EPAC: HILARY - Post-Tropical - Discussion

[Ntxw]

She's tightening up with the eye getting circular again. Curious what recon finds.

[Sciencerocks]

[aspen]

~115 kt FL, ~95 kt SFMR, 957mb (so far) in the NE eyewall.

[GCANE]

Recon dropped from 700mb to 950mb fight level.

[cycloneye]

BULLETIN
Hurricane Hilary Intermediate Advisory Number 9A
NWS National Hurricane Center Miami FL EP092023
1200 PM MDT Fri Aug 18 2023

...HILARY NEAR SOCORRO ISLAND...
...EXPECTED TO PRODUCE FLOODING RAINS AND STRONG WINDS OVER
MUCH OF BAJA CALIFORNIA AND SOUTHERN CALIFORNIA THIS WEEKEND AND
EARLY NEXT WEEK...


SUMMARY OF 1200 PM MDT...1800 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.2N 111.8W
ABOUT 60 MI...110 KM WSW OF SOCORRO ISLAND
ABOUT 360 MI...575 KM SSW OF CABO SAN LUCAS MEXICO
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...939 MB...27.73 INCHES

[aspen]

Lowest pressure was 947.4 mbar extrapolated. Winds seem to be at 95-100 kt

[Yellow Evan]

NHC will be slow to drop the winds but data plus undersampling supports an intensity of 105 knots.

[ScottNAtlanta]

Thing with an EWRC is that it also expands the wind field. That is not good for So Cal as the TS winds will start much further from the center.

[Bocadude85]

18z TVCN shifted to the west a bit, now has landfall solidly in So Cal, NHC might have to expand that TS watch into LA and Ventura counties if the trend continues.

[Yellow Evan]

18z TVCN shifted to the west a bit, now has landfall solidly in So Cal, NHC might have to expand that TS watch into LA and Ventura counties if the trend continues.

Otoh, the 12z ECMWF went further east into Baja.

[Kingarabian]

W ring to the south, the thickest its been in a while. B ring almost wrapping around completely.

[Yellow Evan]

[Yellow Evan]

[Sciencerocks]

[Bocadude85]

18z TVCN shifted to the west a bit, now has landfall solidly in So Cal, NHC might have to expand that TS watch into LA and Ventura counties if the trend continues.

Otoh, the 12z ECMWF went further east into Baja.

Yup saw that soon after I posted this, though still does end up in So Cal as a sheared mess.

[aspen]

https://media.discordapp.net/attachments/733552978572869632/1142191139751989268/stormir.png

https://media.discordapp.net/attachments/733552978572869632/1142190918162726942/stormir.png

https://media.discordapp.net/attachments/733552978572869632/1142190793638027314/stormir.png

https://media.discordapp.net/attachments/733552978572869632/1142190431661199513/stormir.png

https://media.discordapp.net/attachments/733552978572869632/1142191668246880337/goesmeso.png

Recovering rather well. It could hit a second Cat 4 peak when the second recon flight arrives later tonight.

[cycloneye]

Hurricane Hilary Discussion Number 10
NWS National Hurricane Center Miami FL EP092023
300 PM MDT Fri Aug 18 2023

Hilary remains a large and powerful major hurricane. The Air Force
Hurricane Hunters sampled the northern portion of Hilary and found a
higher minimum pressure than expected of 948 mb, 700 mb flight-level
winds of 113 kt, and peak SFMR surface winds of 93 kt. However, the
aircraft did not sample the southern half of the circulation, which
currently has some of the deepest convection. Blending the available
aircraft data and latest satellite intensity estimates yields an
initial intensity of 115 kt.

Hilary continues to slowly bend to the right, and the initial motion
is northwestward or 315/10 kt. A general north-northwest to north
motion with a steady increase in forward speed is expected tonight
and through the weekend as the system is steered by pronounced
steering flow between a strong subtropical ridge over the
south-central U.S. and a mid- to upper-level low off the central
California coast. The models have trended faster this cycle, and
the NHC forecast has followed suit. Based on the latest forecast,
the core of Hilary is expected to be very near the central portion
of Baja California Saturday night and move inland over southern
California by Sunday night. 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 through
tonight, but Hilary is expected to begin weakening on Saturday as it
moves over progressively cooler SSTs and into an environment of
increasing shear and drier air. The NHC intensity forecast is lower
than the previous one, partially due to the lower initial intensity,
and a little higher than the HCCA and IVCN models.


KEY MESSAGES:

1. Heavy rainfall associated with Hilary will begin well in advance
of the center, from the Baja California Peninsula into the
Southwestern United States. Preparations for the impacts of flooding
from rainfall should be completed as soon as possible, as heavy rain
will increase ahead of the center on Saturday. In the Southwestern
United States, flash, urban, and arroyo flooding is expected, with
the potential for dangerous and locally catastrophic impacts.

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

3. Tropical storm conditions are possible by late Sunday in
portions of southern California where a Tropical Storm Watch is in
effect.

4. Large swells generated by Hilary will affect portions of the
coast of southwestern Mexico, the Baja California peninsula, and
south California over the next few days. These swells are likely
to cause life-threatening surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT 18/2100Z 18.7N 112.2W 115 KT 130 MPH
12H 19/0600Z 20.3N 113.2W 115 KT 130 MPH
24H 19/1800Z 22.6N 114.1W 105 KT 120 MPH
36H 20/0600Z 25.6N 115.0W 85 KT 100 MPH
48H 20/1800Z 29.4N 116.1W 65 KT 75 MPH
60H 21/0600Z 34.1N 117.3W 45 KT 50 MPH...INLAND
72H 21/1800Z 39.3N 117.7W 30 KT 35 MPH...POST-TROP/INLAND
96H 22/1800Z...DISSIPATED

$$
Forecaster Cangialosi

[Kingarabian]

T6.5 again but winds need to catch up

[NDG]

I am really surprised they kept Hilary at Cat 4, they sampled the NE quadrant which is where the strongest winds are found on a hurricane when moving NW to NNW and not even Cat 3 winds were found by SFMR.

[bob rulz]

Very interesting to see a direct tropical threat to California. Keeping my eye on this as I don't usually have to worry about tropical threats up here in Utah. Most of the moisture still looks to stay west of me, but even some moisture making it to Salt Lake City would be a big deal. Average rainfall for the entire summer is a bit less than 2"

Here's the Salt Lake City AFD from this afternoon

.DISCUSSION...Another very busy afternoon across the CWA, with
another relatively brief discussion. Afternoon upper air and
satellite analysis indicates a rather unusual feature. Category 4
Hurricane Hilary is offshore the southern tip of Baja California.
Tropical Storm Watches have been hoisted for southern California
for the first time. Meanwhile an upper level low remains off the
coast of California, with broad ridging roughly centered across
the Red River remains in place.

Over the next few days, Hurricane Hilary will shift north and
accelerate while moving into less favorable waters. This will
result in the potential for a weakening Tropical Storm Hilary to
make landfall across southern California later Sunday.

The main message for Utahns, however, is deep tropical moisture
will move into the area well ahead of landfall. The main threat
with now Hurricane Hilary for Utah will be very heavy rain, as
the current track would not support any wind threat. Current
ensembles support the heaviest rain along the Utah/Nevada border
east to the crest of the mountains through Monday; potentially
into Tuesday.

There will not be any real break between our current monsoon
surge and the increase in tropical moisture...with a shift toward
the increasing tropical moisture across at least the western half
of Utah later Saturday.

For now, expanded the flood watch for central and southern Utah
through 06Z Sunday and added in two additional zones with recent
burn scars (the western Uinta Mountains and the Book Cliffs and
Wasatch Plateau) for Saturday. With additional recon flights
increasing the availability of high quality data ingest into the
00Z and later models, will monitor whether additional watch
extensions will be needed for Sunday or Monday.

Takeaway message: the flash flooding threat will remain elevated
through early next week across a sizable portion of the region.
Those who are near dry washes, recent burn scars, in areas with
poor drainage and/or typically see flooding issues with heavy rain
should prepare now for any impacts (especially across the western
half of Utah). This is not the weekend to hike slot canyons,
normally dry washes or other areas with high flood exposure. And
finally, taking a few extra minutes to deviate around a flooded
road. It is worth saving your life. Do not drive through flooded
areas; turn around, don`t drown.