EPAC: DALILA - Post-Tropical

[cycloneye]

Tropical Storm Dalila Discussion Number 7
NWS National Hurricane Center Miami FL EP052019
200 PM PDT Tue Jul 23 2019

Dalila has become less organized since the previous advisory.
Northerly shear and cooler waters has caused the primary
convective area to decrease in coverage and become more separated
from the surface circulation. An ASCAT overpass from around midday
sampled the southeastern portion of the circulation and detected
35 to 40 kt winds, which suggests Dalila could have been
slightly stronger than analyzed this morning. Based on the ASCAT
and the recent degradation of the convective organization, the
initial intensity is set at 35 kt for this advisory.

Dalila is moving northwestward or 325/7 kt. The cyclone is
currently moving around the southwestern portion of a mid-level
ridge over the southwestern United States. As Dalila weakens and
becomes a more vertically shallow system during the next 12 to 24
hours, it should turn west-northwestward to westward within the
low-level steering flow. The latest guidance envelope is not much
different from the previous cycle, and the NHC track forecast is
essentially an update of the previous advisory.

Dalila is currently crossing the 26C isotherm and the northerly
shear is not forecast to abate. As a result, gradual weakening is
anticipated. As the cyclone moves over even cooler SSTs and into a
more stable air mass during the next 24 hours, the system should
lose its remaining deep convection and become a post-tropical
remnant low in 24 to 36 hours. The intensity guidance is in good
agreement, and the updated NHC intensity forecast is close to the
model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 23/2100Z 19.1N 118.2W 35 KT 40 MPH
12H 24/0600Z 19.9N 118.9W 30 KT 35 MPH
24H 24/1800Z 20.7N 120.0W 30 KT 35 MPH
36H 25/0600Z 21.3N 121.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 25/1800Z 21.8N 122.3W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 26/1800Z...DISSIPATED

$$
Forecaster Brown

[cycloneye]

Tropical Storm Dalila Discussion Number 8
NWS National Hurricane Center Miami FL EP052019
800 PM PDT Tue Jul 23 2019

Dalila has changed little during the last several hours. The storm
remains very asymmetric with deep convection limited to the
southeastern quadrant due to northwesterly vertical wind shear. An
ASCAT pass from several hours ago showed maximum winds of about 35
kt, and since the system has been steady state, the initial
intensity is held at that value.

Dalila has just crossed the 26 degree C isotherm and it is headed
for even cooler waters. In addition, a field of stratocumulus
clouds are seen in satellite images near and to the west of the
system, indicative of the nearby stable air mass. These conditions
should lead to weakening soon, and Dalila is expected to become
a tropical depression within the next 12 hours and a remnant low in
a day or so. The global models show the remnant low opening up into
a trough in a few days or less. The NHC intensity forecast is
identical to the previous one and in line with the majority of the
guidance.

The storm is still moving northwestward, but it is gradually turning
to the left. A turn to the west-northwest is forecast during the
next day or so, as the cyclone loses its convection and moves
within the low-level easterly trade wind flow, and that motion
should continue until the system dissipates. The NHC track forecast
is largely an update of the previous one and is near the various
consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT 24/0300Z 19.4N 118.4W 35 KT 40 MPH
12H 24/1200Z 20.0N 119.2W 30 KT 35 MPH
24H 25/0000Z 20.7N 120.2W 30 KT 35 MPH
36H 25/1200Z 21.3N 121.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 26/0000Z 21.8N 122.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 27/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Tropical Depression Dalila Discussion Number 9
NWS National Hurricane Center Miami FL EP052019
200 AM PDT Wed Jul 24 2019

Dalila has maintained a robust low-level circulation based on recent
scatterometer wind data, but those data also indicate that Dalila's
peak winds had decreased to 27-30 kt despite a sharp increase in
deep convection near and southeast of the center. UW-CIMSS ADT and
SATCON estimates suggest a higher intensity of 35-44 kt. However, it
appears that the cooler water that the cyclone is moving over has
stabilized the boundary layer, which is not allowing the normal
downward mixing of stronger winds aloft to reach the surface. Given
the lower ASCAT wind data, Dalila has been downgraded to a 30-kt
tropical depression.

The initial motion estimate is 315/05 kt. There is no significant
change to the previous track and intensity forecast philosophies.
Dalila is expected to move northwestward today, followed by a turn
toward the west-northwest on Thursday when the weakening cyclone
becomes more shallow and comes under the influence of easterly
trade wind flow. The cyclone is now moving over 25 deg C sea-surface
temperatures, with cooler water and more stable air still ahead of
Dalila. As a result, convection is expected to gradually wane during
the next 24 hours, accompanied by a steady spin down of the vortex,
which should result in the system degenerating into a post-tropical
remnant low by Thursday morning, if not sooner. The NHC track and
intensity forecasts closely follow the consensus models HCCA and
IVCN, respectively.

FORECAST POSITIONS AND MAX WINDS

INIT 24/0900Z 19.8N 118.8W 30 KT 35 MPH
12H 24/1800Z 20.4N 119.5W 25 KT 30 MPH
24H 25/0600Z 21.1N 120.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 25/1800Z 21.8N 121.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 26/0600Z 22.2N 122.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 27/0600Z...DISSIPATED

$$
Forecaster Stewart

[cycloneye]

Tropical Depression Dalila Discussion Number 10
NWS National Hurricane Center Miami FL EP052019
800 AM PDT Wed Jul 24 2019

Deep convection associated with the cyclone has continued to
decrease in coverage this morning, however, there is still a
broken band of convection over the southeastern portion of the
circulation. A blend of the latest Dvorak CI numbers from TAFB
and SAB support maintaining an intensity of 30 kt for this
advisory. Dalila will be moving over SSTs of 23-24 deg C later
today, and into a dry and more stable airmass. This should
result in weakening, and the system is expected to degenerate
into a remnant low within 24 hours.

It appears that Dalila has taken a northward jog this morning, but
the longer-term motion estimate is 320/6 kt. There has been no
change to the track forecast reasoning. Dalila should continue
moving northwestward today, then turn west-northwestward as it comes
under the influence of the low-level trade wind flow. The NHC
track forecast has been adjusted slightly north of the previous
advisory due to the more northward initial position, however, the
updated official forecast is still near the middle of the guidance
envelope and close to the multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 20.5N 119.0W 30 KT 35 MPH
12H 25/0000Z 21.1N 119.7W 25 KT 30 MPH
24H 25/1200Z 21.9N 120.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 26/0000Z 22.3N 122.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 26/1200Z 22.7N 123.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 27/1200Z...DISSIPATED

$$
Forecaster Brown

[cycloneye]

Tropical Depression Dalila Discussion Number 11
NWS National Hurricane Center Miami FL EP052019
200 PM PDT Wed Jul 24 2019

Deep convection associated with Dalila has continued to wane since
the previous advisory, and the system has become a swirl of low- to
mid-level clouds with a small area of colder cloud tops over the
eastern semicircle. A recent ASCAT overpass showed maximum winds
of 25 kt, which is used as the initial intensity for this advisory.
Dalila will continue to move over progressively cooler waters, and
into a drier and more stable air mass during the next day or two.
This should result in additional weakening, and Dalila is expected
to degenerate into a remnant low tonight or on Thursday.

Dalila is still moving northwestward or 315/6 kt. As the cyclone
weakens and becomes an increasingly vertically shallow system, it is
forecast to turn west-northwestward within the low-level easterly
flow. The models are in good agreement on this scenario and the NHC
forecast track is close to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 24/2100Z 20.7N 119.8W 25 KT 30 MPH
12H 25/0600Z 21.3N 120.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 25/1800Z 21.9N 121.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 26/0600Z 22.3N 123.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 26/1800Z 22.8N 124.6W 15 KT 15 MPH...POST-TROP/REMNT LOW
72H 27/1800Z...DISSIPATED

$$
Forecaster Brown

[Kingarabian]

Suprised it lasted this long

[Chris90]

She's certainly being an idle Dalila in giving in to her certain demise. Continues to produce convection despite her location and continued march to the north and west over increasingly cooler SSTs. EPAC storms frequently impress me with their resilience.

[cycloneye]

Tropical Depression Dalila Discussion Number 12
NWS National Hurricane Center Miami FL EP052019
800 PM PDT Wed Jul 24 2019

Dalila is hanging on as a tropical depression. After having
little deep convection throughout the day, a new area of
thunderstorms has formed during the past several hours over the
northeastern quadrant, which is over slightly warmer water. The
remainder of the circulation consists of a swirl of low-level
clouds. The initial intensity is held at 25 kt, in agreement with
the earlier ASCAT data and the 00Z Dvorak classification from TAFB.
Dalila is not expected to hold on much longer as a tropical cyclone,
as progressively cooler waters and stable air should cause the deep
convection to dissipate soon. The NHC intensity forecast continues
to show gradual weakening, and ultimately dissipation in 2 to 3
days.

The center of the depression has jogged to the north, likely due to
the development of the convection on its northeast side. Smoothing
through this recent jog yields a motion of 325/6. As the
convection dies, the weak cyclone is expected to turn to the
west-northwest and then the west within the low-level trade wind
flow. The NHC track forecast is a little to the north of the
previous one, based on the more northward initial position, and lies
near the middle of the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 25/0300Z 21.4N 119.8W 25 KT 30 MPH
12H 25/1200Z 21.7N 120.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 26/0000Z 22.2N 121.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 26/1200Z 22.6N 123.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 27/0000Z 22.8N 124.9W 15 KT 15 MPH...POST-TROP/REMNT LOW
72H 28/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Tropical Depression Dalila Discussion Number 13
NWS National Hurricane Center Miami FL EP052019
200 AM PDT Thu Jul 25 2019

Dalila is still technically a tropical cyclone based on the
development of new convection within 70-75 nmi northeast of the
center, which barely results in a Dvorak current intensity estimate
of T1.5/25 kt. In addition, a 0539Z ASCAT-C overpass indicated a few
25-kt vectors were present in the northern semicircle. Therefore,
Dalila remains a 25-kt tropical depression for this advisory. Having
said that, recent satellite trends indicate that the convection is
beginning to separate and move away from the low-level center due to
northwesterly vertical wind shear, and this negative trend should
continue, resulting in Dalila degenerating into a remnant low
pressure system later today while the system moves over 24 deg C
water. Dissipation of the cyclone is expected in 48-72 hours.

Dalila is moving slowly northwestward or 315/05 kt. A turn toward
the west-northwest is expected by this afternoon, followed by a
westward motion on Friday and Saturday, which is expected to
continue until dissipation occurs. The new official track forecast
is similar to the previous advisory track, and lies close to the
simple consensus model TVCE.

FORECAST POSITIONS AND MAX WINDS

INIT 25/0900Z 21.6N 120.4W 25 KT 30 MPH
12H 25/1800Z 22.0N 121.3W 20 KT 25 MPH...POST-TROP/REMNT LOW
24H 26/0600Z 22.5N 122.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 26/1800Z 22.8N 124.2W 15 KT 15 MPH...POST-TROP/REMNT LOW
48H 27/0600Z 23.1N 125.8W 15 KT 15 MPH...POST-TROP/REMNT LOW
72H 28/0600Z...DISSIPATED

$$
Forecaster Stewart

[NotSparta]

Remnant low now

EP, 05, 2019072512, , BEST, 0, 218N, 1205W, 20, 1009, LO

[cycloneye]

Post-Tropical Cyclone Dalila Discussion Number 14
NWS National Hurricane Center Miami FL EP052019
800 AM PDT Thu Jul 25 2019

Dalila's circulation is becoming elongated, and the remaining
thunderstorm activity is displaced well to the northeast. Earlier
scatterometer data revealed that winds were 20 to 25 knots, and most
likely these winds have decreased since then. On this basis, it is
estimated that Dalila has degenerated into a remnant low with 20-kt
winds.

Now that the system is shallow, the remnant low will continue to
move toward the west-northwest at about 6 to 8 kt, steered by the
low-level trade winds. While some intermittent patches of
convection are possible, the system is forecast to dissipate in a
day or so over cooler waters.

This is the last advisory on this system.

FORECAST POSITIONS AND MAX WINDS

INIT 25/1500Z 21.9N 120.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
12H 26/0000Z 22.3N 121.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
24H 26/1200Z 22.7N 123.1W 15 KT 15 MPH...POST-TROP/REMNT LOW
36H 27/0000Z 23.0N 124.9W 15 KT 15 MPH...POST-TROP/REMNT LOW
48H 27/1200Z...DISSIPATED

$$
Forecaster Avila/Taylor