EPAC: HILARY - Post-Tropical - Discussion

[GCANE]

SPC Mesoanalysis has CAPE in the Gulf of CA down to 3000.
Was 7000 yesterday.

[tolakram]

Why would a large Category 4 hurricane have minimal WISHE?

Great question.
Microwave soundings are showing anomalous high temperatures above the ocean indicating low heat transfer to the troposphere and minimal lapse rate into the core.
Only thing I can think of is a large ingestion of extremely high CAPE air from its surroundings.

So, I looked at Earth Null school and there was an area of very high CAPE air over the Gulf of CA.
It looks like Hilary did ingest it, nearly gone now.
May pick up more later as she moves along the Baja Coast

Isn't that derived from model output? If not, where do all these air analysis come from?

[Fancy1002]

SPC Mesoanalysis has CAPE in the Gulf of CA down to 3000.
Was 7000 yesterday.

What does CAPE stand for?

[tolakram]

SPC Mesoanalysis has CAPE in the Gulf of CA down to 3000.
Was 7000 yesterday.

What does CAPE stand for?

Convective Available Potential Energy

[GCANE]

Great question.
Microwave soundings are showing anomalous high temperatures above the ocean indicating low heat transfer to the troposphere and minimal lapse rate into the core.
Only thing I can think of is a large ingestion of extremely high CAPE air from its surroundings.

So, I looked at Earth Null school and there was an area of very high CAPE air over the Gulf of CA.
It looks like Hilary did ingest it, nearly gone now.
May pick up more later as she moves along the Baja Coast

Isn't that derived from model output? If not, where do all these air analysis come from?

I believe its a mix of satellite soundings and then models fill in the holes

[GCANE]

So, I looked at Earth Null school and there was an area of very high CAPE air over the Gulf of CA.
It looks like Hilary did ingest it, nearly gone now.
May pick up more later as she moves along the Baja Coast

Isn't that derived from model output? If not, where do all these air analysis come from?

I believe its a mix of satellite soundings and then models fill in the holes

I believe RAP is the model to fill in the holes

[NDG]

Dry air has compromised the SW eyewall which is now gone. This is earlier than what models were forecasting it.

[GCANE]

Recon heading out of LA

[Sciencerocks]

[GCANE]

Eye is shrinking and doesn't look like its drying out either.

[Kingarabian]

I think regardless whether this weakens sooner than anticipated, the impacts will be the same. Will only affect the technicality of an actual TC landfall over SoCal.

[LarryWx]

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.

This would have happened in 1939 but the NHC didn't exist yet

Furthermore, NHC didn't even issue TS watches and warnings til 1987:

"In 1987, gale watches/warnings were renamed tropical storm watches/warnings."

https://en.m.wikipedia.org/wiki/History ... e_warnings

[cycloneye]

Hurricane Hilary Discussion Number 13
NWS National Hurricane Center Miami FL EP092023
900 AM MDT Sat Aug 19 2023

Although Hilary continues to maintain a well-defined circular eye,
the convective pattern has become increasingly asymmetric during the
past several hours. Deep convection has been eroding on the
system's west side as dry and stable air has been wrapping into
that portion of the circulation. A blend of the latest satellite
intensity estimates supports nudging the initial intensity downward
to 110 kt for this advisory. The Air Force Hurricane Hunters are
scheduled to investigate the system later today, and the data they
collect will provide a better assessment of Hilary's intensity and
structure.

The major hurricane continues to turn to the right, and the latest
initial motion is north-northwestward, or 345/14 kt. The steering
currents are well established and consist of a strong mid-level high
pressure area over the south-central U.S. and a mid- to upper-level
low off the central California coast. The flow between these
features should cause Hilary to accelerate to the north-northwest or
north during the next day or two, with the core of the system
reaching the central portion of the Baja California Peninsula
tonight and southern California Sunday afternoon or evening. Users
are reminded that the exact details of the track forecast, including
where Hilary might make landfall, are of little overall importance
since strong winds and heavy rainfall will extend far from the
center. These hazards will also begin well in advance of the
arrival of the center.

Hilary is expected to weaken quickly while it moves northward due to
significantly cooler waters, drier air, and an increase in vertical
wind shear. Even though weakening is anticipated, Hilary is still
expected to be a hurricane when it moves near or over the central
portion of the Baja California peninsula, but is expected to decay
to a tropical storm before it moves over southern California. The
intensity models are in good agreement, and the NHC forecast is
near the middle of the guidance envelope.


KEY MESSAGES:

1. Preparations for flooding impacts should be completed as soon as
possible, as heavy rainfall will begin well in advance of the
center. In the Southwestern U.S., the potentially historic
amount of rainfall is expected to cause flash, urban, and arroyo
flooding including landslides, mudslides, and debris flows.
Dangerous to locally catastrophic flooding impacts are expected late
tonight through early Monday.

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

3. Tropical storm conditions are expected to begin Sunday afternoon
in portions of the southwestern U.S. within the Tropical Storm
Warning area. Winds could be particularly strong and gusty in and
near areas of higher terrain.

4. Large swells generated by Hilary will affect portions of the
Baja California Peninsula and southern California over the next
couple of days. These swells are likely to cause life-threatening
surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT 19/1500Z 22.3N 113.5W 110 KT 125 MPH
12H 20/0000Z 24.6N 114.1W 90 KT 105 MPH
24H 20/1200Z 28.3N 115.2W 70 KT 80 MPH
36H 21/0000Z 33.4N 116.7W 50 KT 60 MPH...INLAND
48H 21/1200Z 39.6N 117.4W 30 KT 35 MPH...POST-TROP/INLAND
60H 22/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[NDG]

I really doubt the Recon will find Hilary to still be a Cat 3, they better go with SFMR this time.

[NDG]

GFS not doing good with current satellite deterioration of Hilary.

[dexterlabio]

It being possibly below Cat3 strength right now wouldn't be a huge big deviation from the forecast IMO. Impacts in Baja California and SE USA would still be the same, which is mostly heavy rainfall.

Nonetheless, it's kinda crazy that the first area in CONUS to get a tropical storm watch in 2023 is SoCal.

[storm_in_a_teacup]

It’s just wild…I move out of Los Angeles for good and THEN this happens…my friends there are all like “the hurricane was supposed to come when you were there!”

[NDG]

And of course when the recon is about to make its first pass through the eye the recon stops reporting. I guess they don't want to us to see how much it has weakened already well before the forecast. j/k.

[NDG]

Hilary is getting big time decoupled already, wow!!!! That's fast.
Barely Cat 2 if not just Cat 1 winds so far in the NE quadrant.

[NDG]

Pressure up at least 12 mb from earlier today.

URPN15 KNHC 191715
AF305 0309E HILARY HDOB 24 20230819
170330 2252N 11350W 6964 02817 //// +105 //// 107053 060 072 011 01
170400 2250N 11351W 6966 02808 //// +124 //// 106044 047 064 005 05
170430 2248N 11352W 6967 02797 9611 +125 //// 108039 042 060 008 01
170500 2247N 11352W 6969 02789 9592 +138 +137 106029 035 043 005 00
170530 2245N 11353W 6963 02791 9581 +141 +132 093021 026 032 004 00
170600 2243N 11353W 6966 02784 9576 +145 +131 072014 019 022 004 00
170630 2242N 11352W 6973 02774 9567 +156 +126 077008 011 016 001 03
170700 2240N 11352W 6978 02768 9564 +158 +127 180006 009 017 002 03
170730 2238N 11352W 6959 02795 9567 +154 +131 239011 012 013 001 03
170800 2238N 11352W 6959 02795 9570 +155 +130 263013 015 013 002 00
170830 2236N 11354W 6967 02790 9572 +159 +128 283020 022 017 001 00
170900 2234N 11355W 6932 02837 9576 +155 +124 296026 028 018 002 00
170930 2233N 11357W 6937 02838 9583 +158 +121 303032 034 023 002 00
171000 2231N 11358W 6941 02846 9594 +160 +114 305043 047 028 003 00
171030 2230N 11400W 6943 02857 9608 +165 +102 304050 051 037 002 00
171100 2228N 11402W 6945 02871 9633 +157 +102 305057 059 041 001 00
171130 2227N 11403W 6940 02891 9651 +154 +100 299058 060 043 001 00
171200 2226N 11405W 6946 02896 9678 +142 +100 305061 063 044 002 00
171230 2224N 11406W 6939 02917 9687 +149 +079 306063 063 044 002 00
171300 2224N 11406W 6939 02917 9688 +150 +084 306063 064 044 002 00
$$