus models are a bit faster with the northeastward
motion beyond 36 h, and the NHC track was sped up a bit after that
time. Otherwise, only minor changes were made to the NHC track
forecast. It should be noted that several models indicate a farther
left track, with dissipation over water without making landfall.
This scenario is possible if the hurricane rapidly weakens by
Thursday night and starts to decouple due to the aforementioned
increasing southwesterly shear. Regardless of which track scenario
pans out, there is very high confidence that heavy rainfall amounts
leading to significant flooding will occur in Baja California Sur,
especially since the southwesterly upper-level winds favor deep
convection to the right side of Lorena.


Key Messages:

1. Heavy rainfall associated with Lorena will continue to impact
Baja California Sur, moving into southwestern Sonora by Thursday.
These rains are likely to cause life-threatening flash floods and
mudslides.

2. Moisture from Lorena is likely to contribute to heavy rainfall
concerns across Arizona and southern New Mexico through Saturday.
Isolated to scattered instances of flash flooding are possible
across Arizona into Saturday afternoon.

3. The center of Lorena is forecast to move parallel to, but
offshore of, the southwest coast of the Baja California Peninsula
through tonight, and then move closer to the west-central coast of
the peninsula on Thursday. Regardless of the exact track, tropical
storm conditions are likely along portions of the coast of Baja
California Sur where a Tropical Storm Warning is in effect. Tropical
storm conditions are also possible beginning Friday along the east
coast of the Baja California peninsula, where a Tropical Storm Watch
is in effect.

4. Life-threatening surf and rip current conditions will affect
portions of the southern and western coasts of Baja California Sur
during the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT 03/2100Z 22.8N 112.4W 70 KT 80 MPH
12H 04/0600Z 23.6N 113.4W 80 KT 90 MPH
24H 04/1800Z 24.8N 113.9W 70 KT 80 MPH
36H 05/0600Z 26.0N 113.8W 55 KT 65 MPH
48H 05/1800Z 27.2N 113.3W 40 KT 45 MPH
60H 06/0600Z 28.4N 112.5W 35 KT 40 MPH
72H 06/1800Z 29.3N 111.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 07/1800Z...DISSIPATED

$$
Forecaster Hagen/Brown

[cycloneye]

BULLETIN
Hurricane Lorena Intermediate Advisory Number 8A
NWS National Hurricane Center Miami FL EP122025
500 PM MST Wed Sep 03 2025

...LORENA MOVING A LITTLE SLOWER TOWARD THE NORTHWEST...
...LIFE-THREATENING FLASH FLOODING EXPECTED ACROSS BAJA CALIFORNIA
SUR AND SOUTHWESTERN SONORA...


SUMMARY OF 500 PM MST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...23.1N 112.9W
ABOUT 125 MI...200 KM SSW OF CABO SAN LAZARO MEXICO
ABOUT 190 MI...310 KM W OF CABO SAN LUCAS MEXICO
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES

[cycloneye]

EP, 12, 2025090400, , BEST, 0, 231N, 1129W, 75, 981, HU

[Kingarabian]

Southwesterlies kicking in. Right now theyre acting to enhance outflow. But soon will decouple it unless it makes landfall quick.

[Sciencerocks]

[cycloneye]

BULLETIN
Hurricane Lorena Advisory Number 9
NWS National Hurricane Center Miami FL EP122025
800 PM MST Wed Sep 03 2025

...LORENA A LITTLE STRONGER BUT EXPECTED TO WEAKEN QUICKLY ON
THURSDAY AND FRIDAY...
...RISK OF LIFE-THREATENING FLASH FLOODING CONTINUES FOR BAJA
CALIFORNIA SUR AND SOUTHWESTERN SONORA...


SUMMARY OF 800 PM MST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...23.4N 113.2W
ABOUT 110 MI...180 KM SSW OF CABO SAN LAZARO MEXICO
ABOUT 210 MI...340 KM W OF CABO SAN LUCAS MEXICO
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...981 MB...28.97 INCHES





Hurricane Lorena Discussion Number 9
NWS National Hurricane Center Miami FL EP122025
800 PM MST Wed Sep 03 2025

Objective satellite intensity estimates from UW-CIMSS (ADT,
AiDT, and SATCON) have increased by 5 to 10 kt since the Air Force
Reserve reconnaissance mission into Lorena earlier this afternoon.
Since the plane's data suggested an intensity of 70 kt at that
time, the current intensity is estimated to be about 75 kt. That
said, Lorena is probably at its peak intensity. There are already
signs in conventional and microwave satellite imagery that vertical
shear is beginning to strengthen, with a sharpening of the southern
side of the upper-level cloud pattern and some tilt of the
circulation with height. The shear is forecast to gradually
increase over the next couple of days, and Lorena will also be
moving over waters colder than 26 degrees Celsius in about 6 to 12
hours. Therefore, quick weakening is shown in the official
forecast.

Lorena continues to move toward the northwest, or 310 degrees, but
at a slightly slower 10 kt. As the cyclone moves farther into a
break in the subtropical ridge, it is expected to turn northward
and slow down further by Thursday evening, and then move only
slowly north-northeastward into the weekend. The 18z GFS run is
finally playing the same tune as much of the other guidance,
showing Lorena quickly decoupling as the shear removes its deep
convection and leaving the low-level center drifting toward the
west coast of Baja California Sur. Now that there is
near-unanimous agreement that Lorena is unlikely to move quickly
as a deep system toward northwestern Mexico, the NHC track forecast
has been slowed down significantly, blending the previous forecast
with the most recent HCCA and TVCE consensus aids. This new
forecast brings Lorena's center to the west coast of Baja
California Sur in about 48 hours as a weakening tropical cyclone,
with the system reaching the east coast of the peninsula as a
remnant low in about 60 hours. However, based on the latest GFS-
and ECMWF-based simulated satellite imagery, the transition to a
remnant low could occur earlier than that.

Even if Lorena weakens and becomes a remnant low earlier than
previously predicted, abundant moisture will continue to stream
northeastward away from the cyclone. Because of that, there is
still a significant risk of heavy rainfall and flash flooding across
portions of Baja California Sur, Sonora, and southern Arizona and
New Mexico.


Key Messages:

1. Heavy rainfall associated with Lorena will continue to impact
Baja California Sur and shift into southwestern Sonora Thursday.
This will increase the risk of life-threatening flash floods and
mudslides across northwest Mexico.

2. Moisture from Lorena will contribute to heavy rainfall concerns
across Arizona and southwest New Mexico through Saturday. Isolated
to scattered instances of flash flooding are possible across Arizona
into Saturday.

3. The center of Lorena is forecast to move parallel to, but
offshore of, the southwest coast of the Baja California Peninsula
through Thursday, and then move closer to the west-central coast of
the peninsula Thursday night and Friday. Regardless of the exact
track, tropical storm conditions are likely along portions of the
coast of Baja California Sur where a Tropical Storm Warning is in
effect. Tropical storm conditions are also possible late Friday
along the east coast of the Baja California peninsula, where a
Tropical Storm Watch is in effect.

4. Life-threatening surf and rip current conditions will affect
portions of the southern and western coasts of Baja California Sur
during the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 23.4N 113.2W 75 KT 85 MPH
12H 04/1200Z 24.1N 113.9W 65 KT 75 MPH
24H 05/0000Z 25.0N 114.1W 55 KT 65 MPH
36H 05/1200Z 26.0N 113.8W 45 KT 50 MPH
48H 06/0000Z 27.0N 113.4W 35 KT 40 MPH
60H 06/1200Z 28.0N 113.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 07/0000Z 28.8N 112.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 08/0000Z...DISSIPATED

$$
Forecaster Berg

[Sciencerocks]

[cycloneye]

Hurricane Lorena Discussion Number 10
NWS National Hurricane Center Miami FL EP122025
200 AM MST Thu Sep 04 2025

Lorena has become less organized since the last advisory due to the
impacts of increasing vertical shear and decreasing sea surface
temperatures underneath the hurricane. Earlier microwave
imagery indicated that the eyewall had broken open, and current
conventional imagery shows that the low-level center is now
located near the southwestern edge of the convective mass. The
various satellite intensity estimates are now trending down, and
based on this the initial intensity is reduced to a possibly
generous 70 kt.

The initial motion is now a slower 320/7 kt. Lorena is expected to
turn northward with a further decrease in forward speed later today
as the cyclone moves farther into a break in the subtropical ridge.
After that, the guidance is now considerably slower in moving Lorena
to the north-northeast with the 00Z GFS now taking 60 h to reach
Baja California Sur. The NHC forecast track is again slowed down
significantly and blends the previous forecast with the new
consensus models and the 00Z GFS. It should be noted that in
contrast to the right turn of the GFS and the regional hurricane
models, the ECMWF and Canadian models continue to show a left turn
as Lorena approaches the coast that would keep the center offshore
until the cyclone dissipates.

Lorena should rapidly weaken in the increasingly unfavorable
environment, with the cyclone now forecast to weaken to a tropical
storm in 12 h or less. After that, the simulated satellite imagery
from the 00Z GFS and ECMWF shows the cyclone should stop producing
organized convection no later than 48 h, and this could happen
earlier. The new intensity forecast now shows the system decaying to
a remnant low by 48 h. Whether the system crosses Baja or stays
over the cold Pacific waters, it is expected to dissipate completely
by 96 h.

Although Lorena is forecast to rapidly weaken, abundant moisture
will continue to stream northeastward away from the cyclone.
Because of that, there is still a significant risk of heavy
rainfall and flash flooding across portions of Baja California Sur,
Sonora, and southern Arizona and New Mexico.


Key Messages:

1. Heavy rainfall associated with Lorena will continue to impact
Baja California Sur and Sonora Mexico through Friday. This will
increase the risk of life-threatening flash floods and mudslides
across northwest Mexico.

2. Moisture from Lorena will contribute to heavy rainfall concerns
across Arizona and New Mexico through Saturday. Isolated to
scattered instances of flash flooding are possible across Arizona
into Saturday.

3. The center of Lorena is forecast to move parallel to, but
offshore of, the southwest coast of the Baja California Peninsula
today, and then move closer to the west-central coast of the
peninsula tonight and Friday. Regardless of the exact track,
tropical storm conditions are likely along portions of the coast of
Baja California Sur where a Tropical Storm Warning is in effect.
Tropical storm conditions are also possible late Friday along the
east coast of the Baja California peninsula, where a Tropical Storm
Watch is in effect.

4. Life-threatening surf and rip current conditions will affect
portions of the southern and western coasts of Baja California Sur
during the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0900Z 24.0N 113.7W 70 KT 80 MPH
12H 04/1800Z 24.7N 114.2W 60 KT 70 MPH
24H 05/0600Z 25.4N 114.3W 45 KT 50 MPH
36H 05/1800Z 26.1N 113.9W 35 KT 40 MPH
48H 06/0600Z 26.7N 113.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 06/1800Z 27.3N 113.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 07/0600Z 28.0N 112.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 08/0600Z...DISSIPATED

$$
Forecaster Beven

[Yellow Evan]

Shear kicked in sooner than modeled.

[cycloneye]

EP, 12, 2025090412, , BEST, 0, 240N, 1141W, 60, 991, TS

[WaveBreaking]

My guess as to why Lorena kept pump faking an RI episode all day yesterday is that there was probably some dry air in its core that it was never able to get rid of. Which makes sense bc Lorena started out with a somewhat sprawling structure and a small core.

[Travorum]

My guess as to why Lorena kept pump faking an RI episode all day yesterday is that there was probably some dry air in its core that it was never able to get rid of. Which makes sense bc Lorena started out with a somewhat sprawling structure and a small core.

Looking at a combination of microwave, radar, and recon data it seems like Lorena only had a closed-off eyewall for about 6-7 hours, from 10-11z until shortly before recon got in at 17z. Given that combined with the pulsing deep convection all day yesterday I would agree that dry air is the most likely culprit.

[cycloneye]

BULLETIN
Tropical Storm Lorena Advisory Number 12
NWS National Hurricane Center Miami FL EP122025
200 PM MST Thu Sep 04 2025

...RISK OF LIFE-THREATENING FLASH FLOODING CONTINUES FOR BAJA
CALIFORNIA SUR AND SOUTHWESTERN SONORA...


SUMMARY OF 200 PM MST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...24.6N 114.8W
ABOUT 155 MI...255 KM W OF CABO SAN LAZARO MEXICO
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES




Tropical Storm Lorena Discussion Number 12
NWS National Hurricane Center Miami FL EP122025
200 PM MST Thu Sep 04 2025

Strong southwesterly wind shear and cold water temperatures have
taken their toll on Lorena. The convection has completely fallen
apart and detached itself from the low-level circulation today,
leaving an exposed swirl that is evident on GOES-18 visible
channels. An Air Force Reserve Reconnaissance Aircraft, which was
just in the center, measured maximum 850-mb flight-level winds of 52
kt, which corresponds to about 42 kt at the surface. The central
pressure is estimated at 996 mb based on dropsonde data from the
aircraft. Additionally, a recent ASCAT pass showed an area of 35-40
kt winds, mostly in the NW quadrant. The initial intensity
estimate, based on the aforementioned data, has been reduced to 45
kt.

Confidence is high that the cyclone will continue to weaken as it
moves over progressively colder water and into stronger
southwesterly wind shear. The timing of when Lorena is forecast to
weaken to a remnant low has been moved up to 24 h, but it could
occur sooner, as most of the convection has already been sheared off
well to the northeast of the low-level circulation. The latest NHC
track forecast has been shifted slightly to the left, or slightly
farther offshore of the Baja California peninsula, compared to the
previous NHC forecast, closer to the latest models.

Some large rainfall totals have already been observed across
portions of Baja California Sur, and the risk of life-threatening
flash flooding will continue across portions of the area through
Friday. Abundant moisture will continue to stream northeastward
away from the cyclone. Because of that, there is still a
significant risk of heavy rainfall and flash flooding across
portions of Baja California Sur, Sonora, southern Arizona and New
Mexico.


Key Messages:

1. Heavy rainfall associated with Lorena will continue to impact
Baja California Sur and Sonora Mexico through Friday. This will
increase the risk of life-threatening flash floods and mudslides
across northwest Mexico.

2. Moisture from Lorena will contribute to heavy rainfall concerns
across Arizona and New Mexico through Saturday. Isolated to
scattered instances of flash flooding are possible across Arizona
into Saturday.

3. Life-threatening surf and rip current conditions will affect
portions of the southern and western coasts of Baja California Sur
during the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 24.6N 114.8W 45 KT 50 MPH
12H 05/0600Z 25.0N 114.9W 35 KT 40 MPH
24H 05/1800Z 25.4N 114.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 06/0600Z 25.9N 114.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 06/1800Z 26.3N 114.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 07/0600Z 26.7N 115.3W 15 KT 15 MPH...POST-TROP/REMNT LOW
72H 07/1800Z...DISSIPATED

$$
Forecaster Hagen

[Teban54]

Decoupling in real time:

[cycloneye]

BULLETIN
Tropical Storm Lorena Advisory Number 13
NWS National Hurricane Center Miami FL EP122025
800 PM PDT Thu Sep 04 2025

...LORENA EXPECTED TO BECOME POST-TROPICAL VERY SOON...
...MOST IMPORTANTLY, THE RISK OF LIFE-THREATENING FLASH FLOODING
CONTINUES FOR BAJA CALIFORNIA SUR AND SONORA THROUGH FRIDAY...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...24.6N 115.1W
ABOUT 175 MI...285 KM W OF CABO SAN LAZARO MEXICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES



Tropical Storm Lorena Discussion Number 13
NWS National Hurricane Center Miami FL EP122025
800 PM PDT Thu Sep 04 2025

Lorena has not produced deep convection near its center since about
8 AM this morning. Waves of heavy showers and thunderstorms
continue to stream northeastward across Baja California Sur, Sonora,
and northern Sinaloa, but this activity cannot be directly linked
to Lorena's circulation. Weakening is assumed to have occurred
since the earlier aircraft and ASCAT data, and the intensity is set
at 40 kt based on a blend of Dvorak CI numbers and objective
numbers (which are between 30 and 45 kt). With Lorena over cool
waters and southwesterly shear only expected to increase, deep
convection is not forecast to redevelop, and Lorena is likely to
become post-tropical Friday morning. Winds will continue to
steadily decrease, with the remnant low likely to dissipate by late
Sunday.

Lorena has been moving west of the dynamical model guidance over
the past 6 to 12 hours, and the best-performing track models since
this morning have been the simple shallow Trajectory and Beta
Advection (TABS) models. Given that the circulation will remain
shallow, the new NHC track forecast blends the TABS models with the
latest GFS-ECWMF mean and HCCA consensus aid. This puts the new
forecast west of the previous prediction by a somewhat noticeable
degree, showing more of a slow northwestward motion instead of
northward trajectory.

Abundant moisture will continue to stream northeastward away from
Lorena even though it is weakening. Significant rainfall and flash
flooding has already occurred over portions of Baja California Sur,
and the risk of life-threatening flash flooding will continue across
portions of Baja California Sur and Sonora through Friday,
and southern Arizona and New Mexico through Saturday.


Key Messages:

1. Heavy rainfall associated with Lorena will continue to impact
Baja California Sur and Sonora Mexico through Friday. This will
increase the risk of life-threatening flash floods and mudslides
across northwest Mexico.

2. Moisture from Lorena will contribute to heavy rainfall concerns
across Arizona and New Mexico through Saturday. Isolated to
scattered instances of flash flooding are possible across Arizona
into Saturday.

3. Life-threatening surf and rip current conditions will affect
portions of the western coast of Baja California Sur through Friday.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0300Z 24.6N 115.1W 40 KT 45 MPH
12H 05/1200Z 25.0N 115.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 06/0000Z 25.3N 115.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 06/1200Z 25.7N 115.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 07/0000Z 26.1N 116.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 07/1200Z 26.5N 117.6W 15 KT 15 MPH...POST-TROP/REMNT LOW
72H 08/0000Z...DISSIPATED

$$
Forecaster Berg