ATL: OMAR - Advisories

[cycloneye]

Tropical Depression Fifteen Discussion Number 1
NWS National Hurricane Center Miami FL AL152020
500 PM EDT Mon Aug 31 2020

Satellite images indicate that the area of low pressure offshore of
the Carolinas has had convection organized in bands since before
dawn, and scatterometer plus an Air Force Reserve Hurricane
Hunter mission data confirm that the circulation is closed. Thus,
this is now a tropical depression, and the initial wind speed is
set to 30 kt in accordance with 25-30 kt ASCAT-A data plus buoy
42001 readings which earlier had an adjusted 10-m peak of 30 kt.

The depression is moving northeastward at about 10 kt. The system
should gradually turn toward the east-northeast by Wednesday due to
it moving around the northwest side of the subtropical ridge, then
move eastward in a few days around the flat ridge. By late week,
the cyclone could slow and eventually turn back toward the northeast
around a rather strong mid-latitude high pressure system over the
northeast Atlantic. There is considerable spread in the guidance,
which really seems to depend upon whether the system stays coherent,
like the official forecast, or would become a shallow low-level
swirl by 120h and end up slower and south of forecast track. This
forecast is near the corrected-consensus guidance, leaning toward
the ECMWF-based models, and it should be considered of low
confidence.

Gradual strengthening is expected over the next day or so while the
depression remains in a low-to-moderate shear environment. Although
the depression is expected to be traversing the warm Gulf Stream for
the next several days, wind shear is expected to greatly increase by
Wednesday, which should limit intensification. In fact there's
some chance the system could decay and lose any deep convection in
rather strong shear in a few days. However, since it likely will be
moving near the Gulf Stream, I suspect it will continue to pulse
thunderstorm activity and stay alive throughout the period. The NHC
intensity forecast is near or just above the model consensus on
that reasoning, closest to the HWRF model. The cyclone could
become extratropical (or a remnant low) by the end of the forecast,
but this is very uncertain.


FORECAST POSITIONS AND MAX WINDS

INIT 31/2100Z 32.6N 76.5W 30 KT 35 MPH
12H 01/0600Z 33.8N 75.0W 35 KT 40 MPH
24H 01/1800Z 34.9N 72.4W 40 KT 45 MPH
36H 02/0600Z 35.8N 69.7W 40 KT 45 MPH
48H 02/1800Z 36.7N 67.0W 40 KT 45 MPH
60H 03/0600Z 37.6N 63.7W 35 KT 40 MPH
72H 03/1800Z 38.2N 60.5W 35 KT 40 MPH
96H 04/1800Z 39.0N 55.0W 35 KT 40 MPH
120H 05/1800Z 41.5N 49.5W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Blake

[cycloneye]

Tropical Depression Fifteen Discussion Number 2
NWS National Hurricane Center Miami FL AL152020
1100 PM EDT Mon Aug 31 2020

Tropical Depression Fifteen is a sheared tropical cyclone, with the
edge of the deep convection displaced nearly 30 n mi to the east of
the exposed low-level center. An Air Force Reserve Hurricane Hunter
mission earlier this evening provided SFMR instrument measurements
of nearly 30 kt in the southeast quadrant. And, a recent ASCAT
overpass showed several wind vectors in that same general area
between 25-30 kt. Therefore, the initial intensity is being held at
30 kt.

The depression is moving northeast at 12 kt around the northwestern
periphery of the subtropical ridge. A turn to the east-northeast is
expected to occur on Tuesday as the cyclone moves along the
northern periphery of the ridge. Late in the forecast period, what
is left of the cyclone is forecast to get caught in the flow
between building high pressure to its northeast, and an approaching
trough to its northwest, which should induce a more northerly
component of motion. The latest NHC forecast is little changed from
the previous one, and is near the tightly clustered track guidance.

The cyclone has moved into an environment with moderate westerly
shear of about 20 kt, as indicated by the latest UW-CIMSS deep-layer
shear analysis product. The SHIPS guidance by both the GFS and ECMWF
indicate that the shear magnitude will more than double between 18 h
and 36 h from now. So it is anticipated that the only window of
time for the depression to strengthen will be tonight through
tomorrow, while the system is over warm waters and in a moist
atmospheric environment. After 48 h, when the vertical wind shear is
forecast to be between 40 and 50 kt, the cyclone is forecast to
weaken, and by 96 h the NHC forecast now shows the system
degenerating into a remnant low. Exactly what transpires with the
cyclone later in the forecast period remains uncertain, as some of
the global models suggest that the cyclone will open into a trough
in a few days, while others indicate that the system could be
absorbed by a larger mid-latitude trough around day 5. Regardless of
what occurs by those time frames, the models all suggest that the
system should not gain much more strength than it currently has. The
official NHC intensity forecast is in good agreement with the
various intensity consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 33.2N 75.7W 30 KT 35 MPH
12H 01/1200Z 34.2N 74.0W 35 KT 40 MPH
24H 02/0000Z 35.1N 71.2W 35 KT 40 MPH
36H 02/1200Z 36.0N 68.6W 35 KT 40 MPH
48H 03/0000Z 36.9N 65.9W 35 KT 40 MPH
60H 03/1200Z 37.7N 63.3W 30 KT 35 MPH
72H 04/0000Z 38.1N 60.5W 30 KT 35 MPH
96H 05/0000Z 38.7N 55.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 06/0000Z 41.6N 50.4W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Latto

[cycloneye]

Tropical Depression Fifteen Discussion Number 3
NWS National Hurricane Center Miami FL AL152020
500 AM EDT Tue Sep 01 2020

Deep convection remains displaced to the east and southeast of the
depression's low-level center due to increasing west-northwesterly
shear. Maximum winds are still estimated to be 30 kt, with no
appreciable structural changes having occurred since last evening's
ASCAT pass, which showed 25-30 kt winds.

The initial motion is toward the northeast, or 050/11 kt, with the
depression becoming embedded in the mid-latitude westerlies north
of the subtropical ridge. Forecast guidance agrees that the
cyclone will turn east-northeastward and then eastward during the
next 2-3 days, moving farther out into the Atlantic, although there
is greater-than-normal spread among the track models mainly due to
speed differences. In particular, the ECMWF is one of the fastest
models, while the GFS and UKMET hang the cyclone back to the west a
little longer. Since many of the consensus aids, including HCCA,
are closer to the faster model solutions, the NHC track forecast
leans toward the quicker side of things.

UW-CIMSS analyses indicate that the shear has increased to 20-25
kt, and it's only expected to get stronger from here. Some slight
strengthening of the depression can't be ruled out during the next
12-24 hours while the shear vector is aligned with the storm motion,
but by this time tomorrow the shear is likely to be as strong as
35-45 kt out of the northwest. Therefore, little change in
strength is now indicated in the official forecast for the next day
or two. The shear magnitude is expected to peak in about 48 hours,
and the depression is forecast to be a remnant low at that point,
if it hasn't become one already. The GFS dissipates the low in
about 48 hours, but since the other models hang onto it a little
bit longer, the NHC forecast shows dissipation by day 5.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0900Z 34.1N 74.4W 30 KT 35 MPH
12H 01/1800Z 35.0N 72.5W 30 KT 35 MPH
24H 02/0600Z 36.0N 69.7W 30 KT 35 MPH
36H 02/1800Z 36.9N 67.0W 30 KT 35 MPH
48H 03/0600Z 37.5N 63.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 03/1800Z 37.7N 61.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 04/0600Z 37.8N 58.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 05/0600Z 39.2N 53.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 06/0600Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Tropical Depression Fifteen Discussion Number 4
NWS National Hurricane Center Miami FL AL152020
1100 AM EDT Tue Sep 01 2020

The depression has become better organized this morning with the
center embedded in the western side of a growing area of deep
convection. An earlier buoy report recorded adjusted maximum winds
of 32 kt, and roughly half of the estimates show that the depression
is a tropical storm. Conservatively, the winds will be held at 30
kt until we will see what the scatterometer shows this afternoon.
Increasing shear is expected to limit any significant strengthening,
although it does seem more likely than not that this system will
barely make it to a tropical storm later today. The shear is
forecast to get quite strong by tomorrow afternoon, so weakening is
anticipated by then, and persistence of that shear is expected to
cause the cyclone to decay into a remnant low in about 48 hours.
While the initial part of the forecast is a little higher than the
last one, this change is really in the noise level for intensity
prediction and is only noticeable because of the tropical storm
threshold.

The initial motion has turned toward the east-northeast or 060/12
kt. There is reasonable agreement among the guidance that this
motion will continue through tomorrow, and then become eastward
during the next 2-3 days around the northern side of the subtropical
ridge, followed by a northeastward turn by day 4. Similar to the
last forecast, most of the uncertainty is with the speed, rather
than the direction of the cyclone. The new forecast is closer to the
faster guidance and the previous NHC track prediction. Dissipation
is shown at 120h, although a few models have it occuring as early as
days 2-3.


FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 34.7N 73.1W 30 KT 35 MPH
12H 02/0000Z 35.6N 71.1W 35 KT 40 MPH
24H 02/1200Z 36.5N 68.3W 35 KT 40 MPH
36H 03/0000Z 37.2N 65.1W 30 KT 35 MPH
48H 03/1200Z 37.3N 62.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 04/0000Z 37.0N 59.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 04/1200Z 37.0N 57.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 05/1200Z 39.5N 52.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 06/1200Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

Tropical Storm Omar Discussion Number 5
NWS National Hurricane Center Miami FL AL152020
500 PM EDT Tue Sep 01 2020

Satellite images show that the system remains sheared with a
bursting pattern on satellite, occasionally exposing the center,
and a large area of curved bands in the southeastern quadrant of
the circulation. Almost all of the subjective and objective Dvorak
estimates, along with SATCON values, are between 35 to 40 kt, and
the lower number is chosen as the initial wind speed since
scatterometer data suggests 30 to 35 kt. This makes Omar the 15th
named storm of the 2020 Atlantic hurricane season, and is the
earliest 15th storm on record, besting the previous mark by about
a week from Ophelia of 2005.

Any chance for strengthening should end by tomorrow afternoon due
to greatly increasing shear, and weakening is likely to commence by
then. The persistence of the shear should cause the cyclone to
decay into a remnant low in about 48 hours, if not sooner. No
significant changes were made to the previous forecast, which is
near the model consensus.

The initial motion remains east-northeast or 065/13 kt. The
cyclone is being steered by the northern side of the subtropical
ridge, which is forecast to cause a similar motion through tomorrow
and an eastward turn late week due to the orientation of the ridge.
The only notable change to the forecast is a slow down at long
range in most of the guidance, probably due to a shallow system
no longer feeling the stronger deep-layer winds, so the NHC track
prediction follows suit. The remnant low should dissipate in 4-5
days.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 35.3N 71.5W 35 KT 40 MPH
12H 02/0600Z 36.1N 69.4W 35 KT 40 MPH
24H 02/1800Z 36.7N 66.7W 35 KT 40 MPH
36H 03/0600Z 37.2N 63.9W 30 KT 35 MPH
48H 03/1800Z 37.2N 61.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 04/0600Z 37.0N 59.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 04/1800Z 37.0N 57.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 05/1800Z 39.5N 53.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 06/1800Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

Tropical Storm Omar Discussion Number 6
NWS National Hurricane Center Miami FL AL152020
1100 PM EDT Tue Sep 01 2020

Omar is battling strong northwesterly shear, as any burst of
convection that tries to develop near the center is quickly pushed
off well to the southeast of the cyclone's exposed low-level center.
The initial intensity is being held at 35 kt based on a combination
of the latest Dvorak CI values from UW-CIMSS, SAB and TAFB, as
as well as data from a recent ASCAT overpass showing similar winds
compared to earlier today.

These intermittent bursts of convection should sustain Omar as a
tropical storm at least through early Wednesday. However, the shear
is expected to get even stronger by late Wednesday, which should
cause a weakening trend to begin around that time. By Thursday
night, if not sooner, any organized deep convection is expected to
have diminished, and Omar is forecast to become a remnant low. An
approaching frontal system should absorb what is left of the
remnants a couple of days later. The latest NHC intensity forecast
is the same as the previous one, and is in agreement with the
various intensity aids.

Omar continues to move east-northeast, now at 12 kt. The steering
pattern is straightforward over the next few days, as the cyclone
will be steered east-northeast then eastward around the northern
periphery of a subtropical ridge. Later on in the forecast period,
once Omar has become a remnant low, a turn to the northeast is
expected ahead of the approaching frontal boundary. The latest NHC
track forecast is little changed from the previous one, and lies in
the middle of the tightly clustered track guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 35.8N 70.0W 35 KT 40 MPH
12H 02/1200Z 36.4N 68.0W 35 KT 40 MPH
24H 03/0000Z 37.0N 65.4W 35 KT 40 MPH
36H 03/1200Z 37.2N 62.5W 30 KT 35 MPH
48H 04/0000Z 37.0N 60.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 04/1200Z 36.9N 58.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 05/0000Z 37.4N 56.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 06/0000Z 40.0N 52.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 07/0000Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

Tropical Storm Omar Discussion Number 7
NWS National Hurricane Center Miami FL AL152020
500 AM AST Wed Sep 02 2020

UW-CIMSS analyses and SHIPS model diagnostics all indicate that
Omar is being blasted by 40-50 kt of northwesterly shear, and yet a
sizable area of deep convection has been hanging close to the
low-level center for some time now. Based on last evening's ASCAT
pass and the most recent satellite classifications, Omar's initial
intensity remains 35 kt. Despite the shear magnitude, Omar could
maintain tropical storm intensity for another 24 hours or so while
the shear direction remains out of the northwest and the cyclone is
over the warm Gulf Stream. During this period, the NHC forecast is
close to the ICON intensity consensus and the HCCA aid. After 24
hours, Omar should begin moving over waters with lower ocean heat
content, and the shear is forecast to veer more out of the north.
Both of these factors are expected to cause weakening, with Omar
likely to lose its deep convection and become a remnant low in about
2 days. Global models indicate that the remnant low should
dissipate ahead of a cold front by day 4, which is now shown in the
NHC forecast, although the ECMWF shows this happening a day earlier.

Omar is moving toward the east-northeast (070/12 kt), embedded
within the mid-latitude westerlies north of the subtropical ridge.
This steering pattern is forecast to keep Omar on an
east-northeastward or eastward path until it dissipates, but a
breakdown of the zonal flow should cause the cyclone's forward
speed to slow down gradually during the next 2-3 days. The updated
NHC track forecast has been shifted southward a bit in the
direction of the multi-model consensus aids and the GFS and ECMWF
solutions, which both lie along the southern edge of the guidance
envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 36.2N 68.7W 35 KT 40 MPH
12H 02/1800Z 36.6N 66.8W 35 KT 40 MPH
24H 03/0600Z 36.8N 64.0W 35 KT 40 MPH
36H 03/1800Z 36.6N 61.3W 30 KT 35 MPH
48H 04/0600Z 36.3N 59.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 04/1800Z 36.5N 57.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 05/0600Z 37.1N 56.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 06/0600Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Tropical Storm Omar Discussion Number 8
NWS National Hurricane Center Miami FL AL152020
1100 AM AST Wed Sep 02 2020

Although is seems as though we've been predicting it ad nauseam,
the persistent, blistering shear has finally begun to dramatically
affect the cyclone. What remains of the deep convective cloud mass
is separated more than 100 miles east-southeast of the exposed
surface circulation. The initial intensity is held at 35 kt based
on the Dvorak satellite intensity estimates from TAFB and SAB using
the shear scene-type. Omar's winds should begin to decrease later
tonight as the exposed surface center further decouples from the
convective mass. A few of the large-scale models show Omar
dissipating as soon as Friday, but for this NHC intensity forecast,
I'll indicate weakening to a depression Thursday, followed by
degeneration to a remnant low in 36 hours, similar to the
multi-model consensus intensity aids and the LGEM.

Omar's initial motion is estimated to be eastward, or 080/11 kt, and
is being steered by the deep-layer mid-latitude westerlies produced
by a subtropical ridge anchored over the central Atlantic. Omar
should continue on this general course through Friday. On
Saturday, the remnant low is expected to slow a bit, and turn
toward the east-northeast in response to an approaching frontal
boundary moving away from the Canadian Maritimes. No significant
changes were made to the previous track forecast, and the new NHC
forecast is based on a blend of the HCCA and GFEX consensus models.



FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 36.2N 67.4W 35 KT 40 MPH
12H 03/0000Z 36.5N 65.4W 35 KT 40 MPH
24H 03/1200Z 36.5N 62.4W 30 KT 35 MPH
36H 04/0000Z 36.3N 59.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 04/1200Z 36.2N 58.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 05/0000Z 36.4N 56.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 05/1200Z 37.0N 55.8W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 06/1200Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Depression Omar Discussion Number 9
NWS National Hurricane Center Miami FL AL152020
500 PM AST Wed Sep 02 2020

Conventional satellite imagery shows that Omar's cloud pattern is
rapidly deteriorating, and the surface circulation center has
become quite ill-defined. This morning's METOP-A/B scatterometer
passes revealed only a few 33 kt winds well to the southeast of
the center and it's reasonable to determine that those winds are no
longer present. Therefore, the initial intensity is lowered to 30
kt for this advisory and is further supported by the subjective
satellite intensity T-numbers from TAFB and SAB. The latest global
model runs agree with the depression degenerating to a remnant
low in 24 hours, or less, and the NHC intensity forecast follows
suit. Dissipation of the remnant low should occur no later than
Saturday evening.

Omar's initial motion is estimated to be due east, or 090/13 kt,
within the mid-latitude westerlies north of a subtropical ridge
stretching east to west over the central Atlantic. Omar should
continue moving eastward through Friday, although a couple of the
global models are showing a track a bit more east-southeastward.
Around the 60 hour period, the remnant low is expected to reduce in
forward speed, and turn toward the east-northeast in response to an
approaching baroclinic system entering the northwest Atlantic. The
NHC forecast is nudged just a little to the right of the previous
one, and lies close to the HCCA and TVCA consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT 02/2100Z 36.1N 65.7W 30 KT 35 MPH
12H 03/0600Z 36.1N 63.6W 30 KT 35 MPH
24H 03/1800Z 36.0N 61.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 04/0600Z 35.7N 59.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 04/1800Z 35.7N 57.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 05/0600Z 35.9N 56.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 05/1800Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Depression Omar Discussion Number 10
NWS National Hurricane Center Miami FL AL152020
1100 PM AST Wed Sep 02 2020

A brief and small burst of convection developed near the center of
Omar early this evening, only to be quickly sheared well to the
southeast of the exposed low-level center. Any new convection that
developed during the day has been smaller in coverage and shorter
lived, and this trend is expected to continue. The initial
intensity is being held at 30 kt based on a recent ASCAT overpass
showing several peak 30-kt wind vectors in the southern semicircle.
There is no change to the intensity forecast reasoning. Ongoing wind
shear of 40-50 kt should not allow any developing convection to
persist near Omar's center, and the depression should degenerate to
a remnant low sometime on Thursday. This scenario is in agreement
with the global model forecasts. A few days from now, the remnant
low should dissipate as it becomes absorbed by a larger approaching
mid-latitude frontal system.

Omar continues to move east at around 13 kt, to the north of a
subtropical ridge. An east or just south-of-east motion is forecast
through Friday. After that time, the remnants of Omar should turn
east-northeastward to northeastward ahead of the approaching
mid-latitude frontal system. The latest NHC track forecast is very
close to the previous one and is also near the various consensus
aids.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0300Z 36.1N 64.1W 30 KT 35 MPH
12H 03/1200Z 36.0N 62.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 04/0000Z 35.7N 59.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 04/1200Z 35.5N 58.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 05/0000Z 35.9N 57.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 05/1200Z 36.5N 56.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 06/0000Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

Tropical Depression Omar Discussion Number 12
NWS National Hurricane Center Miami FL AL152020
1100 AM AST Thu Sep 03 2020

Surprisingly, Omar's cloud pattern has changed little since it was
classified as a tropical depression yesterday morning. A shapeless
deep convective cloud mass still exists about 60 miles to the
southeast of the sheared, exposed surface circulation center and
the subjective T-numbers from TAFB and SAB are a carbon copy of the
satellite intensity classifications 24 hours ago. Therefore, the
initial intensity is once again held at 30 kt. The large-scale
models as well as the statistical-dynamical intensity guidance show
further weakening to a remnant low in 24 hours, and dissipation as
soon as Saturday morning. Because of Omar's resiliency in such a
harsh upper-level wind surrounding environment, the NHC forecast
shows Omar holding onto depression status for another 12-18 hours,
then finally degenerating to a remnant low Friday.

The initial estimated motion hasn't changed either during the past
24 hours and is toward the east, or 085/11 kt within the deep-layer
westerly flow provided by a subtropical ridge situated over the
central Atlantic. This due east heading should continue through
Friday morning, the a turn toward the east-northeast to northeast
is forecast by Friday night in response to an approaching
mid-latitude frontal zone. The official forecast is similar to the
previous advisory and is based on the HFIP Corrected Consensus
Approach model.


FORECAST POSITIONS AND MAX WINDS

INIT 03/1500Z 35.9N 61.1W 30 KT 35 MPH
12H 04/0000Z 35.8N 59.4W 30 KT 35 MPH
24H 04/1200Z 35.6N 57.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 05/0000Z 36.2N 56.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 05/1200Z 37.8N 55.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 06/0000Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Depression Omar Discussion Number 14
NWS National Hurricane Center Miami FL AL152020
1100 PM AST Thu Sep 03 2020

The larger mass of deep convection from earlier today that was south
of the exposed low-level center of Omar has since dissipated. The
only convection that remains is a few small patches in the eastern
semicircle. The initial intensity is being lowered to 25 kt, and is
based off a recent ASCAT overpass showing peak 26 kt wind vectors.
If the current state of the tropical depression persists through
much of tonight, then by definition the system would no longer
qualify as a tropical cyclone. The only chance for Omar to hang on
despite very strong northerly wind shear is the fact that it is
still over SSTs of about 27 C. After 24 h, dry air is expected to
envelop the system. Therefore, over this weekend whatever remains of
Omar is expected to dissipate ahead of an approaching mid-latitude
frontal system. The official NHC forecast shows Omar degenerating
into a remnant low by Friday morning and dissipating by Sunday
morning, and this scenario is in agreement with the global models.

The depression continues to move east-southeast at 9 kt in steering
flow around a subtropical ridge to its south, and another, larger
low pressure system to its northeast. The other low is forecast to
continue to lift northeastward, which should result in an end to the
southerly component of Omar's motion tonight or early Friday. By
Friday night, a turn to the northeast is expected to occur as Omar
gets caught in southwesterly flow ahead of the approaching frontal
system. The latest NHC track forecast is little changed from the
previous one, and lies near the various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 35.2N 59.1W 25 KT 30 MPH
12H 04/1200Z 35.2N 58.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 05/0000Z 35.6N 57.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 05/1200Z 36.8N 56.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 06/0000Z 38.3N 55.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 06/1200Z...DISSIPATED

$$
Forecaster Latto

[cycloneye]

Tropical Depression Omar Discussion Number 17
NWS National Hurricane Center Miami FL AL152020
500 PM AST Fri Sep 04 2020

Omar continues to hang on as a tropical depression. The cyclone is
producing a small area of thunderstorms to the south of the center,
enough to continue writing advisories on this system for now. The
initial intensity is held at 30 kt based on the earlier ASCAT data.
Omar has been more resistant than expected to the ongoing northerly
wind shear, but the models insist that the continued shear, dry
air, and cooler waters should cause it to decay to a remnant low
this evening or early Saturday and dissipate entirely by Saturday
night.

The tropical depression is still moving eastward at about 5 kt. An
approaching deep-layer trough should cause Omar to turn north-
northeastward tonight and then accelerate in that direction
until it dissipates over the northern central Atlantic this
weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 35.3N 57.3W 30 KT 35 MPH
12H 05/0600Z 36.2N 57.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 05/1800Z 38.0N 56.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 06/0600Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Tropical Depression Omar Discussion Number 20
NWS National Hurricane Center Miami FL AL152020
1100 AM AST Sat Sep 05 2020

Omar is barely a tropical cyclone. The center is completely exposed
to the north of a slowly shrinking area of sheared deep convection.
The initial intensity is held at 30 kt for this advisory. Omar
remains in an environment of northerly wind shear, dry air, and it
is headed toward cool waters. These conditions should cause Omar to
finally become a remnant low soon. Although the forecast shows the
system becoming a remnant low at 24 hours, it certainty could become
one at any time before then after its limited amount of deep
convection dissipates. Satellite images show an approaching cold
front about 300 n mi to the northwest of Omar. This front is
expected to merge with the system, causing Omar or its remnants to
become extratropical by Sunday afternoon.

The tropical depression is now moving northward at 9 kt. A much
faster north-northeast to northeast motion is expected during the
remainder of the weekend as Omar, or its remnants, become more
embedded in the fast steering flow ahead of the aforementioned cold
front.

FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 37.4N 57.3W 30 KT 35 MPH
12H 06/0000Z 39.0N 56.3W 30 KT 35 MPH
24H 06/1200Z 41.9N 53.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/0000Z 45.2N 49.7W 30 KT 35 MPH...POST-TROP/EXTRATROP
48H 07/1200Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Post-Tropical Cyclone Omar Discussion Number 21
NWS National Hurricane Center Miami FL AL152020
500 PM AST Sat Sep 05 2020

Omar continues to separate from a small lingering area of deep
convection that is located more than 100 n mi south-southwest of
the center. During the past couple of days, Omar has produced just
enough convection to maintain its status of a tropical depression,
but now it no longer meets the criteria of sufficently organized
deep convection to be considered a tropical cyclone. Therefore,
this is the last advisory on Omar issued by NHC. The initial
intensity of the remnant low is 30 kt based on earlier ASCAT data
that showed a region of 25-30 kt winds east of the center.

The remnant low is moving northward at 9 kt, a couple of hundred
miles east of a cold front. The models suggest that the remnants
of Omar should accelerate north-northeastward and merge with the
front in about 24 hours, leading to extratropical transition.
Dissipation is expected shortly thereafter.

For additional and future information on this system, see High Seas
Forecasts issued by the National Weather Service, under AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 38.4N 56.9W 30 KT 35 MPH...POST-TROPICAL
12H 06/0600Z 40.2N 55.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 06/1800Z 43.3N 52.2W 30 KT 35 MPH...POST-TROP/EXTRATROP
36H 07/0600Z...DISSIPATED

$$
Forecaster Cangialosi