ATL: WANDA - Advisories

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ATL: WANDA - Advisories

#1 Postby cycloneye » Sat Oct 30, 2021 9:34 pm

BULLETIN
Subtropical Storm Wanda Advisory Number 1
NWS National Hurricane Center Miami FL AL212021
1100 PM AST Sat Oct 30 2021

...SUBTROPICAL STORM WANDA FORMS OVER THE CENTRAL ATLANTIC...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...36.2N 45.4W
ABOUT 1020 MI...1640 KM W OF THE AZORES
ABOUT 825 MI...1330 KM SSE OF CAPE RACE NEWFOUNDLAND
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...SE OR 125 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...988 MB...29.18 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM AST (0300 UTC), the center of Subtropical Storm Wanda was
located near latitude 36.2 North, longitude 45.4 West. The storm is
moving toward the southeast near 21 mph (33 km/h), and a slower
southeast to east-southeast motion is expected during the
next day or two. A turn to the northeast or north is forecast to
occur on Tuesday.

Maximum sustained winds are near 50 mph (85 km/h) with higher gusts.
Little change in strength is forecast during the next few days.

Winds of 40 mph extend outward up to 105 miles (165 km) from the
center.

The estimated minimum central pressure is 988 mb (29.18 inches).


HAZARDS AFFECTING LAND
----------------------
None


NEXT ADVISORY
-------------
Next complete advisory at 500 AM AST.

$$
Forecaster Cangialosi



Subtropical Storm Wanda Discussion Number 1
NWS National Hurricane Center Miami FL AL212021
1100 PM AST Sat Oct 30 2021

The non-tropical low that NHC has been monitoring for subtropical
transition over the central Atlantic appears to have completed the
process this evening. Satellite images indicate that there are no
longer fronts attached to the low, and showers and thunderstorms
have become concentrated near the center. The low has some tropical
characteristics (small radius of maximum wind and concentrated
convection) and some subtropical characteristics (co-located with an
upper-level trough and nearby fronts). The system is designated as
a subtropical storm for now since there appears to be more support
for that status. The initial intensity is estimated to be 45 kt
based on recent ASCAT data, which makes the cyclone Subtropical
Storm Wanda.

The storm has been moving east-southeastward at 18 kt. A slower
east-southeast to southeast motion is expected during the next day
or so as Wanda moves with the deep-layer trough that it is embedded
within. After that time, the trough is expected to cut off, and
Wanda will likely meander on Monday before turning sharply northward
or northeastward by the middle of next week when the system moves
in the flow between the low and a building ridge. Most of the
models agree on the general evolution, but there are notable speed
differences. The NHC track forecast lies near the various consensus
aids.

Wanda will likely maintain its strength during the next several
days. Although the system will remain over relatively cool waters
of about 23-24 C during the next couple of days, cold air aloft
should aid in the continued development of deep convection and could
allow the system to strengthen slightly during that time period.
Beyond that time, Wanda should begin to move over cooler waters and
that will likely end its opportunity to gain strength and lead to
post-tropical transition by the end of the forecast period. The
models are in good agreement on keeping Wanda steady state, and the
NHC intensity forecast lies near the middle of the guidance
envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 31/0300Z 36.2N 45.4W 45 KT 50 MPH
12H 31/1200Z 35.8N 43.9W 45 KT 50 MPH
24H 01/0000Z 35.3N 43.6W 50 KT 60 MPH
36H 01/1200Z 34.3N 43.2W 50 KT 60 MPH
48H 02/0000Z 33.8N 42.1W 45 KT 50 MPH
60H 02/1200Z 34.5N 40.9W 45 KT 50 MPH
72H 03/0000Z 36.4N 39.9W 45 KT 50 MPH
96H 04/0000Z 41.4N 39.6W 45 KT 50 MPH
120H 05/0000Z 46.2N 35.4W 45 KT 50 MPH...POST-TROPICAL

$$
Forecaster Cangialosi
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Re: ATL: WANDA - Advisories

#2 Postby cycloneye » Sun Oct 31, 2021 4:53 am

Subtropical Storm Wanda Discussion Number 2
NWS National Hurricane Center Miami FL AL212021
900 AM GMT Sun Oct 31 2021

Satellite imagery indicates that the convection associated with
Wanda has become better organized since the last advisory, with a
convective band now wrapping more than halfway around the center.
However, the cyclone remains embedded in a deep-layer baroclinic
circulation, and based on this structure, the system is still a
subtropical storm. Satellite intensity estimates are in the 40-50
kt range, and the intensity is set at a possibly conservative 45 kt.

The initial motion is a little slower toward the east-southeast at
105/14 kt. As mentioned in the previous advisory, a slower
east-southeast to southeast motion is expected during the next day
or so as Wanda moves with the deep-layer trough that it is embedded
within. After that time, the trough is expected to cut off, and
Wanda will likely meander on Monday before turning sharply northward
or northeastward by the middle of next week when the system moves in
the flow between the cut off low and a building ridge. By the end
of the forecast period, the cyclone is expected to turn
northeastward in southwesterly mid-latitude flow. The new track
guidance is similar to the previous guidance, but is a little slower
after 72 h. Thus, the new forecast track is similar to the previous
track and also slower in the later periods.

Given the increasing organization, it is likely that Wanda will
strengthen some during the next 24 h. After that, the intensity
guidance suggests little change in strength through 48 h as the
cyclone moves over sea surface temperatures of 24 C. Beyond 48 h,
gradual weakening is expected as Wanda moves over colder waters,
with the system expected to become post-tropical due to a lack of
convection by 120 h. It should be noted that the GFS and UKMET
suggest the possibility that Wanda could transition into a tropical
storm by 48 h. However, due to the expectation that the cyclone
will continue to remain embedded in a cold upper-level trough, the
intensity forecast will not explicitly call for tropical transition
at this time.


FORECAST POSITIONS AND MAX WINDS

INIT 31/0900Z 36.5N 43.9W 45 KT 50 MPH
12H 31/1800Z 36.2N 43.0W 50 KT 60 MPH
24H 01/0600Z 35.3N 42.8W 50 KT 60 MPH
36H 01/1800Z 34.6N 42.0W 50 KT 60 MPH
48H 02/0600Z 34.8N 40.7W 50 KT 60 MPH
60H 02/1800Z 36.2N 39.6W 50 KT 60 MPH
72H 03/0600Z 38.3N 39.0W 45 KT 50 MPH
96H 04/0600Z 43.0N 38.0W 45 KT 50 MPH
120H 05/0600Z 47.0N 32.5W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Beven
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Re: ATL: WANDA - Advisories

#3 Postby cycloneye » Sun Oct 31, 2021 3:43 pm

Subtropical Storm Wanda Discussion Number 3
NWS National Hurricane Center Miami FL AL212021
300 PM GMT Sun Oct 31 2021

Wanda is gradually taking on characteristics of a symmetric
warm-core cyclone, with bands of organized convection now located
across both the northern and southeastern portions of the
circulation. The 500-mb heights are slowing rising, while some
cirrus outflow is becoming evident to the north of the cyclone.
Although Wanda is still considered a subtropical storm due to the
presence of the surrounding baroclinic circulation and
upper-trough, the baroclinic circulation has been getting more
detached from the storm over time. Even though the convective
structure continues to evolve, this convection has not been able to
become more concentrated near the system's core since last night.
Therefore, the initial advisory intensity remains 45 kt, which is
consistent with the latest average of the satellite intensity
estimates from TAFB, and UW-CIMSS ADT and SATCON.

The storm has slowed its forward motion and is now moving at 100/07
kt. A turn to the southeast is expected today as Wanda wobbles
within the upper-level tropospheric trough that it is embedded
within. The upper-trough is forecast to lift out on Monday,
leaving Wanda within the weak steering flow near a cutoff mid-level
trough. By Tuesday, a ridge is forecast to build to the east of
the cyclone, resulting in a turn to the northeast or north, along
with an increase in forward speed. By late this week, Wanda should
accelerate northeastward within the southwesterly mid-latitude flow.
The model guidance is in good agreement on this track scenario, and
the latest NHC track forecast is very similar to the previous one.

Despite being over sea surface temperatures below the ideal warmth
to support a classic tropical cyclone, the colder-than-typical upper
tropospheric temperatures over Wanda should continue to help support
deep convection for the next few days. Therefore, some slight
strengthening is possible during that time. As mentioned above, the
upper-trough is expected to leave Wanda behind by Monday, which
should allow the cyclone to complete a tropical transition by that
time. Various global model solutions within the Florida State
University cyclone phase evolution forecasts agree with this
scenario taking place over the next 24 h. After 72 h, decreasing
water temperatures in the path of Wanda should cause the cyclone to
weaken and become post-tropical by the end of the 5-day forecast
period. The latest NHC intensity forecast is unchanged from the
previous one, with the only change being the tropical phase of
Wanda beginning Monday.


FORECAST POSITIONS AND MAX WINDS

INIT 31/1500Z 36.4N 43.2W 45 KT 50 MPH
12H 01/0000Z 35.9N 42.8W 50 KT 60 MPH
24H 01/1200Z 34.9N 42.4W 50 KT 60 MPH...TROPICAL CYCLONE
36H 02/0000Z 34.8N 41.2W 50 KT 60 MPH
48H 02/1200Z 35.6N 40.0W 50 KT 60 MPH
60H 03/0000Z 37.4N 39.1W 50 KT 60 MPH
72H 03/1200Z 39.4N 38.7W 45 KT 50 MPH
96H 04/1200Z 43.4N 37.3W 45 KT 50 MPH
120H 05/1200Z 47.2N 30.0W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Latto
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Re: ATL: WANDA - Advisories

#4 Postby cycloneye » Sun Oct 31, 2021 3:44 pm

Subtropical Storm Wanda Discussion Number 4
NWS National Hurricane Center Miami FL AL212021
900 PM GMT Sun Oct 31 2021

Wanda has struggled a bit this afternoon, as it appears that some
dry air has entrained into its circulation. Deep convection is now
mainly confined to a band wrapping around the eastern semicircle of
the cyclone. Remarkably, the 3 ASCAT overpasses today missed
the core of Wanda, however, the latest Dvorak intensity estimates
from TAFB, and the UW-CIMMS ADT and SATCON remain consistent, and
indicate an initial advisory intensity of 45 kt.

The storm made a rather abrupt halt in its eastward motion this
morning, and for much of the day has been drifting westward, with an
initial motion of 90/1 kt. Wanda is expected to make a slow, nearly
180 degree turn to the south, east, then northeast through Tuesday
as it pivots around a mid-tropospheric trough. A faster northeast to
north motion is expected through Wednesday as ridging builds to the
east of the cyclone. The model guidance is in reasonable agreement
on this scenario, and there were only minor tweaks to this portion
of the NHC track forecast. Thereafter, the guidance has made quite a
startling change from the previous runs, and is now indicating that
a blocking ridge may build to the north of Wanda by late this week.
This is a major shift in the guidance from previous runs that showed
the cyclone accelerating northeastward into the mid-latitudes. The
latest NHC track forecast tries to adjust for this change by
indicating a slower forward speed and less poleward motion late in
the 5-day forecast period, but this remains well north and east of
the bulk of the guidance. There is also a large amount of spread now
in the guidance beyond 72 h, and therefore, that portion of the
track forecast is of low confidence.

The upper-trough supporting the subtropical nature of Wanda is
forecast to lift out to the northeast by Monday. In addition, over
the past day or so, with each passing advisory cycle the cyclone has
taken on a little more of the appearance of a tropical cyclone
versus a subtropical cyclone. Model guidance is in good agreement on
this transition occurring soon, as per the latest FSU phase space
forecasts. Therefore, Wanda is expected to transition to a tropical
cyclone by Monday. The recent ingestion of dry air may have ended
the chance for further strengthening of the storm, and the latest
NHC intensity forecast shows no change in strength over the next few
days. Beyond 72 h, the intensity forecast becomes murky as there
is now a high level of uncertainty as to where Wanda may be headed
later this week. The previous NHC forecast had the cyclone moving
over much cooler waters late this week. However, the latest shift in
the track guidance suggests the cyclone could remain over the
current 24 degrees C waters throughout the next 5 days. Regardless
of the differing tracks and resulting sea surface temperatures
below, the cold pool of air in the upper troposphere that has been
giving Wanda a chance to maintain its deep convection will begin to
vanish by midweek, therefore, weakening is indicated in the
official NHC intensity forecast. The latest NHC intensity forecast
was decreased slightly from the previous one, and is close to the
various intensity consensus solutions.


FORECAST POSITIONS AND MAX WINDS

INIT 31/2100Z 36.3N 43.2W 45 KT 50 MPH
12H 01/0600Z 35.7N 43.0W 45 KT 50 MPH
24H 01/1800Z 35.2N 42.2W 45 KT 50 MPH...TROPICAL CYCLONE
36H 02/0600Z 35.6N 41.1W 45 KT 50 MPH
48H 02/1800Z 36.8N 40.2W 45 KT 50 MPH
60H 03/0600Z 38.6N 39.7W 45 KT 50 MPH
72H 03/1800Z 40.7N 39.4W 45 KT 50 MPH
96H 04/1800Z 44.1N 37.0W 45 KT 50 MPH
120H 05/1800Z 45.4N 32.0W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Latto
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Re: ATL: WANDA - Advisories

#5 Postby cycloneye » Sun Oct 31, 2021 9:42 pm

Subtropical Storm Wanda Discussion Number 5
NWS National Hurricane Center Miami FL AL212021
300 AM GMT Mon Nov 01 2021

Dry air continues to wrap into the circulation of Wanda, and
consequently, the system is only producing small fragmented
bands of deep convection. An ASCAT pass from a few hours ago
showed maximum winds of about 45 kt in the northwestern quadrant
of the storm, and therefore, the initial intensity is held at that
value. This intensity estimate is also in line with the satellite
classification from TAFB.

After moving east-southeastward for much of the day, Wanda has
abruptly turned southwestward with the latest initial motion
estimated to be 215/7 kt. This erratic motion is related to the
upper-level low that Wanda is co-located with. The storm is likely
to turn back toward the east-southeast or east on Monday and then
track to the northeast on Tuesday as the storm moves in the flow
between the associated trough and a building ridge to its east. By
Thursday and Friday, however, the models show another ridge building
to the north and west of Wanda, and that should slow its northward
progress and will likely cause the storm to turn eastward or
southeastward again by the end of the forecast period. The NHC
track forecast has been adjusted southward at days 4 and 5, trending
toward the latest models.

Wanda is likely to remain fairly steady in strength during the next
several days as dry air and relatively cool SSTs continue to affect
the system. The models are in good agreement, and the NHC intensity
forecast is unchanged from the previous one. Even though the
storm's intensity is not expected to change much, it will likely
transition to a tropical cyclone during the next day or so as it
continues to separate from the nearby fronts and upper low.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 35.6N 44.1W 45 KT 50 MPH
12H 01/1200Z 35.1N 43.3W 45 KT 50 MPH
24H 02/0000Z 35.1N 42.2W 45 KT 50 MPH...TROPICAL CYCLONE
36H 02/1200Z 36.0N 41.4W 45 KT 50 MPH
48H 03/0000Z 37.4N 40.7W 45 KT 50 MPH
60H 03/1200Z 39.2N 40.3W 45 KT 50 MPH
72H 04/0000Z 40.9N 39.9W 45 KT 50 MPH
96H 05/0000Z 43.1N 37.3W 45 KT 50 MPH
120H 06/0000Z 43.0N 33.0W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Cangialosi
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Re: ATL: WANDA - Advisories

#6 Postby cycloneye » Mon Nov 01, 2021 4:31 am

Subtropical Storm Wanda Discussion Number 6...Corrected
NWS National Hurricane Center Miami FL AL212021
900 AM GMT Mon Nov 01 2021

Corrected initial position

Wanda is now located to the west of the axis of the upper-level
trough that it is embedded in. As a result, significant northerly
vertical wind shear has developed over the storm, and between this
and continuing dry air entrainment the associated convection is
less organized than 24 h ago. Various subjective and objective
satellite intensity estimates are in the 40-50 kt range, and based
on continuity from earlier ASCAT data the initial intensity is held
at 45 kt.

After the earlier southwestward motion, Wanda is now turning
southeastward with the initial motion of 125/6. The storm and the
upper-level trough should move northeastward later today and then
northward by 36-48 h as southerly flow between a large
mid-latitude trough over the northwestern Atlantic and a
ridge east of Wanda becomes the dominant steering mechanism. After
72 h, another mid-latitude ridge is expected to build between Wanda
and the western Atlantic trough, and as a result the cyclone is
expected to turn eastward and then southward. The latest track
guidance shows a more northward motion than the previous guidance
between 36-60 h, and a more southward motion after 96 h. The new
forecast track has been nudged in those directions.

The intensity guidance suggests little change in strength during
the next several days as dry air and relatively cool SSTs continue
to affect the system. However, the current shear is expected to
decrease during the next 24-36 h, and this should help the system
to transition to a tropical cyclone. By 120 h, Wanda is expected
to become a post-tropical low as cooler sea surface temperatures
and an even dryer air mass cause the convection to dissipate. The
new intensity forecast is unchanged from the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0900Z 34.5N 43.9W 45 KT 50 MPH
12H 01/1800Z 34.3N 43.3W 45 KT 50 MPH
24H 02/0600Z 34.9N 42.1W 45 KT 50 MPH...TROPICAL CYCLONE
36H 02/1800Z 36.2N 41.3W 45 KT 50 MPH
48H 03/0600Z 38.2N 40.9W 45 KT 50 MPH
60H 03/1800Z 40.1N 40.7W 45 KT 50 MPH
72H 04/0600Z 41.5N 40.0W 45 KT 50 MPH
96H 05/0600Z 43.0N 36.5W 45 KT 50 MPH
120H 06/0600Z 41.0N 33.5W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Beven
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Re: ATL: WANDA - Advisories

#7 Postby cycloneye » Mon Nov 01, 2021 9:45 am

Subtropical Storm Wanda Discussion Number 7
NWS National Hurricane Center Miami FL AL212021
300 PM GMT Mon Nov 01 2021

Wanda has been moving southeastward since the previous advisory and
has now moved back underneath the axis of the upper-level trough
that the cyclone is embedded in. However, strong northwesterly
vertical wind shear of 30-35 kt has persisted and has displaced the
deep convection into the southeastern quadrant. The initial
intensity has been lowered to 40 kt based on a blend of satellite
intensity estimates of 35 kt from TAFB, and 39 kt and 41 kt from
UW-CIMSS ADT and SATCON, respectively.

Although Wanda had been moving southeastward at 10-11 kt as of 1200
UTC, the most recent motion vector appears to be slowly eastward or
090/05 kt. Wanda and the parent upper-level trough should move
eastward this late morning and early afternoon, and then turn
northeastward by this evening, followed by a northward motion by
late Tuesday as southerly steering flow gradually develops between a
larger mid-latitude trough to the west and a ridge to the east. By
day 3, another mid-latitude ridge is forecast to build between Wanda
and the aforementioned larger trough, causing the cyclone to turn
eastward and then southward toward the westernmost Azores. The
latest NHC track guidance has shifted sharply to the east of the
previous forecast track through 72 hours, and the new official track
forecast has followed suit. However, the new advisory track lies
along the western edge of the guidance through day 3, and then lies
in the middle of the track guidance envelope on days 4 and 5.

Although Wanda has weakened slightly, some slight restrengthening
will be possible in the 24-60-h period when the shear is forecast to
decrease sharply down to around 10 kt while the cyclone remains over
23.5-24-deg-C sea-surface temperatures. The weaker shear conditions
should also help Wanda transition to a tropical cyclone. By 96 h,
however, Wanda is forecast to devolve into a post-tropical low due
to the cyclone moving over sub-20-deg-C water temperatures, into a
significantly drier air mass, and into strong southerly vertical
wind shear -- a detrimental combination that should cause the
convection to erode near the center. The new NHC intensity forecast
is essentially unchanged from the previous advisory.


FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 34.0N 43.0W 40 KT 45 MPH
12H 02/0000Z 34.1N 42.0W 40 KT 45 MPH
24H 02/1200Z 35.0N 41.1W 45 KT 50 MPH...TROPICAL CYCLONE
36H 03/0000Z 36.8N 40.2W 45 KT 50 MPH
48H 03/1200Z 39.0N 40.0W 45 KT 50 MPH
60H 04/0000Z 40.8N 39.7W 45 KT 50 MPH
72H 04/1200Z 42.3N 39.0W 45 KT 50 MPH
96H 05/1200Z 43.6N 34.0W 45 KT 50 MPH...POST-TROPICAL
120H 06/1200Z 42.9N 31.5W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Stewart
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Re: ATL: WANDA - Advisories

#8 Postby cycloneye » Mon Nov 01, 2021 4:32 pm

Tropical Storm Wanda Discussion Number 8
NWS National Hurricane Center Miami FL AL212021
900 PM GMT Mon Nov 01 2021

Wanda is now moving east-northeastward and, as a result, has moved
to the east of the upper-level trough axis, while the parent
upper-low has detached and pulled out to the north. As a result,
Wanda has now made the transition from a subtropical cyclone to a
tropical cyclone. This meteorological metamorphosis has been
confirmed by ASCAT data from 1200-1300 UTC that showed Wanda now has
a small radius of maximum winds (RMW) of 30-35 nmi, and that the
outer wind field has weakened and also contracted in size. The
intensity is being held at 40 kt based on the earlier ASCAT data
showing winds of 33-34 kt, and assuming that there is undersampling
owing to the relatively large footprint/resolution of the
scatterometer instrument.

The initial motion estimate is 070/06 kt. A complex steering flow
pattern is forecast to evolve across the northern Atlantic during
the next several days as a series of troughs and ridges in the
mid-latitude westerlies pass over and to the north of Wanda. This
will cause Wanda to make a zig-zag track across the north-central
Atlantic, moving poleward ahead of the troughs and equatorward ahead
of the ridges, resulting in a net eastward propagation toward the
western Azores. The latest NHC model guidance is in fairly good
agreement on the forecast track through day 3, but then diverge on
days 4 and 5, with the GFS and ECMWF taking the cyclone more
southward closer to the Azores and the remaining dynamical models
lifting out Wanda to the north of the Azores. The new NHC official
track forecast is similar to the previous advisory track, and
follows a blend of the GFEX (GFS-ECMWF) and TVCA simple-consensus
models.

Some slight restrengthening will be possible during the next 48 h
or so due to a significant decrease in the deep-layer vertical wind
shear while Wanda moves over slightly warmer sea-surface
temperatures (SST) near 24 deg C. By 96-120 h, Wanda is forecast to
devolve into a post-tropical cyclone due to the unfavorable
combination of sub-20-deg-C SSTs, a significantly drier air mass,
and strong southerly wind shear in excess of 30 kt. The new NHC
intensity forecast remains unchanged from the previous advisory and
is basically in the middle of the tightly packed intensity guidance
suite.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 34.2N 42.2W 40 KT 45 MPH
12H 02/0600Z 34.7N 41.3W 45 KT 50 MPH
24H 02/1800Z 36.0N 40.4W 45 KT 50 MPH
36H 03/0600Z 37.8N 40.0W 45 KT 50 MPH
48H 03/1800Z 39.9N 39.7W 45 KT 50 MPH
60H 04/0600Z 41.7N 39.4W 45 KT 50 MPH
72H 04/1800Z 42.8N 38.3W 45 KT 50 MPH
96H 05/1800Z 43.4N 33.3W 45 KT 50 MPH...POST-TROPICAL
120H 06/1800Z 42.5N 31.0W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Stewart
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Re: ATL: WANDA - Advisories

#9 Postby cycloneye » Mon Nov 01, 2021 9:40 pm

Tropical Storm Wanda Discussion Number 9
NWS National Hurricane Center Miami FL AL212021
300 AM GMT Tue Nov 02 2021

The satellite presentation of Wanda indicates the system is
struggling with the effects of dry air and vertical wind shear
tonight. The center of the cyclone is partially exposed, with dry
mid-level air wrapping around the western and southern portions of
its circulation. The moderate to deep convection associated with
Wanda is displaced to the east and northeast of its center. A
partial ASCAT-B pass shows tropical-storm-force winds are occurring
in the southwestern quadrant of the storm. The latest objective and
subjective satellite estimates range from 35-40 kt, and the initial
intensity is held at 40 kt for this advisory.

Wanda is moving east-northeastward, or 75/6 kt. The complex steering
pattern over the northern Atlantic during the next several days
makes for a challenging track forecast. In the near term, Wanda is
expected to turn toward the northeast and north on Tuesday and
Wednesday as the cyclone is steered by a mid- to upper-level trough
over the north-central Atlantic. The track models are well clustered
for the first couple days of the forecast period, but then
significant differences emerge in the guidance at days 3-5. The new
GFS deviates from its previous run and shows the cyclone
accelerating eastward to northeastward as it eventually merges with
an approaching baroclinic system late this week. Meanwhile, the
ECMWF shows a narrow ridge building to the north and west of Wanda,
which slows its forward motion and eventually turns the cyclone
southward. The other global models generally lie somewhere in
between the divergent GFS/ECMWF solutions. Given the above average
uncertainty and lack of run-to-run model continuity, the NHC
official track forecast remains near or between the HCCA and TVCA
consensus aids.

Overall, little change in strength is expected during the next
several days. While the deep-layer shear is expected to diminish
through midweek, Wanda is forecast to be moving over sub-20 deg C
SSTs by Thursday. Thus, the cyclone only has a small window in which
to sustain enough deep, organized convection to support much
strengthening. Of course, if Wanda deviates from the official track
and races deeper into the mid-latitudes as shown by the GFS, it
would encounter even more hostile conditions and likely transition
to a post-tropical cyclone sooner than forecast. The official NHC
intensity forecast lies closest to the IVCN consensus aid, and
allows for a bit of strengthening in the near term similar to the
previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 34.5N 41.6W 40 KT 45 MPH
12H 02/1200Z 35.3N 40.9W 45 KT 50 MPH
24H 03/0000Z 36.9N 40.2W 45 KT 50 MPH
36H 03/1200Z 38.8N 39.9W 45 KT 50 MPH
48H 04/0000Z 40.9N 39.7W 45 KT 50 MPH
60H 04/1200Z 42.3N 39.2W 45 KT 50 MPH
72H 05/0000Z 42.9N 38.0W 45 KT 50 MPH
96H 06/0000Z 43.2N 33.4W 45 KT 50 MPH...POST-TROPICAL
120H 07/0000Z 43.0N 29.0W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Reinhart
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Re: ATL: WANDA - Advisories

#10 Postby cycloneye » Tue Nov 02, 2021 5:04 am

Tropical Storm Wanda Discussion Number 10
NWS National Hurricane Center Miami FL AL212021
900 AM GMT Tue Nov 02 2021

Wanda has become a little better organized since yesterday evening
with convection, albeit not very deep, now wrapping around the
center of the storm. Apparently the vertical shear over the
cyclone has relaxed somewhat, and the center is now more embedded
within the convection. This implies that some strengthening has
occurred and the intensity estimate is increased to 45 kt for this
advisory. This is also in agreement with a subjective Dvorak
satellite estimate from SAB. Interestingly, satellite-derived SST
analyses indicate that Wanda is currently located over a small patch
of warmer ocean waters, near 25 deg C.

The storm is moving a little faster toward the east-northeast, or
at about 060/7 kt. During the next couple of days, Wanda is likely
to remain embedded within a mid-tropospheric trough . A turn
toward the north is expected during the next 48 to 60 hours
while the system moves along the eastern portion of the
trough. Later in the forecast period, a ridge building to the west
and northwest of Wanda should force a turn toward the east and
east-southeast. The official forecast has been shifted to the
right of the previous NHC track at days 4 and 5, following the
latest dynamical model consensus. It should be noted that the GFS
model shows a track significantly farther south at this later time
frame.

Although Wanda will soon be moving over cooler waters, the SHIPS,
LGEM, and HCCA intensity guidance indicate that the system will
strengthen a little more in the short term, and then more or less
maintain its intensity for the next 48 hours or so. This is
probably due to fairly low vertical shear and relatively cool
upper-tropospheric temperatures during this time. Later, gradual
weakening is likely, due to increased shear and cool waters.
However baroclinic effects could at least partially offset the
weakening process. The official intensity forecast is in good
agreement with the corrected model consensus, HCCA, solution.
Around 72 hours, simulated satellite imagery shows a loss of
tropical cyclone-like cloud structure so the NHC forecast indicates
a post-tropical phase by that time.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 35.0N 40.9W 45 KT 50 MPH
12H 02/1800Z 36.1N 40.3W 50 KT 60 MPH
24H 03/0600Z 37.8N 39.9W 50 KT 60 MPH
36H 03/1800Z 39.8N 39.7W 50 KT 60 MPH
48H 04/0600Z 41.6N 39.5W 50 KT 60 MPH
60H 04/1800Z 42.6N 39.0W 45 KT 50 MPH
72H 05/0600Z 43.0N 37.1W 45 KT 50 MPH...POST-TROPICAL
96H 06/0600Z 41.8N 33.1W 45 KT 50 MPH...POST-TROPICAL
120H 07/0600Z 41.0N 29.4W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Pasch
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Re: ATL: WANDA - Advisories

#11 Postby cycloneye » Tue Nov 02, 2021 9:40 am

Tropical Storm Wanda Discussion Number 11
NWS National Hurricane Center Miami FL AL212021
300 PM GMT Tue Nov 02 2021

After the overnight burst of deep convection and associated improved
organization, dry air has wrapped into the system from all quadrants
and has temporarily eroded Wanda's inner-core convection. Despite
the recent convective degradation, visible satellite imagery
indicates that the cyclone's low-level circulation has improved,
with well-defined, curved low-level cloud lines and shallow
convection having become more evident. Based on improved low-level
structure, the intensity estimate remains at 45 kt despite the
overall loss of deep convection.

During the past 6 h, Wanda has made the expected sharp left-hand
turn and is now moving northward, or 010/08 kt. There are no
significant changes to the previous forecast track or reasoning.
Over the next couple of days, the latest model guidance is in
excellent agreement that Wanda should remain embedded within a
deep-layer trough, and gradually turn toward the north-northeast
later today, followed by a northeastward motion tonight and
Wednesday as the cyclone moves through the trough-to-ridge flow
pattern. By 48-60 hours, the cyclone is forecast to move toward the
east and east-southeast as a ridge builds to the northwest and west
of Wanda. The new NHC official forecast track is very similar to
the previous advisory track, and lies close to the middle of the
simple- and corrected-consensus guidance envelope.

The aforementioned improved low-level structure should act to force
new convection later today and especially tonight during the
nocturnal convective maximum period. Thus, Wanda has another 24-36 h
to strengthen while the system remains over marginally warm
sea-surface temperatures (SST) near 23 deg C and within a
relatively low vertical wind shear environment. Thereafter, slow but
steady weakening is likely due to an increase in southwesterly wind
shear, a decrease in mid-tropospheric moisture, and a decrease in
SSTs. However, baroclinic effects associated with an approaching
mid-tropospheric trough from the west could partially offset the
weakening process. Wanda is expected become a post-tropical cyclone
around 72 h, but this could be delayed if the baroclinic forcing on
day 3 ends up stronger than currently expected. The new official
intensity forecast is essentially just an update of the previous
intensity forecast, and is close to an average of the intensity
consensus models IVCN, NOAA-HCCA, and FSSE.


FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 35.6N 40.6W 45 KT 50 MPH
12H 03/0000Z 37.0N 40.0W 45 KT 50 MPH
24H 03/1200Z 38.8N 39.6W 50 KT 60 MPH
36H 04/0000Z 40.7N 39.5W 45 KT 50 MPH
48H 04/1200Z 42.1N 39.3W 45 KT 50 MPH
60H 05/0000Z 42.7N 38.1W 45 KT 50 MPH
72H 05/1200Z 42.5N 36.1W 45 KT 50 MPH...POST-TROPICAL
96H 06/1200Z 41.0N 33.0W 45 KT 50 MPH...POST-TROPICAL
120H 07/1200Z 42.5N 29.5W 40 KT 45 MPH...POST-TROPICAL

$$
Forecaster Stewart
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Re: ATL: WANDA - Advisories

#12 Postby cycloneye » Tue Nov 02, 2021 3:47 pm

Tropical Storm Wanda Discussion Number 12
NWS National Hurricane Center Miami FL AL212021
900 PM GMT Tue Nov 02 2021

Late-arriving 1201 UTC ASCAT-B scatterometer data indicated that a
small patch of 40-kt winds was located about 30 nmi east and
southeast of the well-defined center. Owing to known undersampling
by the scatterometer instrument for tropical cyclones that possess a
small radius of maximum of winds (RMW), those 40-kt winds support
the previous advisory intensity of 45 kt. That 45-kt intensity
estimate has been maintained for this advisory based on Wanda having
developed a small, closed eye-like feature in shallow convection,
with a curved band of deeper convection having recently developed
in the RMW where those 40-kt ASCAT surface winds were detected.
Wanda's overall convective organization has improved with more and
tighter curved low-level cloud lines now evident in visible
satellite imagery.

The initial motion estimate is northward, or 010/07 kt. There remain
no significant changes to the previous forecast track or reasoning
through 60 h. Thereafter, however, the latest model guidance has
made a significant southward shift in the track on days 3-5. For the
next couple of days, Wanda is forecast to move slowly poleward ahead
of an approaching mid- to upper-tropospheric trough. As the trough
weakens and lifts out to the north of the cyclone on day 3, Wanda is
expected to move slowly eastward before being forced southeastward
to southward by a narrow shortwave ridge that is forecast to trail
the aforementioned trough. The GFS and UKMET models show Wanda
merging with a frontal system on day 4 and lifting out to the
northeast, whereas the ECMWF drives the cyclone farther south ahead
of the cold front and turns the system into a convective-free
post-tropical cyclone on day 5. For now, the official track forecast
remains similar to the previous advisory track through 60 h, and
then shows Wanda turning sharply southeastward on day 4, which is
well to the right of the previous forecast track. The cyclone is
then forecast to lift out to the northeast on day 5 as an
extratropical low pressure system after merging with a cold front.
The official forecast track is similar to the tightly packed
consensus models through 60 h, and then is to the left or north of
the consensus aids in the 72-120-h period. There is
lower-than-normal confidence in the forecast track after 72 h due
to the major difference between the GFS and ECMWF model solutions.

Wanda's robust low-level circulation should be able to continue to
mix out occasional dry air intrusions, allowing for inner-core
convection to redevelop and resultant slight strengthening to occur
during the next 24-48 h. However, if a band of moderate convection
ends up developing around the aforementioned eye-like feature, then
Wanda could strengthen a little more than currently forecast. By day
3 and beyond, slow weakening is expected due to a sharp increase in
vertical wind shear and a decrease in mid-level moisture. Based on
what now appears to be stronger baroclinic forcing in the 60-96-h
period, the status of Wanda has been changed to a tropical cyclone
on day 3, with the day 4 and 5 statuses indicating extratropical
transition due to merger with a frontal system. The new NHC
intensity forecast is basically just an update of the previous
advisory forecast, and remains close to an average of the intensity
consensus models IVCN, NOAA-HCCA, and FSSE.


FORECAST POSITIONS AND MAX WINDS

INIT 02/2100Z 36.6N 40.4W 45 KT 50 MPH
12H 03/0600Z 37.9N 40.0W 50 KT 60 MPH
24H 03/1800Z 39.5N 39.8W 50 KT 60 MPH
36H 04/0600Z 41.1N 39.7W 45 KT 50 MPH
48H 04/1800Z 41.8N 39.4W 45 KT 50 MPH
60H 05/0600Z 41.8N 38.0W 45 KT 50 MPH
72H 05/1800Z 40.0N 37.5W 45 KT 50 MPH
96H 06/1800Z 39.0N 36.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 07/1800Z 43.0N 29.5W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart
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Re: ATL: WANDA - Advisories

#13 Postby cycloneye » Tue Nov 02, 2021 9:53 pm

Tropical Storm Wanda Discussion Number 13
NWS National Hurricane Center Miami FL AL212021
300 AM GMT Wed Nov 03 2021

Bands of convection have continued to wax and wane around the
center of Wanda over the past 6-12 hours, with a band currently
located over the western portion of the cyclone. A timely 2320 UTC
ASCAT-B overpass detected peak winds of around 40 kt and given the
known undersampling of that instrument for small tropical cyclones,
the 45-kt initial intensity is maintained. That is also supported
by a recent SATCON intensity estimate of 42 kt. The ASCAT data did
show that the area of tropical-storm-force winds has increased in
size over the eastern semicircle and now extends outward up to about
80 n mi in that portion of the storm.

Wanda is moving northward or 010/8 kt. The cyclone should continue
moving northward ahead of an approaching mid-latitude trough during
the next 24-36 hours. After that time however, the trough is
expected to weaken and lift northward causing Wanda to slow down
and turn eastward. After 48 hours, the track guidance has
continued its southward shift when a narrow ridge is forecast to
build to the northwest of the system. The NHC track forecast is
again shifted southward in the 60 to 96 h time period. By late in
the period, Wanda is forecast to accelerate northeastward ahead of
yet another mid-latitude trough. There is a bit more confidence in
the latest track prediction as the dynamical model guidance has
come into a bit better agreement, however additional southwestward
or westward adjustments during the middle portion of the forecast
period could be required.

Little overall change in strength is anticipated over the next
several days. As Wanda moves northward during the next day or so,
it will be moving over slightly cooler waters which could cause
the cyclone to struggle to produce deep convection. After day 2,
there are indications of increasing shear, but a nearby baroclinic
zone could help the system maintain its intensity. Later in the
period, shear and decreasing mid-level relative humidity are
likely to cause Wanda to become post-tropical, and by day 5 the
guidance indicates Wanda will merge with a frontal boundary and
become extratropical.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0300Z 37.3N 40.3W 45 KT 50 MPH
12H 03/1200Z 38.5N 40.0W 45 KT 50 MPH
24H 04/0000Z 40.1N 39.9W 45 KT 50 MPH
36H 04/1200Z 41.2N 39.8W 45 KT 50 MPH
48H 05/0000Z 41.2N 39.2W 45 KT 50 MPH
60H 05/1200Z 40.2N 38.1W 45 KT 50 MPH
72H 06/0000Z 38.5N 37.7W 45 KT 50 MPH
96H 07/0000Z 38.0N 36.0W 45 KT 50 MPH...POST-TROPICAL
120H 08/0000Z 43.5N 29.5W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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Re: ATL: WANDA - Advisories

#14 Postby cycloneye » Wed Nov 03, 2021 4:41 am

Tropical Storm Wanda Discussion Number 14
NWS National Hurricane Center Miami FL AL212021
900 AM GMT Wed Nov 03 2021

Wanda has changed little in organization since yesterday evening.
Bands of moderately deep convection continue around the storm
center, but upper-level outflow is not as well-defined as in a
typical tropical cyclone. The advisory intensity estimate
remains at 45 kt, in agreement with a subjective Dvorak satellite
estimate from SAB. This is also in general agreement with earlier
scatterometer observations. The cyclone remains fairly small, with
most of the stronger winds occurring over its eastern semicircle.

The storm continues moving a little east of north, or near 015/7
kt. Wanda should move on the eastern side of a mid-latitude trough
for the next day or so. After that time, the trough is likely to
weaken and this should result in the system slowing down and
turning eastward. In 2 to 3 days, a narrow mid-tropospheric ridge
is forecast to build to the northwest of Wanda which should cause
the cyclone to move southeastward. In 4 to 5 days, the cyclone is
expected to accelerate northeastward ahead of another mid-latitude
trough. The official forecast track is similar to the previous one
except a little more to the northeast in 36-60 hours. This follows
the latest simple and corrected model consensus solutions, and is
also close to the average of the latest ECMWF and GFS model tracks.

The system has maintained its intensity in spite of being over sea
surface temperatures of only about 23 deg C. Wanda will pass over
even cooler waters while it moves farther northward during the next
24 hours or so, which may make it difficult for the system to
produce much deep convection. However, the storm has been resilient
to seemingly hostile conditions so far, and the official forecast
calls for Wanda to maintain its intensity for much of the forecast
period. This is similar to the latest intensity model consensus
guidance. By 96 hours, however, dry air and shear are likely to
result in Wanda losing organized convection and becoming a
post-tropical cyclone. In 5 days, if not sooner, Wanda is likely
to merge with a frontal zone, and return to its former
extratropical status.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 38.0N 40.0W 45 KT 50 MPH
12H 03/1800Z 39.3N 39.8W 45 KT 50 MPH
24H 04/0600Z 41.0N 39.7W 45 KT 50 MPH
36H 04/1800Z 41.9N 39.4W 45 KT 50 MPH
48H 05/0600Z 41.6N 38.1W 45 KT 50 MPH
60H 05/1800Z 40.0N 37.0W 45 KT 50 MPH
72H 06/0600Z 38.5N 36.5W 45 KT 50 MPH
96H 07/0600Z 39.7N 34.5W 45 KT 50 MPH...POST-TROPICAL
120H 08/0600Z 46.0N 27.0W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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Re: ATL: WANDA - Advisories

#15 Postby cycloneye » Wed Nov 03, 2021 10:00 am

Tropical Storm Wanda Discussion Number 15
NWS National Hurricane Center Miami FL AL212021
300 PM GMT Wed Nov 03 2021

Wanda appears well organized this morning, with visible satellite
imagery indicating cyclonically curved convective bands wrapping
practically all the way around the circulation center. However, the
cloud top temperatures associated with this activity are not very
cold, peaking between minus 50 to 55 C in the deepest convection. An
ASCAT-A scatterometer pass at 1021 UTC also did not show much change
in the peak derived winds (39-kt), although the 34-kt radii have
expanded a bit. Subjective Dvorak satellite estimates this morning
also remain unchanged at CI 2.5/35 kt from TAFB and CI 3.0/45 kt
from SAB. The current intensity is held at 45 kt for this advisory,
assuming some undersampling in the scatterometer data.

The storm is moving a little faster to the north-northeast at 015/9
kt. The short-term track philosophy is fairly straightforward, as
Wanda continues to be steered generally northward by a narrow
mid-level ridge centered to the east of the cyclone. The track
guidance remains in good agreement on this evolution over the next
24 hours. Thereafter, the spread in track solutions increases quite
dramatically, owing to uncertainty related to the degree of
influence an approaching shortwave trough to the north has on Wanda.
For now, both the deterministic ECMWF and GFS solutions show this
shortwave trough bypassing the cyclone to the north, and in its wake
a narrow but sharp mid-level ridge develops west of Wanda, resulting
in the cyclone being steered back southward between 48-72 hours.
However, the spread in track solutions from both the GFS and ECMWF
ensemble members is very large at this time frame. In fact, the 06z
GFS ensemble track spread at 60 h is more than 500 n mi, far greater
than the average forecast track errors for that period. Finally, a
stronger shortwave trough is expected to pick up Wanda in the latter
portion of the forecast period, resulting in an abrupt acceleration
to the northeast. The official track forecast is similar to the
previous one for the first 24 hours, but has been nudged a little
south between 48-72 h following the consensus aids. Given the high
spread of ensemble solutions beyond 36 h, the track forecast beyond
that time is of low confidence.

While Wanda's winds have not increased over the past 24 hours, its
structure on satellite imagery has improved, with convective banding
wrapping around the low-level center, aided by low vertical wind
shear over the system. Even though Wanda is over marginally warm
sea-surface temperatures (SSTs) that decrease further along the
track over the next 36 hours, this negative factor will be offset by
cooling upper-level temperatures overhead. The trough forecast to
bypass Wanda to the north could also provide a bit of baroclinic
enhancement aiding ascent over the cyclone. Most of the intensity
guidance responds to this environment by showing some slight
strengthening and the latest NHC forecast now shows a peak intensity
of 50 kt in the 36-48 h time-frame. Afterwards, some increase in
shear and decreasing mid-level moisture may lead to weakening,
though this could be offset by Wanda moving back over warmer SSTs as
it tracks back south. The official intensity forecast is a bit
higher than the previous one, but ultimately still shows Wanda
losing tropical characteristics by the end of the forecast period as
it merges with an approaching mid-latitude trough.


FORECAST POSITIONS AND MAX WINDS

INIT 03/1500Z 38.8N 39.8W 45 KT 50 MPH
12H 04/0000Z 40.1N 39.7W 45 KT 50 MPH
24H 04/1200Z 41.4N 39.6W 45 KT 50 MPH
36H 05/0000Z 41.9N 38.9W 50 KT 60 MPH
48H 05/1200Z 40.9N 37.5W 50 KT 60 MPH
60H 06/0000Z 39.2N 36.6W 45 KT 50 MPH
72H 06/1200Z 38.1N 36.6W 45 KT 50 MPH
96H 07/1200Z 40.1N 33.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 08/1200Z 47.1N 27.1W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin
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Re: ATL: WANDA - Advisories

#16 Postby cycloneye » Wed Nov 03, 2021 3:51 pm

Tropical Storm Wanda Discussion Number 16
NWS National Hurricane Center Miami FL AL212021
900 PM GMT Wed Nov 03 2021

Wanda's overall convective pattern has continued to improve since
the previous advisory with a curved convective band now wrapping
almost completely around the center, resulting in a 50-60-nmi wide
banded eye feature. However, the horizontal thickness of the
convective band has been waxing and waning, and cloud tops are only
around -50C to -55C. Satellite intensity estimates from TAFB and SAB
are a consensus T3.0/45 kt, while UW-CIMSS SATCON intensity
estimates range from 34 kt to 44 kt, respectively. Based on these
data, Wanda's intensity is being maintained at 45 kt. Although a
distinct eye feature is now evident, which would suggest a stronger
storm, a lower intensity is warranted since the cooler water beneath
the cyclone is likely creating a more stable boundary layer, which
is likely inhibiting the normal downward mixing of higher winds
aloft. This physical assumption is supported by weaker wind speeds
noted in earlier scatterometer surface wind data.

The initial motion estimate is a little east of due north, or 010/09
kt. There is no significant change to the previous forecast track
and rationale. An approaching mid-/upper-level trough from the west
should continue to lift Wanda northward for the next day or so,
followed by slowing and a sharp turn to the east by Thursday night
as the aforementioned trough weakens and lifts out to the north of
the cyclone. Subsequent ridging behind the trough will then force
Wanda southeastward to southward on Friday, followed by another
abrupt turn and acceleration to the northeast on Saturday as a
second and stronger deep-layer trough captures the cyclone. Despite
this complexity in the evolving steering pattern, the latest NHC
model guidance is in very agreement throughout the 120-h forecast
period on this track scenario. The new NHC forecast track is very
similar to the previous advisory track, and lies near or slightly
to the right of the tightly packed simple- and corrected-consensus
track models.

The improved inner-core convective structure argues for at least
some slight strengthening during the next couple of days despite
the expected 20-21-deg-C sea-surface temperatures (SST) beneath the
cyclone. Some cooling aloft associated with the aforementioned
second upper-level trough may help to offset the negative effects of
the relatively cool SSTs on day 3. In the 96-120-h period, Wanda is
expected to interact, and eventually merge, with a cold front
and become an extratropical low pressure system with gale-force
winds. The new official intensity forecast is very similar to the
previous advisory, and closely follows a blend of the intensity
consensus models IVCN, NOAA-HCCA, and Florida State FSSE.


FORECAST POSITIONS AND MAX WINDS

INIT 03/2100Z 39.8N 39.5W 45 KT 50 MPH
12H 04/0600Z 41.0N 39.4W 50 KT 60 MPH
24H 04/1800Z 41.9N 39.1W 50 KT 60 MPH
36H 05/0600Z 41.8N 38.0W 50 KT 60 MPH
48H 05/1800Z 40.3N 37.0W 50 KT 60 MPH
60H 06/0600Z 38.8N 36.9W 45 KT 50 MPH
72H 06/1800Z 38.1N 36.6W 45 KT 50 MPH
96H 07/1800Z 42.4N 31.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 08/1800Z 51.5N 19.2W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

NNNN
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Re: ATL: WANDA - Advisories

#17 Postby cycloneye » Wed Nov 03, 2021 9:40 pm

Tropical Storm Wanda Discussion Number 17
NWS National Hurricane Center Miami FL AL212021
300 AM GMT Thu Nov 04 2021

Wanda's convective pattern has waned slightly since this afternoon.
Earlier there were convective bands noted wrapping around the
center, but now the primary band only wraps around the southern and
western portions of the circulation. Subjective and objective Dvorak
satellite estimates have not changed appreciably since earlier
today, and recent scatterometer wind data and UW/CIMSS SATCON
estimates still support an initial intensity of 45 kt.

Wanda is moving northward or 005/08 kt. The track forecast reasoning
is unchanged once again. A mid-latitude trough approaching from the
west should cause Wanda to move northward for another 6-12 hours,
but after that time the trough is forecast to lift northward. As
subsequent ridging builds behind the trough, Wanda is expected to
turn sharply eastward, and then south-southeastward to southward on
Friday. Another mid-latitude trough moving across Newfoundland by
the weekend should finally cause Wanda to begin to accelerate
northeastward after 72 hours. The dynamical model guidance remains
in relatively good agreement on the evolution of the steering
pattern over the next several days, and the NHC track forecast is
near the middle of the guidance envelope.

Despite Wanda being over 20-21C sea surface temperatures, some
cooling aloft is forecast over the next couple of days. That,
along with generally favorable upper-level winds could allow for
some slight strengthening within the next day or so. The global
models indicate that Wanda will merge with a frontal system on
Sunday, resulting in the system's transition into an extratropical
low. The updated NHC intensity forecast is unchanged from the
previous advisory and is a blend of the IVCN and HCCA consensus
aids.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 40.6N 39.6W 45 KT 50 MPH
12H 04/1200Z 41.6N 39.5W 50 KT 60 MPH
24H 05/0000Z 42.0N 38.8W 50 KT 60 MPH
36H 05/1200Z 41.0N 37.7W 50 KT 60 MPH
48H 06/0000Z 39.0N 37.3W 50 KT 60 MPH
60H 06/1200Z 37.8N 37.4W 45 KT 50 MPH
72H 07/0000Z 38.1N 36.6W 45 KT 50 MPH
96H 08/0000Z 44.7N 29.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/0000Z 51.0N 20.0W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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Re: ATL: WANDA - Advisories

#18 Postby cycloneye » Thu Nov 04, 2021 4:24 am

Tropical Storm Wanda Discussion Number 18
NWS National Hurricane Center Miami FL AL212021
900 AM GMT Thu Nov 04 2021

Wanda continues to exhibit bands of moderately deep convection, and
these bands are strongest most numerous over the western portion of
the circulation. The upper-level outflow has become better
defined, also over the western semicircle. Overall, however, the
intensity of the convection has diminished slightly over the past
several hours. The advisory intensity is held at 45 kt, which is
in agreement with Dvorak Current Intensity numbers from both SAB
and TAFB. This is also in good agreement with earlier
scatterometer measurements.

The initial motion continues to be just east of north, or 010/8 kt
along the eastern side of a mid-latitude shortwave trough. This
trough is expected to weaken very soon and Wanda should slow its
forward speed later this morning. During the next 48 hours, a
narrow ridge is forecast to build to the northwest of the cyclone
and force it to turn eastward tonight and then southward on Friday.
By 72 hours, another mid-latitude trough approaching Wanda should
finally cause the system to begin to accelerate northeastward. The
dynamical model guidance is in reasonably good agreement on the
evolution of the steering pattern over the next several days.
There has been little change to the official track forecast, which
remains close to the model consensus, and near the middle of the
guidance envelope.

Although Wanda is located over cool 20-21 deg C sea surface
temperatures, it has been able to maintain some deep convection and
winds of 45 kt. On its projected path during the next day or two,
water temperatures beneath Wanda are not likely to get much cooler
and the upper-tropospheric temperatures are forecast to decrease
somewhat. This could allow for some slight strengthening, as
indicated by the official intensity forecast. In 4 to 5 days, the
global models show the system becoming embedded in a frontal zone
over the north Atlantic, so the NHC forecast calls for Wanda to
revert back to extratropical status by that time.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0900Z 41.5N 39.5W 45 KT 50 MPH
12H 04/1800Z 42.1N 39.3W 50 KT 60 MPH
24H 05/0600Z 41.7N 38.2W 50 KT 60 MPH
36H 05/1800Z 40.1N 37.5W 50 KT 60 MPH
48H 06/0600Z 38.4N 37.5W 50 KT 60 MPH
60H 06/1800Z 38.2N 37.0W 45 KT 50 MPH
72H 07/0600Z 39.8N 35.0W 45 KT 50 MPH
96H 08/0600Z 47.0N 26.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/0600Z 52.0N 16.0W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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Re: ATL: WANDA - Advisories

#19 Postby cycloneye » Thu Nov 04, 2021 10:01 am

Tropical Storm Wanda Discussion Number 19
NWS National Hurricane Center Miami FL AL212021
300 PM GMT Thu Nov 04 2021

Wanda continues to maintain bands of moderately deep convection
near the center, and the cyclone continues to display anticyclonic
outflow. However, cold air clouds are wrapping around the southern
side of the circulation, and in the big picture Wanda appears to be
embedded in a larger-scale baroclinic low. A recent ASCAT-A
overpass suggests that the maximum winds are now near 40 kt, which
is between the satellite intensity estimates from TAFB and SAB.

The initial motion is northward or 000/5 kt. During the next
couple of days, a narrow mid-latitude ridge is forecast to build to
the northwest of the cyclone, which should cause Wanda to turn
southeastward and southward by the 48 h point. By 60-72 h, another
mid-latitude trough approaching Wanda should finally cause the
system to begin to accelerate northeastward, with this motion
persisting through the end of the forecast period. The new
guidance shows a little more southward motion by 48 h than the
previous guidance, and the new forecast track is adjusted a little
southward near that time.

Little change in strength is likely during the next 24 h as Wanda
remains over sea surface temperatures of near 20C. By 48 h, the
southward motion brings the center over slightly warmer water, and
some modest strengthening is possible by that time. Many of the
guidance models show more strengthening and a higher intensity than
the official forecast between 48-72 h, and some adjustment may be
needed to that part of the forecast in later advisories if this
trend persists. By 96 h, Wanda is expected to merge with a frontal
system and become extratropical over the northeastern Atlantic.


FORECAST POSITIONS AND MAX WINDS

INIT 04/1500Z 41.9N 39.6W 40 KT 45 MPH
12H 05/0000Z 42.1N 38.9W 40 KT 45 MPH
24H 05/1200Z 41.0N 38.0W 40 KT 45 MPH
36H 06/0000Z 39.1N 37.7W 45 KT 50 MPH
48H 06/1200Z 38.1N 37.7W 50 KT 60 MPH
60H 07/0000Z 38.7N 36.6W 50 KT 60 MPH
72H 07/1200Z 41.0N 33.7W 50 KT 60 MPH
96H 08/1200Z 48.5N 23.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/1200Z 51.5N 13.5W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven
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Re: ATL: WANDA - Advisories

#20 Postby cycloneye » Thu Nov 04, 2021 3:45 pm

Tropical Storm Wanda Discussion Number 20
NWS National Hurricane Center Miami FL AL212021
900 PM GMT Thu Nov 04 2021

Wanda continues to maintain bands of moderately deep convection
near the center, mainly over the northwestern semicircle. The
cyclone also continues to show anticyclonic outflow. However,
cold air clouds continue to wrap around the southern side of the
circulation, and in the big picture Wanda still gives the appearance
of being embedded in a larger-scale baroclinic low. There has been
little change in the satellite intensity estimates since the
previous advisory, so the initial intensity is held at 40 kt.

Wanda is starting its anticipated turn and the initial motion is now
045/5. During the next day or two, a narrow mid-latitude ridge is
forecast to build to the northwest of the cyclone, and this should
cause Wanda to turn southeastward and southward by the 48 h point.
By 60-72 h, another mid-latitude trough approaching Wanda should
cause a northeastward turn with acceleration, with this motion
persisting through the end of the forecast period. The new guidance
again shows a little more southward motion by 48 h than the previous
guidance, and the new forecast track is adjusted a little southward
near that time.

Little change in strength is likely during the next 24 h as Wanda
remains over sea surface temperatures of near 20C. By 48 h, the
southward motion brings the center over slightly warmer water, and
at that time the cyclone should interact with an upper-level low
that develops nearby. This combination could allow some
strengthening, and the intensity forecast show modest strengthening
from 24-48 h. Many of the guidance models continue to show more
strengthening and a higher intensity than the official forecast
between 48-72 h, and some adjustment may be needed to that part of
the forecast in later advisories if this trend persists. Between
72-96 h, Wanda is expected to merge with a frontal system and
become extratropical over the northeastern Atlantic.


FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 42.4N 39.2W 40 KT 45 MPH
12H 05/0600Z 41.9N 38.7W 40 KT 45 MPH
24H 05/1800Z 40.1N 38.2W 40 KT 45 MPH
36H 06/0600Z 38.5N 38.1W 45 KT 50 MPH
48H 06/1800Z 38.0N 37.7W 50 KT 60 MPH
60H 07/0600Z 39.2N 35.9W 50 KT 60 MPH
72H 07/1800Z 42.6N 32.2W 50 KT 60 MPH
96H 08/1800Z 49.0N 23.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/1800Z 53.0N 12.5W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven
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