EPAC: KRISTY - Remnants - Discussion

[cycloneye]

Hurricane Kristy Discussion Number 10
NWS National Hurricane Center Miami FL EP122024
800 PM PDT Wed Oct 23 2024

After rapidly intensifying throughout the day, Kristy's impressive
strengthening trend appears to have paused. The very powerful major
hurricane remains quite compact and symmetric with a ring of intense
deep convection surrounding its tiny eye. The initial wind speed is
held at 135 kt based on a blend of the latest satellite intensity
estimates that range between 125 and 140 kt. However, it is
possible that Kristy is a little stronger as the maximum wind speed
of compact hurricanes are sometimes underestimated. There are also
signs that Kristy could be beginning an eyewall replacement cycle,
which is common in strong hurricanes in near ideal environmental
conditions.

Kristy continues to move swiftly westward at 17 kt on the south side
of a strong ridge centered near Baja California. A turn to the
west-northwest with some decrease in forward speed is expected
during the next day or two as the hurricane moves along the
southwestern periphery of the ridge. A sharper turn to the
northwest or north-northwest is expected Friday night and continuing
through the weekend when the hurricane moves in the flow between the
ridge and a large-scale trough. The NHC track forecast is nudged to
the north of the previous one to come into better agreement with the
latest models.

The major hurricane is expected to remain in generally conducive
environmental conditions for about another day, so the intensity
changes will be largely governed by internal dynamics during that
time. However, steady to rapid weakening should begin by early
Friday when Kristy moves into an environment of progressively
stronger shear, cooler waters, and notably drier air. The models
are in fairly good agreement, and this forecast is close to the
latest HCCA guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 24/0300Z 14.2N 117.2W 135 KT 155 MPH
12H 24/1200Z 14.2N 119.6W 135 KT 155 MPH
24H 25/0000Z 14.6N 122.3W 130 KT 150 MPH
36H 25/1200Z 15.5N 124.9W 125 KT 145 MPH
48H 26/0000Z 16.9N 127.1W 115 KT 130 MPH
60H 26/1200Z 18.7N 129.0W 100 KT 115 MPH
72H 27/0000Z 20.5N 130.7W 75 KT 85 MPH
96H 28/0000Z 21.7N 132.4W 40 KT 45 MPH...POST-TROPICAL
120H 29/0000Z 20.5N 135.8W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Cangialosi

[REDHurricane]

RAMMB SLIDER is still adamant that Kristy will make a historic landfall over the Bay Area

https://i.imgur.com/Sbe69Zm.gif

There's a joke in here somewhere about Stockton getting a direct hit from a cat 5 hurricane and actually looking better afterwards

[kevin]

All hurricane models are hinting towards a secondary peak for Kristy within the next 24 hours so an operational cat 5 might still not be impossible.

NHC = current intensity 933 mb, 130 kt

00z hurricane models
HWRF = current intensity 929 mb, 128 kt -> peaks at 926 mb, 138 kt in 6 hours
HMON = current intensity 954 mb, 100 kt -> peaks at 949 mb, 113 kt in 20 hours
HAFS-A = current intensity 929 mb, 130 kt -> peaks at 922 mb, 147 kt in 17 hours
HAFS-B = current intensity 934 mb, 124 kt -> peaks at 930 mb, 142 kt in 14 hours

[cycloneye]

Hurricane Kristy Discussion Number 11
NWS National Hurricane Center Miami FL EP122024
200 AM PDT Thu Oct 24 2024

Kristy looks a little less impressive this evening, as satellite
imagery indicates that the eye has clouded over. There are hints
in infrared imagery that the hurricane is undergoing an eyewall
replacement cycle, although there are no recent microwave images to
definitively show this. The subjective and objective satellite
intensity estimates have decreased a little over the past 6 h, and
based on this the initial intensity is decreased to 130 kt. The
wind radii have been revised based on recent scatterometer
overpasses showing that Kristy has gotten a little larger in size.

The initial motion is now 270/17 kt. Kristy is currently on the
south side of a deep-layer ridge over the northeastern Pacific. A
turn to the west-northwest with some decrease in forward speed is
expected during the next day or two as the hurricane moves along the
southwestern periphery of the ridge. A sharper turn to the
northwest or north-northwest is expected by 48 h as Kristy moves
between the ridge and a large mid- to -upper-level trough located
east and northeast of the Hawaiian Islands. By the end of the
forecast period, Kristy is expected to shear apart, with the
cyclone or its remnants turning west-southwestward in the
low-level flow. The new forecast track is similar to the previous
track, and it lies near or just to the southwest of the consensus
models.

Kristy is expected to remain over warm water and in a conducive
light shear environment for the next 24-36 h. Based on this and an
expectation that the hurricane will complete an eyewall
replacement, the intensity forecast shows some re-intensification
during this time. After 36 h, the environment becomes much more
hostile, with strong shear, a much drier air mass, and cooler sea
surface temperatures along the forecast track. All guidance agrees
that rapid weakening should occur, and the new intensity forecast
follows the trend of the guidance. Kristy should lose its
convection and become post-tropical by 96 h, and while the forecast
includes a 120 h point as a remnant low there is a possibility the
system will degenerate to a trough by that time.


FORECAST POSITIONS AND MAX WINDS

INIT 24/0900Z 14.1N 118.9W 130 KT 150 MPH
12H 24/1800Z 14.2N 121.2W 135 KT 155 MPH
24H 25/0600Z 14.9N 123.7W 130 KT 150 MPH
36H 25/1800Z 16.0N 126.0W 120 KT 140 MPH
48H 26/0600Z 17.7N 128.0W 110 KT 125 MPH
60H 26/1800Z 19.5N 129.8W 85 KT 100 MPH
72H 27/0600Z 21.1N 131.1W 60 KT 70 MPH
96H 28/0600Z 21.7N 133.1W 35 KT 40 MPH...POST-TROPICAL
120H 29/0600Z 20.0N 137.5W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

[Hurricane2022]

The cloud tops of Kristy have cooled significantly and the eye warmed & became more round again although i'm not sure if she has finished that ERC. But i'm still expecting an (another) C5 later today.

[aspen]

Eye continues to gradually warm and the CDO is becoming better, no longer showing signs that there’s an outer eyewall under there. However, it would be nice to get a MW pass to see if the EWRC has indeed finished.

[Kingarabian]

Eye is indeed attempting to warm. If we get the same clear eye as yesterday, it would be stronger based on Dvorak.

[kevin]

Final T# and raw T# are both at 7.0 and thus support 140 kt. CI# is still at 7.2 (146 kt) due to the earlier peak before the EWRC, but either way Dvorak seems to support a cat 5 now. IR imagery is also still improving. AiDT supports 130 kt, DMINT 129 kt, DPRINT 120 kt. A blend would thus give a current intensity 130 - 135 kt. If Kristy continues to improve and we reach >T7.0 in the next few hours I wouldn't rule out a cat 5 upgrade at the next advisory.

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 24 OCT 2024 Time : 114022 UTC
Lat : 13:57:36 N Lon : 119:39:36 W


CI# /Pressure/ Vmax
7.2 / 920.3mb/146.0kt


Final T# Adj T# Raw T#
7.0 7.0 7.0

Estimated radius of max. wind based on IR : 7 km

Center Temp : -17.2C Cloud Region Temp : -75.4C

Scene Type : EYE

[cycloneye]

No cat 5.

EP, 12, 2024102412, , BEST, 0, 140N, 1197W, 130, 933, HU

[aspen]

Continued improvement on IR, however I doubt it’s enough for SAB to pull the T7.0 trigger. The eye hasn’t warmed up enough yet, and while the W ring is extremely thick and cloud tops are even cooler, the CMG ring is broken on the north side. Probably another 1-2 hours or so of eye clearing should be enough for T7.0, perhaps with T7.5 on the table if the CMG band can wrap all the way around.

Doesn’t make sense to hold at 130 kt when the system is clearly improving, hopefully they go with 135 kt at 11am.

[Travorum]

With eye temps back in the positive and the CDO colder than it was last night, Kristy is probably going to look as good as it ever has over the next few hours. Raw T# is up to 7.5 with CI# at 7.2, SAB had their 12z fix at T6.5 as the eye was a lot cooler an hour ago.

----- Current Analysis -----
Date : 24 OCT 2024 Time : 124022 UTC
Lat : 13:56:23 N Lon : 119:51:36 W


CI# /Pressure/ Vmax
7.2 / 920.3mb/146.0kt


Final T# Adj T# Raw T#
7.1 7.5 7.5

Estimated radius of max. wind based on IR : 10 km

Center Temp : +6.9C Cloud Region Temp : -76.8C

[Kingarabian]

If the eye can go WMG it'll be an instantaneous T7.5. This may rival Rick 2009.

[cycloneye]

Hurricane Kristy Discussion Number 12
NWS National Hurricane Center Miami FL EP122024
800 AM PDT Thu Oct 24 2024

Kristy's satellite presentation has improved this morning as the eye
has reappeared on infrared and visible imagery, with deep convection
wrapping around the center. A recent AMSR2 microwave pass depicted
that the system has completed an eyewall replacement cycle, with an
inner core becoming re-established and contracting towards the
center. Subjective Dvorak satellite intensity estimate data-T values
have increased since the previous advisory with T6.5 from both
TAFB and SAB. Given these intensity estimates and recent satellite
images, the intensity is set to 130 kt for this advisory.

The hurricane is moving westward at an estimated motion of 270/15
kt, being steered by a ridge located over the northeastern Pacific.
Kristy will gradually round the southwestern portion of the ridge
over the next day or so, with a turn to the northwest then
north-northwest continuing through the weekend between the flow of
the aforementioned ridge and a trough to the west. By the end of the
weekend, Kristy is forecast to rapidly weaken with the remnants
turning west-southwestward within the low-level steering flow. The
NHC forecast was nudged slightly to the right of the previous
forecast, closer to the simple consensus aids.

Kristy is forecast to remain within a favorable environment for the
next 24 hours or so, with warm sea surface temperatures and light
vertical wind shear. The intensity forecast calls for some slight
re-intensification during this time, although recent microwave
imagery depicts that another eyewall replacement cycle could occur,
which would cause some intensity fluctuations in the short term.
Thereafter, the environment quickly becomes hostile with strong wind
shear, drier air and cooler sea surface temperatures along the
forecast track of Kristy. Guidance is in fairly good agreement that
rapid weakening should occur through the end of the forecast period.
Model simulated satellite imagery depicts that Kristy will begin to
lose convection and become a post-tropical remnant low around 72 h,
and depicts the system opening into a trough by 120 h. The NHC
intensity forecast follows these trends, showing rapid weakening,
and now has the remnant low status at 72h, and dissipation at 120 h.


FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 14.1N 120.3W 130 KT 150 MPH
12H 25/0000Z 14.4N 122.3W 135 KT 155 MPH
24H 25/1200Z 15.3N 124.8W 120 KT 140 MPH
36H 26/0000Z 16.8N 126.9W 110 KT 125 MPH
48H 26/1200Z 18.6N 128.7W 95 KT 110 MPH
60H 27/0000Z 20.6N 130.0W 70 KT 80 MPH
72H 27/1200Z 22.3N 131.2W 50 KT 60 MPH...POST-TROPICAL
96H 28/1200Z 21.5N 133.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 29/1200Z...DISSIPATED

$$
Forecaster Kelly/B.Adams

[aspen]

This is easily a Cat 5 now. Once again, a T6.5 SAB fix dragged it down. I’m surprised the NHC didn’t go 5 kt higher than the BT to account for clear improvement since then.

Hopefully Kristy keeps up its appearance until the next fix and advisory, although that rarely happens.

[Travorum]

First light on Kristy this morning:

[Kingarabian]

Eye is rapidly warming.

[Travorum]

For reference here is the automatic Dvorak ADT estimate all cat 5 hurricanes in the last 10 years.

Beryl (2024) = CI 6.9 / raw T# 7.0 / ADT intensity 928mb, 137kt
Lee (2023) = CI 6.8 / raw T# 7.0 / ADT intensity 930mb, 135kt
Ian (2022) = CI 6.9 / raw T# 7.2 / ADT intensity 922mb, 137kt
Lorenzo (2019) = CI 7.1 / raw T# 7.3 / ADT intensity 914mb, 143kt
Dorian (2019) = CI 6.4 / raw T# 6.5 / ADT intensity 936mb, 125kt
Michael (2018) = CI 7.2 / raw T# 7.4 / ADT intensity 909mb , 146kt
Maria (2017) = CI 7.1 / raw T# 7.3 / ADT intensity 922mb, 143kt
Irma (2017) = CI 7.3 / raw T# 7.4 / ADT intensity 915mb, 149kt
Matthew (2016) = CI 7.0 / raw T# 7.4 / ADT intensity 924mb, 140kt

And some hurricanes that peaked at 135 kt.

Sam (2021) = CI 6.6 / raw T# 6.7 / ADT intensity 939mb, 130kt
Iota (2020) = CI 7.0 / raw T# 7.5 / ADT intensity 922mb, 140kt
Jose (2017) = CI 6.3 / raw T# 6.4 / ADT intensity 942mb, 122kt
Joaquin (2015) = CI 6.5 / raw T# 6.7 / ADT intensity 928mb, 127kt

And Eta just because it's my profile picture
Eta (2020) = CI 7.3 / raw T# 8.4 / ADT intensity 917mb, 149kt

Reposting this from the Kirk thread as it seems relevant now. Here are Kirk, Milton, and Kristy (so far):

Kirk (2024) = CI 7.0 / raw T# 7.1 / ADT intensity 919mb, 140kt
Milton (2024) = CI 7.7 / raw T# 8.0 / ADT intensity 897mb, 161kt
Kristy (2024) = CI 7.4 / raw T# 7.5 / ADT intensity 915mb, 152kt

[Sciencerocks]

[aspen]

CDO is warming a bit, possibly due to the potential EWRC mentioned in the 11am discussion.

Yeah this isn’t getting operationally assessed as a Cat 5. If I had a nickel for every time a 2024 K-named storm got a T7.0+ on ADT but was held back by an unfortunately times T6.5 SAB fix, I’d have two nickels, which isn’t a lot but it’s weird that it happened twice.

[Hurricane2022]

Satcon is at 153 kt and ADT is at 152 kt now. I'm 100% sure that we will see and upgrade to atleast 140 kt even if SAB continues to be trash. I personally would estimate 145 kt/920 mb rn.