EPAC: OLAF - Post-Tropical

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Re: EPAC: OLAF - Tropical Storm

#81 Postby Yellow Evan » Sat Oct 17, 2015 7:27 am

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#82 Postby psyclone » Sat Oct 17, 2015 9:46 am

I keep checking in here to see what a real storm looks like...I don't expect disappointment.
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Re: EPAC: OLAF - Tropical Storm

#83 Postby cycloneye » Sat Oct 17, 2015 9:46 am

TROPICAL STORM OLAF DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015
800 AM PDT SAT OCT 17 2015

Olaf's cloud pattern has not exhibited much overall change since
the last advisory in conventional satellite imagery. The cyclone
is characterized by a small CDO with one primary band over the
western half of the circulation, though the band is detached from
the main convective mass and fragmented. The convective
distribution is suggestive of some northwesterly shear, as shown in
GFS- and ECMWF-based SHIPS output, but a partial 1030 UTC AMSU pass
indicated a mid-level eye, perhaps not completely coincident with
the low-level center. Dvorak intensity estimates are consensus
T3.0/45 kt, but the initial intensity is increased to 50 kt on the
basis of the greater organization seen in microwave imagery.

The initial motion estimate is 270/11. The mid-level subtropical
ridge steering Olaf westward is about to weaken in response to the
long tail of a mid- to upper-level trough near the U.S. west coast
settling southward to the north of the cyclone. The weaker ridge
should induce a slower forward speed with a gradual increase in
latitude during the next couple of days. After 48 hours, a large
anticyclone forming in the east-central subtropical Pacific near
140W is forecast to shift eastward while a weakness develops along
150W. Global models show Olaf moving in the flow between these two
synoptic features, which should result in a northwestward and then
north-northwestward turn after 96 hours. The official track
forecast is nearly unchanged through 36 hours. After that time, the
track forecast is shifted westward in agreement with a leftward-
shifting multi-model consensus and a majority of ECMWF ensemble
members that were farther west than the operational ECMWF solution
that lies east of the multi-model consensus. The new track forecast
is on the western side of the guidance envelope.

Except for the northwesterly shear, there are no obvious impediments
to continued strengthening for the next few days. Exactly how much
the shear is a factor, however, remains to be seen, but its most
likely effect would be to possibly slow the rate of intensification.
According to the SHIPS output, the northwesterly shear diminishes
after 36 hours, and with all other large-scale factors favoring
intensification, Olaf is likely to become a major hurricane in 2
or 3 days. Late in the forecast period, once Olaf gains enough
latitude, a drier environment with an increase in southerly or
south-southwesterly shear should result in weakening. The official
intensity forecast is near the multi-model consensus through 36
hours and generally above it after that time.


FORECAST POSITIONS AND MAX WINDS

INIT 17/1500Z 9.4N 129.5W 50 KT 60 MPH
12H 18/0000Z 9.5N 130.9W 60 KT 70 MPH
24H 18/1200Z 9.8N 132.5W 75 KT 85 MPH
36H 19/0000Z 10.3N 134.1W 90 KT 105 MPH
48H 19/1200Z 11.0N 135.8W 100 KT 115 MPH
72H 20/1200Z 12.6N 139.0W 100 KT 115 MPH
96H 21/1200Z 14.7N 141.4W 95 KT 110 MPH
120H 22/1200Z 16.9N 142.5W 85 KT 100 MPH

$$
Forecaster Kimberlain
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#84 Postby Kingarabian » Sat Oct 17, 2015 12:57 pm

Looks like it weakened again.
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#85 Postby cycloneye » Sat Oct 17, 2015 3:34 pm

TROPICAL STORM OLAF DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015
200 PM PDT SAT OCT 17 2015

There appears to have been a temporary interruption to Olaf's
intensification this morning, which could be related to a couple of
different factors. Microwave imagery from earlier suggested that
the cyclone ingested a tongue of relatively drier air. There is
also moderate northwesterly shear still affecting the system.
Nevertheless, there are some signs that Olaf could be about to
resume an intensification. The cyclone has maintained a small CDO,
but there is now greater definition to inner-core features than 12
to 24 hours ago, and the convective bands have lengthened and gained
greater curvature. While satellite classifications remain a
consensus T3.0/45 kt at 1800 UTC, the initial intensity estimate of
50 kt from the previous advisory is maintained.

The initial motion estimate is 265/11. The mid-level subtropical
ridge steering Olaf westward should weaken soon in response to the
long tail of a mid- to upper-level trough near the U.S. west coast
settling southward to the north of the cyclone. The weaker ridge
should induce a west-northwestward course at a reduced forward speed
during the 2 to 3 days. After about 72 hours, a large anticyclone
forming in the east-central subtropical Pacific near 140W is
forecast to shift eastward while a weakness develops along farther
west. Global models show Olaf moving in the flow between these two
synoptic features, resulting in a northwestward and then north-
northwestward turn after 96 hours. The guidance has shifted toward
the left again this cycle, especially later in the forecast period,
and the official track forecast is moved in that direction. Since
most of the global models depicted Olaf farther north than where it
currently is, it would not be surprising if further leftward
adjustments are necessary.

Other than some northwesterly shear over Olaf during the next day or
so, the large-scale environment is conducive for Olaf to intensify.
The shear could slow the rate of intensification, but it would not
appear strong enough not to allow Olaf to strengthen at least at the
climatological rate of development of one Dvorak T-number per day.
A diminution of the shear by 36 hours, in combination with other
very conducive environmental factors, should allow Olaf to
strengthen to near major hurricane strength in 2 to 3 days. Olaf
is also expected to become a much larger cyclone during the next
several days, with an impressive expansion of the wind field
depicted in global models. Late in the forecast period, once Olaf
gains enough latitude, a drier environment with an increase in
southerly or south-southwesterly shear should result in weakening.
The new intensity forecast is identical to the previous one and is
closest to the FSU Superensemble output and near the upper edge of
the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 17/2100Z 9.2N 130.5W 50 KT 60 MPH
12H 18/0600Z 9.3N 131.8W 60 KT 70 MPH
24H 18/1800Z 9.8N 133.5W 75 KT 85 MPH
36H 19/0600Z 10.3N 135.2W 90 KT 105 MPH
48H 19/1800Z 11.0N 136.9W 100 KT 115 MPH
72H 20/1800Z 12.9N 139.9W 100 KT 115 MPH
96H 21/1800Z 15.2N 142.0W 95 KT 110 MPH
120H 22/1800Z 17.3N 142.8W 85 KT 100 MPH

$$
Forecaster Kimberlain
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Re: EPAC: OLAF - Tropical Storm

#86 Postby cycloneye » Sat Oct 17, 2015 4:16 pm

Interesting fact:

Philip Klotzbach ‏@philklotzbach · 6m6 minutes ago
#Olaf is the farthest south (9.2N) a TC (>=35 kts) has been in the NE Pacific since Alvin on 5/16/2013.
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#87 Postby Kingarabian » Sat Oct 17, 2015 7:01 pm

Models have been on and off about this but the Euro and GFS ensembles are well west of their operational counterparts. Something to keep an eye about.
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#88 Postby Kingarabian » Sat Oct 17, 2015 8:52 pm

Image

Looks like all systems go. Dry air almost completely worked out. Partial eyewall has been evident for most of the day and with the CDO now expanding I think it takes off from here. Well it should. Shear appears to have relaxed in the time being.
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#89 Postby 1900hurricane » Sat Oct 17, 2015 8:58 pm

Overall structure looks very good.
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#90 Postby cycloneye » Sat Oct 17, 2015 9:40 pm

TROPICAL STORM OLAF DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015
800 PM PDT SAT OCT 17 2015

After the pause noted in the previous advisory, Olaf has resumed
intensification this evening. Well-defined convective bands
with cloud tops colder than -80C have formed around the center, and
microwave data show a developing 15 n mi wide eye. Satellite
intensity estimates have increased to 55 kt from TAFB and SAB, and
there is a recent CIMSS AMSU intensity estimate of 52 kt. Based on
these data, the initial intensity is increased to 55 kt.

The initial motion is 270/8. Olaf is now moving slower as the
subtropical ridge to the north weakens in response to the influence
of a mid- to upper-level trough near the U. S. west coast. A
general west-northwestward motion is expected for the next two days
or so as the cyclone moves on the south side of the weakened ridge.
After that time, a second mid- to upper-level trough passing north
of the Hawaiian Islands is forecast to cause a break in the ridge,
allowing Olaf to turn northwestward by 72 hours and northward by
120 hours. There is little overall change in the guidance since the
last advisory. Thus, the new forecast track is very similar to the
previous track and lies near the center of the track guidance
envelope.

There is still some light northwesterly shear over Olaf. However,
this is forecast to diminish during the next 24 hours, and improving
cirrus outflow suggests this may already be occurring. Based on
this, warm sea surface temperatures, and a moist environment,
continued strengthening is expected during the next 48 hours.
After 72 hours, developing southerly shear and dry air entrainment
are expected to cause Olaf to weaken. The new intensity forecast
is similar to the previous forecast and is in best agreement with
the Florida State Superensemble. It should be noted that the small
inner core seen in microwave imagery could allow rapid
intensification, and the Rapid Intensification Index of the SHIPS
model has a 25-30 percent chance of a 30-kt increase in intensity
during the next 24 hours. Should this occur, Olaf could get
significantly stronger than currently forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 18/0300Z 9.2N 131.0W 55 KT 65 MPH
12H 18/1200Z 9.4N 132.3W 65 KT 75 MPH
24H 19/0000Z 9.9N 134.1W 80 KT 90 MPH
36H 19/1200Z 10.4N 135.8W 90 KT 105 MPH
48H 20/0000Z 11.2N 137.4W 100 KT 115 MPH
72H 21/0000Z 13.5N 140.5W 100 KT 115 MPH
96H 22/0000Z 15.5N 142.0W 95 KT 110 MPH
120H 23/0000Z 18.0N 142.5W 80 KT 90 MPH

$$
Forecaster Beven
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#91 Postby Yellow Evan » Sat Oct 17, 2015 10:37 pm

Looking better. May become a hurricane within 12 hours as an inner core is becoming established. This has the best south-southwesterly outflow channel the basin has since since Linda, and global insist on poleward outflow becoming more established on Monday and Tuesday. At last, this appears well on its way to major hurricane intensity, and the only real limiting factor is inner core dynamics for the next 3-4 days.
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#92 Postby Kingarabian » Sat Oct 17, 2015 11:29 pm

Still fighting dry air:

Image

This is odd. EPAC storms usually fight dry air easily...
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#93 Postby Yellow Evan » Sun Oct 18, 2015 12:10 am

Image

Quite pretty.
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#94 Postby Kingarabian » Sun Oct 18, 2015 2:10 am

We have hurricane Olaf!
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Re:

#95 Postby Extratropical94 » Sun Oct 18, 2015 3:37 am

Kingarabian wrote:We have hurricane Olaf!


Yup, should be official in a few minutes.

19E OLAF 151018 0600 9.3N 131.4W EPAC 65 991
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Re: EPAC: OLAF - Tropical Storm

#96 Postby NotoSans » Sun Oct 18, 2015 4:10 am

000
WTPZ44 KNHC 180851
TCDEP4

HURRICANE OLAF DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015
200 AM PDT SUN OCT 18 2015

Olaf has intensified overnight. Satellite images show that
convection has deepened with a sizable area of -90C cloud tops near
the center, along with an eye occasionally appearing on the
night-visible channel. Microwave data also show that the eye has
become better defined, and the feature has even become more distinct
in the lower resolution AMSU data. With the appearance of the eye
in conventional satellite data and the increase in convection near
the center, the initial wind speed is set to 65 kt, near the Dvorak
estimate from SAB. It is also worth noting that ASCAT data show that
Olaf has also grown in size significantly from yesterday, and this
is reflected in the larger initial and forecast wind radii.

Olaf should continue to intensify during the next couple of days
with favorable environmental conditions of low shear, warm water and
high mid-level moisture in the forecast. Rapid intensification is a
distinct possibility, with the SHIPS-RI index showing about a 40
percent chance of a 30-kt increase in the next 24 hours. The
intensity forecast will bring Olaf up to major hurricane strength in
36 hours, in line with the highest guidance from the LGEM model and
the Florida State Superensemble. In a few days, some southerly shear
and dry air entrainment is possible, which could lead to Olaf
beginning a weakening trend. Little change was made to the long
range intensity forecast, close to a blend of the previous NHC
prediction and the intensity consensus.

ASCAT and satellite data were very helpful in determining an
initial motion of 275/8. A motion to the west and then west-
northwest is expected for the next two days or so while the cyclone
moves on the south side of the subtropical ridge. After that time,
a mid- to upper-level trough passing north of the Hawaiian Islands
is forecast to cause a break in the ridge, allowing Olaf to turn
northwestward by 96 hours and northward by 120 hours. Although
guidance is in general agreement on the large-scale pattern, the
timing of the northward turn is in some question, especially since
Olaf has been struggling to gain latitude. Overall, the guidance
has generally been showing a later turn, with the ECMWF/UKMET models
having a weaker trough and less of a ridge breakdown. The NHC track
forecast is shifted west toward the latest consensus aids, although
it still lies east of the model consensus.

At 9.4N, Olaf is the lowest-latitude hurricane formation in the
eastern Pacific dataset. Reliable records in the basin go back to
about 1971.



FORECAST POSITIONS AND MAX WINDS

INIT 18/0900Z 9.4N 131.9W 65 KT 75 MPH
12H 18/1800Z 9.6N 133.2W 75 KT 85 MPH
24H 19/0600Z 10.0N 135.1W 90 KT 105 MPH
36H 19/1800Z 10.6N 136.9W 100 KT 115 MPH
48H 20/0600Z 11.3N 138.6W 110 KT 125 MPH
72H 21/0600Z 13.3N 141.7W 105 KT 120 MPH
96H 22/0600Z 15.0N 143.5W 95 KT 110 MPH
120H 23/0600Z 17.5N 143.5W 80 KT 90 MPH

$$
Forecaster Blake
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#97 Postby Kingarabian » Sun Oct 18, 2015 6:18 am

00Z Euro ensembles

Image
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Re: EPAC: OLAF - Hurricane

#98 Postby Chris_in_Tampa » Sun Oct 18, 2015 7:06 am

NotoSans wrote:At 9.4N, Olaf is the lowest-latitude hurricane formation in the
eastern Pacific dataset. Reliable records in the basin go back to
about 1971.

Olaf didn't want to be frozen out of the record books.

Pictured is the point at which hurricanes in the East Pacific basin, from 1949 to present, became a hurricane.

Included in some images is Olaf's previous best track positions through October 18th at 0Z. All images include Olaf's 9Z NHC advisory position, where the storm was designated a hurricane, at 9.4N 131.9W. (Best track data, which is subject to revision, currently indicates the storm became a hurricane at 6Z at 9.3N 131.4W)

Image

Image

Or the funner image of the above image:

Image

The image below includes information from the East Pacific best track database since 1949, including post tropical positions, for positions with 65 knot or higher wind. It does not include anywhere along a path where something was a tropical storm or less.

Image
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#99 Postby Alyono » Sun Oct 18, 2015 8:20 am

the deterministics seem to turn this a bit too soon. Only the MU ensemble has quick recurve
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#100 Postby Yellow Evan » Sun Oct 18, 2015 9:21 am

What?

TXPZ29 KNES 181222
TCSENP

A. 19E (OLAF)

B. 18/1200Z

C. 9.5N

D. 132.4W

E. THREE/GOES-W

F. T4.0/4.0/D1.0/24HRS

G. IR/EIR

H. REMARKS...CENTER IS EMBEDDED IN W RESULTING IN A DT OF 5.0. DT IS
NOT CLEAR CUT. MET AND PT = 4.0. FT IS BASED ON MET.

I. ADDL POSITIONS

NIL


...KIBLER

I'm getting about 1.35 banding vis, which would be T4.5 DT.
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