EPAC: ALETTA - Post-Tropical

[xtyphooncyclonex]

This is my first time tracking an East Pacific hurricane in a long, long while. I gotta say though that I am stunned. Fortunately, this one's a fish. I have to make the most out of my 120-day summer vacation; I'm glad it's turning out to be fruitful.

[gatorcane]

it appears the ECMWF model really missed the intensity forecast with this one. I see the GFS was showing a stronger cyclone relatively speaking compared to the ECMWF.

[zeehag]

over the years i lived nanoseconds south east of cabo corrientes i noticed that the area offshore there seems to make canes happy.
they do a lil rapid intensification dance and come out beautiful.
what is it about the cape of currents that allows for this repetitive behavior?
we saw lightning and heard impressive thunder as they grew and performed their ri dance off our coast.
was magnificent.

[CrazyC83]

That was an impressive rapid intensification trend...it looks to have peaked though. I'd probably have set the peak intensity at 125 kt.

Now, will it weaken as fast as it went up? That often happens in the EPAC.

[Ntxw]

Visible

[gatorcane]

Visible

http://i65.tinypic.com/wswfup.gif

Wow very nice looking major hurricane.

[SSL]

Visible

Already starting to get sheared on the south side. Aletta may not be long for this world at this point...

[Kingarabian]

SAB had 6.0 while ADT is still near 6.5. CDO is still pretty thick + a warm eye. Maintaining pretty well. Interesting that it hasn't undergone an EWRC yet.

[Kingarabian]

it appears the ECMWF model really missed the intensity forecast with this one. I see the GFS was showing a stronger cyclone relatively speaking compared to the ECMWF.

The Euro had a much lower pressure maybe a week ago in regards to Aletta(950mb). Ever since, it keeps coming in with pressures between 980-992. Euro seems to always do this in the EPAC. It seems that it doesn't handle EPAC storm intensities particular well.

[Yellow Evan]

Not embedded in B. This is a T5.5.

TXPZ21 KNES 081825
TCSENP

A. 02E (ALETTA)

B. 08/1800Z

C. 15.9N

D. 111.5W

E. ONE/GOES-W

F. T6.0/6.0/D1.5/24HRS

G. IR/EIR/VIS

H. REMARKS...AN EYE EMBEDDED IN BLACK GIVES AN EYE NUMBER OF 5.5. AN OFF
WHITE EYE WITH A SURROUNDING TEMPERATURE OF BLACK GIVES AN EYE ADJUSTMENT
OF PLUS 0.5, RESULTING IN A DT OF 6.0. MET IS 5.5 AND THE PT IS 6.0. FT
IS BASED ON DT.

I. ADDL POSITIONS

NIL


...HOSLEY

[cycloneye]

Hurricane Aletta Discussion Number 13
NWS National Hurricane Center Miami FL EP022018
300 PM MDT Fri Jun 08 2018

Aletta remains a formidable category 4 hurricane, although there
has been some weakening of the core convection during the day. The
current intensity is held at 120 kt which is a blend of subjective
Dvorak estimates from TAFB and SAB along with objective Dvorak
values. After the notable strengthening episode over the last 24
hours, it appears that the intensity has leveled off. This is
also consistent with GOES-16 measurements of increased inner-core
lightning observed to be occurring to the east of the eastern
eyewall, which some research suggests corresponds to a halting of
the intensification process. Since vertical shear is expected to
increase in 12 to 24 hours, a weakening trend is forecast to begin
late tonight or tomorrow. A more rapid weakening will likely
commence on Sunday as Aletta begins to traverse cooler waters. The
official intensity forecast is at the upper bound of the numerical
guidance.

The hurricane has moved on a more westward course today, and the
initial motion estimate is now 290/5 kt. Aletta is moving along
the southwestern periphery of a mid-level high pressure area and
should continue to do so over the next day or two. Later in the
forecast period, the weakening and increasingly shallower cyclone
should turn westward and south of westward, following the low-level
tradewind flow. The official forecast is close to the dynamical
model consensus TVCE and is somewhat south of the previous NHC
track.

FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 16.0N 111.7W 120 KT 140 MPH
12H 09/0600Z 16.5N 112.6W 120 KT 140 MPH
24H 09/1800Z 17.2N 113.6W 100 KT 115 MPH
36H 10/0600Z 17.9N 114.5W 75 KT 85 MPH
48H 10/1800Z 18.3N 115.4W 55 KT 65 MPH
72H 11/1800Z 18.6N 117.5W 30 KT 35 MPH
96H 12/1800Z 18.6N 119.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 13/1800Z 18.0N 121.0W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Pasch

[HurricaneRyan]

Does Aletta set the stage for the rest of the season? Last time we had major hurricanes in june, the season was active, except in 2010.

[Yellow Evan]

Does Aletta set the stage for the rest of the season? Last time we had major hurricanes in june, the season was active, except in 2010.

I mean we were likely to have an active season either way but strictly speaking no since the EPAC has such a broad peak.

[Yellow Evan]

it appears the ECMWF model really missed the intensity forecast with this one. I see the GFS was showing a stronger cyclone relatively speaking compared to the ECMWF.

The Euro had a much lower pressure maybe a week ago in regards to Aletta(950mb). Ever since, it keeps coming in with pressures between 980-992. Euro seems to always do this in the EPAC. It seems that it doesn't handle EPAC storm intensities particular well.

I recall plenty of instances, especially in 2015-2016 where the ECMWF called for intense hurricanes in the basin. It may have even busted too high for Hilary last year but don't quote me on that.

[cycloneye]

Hurricane Aletta Discussion Number 14
NWS National Hurricane Center Miami FL EP022018
900 PM MDT Fri Jun 08 2018

Aletta's weakening phase has begun, with the eye becoming cloud
filled in visible satellite imagery since the last advisory.
An analysis from CIMSS at the University of Wisconsin indicates that
vertical shear has increased to 15-20 kt out of the south-southwest,
and a 2309 UTC SSMI/S pass confirms that the hurricane's structure
is responding to that shear. All final-T numbers have decreased,
and the initial intensity is set at 110 kt as a blend of the various
final-T and CI numbers. This is also supported by the latest SATCON
estimate.

Vertical shear is forecast to strengthen during the next 36 hours,
and Aletta will be moving over marginally warm sea surface
temperatures, both of which should cause the cyclone to continue
weakening. The new intensity models are now showing a much more
significant rate of weakening, and the updated NHC intensity
forecast follows suit, bringing down the winds much faster than
shown in the previous forecast. The NHC forecast is near the top
end of the guidance for the first 24 hours and then close to the
ICON intensity consensus from 36 hours and beyond. Interestingly,
the HCCA guidance weakens Aletta to a tropical storm within 24
hours, so it wouldn't be surprising if the hurricane weakens faster
than shown in the official forecast. Aletta is now forecast to
degenerate into a remnant low by day 3.

The initial motion estimate is 285/5 kt. Since Aletta is moving
around the southwestern periphery of a mid-level ridge centered over
northwestern Mexico, the cyclone is expected to maintain a slow
west-northwestward or northwestward motion for the next 36 hours.
After that time, the weakening storm should turn back toward the
west and eventually southwest as it becomes increasingly steered by
the low-level trade winds and the flow around another developing
tropical cyclone to the east. The new NHC track forecast is a
little south of the previous forecast to account for an overall
southward shift in the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT 09/0300Z 16.2N 112.3W 110 KT 125 MPH
12H 09/1200Z 16.6N 113.1W 95 KT 110 MPH
24H 10/0000Z 17.3N 114.2W 75 KT 85 MPH
36H 10/1200Z 17.7N 115.2W 55 KT 65 MPH
48H 11/0000Z 17.8N 116.3W 40 KT 45 MPH
72H 12/0000Z 17.8N 118.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 13/0000Z 17.5N 121.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 14/0000Z 16.5N 122.5W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

[CrazyC83]

It should weaken really quickly. Shear is picking up and water temperatures really drop off ahead of it.

[cycloneye]

Hurricane Aletta Discussion Number 15
NWS National Hurricane Center Miami FL EP022018
300 AM MDT Sat Jun 09 2018

Aletta's cloud pattern has continued to gradually degrade
overnight. The eye is no longer apparent in infrared satellite
pictures and the overall cloud pattern has become less symmetric
due to the effects of southerly wind shear. Recent microwave
imagery also shows that the southwestern portion of the inner
core has eroded and most of the convective banding is located
over the northeastern portion of the circulation. Subjective and
objective Dvorak T-numbers have decreased and a blend of the
Final-T and CI-numbers yields an initial intensity estimate of
95 kt.

Aletta should continue to weaken during the next day or two as the
vertical wind shear increases and the cyclone moves over gradually
decreasing sea surface temperatures. These conditions are expected
to cause a rapid decrease in intensity during the next 24 to 36 h.
After that time, Aletta is forecast to move over SSTs below 26
degrees Celsius and into a less favorable thermodynamic environment,
which should result in a continued spin down and degeneration
of the system to a remnant low within 72 hours. The intensity
guidance is in fairly good agreement and the NHC intensity forecast
is close to the ICON consensus.

The initial motion estimate remains 285/5 kt. There has been
no significant change to the track forecast reasoning since the
previous advisory. Aletta should continue to move around the
southwestern portion of a mid-level ridge over northwestern Mexico
during the next day or so. After Aletta weakens and becomes a more
vertically shallow system, it should turn westward, then
southwestward in the low-level trade wind flow. The overall
guidance envelope has once again shifted southward and the updated
NHC track forecast has been moved in that direction to be closer to
the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 09/0900Z 16.2N 112.7W 95 KT 110 MPH
12H 09/1800Z 16.6N 113.5W 80 KT 90 MPH
24H 10/0600Z 17.0N 114.6W 60 KT 70 MPH
36H 10/1800Z 17.2N 115.6W 45 KT 50 MPH
48H 11/0600Z 17.2N 116.9W 35 KT 40 MPH
72H 12/0600Z 17.0N 119.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 13/0600Z 16.6N 120.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 14/0600Z 16.0N 121.8W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

[doomhaMwx]

 https://twitter.com/UWCIMSS/status/1005107988284125188

[Ntxw]

Looks to be winding down. She should pick up a point here and there for ACE which will end up ~10 units or about so.

[cycloneye]

Hurricane Aletta Discussion Number 16
NWS National Hurricane Center Miami FL EP022018
900 AM MDT Sat Jun 09 2018

Recent microwave data indicates that the cloud pattern of Aletta
continues to lose organization due to southerly vertical wind
shear, with the remains of the eye located near the south edge of
the main convective area. The initial intensity is reduced to a
possibly generous 85 kt based on a combination of subjective and
objective satellite intensity estimates.

Rapid weakening should continue due to a combination of shear,
decreasing sea surface temperatures along the forecast track, and
entrainment of dry air. Aletta is currently forecast to drop below
hurricane strength in less than 24 h, weaken to a depression by 48
h, and subsequently degenerate to a remnant low by 72 h. The new
intensity forecast follows the trend of the tightly clustered
intensity guidance.

The initial motion is now 295/5. The cyclone should move generally
northwestward around the southwestern portion of a mid-level ridge
over northwestern Mexico during the next day or so. After Aletta
weakens and becomes a more vertically shallow system, it should turn
westward, and then southwestward, in the low-level trade wind flow.
In contrast to the last advisory, the guidance envelope for this
advisory has has shifted somewhat to the north. The new forecast
track is similar to, but just north of the previous forecast, and it
lies to the south of the center of the guidance envelope and the
group of consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 16.4N 113.1W 85 KT 100 MPH
12H 10/0000Z 16.9N 113.9W 70 KT 80 MPH
24H 10/1200Z 17.3N 115.0W 55 KT 65 MPH
36H 11/0000Z 17.4N 116.2W 40 KT 45 MPH
48H 11/1200Z 17.4N 117.4W 30 KT 35 MPH
72H 12/1200Z 17.0N 119.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 13/1200Z 16.5N 121.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 14/1200Z 15.5N 122.5W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven