EPAC: LORENA - Hurricane - Discussion

[Sciencerocks]

[TomballEd]

Over a month early and likely not a strong Cat 2 like Hurricane Rosa, but the modeled path, a storm stripped of its LL circulation crossing the mountains but having an MLC with tropical moisture above the surface, rain threat for CONUS?

[vbhoutex]

Over a month early and likely not a strong Cat 2 like Hurricane Rosa, but the modeled path, a storm stripped of its LL circulation crossing the mountains but having an MLC with tropical moisture above the surface, rain threat for CONUS?

I presume you've seen our local ocm and others in thee state are suggesting we will have a problem in Texas. I would expect it is a strong possibility.

[cycloneye]

EP, 12, 2025090218, , BEST, 0, 189N, 1083W, 45, 1002, TS

[Kingarabian]

Over a month early and likely not a strong Cat 2 like Hurricane Rosa, but the modeled path, a storm stripped of its LL circulation crossing the mountains but having an MLC with tropical moisture above the surface, rain threat for CONUS?

I presume you've seen our local ocm and others in thee state are suggesting we will have a problem in Texas. I would expect it is a strong possibility.

This thing is massive. GFS has the remnants of Lorena moving slowly over Texas with an abundant amount of moisture.

[Kingarabian]

Warm spot?

[cycloneye]

BULLETIN
Tropical Storm Lorena Advisory Number 4
NWS National Hurricane Center Miami FL EP122025
Issued by the NWS Weather Prediction Center College Park MD
200 PM MST Tue Sep 02 2025

...TROPICAL STORM LORENA STRENGTHENING AND FORECAST TO BECOME A
HURRICANE TOMORROW...
...TROPICAL STORM WATCHES ISSUES FOR WESTERN PORTION OF BAJA
CALIFORNIA SUR...

SUMMARY OF 200 PM MST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...19.4N 109.0W
ABOUT 310 MI...495 KM W OF MANZANILLO MEXICO
ABOUT 250 MI...400 KM SSE OF CABO SAN LUCAS MEXICO
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of Mexico has issued a Tropical Storm Watch from Cabo
San Lucas northward to Cabo San Lazaro on the western coast of Baja
California Sur.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
* Cabo San Lucas northward to Cabo San Lazaro on the western coast
of Baja California Sur in Mexico.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

Interests elsewhere in southwestern Mexico and the Baja California
peninsula should monitor the progress of this system. Additional
watches may be required later tonight or on Wednesday.



Tropical Storm Lorena Discussion Number 4
NWS National Hurricane Center Miami FL EP122025
Issued by the NWS Weather Prediction Center College Park MD
200 PM MST Tue Sep 02 2025

A 1548z METOP-B ASCAT pass provided solid coverage of Lorena's
overall wind field with also resulted in a northward adjustment to
the initial position. Since the ASCAT pass, GOES-East visible
imagery continues to show improving overall organization within an
ideal environment for further strengthening. Symmetric banding
features support Dvorak DT numbers of 3.0 and 3.5 from TAFB and SAB,
respectively. The recent inner core convection bursting with cloud
tops below -80C further suggest a strengthening trend, even without
recent microwave imagery to analyze its inner core structure. The
initial intensity is set at 45 kt, as a blend of the two operational
Dvorak estimates, along with other objective intensity estimates.

Since the prior advisory, Lorena is moving a bit faster at 13 kt to
the northwest as its being steered by the southwestern periphery of
the larger scale mid-level ridge. With the small northward
readjustment of position, the northwestward track will continue
through the next 48 hours, but this brings the center and wind field
closer to Baja California compared to the prior track forecast. As
such, the overall forecast track is a bit faster and shifted north
and east relative to prior forecast, following trends in the latest
track guidance. Due to the uncertainty that Tropical Storm force
winds may affect areas along the southwestern coasts of Baja
California Sur, the Government of Mexico has issued Tropical Storm
Watches from Cabo San Lucas northward to Cabo San Lazaro. Any
further deviations north and/or eastward may result in further
expansion of watches and/or warning conditions over the next 24 to
48 hours. Deep layer vertical shear and overall decaying
sea-surface environment will slow the forward speed, with slow
recurvature expected after 48 hours west of Baja California Sur.
The shear results in an expanding track forecast suite, though will
continue to prior trends and overall means recurving the cyclone
toward the central Baja California with initial landfall forecast
after 72 hours. What remains of the circulation will cross the
Peninsula tracking northeast with a second landfall along coastal
Sonora towards the end of the forecast period.

Lorena is expected to remain fairly small inner core, though with
ample moisture and warm sea-surface temperatures for the next 24 to
36 h, forecasts are for steady intensification toward hurricane
status by Wednesday. There is some potential that Lorena may rapidly
intensify in the short term given its structure and favorable
environment. As Lorena crosses the 26 C isotherm in 2-3 days,
vertical wind shear will also increase and the overall intensity
should start to weaken by late in the week. As the cyclone turns
northeastward, slow weakening is expected with eventual dissipation
over Sonora by Saturday. The intensity forecast is on the higher
end of the guidance envelope.


Key Messages:

1. Heavy rainfall associated with Tropical Storm Lorena will begin
to affect Baja California Sur on Wednesday, and southwestern Sonora
by Thursday. This will increase the risk of life-threatening flash
floods and mudslides, especially in areas of higher terrain.

2. Lorena is forecast to approach the Baja California peninsula
later this week. Due to the uncertainty that Tropical Storm force
winds may affect areas along the southwestern coasts of Baja
California Sur, the Government of Mexico has issued Tropical Storm
Watches from Cabo San Lucas northward to Cabo San Lazaro. Residents
should closely monitor the latest forecast updates and ensure that
they have their preparedness plan in place.

FORECAST POSITIONS AND MAX WINDS

INIT 02/2100Z 19.4N 109.0W 45 KT 50 MPH
12H 03/0600Z 20.6N 110.4W 55 KT 65 MPH
24H 03/1800Z 21.8N 112.0W 65 KT 75 MPH
36H 04/0600Z 22.9N 113.1W 75 KT 85 MPH
48H 04/1800Z 24.1N 113.8W 70 KT 80 MPH
60H 05/0600Z 25.1N 113.8W 55 KT 65 MPH
72H 05/1800Z 26.2N 113.3W 45 KT 50 MPH
96H 06/1800Z 28.4N 111.8W 35 KT 40 MPH
120H 07/1800Z 29.9N 110.3W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Gallina/Papin

[Sciencerocks]

[cycloneye]

BULLETIN
Tropical Storm Lorena Intermediate Advisory Number 4A
NWS National Hurricane Center Miami FL EP122025
500 PM MST Tue Sep 02 2025

...LORENA STRENGTHENING...

SUMMARY OF 500 PM MST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...19.8N 109.2W
ABOUT 220 MI...350 KM SSE OF CABO SAN LUCAS MEXICO
ABOUT 230 MI...370 KM W OF CABO CORRIENTES MEXICO
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES


SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
* West Coast of Baja California Sur from Cabo San Lucas northward
to Cabo San Lazaro

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

Interests elsewhere in southwestern Mexico and the Baja California
peninsula should monitor the progress of this system. Additional
watches may be required later tonight or on Wednesday.

[cycloneye]

EP, 12, 2025090300, , BEST, 0, 198N, 1092W, 55, 997, TS

[cycloneye]

BULLETIN
Tropical Storm Lorena Advisory Number 5
NWS National Hurricane Center Miami FL EP122025
800 PM MST Tue Sep 02 2025

...LORENA COULD RAPIDLY INTENSIFY THROUGH WEDNESDAY...


SUMMARY OF 800 PM MST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...20.2N 109.7W
ABOUT 185 MI...300 KM S OF CABO SAN LUCAS MEXICO
ABOUT 260 MI...415 KM W OF CABO CORRIENTES MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES


SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
* West Coast of Baja California Sur from Cabo San Lucas northward
to Cabo San Lazaro

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

Interests elsewhere on the Baja California peninsula and in
southwestern Mexico should monitor the progress of Lorena.
Additional watches or warnings may be required on Wednesday.



Tropical Storm Lorena Discussion Number 5
NWS National Hurricane Center Miami FL EP122025
800 PM MST Tue Sep 02 2025

A pair of AMSR2 and GMI microwave passes from several hours ago
revealed that Lorena's structure has improved significantly through
the day, with the 37-GHZ channel in particular showing a
well-defined cyan ring. The center is embedded beneath a Central
Dense Overcast, and Dvorak intensity estimates from TAFB and SAB
are a consensus T3.5/55 kt. This is also supported by some of the
UW-CIMSS objective numbers, and the initial intensity is therefore
set--possibly conservatively given the structure--at 55 kt.

Lorena has a low-level structure and small size that would make it
a prime suspect for rapid intensification, especially since it will
be in an environment of low shear and over warm ocean temperatures
for the next 36 hours. In fact, the SHIPS Rapid Intensification
(RI) index now shows a 3 in 4 chance of a 30-kt increase in
Lorena's winds over the next 24 hours. The NHC intensity forecast
therefore explicitly shows RI during the next day or so and most
closely follows the SHIPS and LGEM models, which are the highest
guidance, during that time. After 36 hours, increasing shear and
colder water temperatures are expected lead to weakening, which
itself could be rapid due to Lorena's small size. Although there
is significant uncertainty on where Lorena will end up in 4-5 days
(see discussion below), the cyclone will likely not exist anymore
by day 5, and that is when dissipation is shown in the forecast.

Lorena continues to move northwestward, or 315/12 kt. The first 36
hours or so of the track forecast are fairly straightforward, with
a slower northwestward motion expected while the cyclone moves
around the western periphery of a mid-level high centered over
Mexico. Things are trickier after 36 hours. Lorena will be moving
through a weakness in the subtropical ridge, but how much northward
progress it makes will depend on how long it remains strong. A
minority of models, particularly the GFS, keep a stronger Lorena
moving northeastward across the Baja California peninsula toward
Sonora. However, moderate to strong southwesterly shear is likely
to set in over Lorena in 48-72 hours, and a good chunk of the other
models, including many of the GEFS ensemble members, keep a
weakening Lorena offshore the west coast of the Baja California
peninsula with landfall never occurring. This new NHC forecast
blends the previous official forecast with the latest HCCA, Florida
State Superensemble, and GEFS ensemble mean, showing a slower
motion on day 4 and 5, and introducing the possibility that Lorena
doesn't reach mainland Mexico as a tropical cyclone.


Key Messages:

1. Heavy rainfall associated with Tropical Storm Lorena will begin
to affect Baja California Sur on Wednesday, southwestern Sonora by
Thursday, and contribute to heavy rainfall concerns across Arizona
late Wednesday through Friday. This will increase the risk of
life-threatening flash floods and mudslides across Mexico,
especially in areas of higher terrain. Isolated to scattered
instances of flash flooding are possible across Arizona through
Friday.

2. Although rapid intensification is possible through Wednesday
while Lorena is offshore, the storm is expected to weaken while it
approaches the Baja California peninsula on Thursday and Friday.
Regardless, tropical storm conditions are possible through Thursday
along portions of the west coast of Baja California Sur.
Interests in Baja California Sur should closely monitor the latest
forecast updates.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0300Z 20.2N 109.7W 55 KT 65 MPH
12H 03/1200Z 21.2N 111.1W 70 KT 80 MPH
24H 04/0000Z 22.3N 112.6W 85 KT 100 MPH
36H 04/1200Z 23.4N 113.5W 90 KT 105 MPH
48H 05/0000Z 24.6N 113.9W 75 KT 85 MPH
60H 05/1200Z 25.6N 113.8W 55 KT 65 MPH
72H 06/0000Z 26.6N 113.3W 40 KT 45 MPH
96H 07/0000Z 28.1N 112.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 08/0000Z...DISSIPATED

$$
Forecaster Berg

[Hurricane2022]

...and the initial intensity is therefore set--possibly
conservatively given the structure--at 55 kt.

The SHIPS Rapid Intensification (RI) index now shows a 3 in 4
chance of a 30-kt increase in Lorena's winds over the next 24 hours.
The NHC intensity forecast therefore explicitly shows RI during the
next day or so...

Barring any unexpected shear or dry air intrusion, I fully expect Lorena to become a (low-end) major now.

[cycloneye]

BULLETIN
Hurricane Lorena Advisory Number 6
NWS National Hurricane Center Miami FL EP122025
200 AM MST Wed Sep 03 2025

...LORENA BECOMES A HURRICANE...
...NEW WARNINGS AND WATCHES ISSUED FOR BAJA CALIFORNIA SUR...


SUMMARY OF 200 AM MST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...21.2N 110.4W
ABOUT 120 MI...195 KM SSW OF CABO SAN LUCAS MEXICO
ABOUT 275 MI...445 KM SSE OF CABO SAN LAZARO MEXICO
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...990 MB...29.24 INCHES




Hurricane Lorena Discussion Number 6
NWS National Hurricane Center Miami FL EP122025
200 AM MST Wed Sep 03 2025

Satellite imagery and data from the Mexican radar at Cabo San Lucas
indicate that Lorena continues to become better organized, with the
radar imagery showing an eyewall wrapped 50-70 percent of the way
around the center. Satellite intensity estimates are now in the
55-65 kt range, with subjective estimates from TAFB and SAB being
65 kt. Based on these data, the initial intensity is increased to
65 kt and Lorena is upgraded to a hurricane.

Steady to rapid intensification is likely during the next 24 h,
and while the forecast peak intensity of 85 kt is above the upper
edge of the intensity guidance it might be conservative. After
that time, Lorena is forecast to move over cooler sea surface
temperatures and into an area of southwesterly vertical shear.
This should cause significant weakening, and Lorena is expected to
weaken back to a tropical storm by 60 h. There is significant
uncertainty as to whether Lorena will make landfall in Baja
California Sur (see discussion below). If it does, the system
should continue weakening and dissipate over northwestern Mexico by
120 h. If it doesn't, the cyclone should continue to weaken over
cold water, with dissipation likely west of Baja California Sur
by 120 h.

The initial motion is now 320/12 kt. The first 24 h or so of
the track forecast remain fairly straightforward, with a slower
northwestward motion expected while the cyclone moves around the
western periphery of a mid-level high centered over Mexico. After
that time, Lorena will be moving into a weakness in the subtropical
ridge as it starts to encounter the less favorable environment.
The GFS model maintains a stronger and deeper Lorena and breaks open
the weakness in about 36 h, allowing the cyclone to recurve
north-northeastward into northwestern Mexico. The ECMWF and
Canadian models have a weaker Lorena and take about 12 h longer to
break open the ridge. This results in Lorena shearing apart with
the low-level center turning westward over the Pacific west of Baja
California Sur. Based on current intensity trends, the track
forecast leans toward the GFS solution and shows Lorena crossing
Baja California Sur in 60-72 h. However, there is still the
possibility that the cyclone does not reach the coast of Mexico. The
new forecast track is similar to the previous track and lies along
the east side of the consensus models.


Key Messages:

1. Heavy rainfall associated with Tropical Storm Lorena will
continue to impact Baja California Sur, moving into southeastern
Baja California and southwestern Sonora by Thursday, and contribute
to heavy rainfall concerns across Arizona late Wednesday through
Friday. This will increase the risk of life-threatening flash floods
and mudslides across Mexico, especially in areas of higher terrain.
Isolated to scattered instances of flash flooding are possible
across Arizona through Friday.

2. Although rapid intensification is possible through tonight while
Lorena is offshore, the storm is expected to weaken while it
approaches the Baja California peninsula on Thursday and Thursday
night. Regardless, tropical storm conditions are likely along
portions of the coast of Baja California Sur where a Tropical Storm
Warning has been issued. Tropical Storm conditions are also
possible through Friday along other portions of the west coast of
Baja California Sur where a Tropical Storm Watch is in effect.
Interests in Baja California Sur should closely monitor the latest
forecast updates.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 21.2N 110.4W 65 KT 75 MPH
12H 03/1800Z 22.2N 111.7W 75 KT 85 MPH
24H 04/0600Z 23.2N 113.0W 85 KT 100 MPH
36H 04/1800Z 24.2N 113.7W 80 KT 90 MPH
48H 05/0600Z 25.3N 113.9W 65 KT 75 MPH
60H 05/1800Z 26.4N 113.7W 50 KT 60 MPH
72H 06/0600Z 27.4N 113.3W 35 KT 40 MPH
96H 07/0600Z 29.5N 111.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 08/0600Z...DISSIPATED

$$
Forecaster Beven