EPAC: EMILIA - Remnants - Discussion

[cycloneye]

Tropical Storm Emilia Discussion Number 13
NWS National Hurricane Center Miami FL EP052024
800 AM PDT Wed Aug 07 2024

Conventional satellite imagery and a recent SSMI/S microwave
overpass indicate that Emilia has become better organized this
morning. The northeasterly shear impeding the system's northeast
quadrant has decreased, allowing for improved outflow aloft. A
Central Dense Overcast (CDO) with cloud tops of -88C has formed over
the surface center, and the microwave image revealed a banding eye
feature wrapping from the south side of the cyclone. The satellite
intensity estimates from TAFB and SAB are 65 kt and 55 kt,
respectively, and a recent SATCON analysis indicated 57 kt. Based
on a blend of these data, the initial intensity is raised to 60 kt.

Although the northeasterly deep-layer shear that has been inhibiting
Emilia's growth has subsided, the cyclone is expected to move over
decreasing oceanic surface temperatures later today while the
thermodynamic environment becomes less conducive. Therefore,
weakening is expected to commence by Thursday morning. By the
48-hour period, Emilia should spin down and degenerate into a
post-tropical remnant low, and this is in agreement with the
deterministic models and the statistical hurricane intensity
guidance.

The initial motion is estimated to be northwestward, or 320/15 kt.
A gradual turn to the west-northwest with a slower forward speed is
expected on Thursday while the cyclone moves around the southwest
periphery of a mid-tropospheric subtropical high. Toward the end of
the period, vertically shallow Emilia is expected to turn toward the
west within the low-level trade wind flow and eventually open up
into a trough around day 5. Only slight along-track adjustments
were made to this forecast, closely following the various consensus
aids.


FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 17.6N 117.0W 60 KT 70 MPH
12H 08/0000Z 19.2N 118.9W 60 KT 70 MPH
24H 08/1200Z 20.5N 121.9W 50 KT 60 MPH
36H 09/0000Z 21.3N 124.5W 40 KT 45 MPH
48H 09/1200Z 21.9N 126.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 10/0000Z 22.4N 128.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 10/1200Z 22.9N 131.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 11/1200Z 23.7N 134.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 12/1200Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Storm Emilia Discussion Number 14
NWS National Hurricane Center Miami FL EP052024
200 PM PDT Wed Aug 07 2024

Emilia's cloud pattern has become a little ragged-looking since
earlier today, and the low-level center appears to be located near
the northern edge of the main area of deep convection. The storm's
circulation has been interacting with Fabio, which is rotating
around the western side of Emilia while dissipating. Emilia is
expected to absorb the remnant disturbance of Fabio within the next
day or so. The current intensity is set at 55 kt based on a blend
of subjective Dvorak classifications from TAFB and SAB. This is
also within the range of various objective intensity estimates from
UW-CIMSS.

The system appears to be continuing on a generally northwestward
track, with an initial motion estimate of 305/16 kt. The steering
flow associated with a mid-level ridge to the north of Emilia is
likely to cause a generally west-northwestward motion for the next
few days. The official forecast track lies roughly in the middle
of the track guidance suite.

Although the vertical shear over Emilia is expected to remain fairly
low, The cyclone will be traversing progressively cooler waters
during the next 48 hours or so. Low- to mid-level relative humidity
is also forecast to decrease during this period as well. Therefore,
gradual weakening is anticipated during the next couple of days and
Emilia should become a post-tropical remnant low on Friday. This is
similar to the scenario shown by the previous official forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 19.1N 117.7W 55 KT 65 MPH
12H 08/0600Z 20.5N 119.8W 50 KT 60 MPH
24H 08/1800Z 21.5N 123.0W 45 KT 50 MPH
36H 09/0600Z 22.2N 125.1W 35 KT 40 MPH
48H 09/1800Z 22.8N 127.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 10/0600Z 23.4N 129.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 10/1800Z 23.9N 131.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 11/1800Z 24.9N 135.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 12/1800Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Tropical Storm Emilia Discussion Number 15
NWS National Hurricane Center Miami FL EP052024
800 PM PDT Wed Aug 07 2024

Emilia seems to be in the final stages of fully absorbing the
remnants of Fabio, which now appear fully enveloped in Emilia's
larger circulation. With that said, the merger has not benefited
Emilia, and most of its deep central convection has collapsed as the
system approaches cooler waters. While there hasn't been recent
microwave data over the system, subjective and objective satellite
intensity estimates have either stayed the same or decreased
slightly. The initial intensity is nudged downward to 50 kt for this
advisory.

The interaction with Fabio may have resulted in a brief acceleration
in Emilia's forward motion, but the longer term motion is now off to
the west-northwest at 290/16-kt. The steering associated with a
mid-level ridge to the north should continue to result in a
west-northwestward motion for most of the forecast period. The NHC
track forecast is very similar to the prior advisory, and still lies
in the middle of the track guidance envelope.

As mentioned in the prior advisory, the shear is forecast to remain
low over Emilia, but the tropical storm is also forecast to cross
the 26 C isotherm tonight and move over increasingly cool ocean
waters. In addition, the storm will also be traversing an
increasingly dry and stable air mass along the forecast track. Thus,
gradual weakening is forecast to continue, with Emilia expected to
become a remnant low in about 48 hours, about the time when the GFS
and ECMWF simulated satellite shows organized convection
dissipating. It will likely take a few more days for the circulation
to spin down to the point it opens up into a trough, sometime
between days 4 to 5.


FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 20.5N 119.9W 50 KT 60 MPH
12H 08/1200Z 21.5N 122.4W 45 KT 50 MPH
24H 09/0000Z 22.3N 124.8W 40 KT 45 MPH
36H 09/1200Z 23.1N 127.1W 35 KT 40 MPH
48H 10/0000Z 23.7N 129.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 10/1200Z 24.4N 131.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 11/0000Z 25.0N 133.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 12/0000Z 25.5N 136.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 13/0000Z...DISSIPATED

$$
Forecaster Papin

[Teban54]

I'll add Emilia to my list of storms that could have been stronger if not for Fujiwhara. Other examples include Hilary 2017, John 2018, and Philippe or Rina 2023 in the Atlantic.

[cycloneye]

Tropical Storm Emilia Discussion Number 17
NWS National Hurricane Center Miami FL EP052024
Issued by the NWS Weather Prediction Center College Park MD
800 AM PDT Thu Aug 08 2024

Emilia is producing small bursts of convection near its center this
morning, with little convective activity elsewhere within the
circulation. Based on a blend of the latest Dvorak current intensity
estimates from TAFB and SAB, the initial intensity is held at 35 kt.
This is also in good agreement with the overnight scatterometer
data that showed 30-35 kt winds with the storm.

The center of Emilia has been tugged slightly south of the previous
forecast track by recent convective bursts, but the long-term motion
remains west-northwestward (285/16 kt). The storm is expected to
continue on a west-northwestward to westward heading with a slower
forward speed over the next few days. The latest NHC track forecast
follows the multi-model consensus trends and has been nudged a bit
south of the previous prediction. Emilia is moving over cooler
waters and into a drier, more stable environment, making it unlikely
that Emilia will remain a tropical cyclone for much longer. The
updated NHC forecast shows Emilia becoming a post-tropical remnant
low in 24 h. The weakening system will likely take a few days to
spin down, and the global models indicate the cyclone should open
into a trough and dissipate by day 5.


FORECAST POSITIONS AND MAX WINDS

INIT 08/1500Z 21.2N 123.3W 35 KT 40 MPH
12H 09/0000Z 21.8N 125.1W 35 KT 40 MPH
24H 09/1200Z 22.7N 127.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 10/0000Z 23.5N 129.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 10/1200Z 24.2N 131.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 11/0000Z 24.7N 133.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 11/1200Z 24.9N 134.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 12/1200Z 24.5N 138.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 13/1200Z...DISSIPATED

$$
Forecaster Reinhart

[cycloneye]

Tropical Storm Emilia Discussion Number 18
NWS National Hurricane Center Miami FL EP052024
200 PM PDT Thu Aug 08 2024

Emilia appears to be in its final stage as a tropical cyclone. Deep
convection is limited to a few small clusters over the western
semicircle as the system is being influenced by some easterly
vertical wind shear. The intensity is held at 35 kt for this
advisory in general agreement with objective estimates from
UW-CIMSS, although this could be generous.

Visible imagery indicates that the center appears to be located
somewhat to the east of previous estimates. After some adjustments,
the initial motion estimate is a little slower, or 290/12 kt. A
mid-level ridge is expected to be maintained to the north of Emilia
for the next few days. Based on this steering pattern, the cyclone
should continue its generally west-northwestward heading for the
next day or two followed by a more westward to west-southwestward
movement within the shallow low-level flow. The NHC forecast track
is close to the multi-model consensus guidance TVCE.

Over the next day or two, the cyclone will be moving over SSTs
cooler than 23 deg C in an environment of relatively dry air. This
should cause the system to degenerate into a remnant low very soon
as shown by the official intensity forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 21.6N 123.8W 35 KT 40 MPH
12H 09/0600Z 22.2N 125.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 09/1800Z 22.9N 127.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 10/0600Z 23.5N 129.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 10/1800Z 24.0N 131.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 11/0600Z 24.4N 133.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 11/1800Z 24.5N 135.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 12/1800Z 24.0N 138.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 13/1800Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Bye.

Tropical Storm Emilia Discussion Number 18
NWS National Hurricane Center Miami FL EP052024
200 PM PDT Thu Aug 08 2024

Emilia appears to be in its final stage as a tropical cyclone. Deep
convection is limited to a few small clusters over the western
semicircle as the system is being influenced by some easterly
vertical wind shear. The intensity is held at 35 kt for this
advisory in general agreement with objective estimates from
UW-CIMSS, although this could be generous.

Visible imagery indicates that the center appears to be located
somewhat to the east of previous estimates. After some adjustments,
the initial motion estimate is a little slower, or 290/12 kt. A
mid-level ridge is expected to be maintained to the north of Emilia
for the next few days. Based on this steering pattern, the cyclone
should continue its generally west-northwestward heading for the
next day or two followed by a more westward to west-southwestward
movement within the shallow low-level flow. The NHC forecast track
is close to the multi-model consensus guidance TVCE.

Over the next day or two, the cyclone will be moving over SSTs
cooler than 23 deg C in an environment of relatively dry air. This
should cause the system to degenerate into a remnant low very soon
as shown by the official intensity forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 21.6N 123.8W 35 KT 40 MPH
12H 09/0600Z 22.2N 125.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 09/1800Z 22.9N 127.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 10/0600Z 23.5N 129.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 10/1800Z 24.0N 131.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 11/0600Z 24.4N 133.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 11/1800Z 24.5N 135.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 12/1800Z 24.0N 138.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 13/1800Z...DISSIPATED

$$
Forecaster Pasch