CPAC: OLIVIA - Post-Tropical

[Ntxw]

I'm giving a 90% chance that Olivia will be upgraded to CAT4 at 00z

it better be . After all the attempts she deserves it. Also I'm sure many following would like the 6 majors being Cat 4+ streak alive.

[1900hurricane]

Pretty easy analysis. Clear cut DT of 6.0 (below) with 116 kt SATCON. Expected KZC and SATCON pressure were even the same.

[supercane4867]

The only storm in satellite era that brought direct impacts to Hawaii from the east as an intact TC is Iselle ( it weakened but still made onshore as a decent TS)

[Kingarabian]

The NHC had some doubts about the intensity late in the forecast period. With Olivia exceedingly taking on annular characteristics, unfortunately theres a better chance than what the models show that it maintains major hurricane status in its trek towards Hawaii.

[Ntxw]

[xtyphooncyclonex]

17E OLIVIA 180907 0000 18.9N 129.1W EPAC 115 948

[Chris90]

17E OLIVIA 180907 0000 18.9N 129.1W EPAC 115 948

Finally. At 129.1W too, right by this season's sweet spot that starts right around there at about 130W.
I know it is probably crazy, but it was really going to irk me if this never made it to 115kts when all the other majors this season achieved it, and after Olivia has tried more than once.

[cycloneye]

Hurricane Olivia Discussion Number 26
NWS National Hurricane Center Miami FL EP172018
800 PM PDT Thu Sep 06 2018

Olivia's satellite presentation is an outstanding example of an
annular hurricane with the shape of a truck tire. In fact, the
Annular Hurricane Index on the SHIPS model output is 100. The
hurricane has a distinct clear eye surrounded by a ring of very deep
convection. The Dvorak numbers, both objective and subjective, are
T6.0, and on this basis, the winds are increased to 115 kt in this
advisory. The current annular pattern indicates that hurricane
should weaken more slowly that indicated by guidance in the short
term. Nevertheless, since the ocean is a little bit cooler along the
forecast track, very gradual weakening is forecast through the next
5 days. The confidence in the intensity forecast is not very high.

On the contrary, the confidence in the track forecast is high.
Olivia is fully embedded within the easterly flow south of a
subtropical high, and the hurricane is moving toward the
west-northwest or 290 degrees at 12 kt. The subtropical high will
persist, and most likely expand farther westward, and this flow
pattern will force Olivia to move on the general westward track or
even south of due west by the end of the forecast period. Guidance
for the next 5 days is in extremely good agreement, and the NHC
forecast in on top of the skinny guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 19.1N 129.7W 115 KT 130 MPH
12H 07/1200Z 19.7N 131.6W 115 KT 130 MPH
24H 08/0000Z 20.5N 134.2W 100 KT 115 MPH
36H 08/1200Z 21.2N 136.8W 90 KT 105 MPH
48H 09/0000Z 21.5N 139.5W 85 KT 100 MPH
72H 10/0000Z 21.8N 144.5W 75 KT 85 MPH
96H 11/0000Z 22.0N 148.5W 70 KT 80 MPH
120H 12/0000Z 21.5N 152.5W 65 KT 75 MPH

$$
Forecaster Avila

[Kingarabian]

[Chris90]

Wouldn't surprise me if Olivia was stronger than 115kts right now. We've seen with these annular hurricanes before that they can put down stronger winds than what satellites estimate. She might be up there around 125-130kts right now.
I am really looking forward to the day when CYGNSS is fully operational and we hopefully start getting a lot of great data on EPAC/CPAC storms.

[Kingarabian]

This 2 hour old F18 pass supports your reasoning.

But likely has leveled off due to the cold tops warning although the eye remains very warm.

00z GFS and 00z UKMET show Olivia affecting the Big Island. 00z CMC affects Maui and its surrounding islands.

[Kingarabian]

Warm eye remains but its CDO has shrunk considerably. It's hampering down in the face of dry air and marginal SST's. Astonishing how annular canes go to the fullest extent to survive in non-ideal conditions.

[Kingarabian]

00z Euro has a slight shift east and shows a 999mb Molokai landfall.

[Kingarabian]

Hour and a half old AMSU pass shows Olivia's core well intact:

[Blown Away]

It’s like Hawaii is under attack, came up short from the south so let’s try over the top from NE with Olivia...

[Kingarabian]

07/0600 UTC 19.4N 130.4W T5.0/6.0 OLIVIA -- East Pacific

[1900hurricane]

It'll be interesting to see how far west Olivia manages to get. Many EPS members dissipate Olivia not too long after Hawaii, but there are a few that bring Olivia into the WPac as a decent system.

[Kingarabian]

Hurricane Olivia Discussion Number 27...Corrected
NWS National Hurricane Center Miami FL EP172018
200 AM PDT Fri Sep 07 2018

Corrected second paragraph about previous category-4 strength

Olivia's overall cloud structure in infrared and passive microwave
satellite imagery has changed little since the previous advisory,
except that the cloud tops have warmed significantly around the
well-defined, 20-nmi-diameter eye. As a result, both subjective and
objective intensity estimates have decreased markedly since Olivia
briefly gained category-4 strength on the previous advisory.
However, microwave imagery indicates that Olivia has evolved into an
annular hurricane, with only inner-core convection present and no
banding features. As a result, the initial intensity only been
decreased to 110 kt, which is a typical slower rate of weakening for
annular hurricanes.

The initial motion estimate is 290/13 kt. There is no significant
change to the previous forecast track or reasoning. Olivia is
expected to continue moving west-northwestward for the next 24-36
hours, followed by a westward motion as the hurricane nudges up
against a strong deep-layer subtropical ridge that stretches from
Mexico and the southwestern U.S. westward into the central Pacific.
The new NHC forecast track is essentially just an extension of the
previous advisory track and is down the middle of the very tightly
packed model guidance, closest to the speed of the TVCN consensus
track model.

As mentioned in the previous advisory discussion, the current
annular pattern indicates that Hurricane Olivia should weaken more
slowly than indicated by guidance, even though the cyclone will be
moving over slightly cooler SSTS of about 25.5 deg C by 36 h. The
low shear environment that the cyclone will be embedded in should
help to offset some of the negative effects of the cooler waters.
After that time, Olivia will move back over slightly warmer
waters and remain in a low shear environment, so a little leveling
off in the weakening process is forecast until 96 hours. On day 5,
however, southwesterly vertical wind shear of 15-20 kt is expected
to induce more significant weakening at that time. The official
intensity forecast is similar to, but higher than, the consensus
models, and more closely follows a blend of the dynamical models
HWRF and HMON.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 19.6N 131.2W 110 KT 125 MPH
12H 07/1800Z 20.2N 133.1W 100 KT 115 MPH
24H 08/0600Z 20.9N 135.7W 90 KT 105 MPH
36H 08/1800Z 21.4N 138.3W 80 KT 90 MPH
48H 09/0600Z 21.7N 140.9W 75 KT 85 MPH
72H 10/0600Z 22.0N 145.6W 70 KT 80 MPH
96H 11/0600Z 21.9N 149.6W 65 KT 75 MPH
120H 12/0600Z 21.0N 153.5W 55 KT 65 MPH

$$
Forecaster Stewart

[Kingarabian]

Between Oahu and the Big Island I only see about 20-30kts of shear in the time period Olivia will be near Hawaii. As crazy as it sounds, that alone may not weaken Olivia significantly enough if its a robust hurricane at that time as Lane, Miriam, and Norman, have proven.

[Kingarabian]

Low level core holding strong, but the eyewall has opened up.



24 hours to go before conditions improve again. Will be interesting to see how this plays out.