EPAC: HILARY - Post-Tropical - Discussion

[BobHarlem]

12z early models.

TVCN shows landfall just north of Carlsbad, near Camp Pendleton,

[aspen]

I’m thinking recon will find a low-end 4 or a high-end 3 when it finally arrives. There’s very clearly an EWRC (and/or maybe some upwelling) impacting Hilary’s satellite presentation. It has maybe 18 hours maximum before SSTs/MPI start rapidly dropping.

[GCANE]

Eye has shrunk and a lot more ragged looking than a few hours ago

[Sciencerocks]

[cycloneye]

Hurricane Hilary Discussion Number 9
NWS National Hurricane Center Miami FL EP092023
900 AM MDT Fri Aug 18 2023

After an impressive 70-kt increase in winds over the past 24 hours,
Hilary's intensity has leveled off. Satellite data indicate that
Hilary remains an impressive major hurricane with a 15-20 n mi
diameter eye and symmetric convective cloud pattern surrounding that
feature. A blend of the latest satellite intensity estimates
support holding the initial intensity steady at 125 kt. Microwave
data is showing some signs of a double eyewall structure, which is
quite common in strong hurricanes like Hilary. Hilary is quite
large with its tropical-storm-force winds extending up to 250 n mi
from the center. The Air Force Hurricane Hunters are scheduled to
investigate the hurricane later today, and the data they collect
will provide a better assessment of the system's strength and
structure.

Hilary has turned to the northwest with the initial motion estimated
to be 305/9 kt. A general north-northwest to north motion with a
steady increase in forward speed is expected later today and through
the weekend as the system is steered by the flow between a strong
subtropical ridge over the south-central U.S. and a mid- to
upper-level low off the central California coast. This pattern
should take the core of Hilary near the central Baja California
Peninsula coast Saturday night and then inland over southern
California Sunday night. The models are in fairly good agreement,
and little change was made to the previous track forecast. It
should be noted that strong winds and heavy rains will occur well
ahead of the center.

Fluctuations in the hurricane's strength are expected today, but
Hilary is expected to begin weakening late tonight as it moves over
progressively cooler SSTs and into an environment of increasing
shear and drier air. The NHC intensity forecast follows the HCCA
and IVCN models and is largely an update of the previous one.

Based on the forecast, a Tropical Storm Watch has been issued for
portions of southern California. This is the first time NHC has
issued a watch for that region. Supplemental soundings (weather
balloons) are being launched by much of the National Weather Service
offices across the western U.S. This effort is highly appreciated
as the data should help provide a better assessment of the
environment and steering pattern ahead of Hilary.


KEY MESSAGES:

1. Heavy rainfall associated with Hilary could produce areas of
flash flooding and result in landslides over portions of the Baja
California Peninsula late tonight through late Sunday. Rainfall
impacts from Hilary within the Southwestern United States are
expected to peak this weekend into Monday. Flash, urban, and arroyo
flooding is expected, with the potential for rare and dangerous
impacts.

2. Hurricane conditions are expected within portions of the
hurricane warning area along the west-central coast of the Baja
California Peninsula on Sunday and are possible in the Hurricane
Watch area.

3. Tropical storm conditions are possible on Sunday in portions of
southern California where a Tropical Storm Watch has been issued.

4. Large swells from Hilary will spread northward along the coast of
southwestern Mexico and the Baja California Peninsula. These swells
will reach the Gulf of California and northern portions of the Baja
California Peninsula later this weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 18/1500Z 17.9N 111.4W 125 KT 145 MPH
12H 19/0000Z 19.2N 112.5W 130 KT 150 MPH
24H 19/1200Z 21.3N 113.6W 115 KT 130 MPH
36H 20/0000Z 23.7N 114.4W 100 KT 115 MPH
48H 20/1200Z 26.8N 115.2W 85 KT 100 MPH
60H 21/0000Z 30.4N 116.4W 65 KT 75 MPH
72H 21/1200Z 35.2N 117.4W 45 KT 50 MPH...INLAND
96H 22/1200Z...DISSIPATED

$$
Forecaster Cangialosi

[aspen]

SoCal is now under a Tropical Storm Watch. I never thought I’d see that.

[ScottNAtlanta]

SoCal is now under a Tropical Storm Watch. I never thought I’d see that.

According to the NHC discussion, it's the first time this has ever happened.

[GCANE]

Very prominent moat on water vapor now

https://www.tropicaltidbits.com/sat/sat ... uct=wv_mid

[aspen]

Very prominent moat on water vapor now

https://www.tropicaltidbits.com/sat/sat ... uct=wv_mid

Really deep into an EWRC now. I wonder if there’s enough time left for the new eye to take over before Hilary starts running into lowering SSTs and dry air.

There’s a huge band to the south with a gap that looks like it could draw dry air into the circulation, but that area seems nice and moist on that WV filter.

[Landy]

Didn't expect the system update back in February for administering watches in this area to be used so soon but here we are.

URGENT - IMMEDIATE BROADCAST REQUESTED
Hilary Local Watch/Warning Statement/Advisory Number 9
National Weather Service San Diego CA EP092023
829 AM PDT Fri Aug 18 2023

CAZ043-182330-
/O.NEW.KSGX.TR.A.2009.230818T1529Z-000000T0000Z/
San Diego County Coastal Areas-
829 AM PDT Fri Aug 18 2023

...TROPICAL STORM WATCH IN EFFECT...

A Tropical Storm Watch means tropical storm-force winds are possible
somewhere within this area within the next 48 hours

* LOCATIONS AFFECTED
- Oceanside
- Carlsbad
- Chula Vista
- San Diego

[GCANE]

Very prominent moat on water vapor now

https://www.tropicaltidbits.com/sat/sat ... uct=wv_mid

Really deep into an EWRC now. I wonder if there’s enough time left for the new eye to take over before Hilary starts running into lowering SSTs and dry air.

There’s a huge band to the south with a gap that looks like it could draw dry air into the circulation, but that area seems nice and moist on that WV filter.

I checked CAPE in the Gulf of California and I didn't realize it was that high.
Looks to be 7000.
Its hard to tell on the SPC Mesoscale Analysis since the gradients are so tight.
From what on saw on GFS, Hiliary will just about ingest all of that as she runs up the Baja Coast.
Will be interesting to see how much of that influences intensity.

[Iceresistance]

This is possibly a once-in-a-generation threat for California, the only other storm that made landfall in California as a tropical cyclone was the Long Beach tropical storm in 1939.

Rainfall potential is insane, Weather Prediction Center has over 7 inches in some spots in Southern California

[ElectricStorm]

I'm guessing the plane finds around 105-110kts and 950mb. Looked great earlier but really ragged now

[Kingarabian]

Next 24 hours are crucial if this actually/technically reaches SoCal as a TC or not.
Regardless, impacts will be the same.

[Kingarabian]

Meld in progress. Dry but very impressive core. Could see a larger eye soon.

[Jr0d]

Eye has shrunk and a lot more ragged looking than a few hours ago

Unfortunately recon missed the max intensity by about 6 to 12 hours.

[Yellow Evan]

There’s an 18-24 window to reintensify unless another ERC starts but I think the ERC took a heavy toll on the system as usual. I don’t think Hilary is still a major hurricane.

[SconnieCane]

I'm guessing the plane finds around 105-110kts and 950mb. Looked great earlier but really ragged now

Seems recon can never intercept the peak on these things. I used to think pinning down tropical cyclone intensity was a much more exact science than tornado ratings. It still is, but there's a lot more estimation and educated guesswork involved despite having the benefit of in-situ measurements (assuming that option is actually used, which in the Pacific it usually isn't).

[Socalhurcnegirl227]

SoCal is now under a Tropical Storm Watch. I never thought I’d see that.

What a time to be alive

[GCANE]

Looks like recon is starting to descend