EPAC: ALETTA - Post-Tropical

[Chris90]

In regards to the hype, I think if a storm is going to be the one to generate hype, it's storms like Aletta. I'm all for people hyping up pacific fish storms that don't threaten land. These are the ones I want to see become beautiful majors.

Aletta does seem to be struggling a bit more today than she was last night. Last night I thought she would be a hurricane within 24 hours. Looks like she might need 12-24 more hours to work out structure and dry air issues. I still think she'll reach hurricane status though. If not a major, I think she'll at least make a decent run for Cat 2.

[NDG]

Looking at zoomed in hr vis satellite loop I can see several eddies rotation around around a larger circulation, MLC is still to the NE of the low level center. The Euro has been right at along during the past couple of days of Aletta not deepening much over the next couple of days.

[Yellow Evan]

I'm gonna be honest. I think Storm2k is hyping Aletta a bit to much. Wind shear is low and waters are warm but typical for this time of year, dry air is causing problems, and ASCAT suggest the center isn't well defined, although it's an improvement from yesterday. This likely becomes a hurricane but this is going to have to consolidate a bit for serious intensification. There's like 60 hours left, but if this isn't a hurricane by tomorrow night, forget a major hurricane.

I understand last year was a dull in regards to EPAC activity, but let's not forget how potent this basin can be and how storms are generally under-forecast-ed and exceed expectations.

The EPAC has a long track record of storms, especially smaller ones, bombing out at the last minute and getting much stronger than expected. And this one could very well do so, but given it's current poorly organized structure, I wouldn't give this more than a 35-40% chance of becoming a major, with somewhat drier air to the west. If this can put together an inner core by tomorrow evening, then, we'll talk.

[cycloneye]

Finnally consolidating?

[Kingarabian]

SAB up to 3.0.

[Kingarabian]

Finnally consolidating?

[img]http://www.ssd.noaa.gov/PS/TROP/floaters/02E/imagery/avn_lalo-animated.gif[img]

Looks like the convection mass continues to move over the LLC. Still needs work.

4 hour old SSMIS pass:


2 hour old AMSU pass:

[cycloneye]

00z Best Track up to 45kts:

EP, 02, 2018060700, , BEST, 0, 143N, 1081W, 45, 999, TS

[Yellow Evan]

06/2345 UTC 14.3N 108.1W T3.0/3.0 ALETTA -- East Pacific

[cycloneye]

Tropical Storm Aletta Discussion Number 5
NWS National Hurricane Center Miami FL EP022018
900 PM MDT Wed Jun 06 2018

Deep convection has been bursting just to the northeast of the
center during the past few hours, although a recent SSMI/S overpass
suggests that the low-level circulation continues to consist of
multiple swirls rotating around a common center. Because of the
increase in convection, subjective satellite intensity estimates
from TAFB and SAB have gone up to T3.0, so the initial intensity is
set at 45 kt.

There is about 15 kt of deep-layer southwesterly shear impinging on
Aletta according to analyses from UW-CIMSS, which can be seen in the
motions of the high cirrus emanating away from additional convection
to the southwest. The global models aren't picking up on this shear
very well, with the SHIPS diagnostics currently showing shear just
under 10 kt. It now appears that some westerly shear could persist
over Aletta for the next few days, and thus only modest
intensification is expected over waters that are 27-29 degrees
Celsius. The NHC official forecast still calls for Aletta
to reach hurricane strength in a couple of days, and the updated
forecast is close to the HCCA guidance and the intensity consensus
through 48 hours. The intensity models are showing a faster
weakening rate starting on day 3 due to cooler waters and higher
shear, and although the NHC forecast has been trended downward to
account for this, it still lies above much of the guidance later in
the forecast period.

The latest fixes indicate that Aletta is slowing down, and the
initial motion estimate is 275/6 kt. A mid-level ridge centered
over northwestern Mexico should continue to steer the cyclone slowly
westward for a day or two. A continued slow motion to the
west-northwest or northwest is then expected starting in 48 hours
once Aletta reaches a break in the subtropical ridge. The ECMWF
remains on the southern side of the guidance envelope, while the
GFS, HMON, and HWRF lie on the northern edge. Since the upper-level
patterns among these models are similar, the discrepancies among
their respective tracks appear related to how strong they each make
the cyclone, as the models with a stronger cyclone forecast a
more northerly track. The new NHC forecast is closest to the HCCA
guidance and is not too different from the previous official
forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 14.3N 108.4W 45 KT 50 MPH
12H 07/1200Z 14.5N 109.4W 50 KT 60 MPH
24H 08/0000Z 14.7N 110.4W 55 KT 65 MPH
36H 08/1200Z 14.9N 111.4W 60 KT 70 MPH
48H 09/0000Z 15.2N 112.3W 65 KT 75 MPH
72H 10/0000Z 16.3N 113.8W 75 KT 85 MPH
96H 11/0000Z 17.5N 115.5W 55 KT 65 MPH
120H 12/0000Z 18.0N 117.0W 35 KT 40 MPH

$$
Forecaster Berg

[TheAustinMan]

You can see some of that shear that the NHC mentioned in their latest discussion on water vapor imagery as some of the old cirrus seems to be emanating from a focal point offset from the center of circulation. However, the recent convective burst is blasting some of that upper-level flow away, so for now Aletta seems to be managing the shear problem somewhat. Dry air presents itself out west, but the storm has a bit of a moisture bubble to defend itself; certainly not invulnerable to the occasional entrainment, though.

4.36 MB. Source: Generated by myself from GOES-16 data.

[Kingarabian]

Briefly transitioned from a CDO into a CCC, now back to a CDO:


3 Hour old M/W pass shows an eyewall forming:


Very close to a hurricane or probably is one already.

SAB up to 3.5.

[cycloneye]

BULLETIN
Tropical Storm Aletta Advisory Number 6
NWS National Hurricane Center Miami FL EP022018
300 AM MDT Thu Jun 07 2018

...ALETTA EXPECTED TO BECOME A HURRICANE LATER TODAY OR FRIDAY...


SUMMARY OF 300 AM MDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...14.6N 109.2W
ABOUT 445 MI...715 KM SW OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.36 INCHES


Tropical Storm Aletta Discussion Number 6
NWS National Hurricane Center Miami FL EP022018
300 AM MDT Thu Jun 07 2018

The cloud pattern has become a little better organized and the
low-level center appears to be more embedded within the deep
convection than several hours ago. Although the outflow is fair,
there are still shear at some level affecting the cyclone by
observing the motion of the cirrus clouds. T-numbers from all
agencies including the UW-CIMSS objective values have increased to
3.5 on the Dvorak scale, so the initial intensity has been increased
to 55 kt.

Guidance suggests some modest intensification, although there is a
difference between the GFS-based SHIPS model and the ECMWF-based
one. The latter is less aggressive and barely forecast Aletta
to become a hurricane. The NHC follows the intensity consensus and
the FSU super-ensemble, and calls for Aletta to become a hurricane
within the next 12 to 24 hours. After 3 days, the environment
becomes unfavorable and a gradual weakening should then begin.

Aletta is moving toward the west or 280 degrees at about 6 kt
around the periphery of a subtropical ridge over Mexico. This
pattern should continue to steer the cyclone on a general
westward course for a day or two, and then the cyclone sould turn to
the west-northwest or northwest toward a weakness of the ridge. The
NHC forecast is very close to the FSU super-ensemble, and is in the
middle of the wide guidance envelope bounded by the GFS to the north
and the ECMWF to the south.



FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 14.6N 109.2W 55 KT 65 MPH
12H 07/1800Z 14.7N 110.0W 65 KT 75 MPH
24H 08/0600Z 14.9N 111.0W 70 KT 80 MPH
36H 08/1800Z 15.3N 111.7W 75 KT 85 MPH
48H 09/0600Z 15.7N 112.5W 75 KT 85 MPH
72H 10/0600Z 17.0N 114.0W 65 KT 75 MPH
96H 11/0600Z 18.0N 116.0W 45 KT 50 MPH
120H 12/0600Z 18.0N 117.5W 30 KT 35 MPH

$$
Forecaster Avila

[cycloneye]

Tropical Storm Aletta Discussion Number 7
NWS National Hurricane Center Miami FL EP022018
900 AM MDT Thu Jun 07 2018

The low-level center of Aletta has been somewhat difficult to locate
this morning. Moderate westerly shear still appears to be affecting
the tropical storm, and a recent SSMIS pass at 1329 UTC indicates
that the low-level center is displaced slightly to the west of the
mid-level center. A pronounced dry slot is present in IR and WV
imagery, though a recent burst of convection near the center
suggests that it may no longer be substantially inhibiting
convection. Subjective Dvorak intensity estimates from TAFB and SAB
at 1200 UTC were 55 kt, while objective estimates from SATCON and
the ADT are around 60 kt. Given the increase of convection near the
center since the TAFB and SAB classifications, the initial intensity
has been raised to 60 kt.

Little change has been made to the intensity forecast, which is
slightly above the consensus guidance IVCN and HCCA, but below a
mean of the dynamical hurricane models. The westerly shear
currently affecting Aletta is expected to decrease over the next 12
to 24 hours, allowing the tropical storm to strengthen. By 48 hours,
increasing shear and decreasing SSTs will likely induce a weakening
trend that should accelerate through 72 h. Aletta will likely
become a remnant low sometime near or just after 120 h.

Aletta appears to have taken a slight turn toward the northwest this
morning but the longer-term motion estimate is 290 at about 5 kt.
Aletta will be steered generally west-northwest to northwestward
over the next 5 days, with the largest source of uncertainty being
how deep the circulation will be. A stronger, deeper cyclone will
likely track farther north in response to an upper-level trough to
the northwest, as shown by the GFS. A weaker cyclone will instead
be steered more by the mid-level ridge to the north, and move on a
heading closer to due west, as shown by the ECMWF. The NHC forecast
splits these solutions, and is consistent with the intensity
forecast which also is also lower than the GFS but well above the
ECMWF.


FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 14.9N 109.3W 60 KT 70 MPH
12H 08/0000Z 15.1N 110.1W 65 KT 75 MPH
24H 08/1200Z 15.4N 111.0W 70 KT 80 MPH
36H 09/0000Z 15.8N 112.0W 75 KT 85 MPH
48H 09/1200Z 16.4N 112.7W 75 KT 85 MPH
72H 10/1200Z 17.6N 114.2W 60 KT 70 MPH
96H 11/1200Z 18.5N 116.0W 40 KT 45 MPH
120H 12/1200Z 18.5N 117.5W 30 KT 35 MPH

$$
Forecaster Zelinsky

[hurricanes1234]

I think this should be a hurricane pretty soon.

[Yellow Evan]

Pretty clear cut T4.0 to me.

[Hypercane_Kyle]

Yup, I'd say this is a hurricane now:

[Yellow Evan]

07/1800 UTC 15.1N 109.5W T4.5/4.5 ALETTA -- East Pacific

[Yellow Evan]

At the last floater update on 16z, this was T4.5BO CBD IMO. Anyway, here is SAB's reasoning:

TXPZ21 KNES 071824
TCSENP

A. 02E (ALETTA)

B. 07/1800Z

C. 15.1N

D. 109.5W

E. ONE/GOES-W

F. T4.5/4.5/D2.0/24HRS

G. IR/EIR/VIS

H. REMARKS...AN EYE EMBEDDED WITHIN 0.4 DEGREES OF MEDIUM GRAY RESULTS
IN AN EYE NUMBER OF 4.5. NO EYE ADJUSTMENT IS MADE FOR AN OFF WHITE EYE
SURROUNDED BY LIGHT GRAY, RESULTING IN A DT OF 4.5. THE MET IS 4.0 AND
THE PT IS 4.5 FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...HOSLEY

[hurricanes1234]

I'd be surprised if it's lower than 70-75 knots right now.

[Yellow Evan]

EP, 02, 2018060718, , BEST, 0, 151N, 1096W, 65, 987, HU, 34, NEQ, 80, 70, 70, 70, 1010, 240, 20, 0, 0, E, 0, , 0, 0, ALETTA, M, 0, , 0, 0, 0, 0, genesis-num, 003,
EP, 02, 2018060718, , BEST, 0, 151N, 1096W, 65, 987, HU, 50, NEQ, 40, 40, 30, 40, 1010, 240, 20, 0, 0, E, 0, , 0, 0, ALETTA, M, 0, , 0, 0, 0, 0, genesis-num, 003,
EP, 02, 2018060718, , BEST, 0, 151N, 1096W, 65, 987, HU, 64, NEQ, 20, 0, 0, 20, 1010, 240, 20, 0, 0, E, 0, , 0, 0, ALETTA, M, 0, , 0, 0, 0, 0, genesis-num, 003,