ATL: DEXTER - Advisories

[cycloneye]

BULLETIN
Tropical Storm Dexter Advisory Number 1
NWS National Hurricane Center Miami FL AL042025
1100 PM AST Sun Aug 03 2025

...TROPICAL STORM DEXTER FORMS OVER THE WESTERN ATLANTIC...
...FORECAST TO MOVE AWAY FROM THE U.S. COAST AND STAY NORTH OF
BERMUDA...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...34.3N 69.4W
ABOUT 300 MI...480 KM WNW OF BERMUDA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...ENE OR 70 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES



Tropical Storm Dexter Discussion Number 1
NWS National Hurricane Center Miami FL AL042025
1100 PM AST Sun Aug 03 2025

The area of low pressure located several hundred miles off the coast
of North Carolina has been producing persistent deep convection for
much of the day, and it appears to have separated from the frontal
zone from which it formed. Although surface troughing still extends
northeast and southwest of the low itself, model analyses show
that the low is now located southeast of the strongest temperature
and moisture gradients, indicating that it is no longer frontal and
has made the transition to a tropical storm. The low-level center
is located on the southwestern edge of the deep convection due to
moderate southwesterly shear. Maximum winds are estimated to be 40
kt based on a very recent ASCAT pass, and the cyclone is therefore
being designated as Tropical Storm Dexter.

The initial motion is east-northeastward, or 070/10 kt, with Dexter
embedded within mid-latitude westerly flow on the northwestern side
of the subtropical ridge. Remaining north of the ridge, Dexter is
expected to move on a northeasterly or east-northeasterly trajectory
for the next 3-4 days. While there is not much cross-track spread
among the guidance, there are some speed differences, most notably
with the GFS showing Dexter getting trapped beneath the ridge and
meandering for a couple of days. The NHC track forecast goes with
the more progressive solution, and is closest to the HCCA and GDM
ensemble mean.

The moderate shear currently affecting Dexter is expected to
increase to over 20 kt in 12-24 hours, and then to about 30 kt in
36-48 hours. As a result, not much strengthening is anticipated.
Much of the intensity guidance shows a fairly steady intensity
between 40-50 kt through 72 hours, and the NHC forecast therefore
takes the middle of the road and shows a peak of 45 kt. Dexter is
likely to be post-tropical by 60 hours, if not sooner, as the
stronger shear strips the storm's convection away. The bulk of the
global models suggest it could then become extratropical again by
day 4 and then be absorbed by a front by day 5, but there is a lot
of uncertainty in that forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 34.3N 69.4W 40 KT 45 MPH
12H 04/1200Z 35.1N 67.7W 45 KT 50 MPH
24H 05/0000Z 36.4N 65.3W 45 KT 50 MPH
36H 05/1200Z 37.7N 63.1W 45 KT 50 MPH
48H 06/0000Z 38.5N 61.3W 45 KT 50 MPH
60H 06/1200Z 39.0N 59.3W 45 KT 50 MPH...POST-TROPICAL
72H 07/0000Z 39.3N 56.9W 40 KT 45 MPH...POST-TROPICAL
96H 08/0000Z 40.5N 50.8W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 09/0000Z...DISSIPATED

$$
Forecaster Berg

[cycloneye]

Tropical Storm Dexter Discussion Number 2
NWS National Hurricane Center Miami FL AL042025
500 AM AST Mon Aug 04 2025

Dexter remains a sheared tropical storm. Animated Proxy-Visible
imagery shows a partially exposed low-level center near the western
edge of the convective canopy, a function of moderate shear. With
little change in the convective signature or satellite estimates
during the past few hours, the initial intensity will stay at 40 kt
for this advisory.

The initial motion continues east-northeastward at 10 kt, with
Dexter steered by mid-latitude westerly flow on the northwestern
side of the subtropical ridge. Model guidance has come into better
agreement on the system moving to the northeast or east-northeast
for the next few days due to flow from that ridge, with fewer
outlier solutions to note. Generally the models are a bit slower
than the last cycle, and the NHC forecast follows that trend, though
is still on the faster side of the guidance.

The moderate shear currently affecting Dexter is expected to
increase to over 20 kt by late today, with increasing environmental
mid-level dry air. This should limit the potential strengthening to
the short term, and the NHC forecast is similar to the previous one,
near the model consensus. While strong shear expected in a couple
of days would normally cause weakening, there is some chance of a
favorable trough interaction causing non-tropical intensification,
as shown by the 00Z ECMWF model. Most of the global models,
however, do not show the trough phasing with Dexter, though they are
showing a stronger extratropical low. The new forecast is just a
little higher at 72-96h than the last forecast, and is now below the
long-range model consensus. Dexter's extratropical disposition
should be considered fairly uncertain at this time.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0900Z 34.6N 68.3W 40 KT 45 MPH
12H 04/1800Z 35.5N 66.7W 45 KT 50 MPH
24H 05/0600Z 36.8N 64.6W 45 KT 50 MPH
36H 05/1800Z 37.8N 62.9W 45 KT 50 MPH
48H 06/0600Z 38.6N 61.1W 45 KT 50 MPH
60H 06/1800Z 39.1N 58.5W 45 KT 50 MPH...POST-TROPICAL
72H 07/0600Z 39.5N 55.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 08/0600Z 41.5N 48.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 09/0600Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

Tropical Storm Dexter Discussion Number 3
NWS National Hurricane Center Miami FL AL042025
1100 AM AST Mon Aug 04 2025

Several bursts of deep convection have formed with Dexter this
morning, but the latest visible satellite images suggest the center
is on the far western edge of the cirrus canopy, partially exposed.
The intensity estimates from SAB and TAFB remain unchanged for 12
UTC, and objective estimates from UW-CIMSS (ADT, DPRINT, DMINT)
support maintaining a current intensity of 40 kt this advisory.

Dexter continues to move northeastward, a bit faster than earlier at
050/12 kt. This general motion is forecast to continue for the next
couple of days with a brief slowdown as the storm is steered by a
narrow subtropical ridge located to its southeast. In around 60 h, a
shortwave trough dropping southward from Atlantic Canada may try to
phase with Dexter. However, the global and ensemble model guidance
is split if their interaction will be favorable, causing the storm
to accelerate northeastward, or unfavorable, leaving Dexter behind
as a convection-less remnant low. For this cycle, the track
guidance has shifted a bit faster to the northeast, and the NHC
track has also been shifted faster, but generally along the same
track as the previous advisory. It is worth noting that the Google
Deep Mind ensemble mean (GDMI) is a significant fast outlier, and it
will be interesting to see if the overall model guidance continues
to trend faster with Dexter's motion.

Intensity-wise, Dexter is likely to face an increasingly hostile
environment, with westerly vertical wind shear increasing above 30
kt in about 24 h. Thus, only a little additional strengthening is
shown in the forecast for today, then capping the intensity at 45 kt
through the rest of this week. However, since the cyclone will
remain over the warm Gulf Stream waters until it passes poleward of
40N, it will likely continue to produce periodic bursts of deep
convection, helping to maintain its intensity in the face of the
unfavorable shear. After 60 h, the guidance remains split on whether
or not Dexter will become a remnant low, or phase with the
upper-level trough nearby, becoming a stronger extratropical low.
While the latest intensity forecast shows the latter solution
panning out, as mentioned previously, Dexter's final structure
remains quite uncertain near the end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT 04/1500Z 35.2N 67.4W 40 KT 45 MPH
12H 05/0000Z 36.5N 65.4W 45 KT 50 MPH
24H 05/1200Z 37.6N 63.4W 45 KT 50 MPH
36H 06/0000Z 38.5N 61.6W 45 KT 50 MPH
48H 06/1200Z 39.4N 59.1W 45 KT 50 MPH
60H 07/0000Z 40.1N 55.4W 45 KT 50 MPH
72H 07/1200Z 41.0N 50.7W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 08/1200Z 43.9N 43.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/1200Z 46.5N 36.1W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin

[cycloneye]

Tropical Storm Dexter Discussion Number 4
NWS National Hurricane Center Miami FL AL042025
500 PM AST Mon Aug 04 2025

There is not a lot new to report with Dexter this afternoon. The
center remains partially exposed, with periodic bursts of deep
convection firing off along the downshear-right side of the storm.
This activity continues to struggle rotating upshear due to westerly
vertical wind shear which has now increased above 20 kt. The 18 UTC
Dvorak estimates from TAFB and SAB were T3.0/45 kt and T2.0/30 kt
respectively. Objective intensity estimates also range from 35 to 45
kt. Earlier scatterometer data received after the prior advisory
only had a peak value of 33 kt. The initial intensity remains 40 kt
for this advisory, a blend of all the various intensity estimates.

There are several mesovorticies rotating around the mean center, but
Dexter in general remains on a northeastward heading at 050/13 kt. A
narrow mid-level ridge oriented northeast to southwest from the
Azores to Bermuda should enable Dexter to continue moving
northeastward to east-northeastward, as long as it remains
vertically coherent. The vertical depth likely plays a role in
Dexter's future forward motion, with significant along-track spread
persisting in the track guidance this afternoon. The NHC track
forecast is on the faster side of the guidance envelope, close to
the most recent 12 UTC ECMWF forecast track. However, it remains
possible that Dexter completely decouples from its mid-level
circulation and misses phasing with the trough digging southward
from Atlantic Canada. Instead of accelerating northeastward, this
latter scenario could result in the storm slowing down as it becomes
a shallow cyclone. For now, the latest NHC track forecast is close
to the prior one.

As shear continue to increase over the tropical cyclone, forecasted
to be above 30 kt in 12 h, its window for further tropical
intensification is closing. The intensity guidance is a bit lower
this afternoon. In response, the NHC intensity forecast now holds
Dexter at 40 kt until it undergoes extratropical transition sometime
between 60-72 h, where a slight amount of intensification is still
shown. The intensity forecast is in the middle of the guidance
envelope. As mentioned previously, Dexter's final structure remains
quite uncertain near the end of the forecast period, and it is
entirely possible the storm could become a remnant low instead of an
extratropical cyclone by the latter half of this week.


FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 36.1N 66.2W 40 KT 45 MPH
12H 05/0600Z 37.1N 64.5W 40 KT 45 MPH
24H 05/1800Z 38.2N 62.5W 40 KT 45 MPH
36H 06/0600Z 39.2N 60.3W 40 KT 45 MPH
48H 06/1800Z 39.8N 57.5W 40 KT 45 MPH
60H 07/0600Z 40.7N 53.2W 40 KT 45 MPH
72H 07/1800Z 42.5N 48.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 08/1800Z 45.0N 41.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/1800Z 48.2N 29.9W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin

[StormWeather]

146
WTNT44 KNHC 050239
TCDAT4

Tropical Storm Dexter Discussion Number 5
NWS National Hurricane Center Miami FL AL042025
1100 PM AST Mon Aug 04 2025

Dexter continues to be disrupted by strong westerly vertical wind
shear, with its associated deep convection being displaced to the
east of the low-level center. The storm's cloud pattern is very
ragged-looking at this time and lacks convective banding features.
Satellite-based intensity estimates using subjective and objective
methods range from 30 kt to 47 kt. Blending these values, the
advisory intensity estimate remains 40 kt, though a recent
scatterometer pass suggests this might be generous.

Although there is some uncertainty in the center location using
infrared imagery, it appears that the forward speed has slowed
somewhat and the current motion estimate is around 050/11 kt.
Dexter is near the southern edge of a belt of mid-level westerlies.
The track guidance is in general agreement on a northeastward to
east-northeastward motion for the next several days. However, it
is possible that the system could become completely decoupled and
move more slowly in the low-level flow. The official forecast
assumes that the cyclone will retain enough vertical coherency to
be steered at least partially by the mid-level flow. The NHC track
forecast is fairly close to the latest corrected consensus, HCCA,
guidance.

There is no sign that the strong shear in Dexter's environment will
abate. In fact, the SHIPS model indicates that the vertical wind
shear will increase even more over the next few days. Therefore,
it is not likely that the system will be able to strengthen as a
true tropical cyclone. The official forecast allows for slight
intensification due to baroclinic processes. Simulated infrared
imagery and the FSU phase space predictions from the global
models suggest that Dexter will likely make the transition
into an extratropical cyclone in 2-3 days.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0300Z 36.8N 65.6W 40 KT 45 MPH
12H 05/1200Z 37.8N 64.1W 40 KT 45 MPH
24H 06/0000Z 38.9N 62.1W 40 KT 45 MPH
36H 06/1200Z 39.6N 59.7W 40 KT 45 MPH
48H 07/0000Z 40.2N 56.7W 40 KT 45 MPH
60H 07/1200Z 41.2N 52.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 08/0000Z 42.8N 48.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 09/0000Z 46.0N 39.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 10/0000Z 49.0N 29.0W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

[cycloneye]

Tropical Storm Dexter Discussion Number 6
NWS National Hurricane Center Miami FL AL042025
500 AM AST Tue Aug 05 2025

Dexter appears to be weakening. The low-level circulation has
become totally exposed this morning- a consequence of continued
strong vertical wind shear. Satellite intensity estimates have
fallen so the initial wind speed is reduced to 35 kt. Little
change is expected for the next day or so as Dexter battles the
shear. While normally the storm would just decay after the waters
become cooler in a couple days, most models are now showing
re-intensification due to a favorable trough interaction. This was
first shown by the ECMWF yesterday, and now other models are on
board. The short-term part of the forecast was lowered based on the
initial wind speed, and little change was made to the longer-term
intensities.

The storm continues moving east-northeastward at about 10 kt. An
east-northeast to northeast track is likely for the next couple of
days due to mid-latitude westerly flow. The aforementioned trough
interaction should cause a faster forward motion in a few days.
The new forecast is similar to the previous one, mostly ignoring
the slow GFS solution. Extratropical transition is expected
between 36-48 h, and the low is forecast to decay into a trough in
roughly 4-5 days.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0900Z 37.3N 64.4W 35 KT 40 MPH
12H 05/1800Z 38.2N 62.9W 35 KT 40 MPH
24H 06/0600Z 39.2N 60.7W 35 KT 40 MPH
36H 06/1800Z 39.9N 57.6W 40 KT 45 MPH
48H 07/0600Z 40.6N 54.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
60H 07/1800Z 42.0N 50.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 08/0600Z 43.5N 45.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 09/0600Z 46.5N 35.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 10/0600Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

Tropical Storm Dexter Discussion Number 7
NWS National Hurricane Center Miami FL AL042025
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Tue Aug 05 2025

Dexter continues to be in a weakened state this morning. The
low-level circulation is still partially exposed to the
the west of the deeper convection, and cloud tops with the deeper
convection have warmed this morning. The initial wind speed
remains 35 kt and little change in this intensity is expected
today. Most models continue to show some re-intensification due to
a favorable trough interaction by Wednesday into Thursday. Thus
little to no change was made to the intensity forecast, although
there remains some uncertainty with how quickly this modest
re-intensification occurs.

Overall little change was made to either the track or intensity
forecast with this package. There is some model spread with the
forward speed of Dexter, with the GFS remaining an outlier on the
slower side of the model spread, and the ECMWF faster. However, run
to run continuity in the models has been low with these details,
and the previous forecast remains well within this spread. Expect
that we will continue to see run to run variability, and thus there
was no strong evidence that a change in the track forecast was
needed at this time. Thus the new forecast is similar to the
previous one, and continues to give less weight to the slower GFS.
Extratropical transition is expected between 36-48 h, and the low is
forecast to decay into a trough in roughly 4-5 days.


FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 38.0N 63.4W 35 KT 40 MPH
12H 06/0000Z 38.8N 62.0W 35 KT 40 MPH
24H 06/1200Z 39.6N 59.1W 40 KT 45 MPH
36H 07/0000Z 40.4N 56.0W 40 KT 45 MPH
48H 07/1200Z 41.5N 52.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
60H 08/0000Z 42.9N 47.7W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 08/1200Z 44.4N 43.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 09/1200Z 46.0N 34.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 10/1200Z...DISSIPATED

$$
Forecaster Chenard/Shieh

[cycloneye]

Tropical Storm Dexter Discussion Number 8
NWS National Hurricane Center Miami FL AL042025
500 PM AST Tue Aug 05 2025

This afternoon Dexter continues to exhibit a pulsing convective
structure. After briefly becoming exposed earlier today, the
low-level circulation has tucked underneath a renewed convective
burst on its down-shear side. Despite its ragged appearance, an
earlier scatterometer pass indicated that Dexter's circulation had
tightened up some with a smaller radius of maximum wind. The peak
wind value retrieved was 35 kt, which still supports a current
intensity of 35 kt this advisory. This value is higher than the 18
UTC subjective Dvorak intensity estimates, but a bit lower than the
some of the objective intensity estimates (DMINT, SATCON).

Dexter continues to move off to the northeast, with the latest
motion estimated at 055/11 kt. This direction of motion is expected
to continue for the next few days with a gentle bend towards the
east-northeast, across the North Atlantic. However, the speed of the
forward motion continues to be uncertain, with large along-track
spread in the guidance. The GFS continues to be on the slow end,
while the ECMWF and Google Deep Mind ensemble mean (GDMI) are on the
faster end of the guidance suite. The latest NHC track forecast
continues to favor the faster track solutions, and is a blend of the
prior forecast track, with some of the more reliable consensus aids
(HCCA).

Vertical wind shear over the system is now above 30 kt out of the
west-southwest, and is forecast to increase further over the next
24-48 hours. However, the majority of the intensity guidance
indicates Dexter may strengthen due to baroclinic dynamics from a
favorable trough interaction. Thus, the NHC intensity forecast shows
some strengthening, peaking Dexter as a 50 kt extratropical cyclone
in about 48 hours. This forecast is roughly in the middle of the
intensity guidance envelope, though notably lower than the latest
HAFS-A/B forecasts, which develop a potent sting-jet-like structure
as Dexter becomes extratropical. After the extratropical low
occludes, it should gradually weaken, eventually opening up into a
trough by the end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 38.6N 62.2W 35 KT 40 MPH
12H 06/0600Z 39.2N 60.5W 35 KT 40 MPH
24H 06/1800Z 39.9N 57.6W 40 KT 45 MPH
36H 07/0600Z 40.6N 53.9W 40 KT 45 MPH
48H 07/1800Z 41.9N 49.8W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 08/0600Z 43.1N 46.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 08/1800Z 44.0N 42.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 09/1800Z 45.3N 33.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 10/1800Z...DISSIPATED

$$
Forecaster Papin

[cycloneye]

Tropical Storm Dexter Discussion Number 9
NWS National Hurricane Center Miami FL AL042025
1100 PM AST Tue Aug 05 2025

Strong westerly vertical wind shear continues over Dexter. Although
vigorous deep convection continues to form within the circulation,
this activity is persistently displaced to the east of the estimated
low-level center. The cloud pattern remain rather ragged-looking
with no well-defined banding features. The current intensity
estimate is 35 kt, which is a blend of subjective Dvorak estimates
from TAFB and SAB. Objective intensity estimates are somewhat
higher, but since the organization of the system has not improved
since earlier today, the intensity is not increased on this
advisory.

Dexter is estimated to be moving east-northeastward, or around
060/10 kt. The cyclone continues moving along the southern side of
a belt of mid-level westerlies. An upstream trough is expected pass
just north of the system within the next 1-2 days, and Dexter will
probably accelerate a little due to the influence of the trough.
The official track forecast is very similar to the previous NHC
prediction and close to the dynamical model consensus.

As diagnosed by the Decay-SHIPS guidance, vertical wind shear is
predicted to increase even further during the next 48 hours.
Typically this would lead to weakening of a tropical cyclone.
However, Dexter is expected to intensify somewhat due to its
interaction with the approaching upper-level trough and baroclinic
forcing, while losing its tropical characteristics. The NHC
intensity forecast is about in the middle of the model guidance.
This is also close to the latest HCCA corrected consensus solution.

FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 38.9N 61.3W 35 KT 40 MPH
12H 06/1200Z 39.6N 59.3W 35 KT 40 MPH
24H 07/0000Z 40.0N 56.1W 45 KT 50 MPH
36H 07/1200Z 41.1N 52.1W 50 KT 60 MPH
48H 08/0000Z 42.5N 48.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 08/1200Z 44.0N 44.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 09/0000Z 44.7N 40.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 10/0000Z 45.8N 31.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 11/0000Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Tropical Storm Dexter Discussion Number 10
NWS National Hurricane Center Miami FL AL042025
500 AM AST Wed Aug 06 2025

Dexter continues to have vigorous deep convection in the eastern
portion of the circulation, partially obscuring its low-level
center. Observations from an earlier scatterometer pass had some
rain-contaminated vectors between 40 to 42 kt. Subjective and
objective satellite intensity estimates have continued to generally
rise overnight and have a wide range of 30 to 50 kt. The initial
intensity is set to 40 kt, in the middle of this range and closest
to the UW-CIMSS DPRINT estimate.

The tropical storm is moving east-northeastward at 11 kt. The track
forecast reasoning has not changed. Dexter should continue along
the southern side of mid-level westerlies until interacting with a
trough to the north in the next day or so. The trough will likely
accelerate Dexter to the east-northeast, though models have some
along track spread. The official track forecast is similar to the
previous prediction and lies closest to the simple corrected
consensus aids.

Dexter has about another day or so as a tropical system. It is
currently experiencing strong vertical wind shear, which is only
expected to increase during the next 24 to 48 h. However, models
continue to predict that the interaction with the trough to north in
the next day or so should strengthen Dexter while it undergoes
extratropical transition. It should be noted that during the
extratropical phase of the forecast, there is quite a bit of spread
in the intensity guidance. Several models during the 36 to 60 h
time frame show the cyclone reaching hurricane-force. The NHC
intensity forecast has been raised to a peak of 60 kt at 48 h, very
near the corrected consensus aid, HCCA. There remains the
possibility that upward adjustments in the intensity forecast could
be need in future advisories.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 39.4N 59.9W 40 KT 45 MPH
12H 06/1800Z 39.8N 57.7W 45 KT 50 MPH
24H 07/0600Z 40.6N 54.1W 50 KT 60 MPH
36H 07/1800Z 41.9N 50.1W 55 KT 65 MPH...POST-TROP/EXTRATROP
48H 08/0600Z 43.2N 46.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
60H 08/1800Z 44.5N 42.3W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 09/0600Z 45.2N 38.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 10/0600Z 46.0N 30.1W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 11/0600Z...DISSIPATED

$$
Forecaster Bucci

[cycloneye]

BULLETIN
Tropical Storm Dexter Advisory Number 11
NWS National Hurricane Center Miami FL AL042025
1100 AM AST Wed Aug 06 2025

...DEXTER STRENGTHENS A LITTLE MORE...
...LIKELY TO BECOME A POWERFUL EXTRATROPICAL CYCLONE BY FRIDAY AS IT
TRAVERSES THE NORTH ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...39.9N 58.2W
ABOUT 535 MI...860 KM SSW OF CAPE RACE NEWFOUNDLAND
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...ENE OR 65 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES



Tropical Storm Dexter Discussion Number 11
NWS National Hurricane Center Miami FL AL042025
1100 AM AST Wed Aug 06 2025

This morning, Dexter's structure continues to be quite resilient
against an estimated 35-40 kt of westerly vertical wind shear over
the storm. Deep convection continues to burst, still primarily
down-shear, but an earlier AMSR2 microwave pass showed a bit more
banding-type structure on the 37 GHz channel. Subjective Dvorak
estimates from TAFB and SAB are now both T3.0/45 kt, and there were
a few GOES-19 derived motion wind vectors up to 52 kt near 850 mb on
the west side of Dexter's low-level circulation. These data support
raising the initial intensity to 45 kt for this advisory.

Dexter remains on an east-northeastward heading, a bit faster than
earlier at 060/13 kt. The tropical storm is being steered by the
mid-latitude westerly flow on the downstream side of a southward
digging shortwave trough moving out of Atlantic Canada. The guidance
has finally come into good agreement on this trough capturing Dexter
in 36 h, leading to further acceleration east-northeastward until
the trough and Dexter fully phase. The track guidance this cycle is
a touch faster than earlier, and the latest NHC track forecast was
nudged a little faster compared to the prior forecast cycle.

Dexter's recent intensification is likely not fully tropical in
nature. In fact, Dexter is currently positioned in the right
entrance region of a 120 kt upper-level jet streak, which is likely
providing some enhanced upper-level divergence and aiding the deep
convection over the cyclone. The digging shortwave trough will also
start impinging on the cyclone, initiating extratropical transition.
This process should be complete in about 36 h, when both the GFS and
ECMWF models show deep convection separating from Dexter's core.
However, this will be a dynamic extratropical transition, with all
the various hurricane-regional models suggesting the development of
a sting jet, or branch of rapidly descending dry air, curving
cyclonically around the cyclone's western flank. The NHC intensity
forecast shows Dexter peaking as a 60-kt extratropical cyclone in
about 36 h in response to this feature, and both HAFS-A/B suggest
this intensity could be conservative. After the extratropical
cyclone occludes, the winds should decrease again as it loses its
baroclinic forcing, with the low opening up to a trough by the end
of the forecast period over the far northeastern Atlantic.



FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 39.9N 58.2W 45 KT 50 MPH
12H 07/0000Z 40.4N 55.4W 50 KT 60 MPH
24H 07/1200Z 41.5N 51.4W 55 KT 65 MPH
36H 08/0000Z 42.9N 47.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 08/1200Z 44.4N 43.6W 55 KT 65 MPH...POST-TROP/EXTRATROP
60H 09/0000Z 45.2N 39.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 09/1200Z 45.6N 34.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 10/1200Z 47.0N 26.2W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 11/1200Z...DISSIPATED

$$
Forecaster Papin

[cycloneye]

Tropical Storm Dexter Discussion Number 12
NWS National Hurricane Center Miami FL AL042025
500 PM AST Wed Aug 06 2025

Similar to the past couple of days, the high vertical wind shear
over Dexter caused its low-level circulation to become exposed to
the west of the the deep convection earlier this afternoon. A
scatterometer pass received after the prior advisory also suggested
that Dexter's vortex is becoming more elongated, with signs of a
baroclinic zone starting to take shape to the northeast of the
center. These signatures suggest that Dexter may soon undergo
extratropical transition. The earlier scatterometer pass had a peak
wind retrieval of 43 kt, and that value, combined with similar
subjective and objective intensity estimates, support maintaining 45
kt this advisory.

Dexter continues to gradually accelerate to the east-northeast,
with the estimated motion now at 070/14 kt. The storm remains well
embedded in the mid-latitude westerly flow as a shortwave trough
drops southward towards Dexter. The subsequent trough interaction is
forecast to keep Dexter moving quickly east-northeastward with just
a subtle bend northeastward from 24-48 h. Compared to 24 h ago, the
track guidance is in much better agreement with less along-track
spread, and the latest NHC track forecast is very similar to the
prior advisory, near the simple and corrected consensus aids.

With vertical wind shear now around 40 kt and the cyclone also
crossing the north edge of the Gulf Stream, most of the subsequent
strengthening shown in the intensity forecast will be due to
baroclinic processes as Dexter undergoes extratropical transition.
The global and regional hurricane model fields shows Dexter's
metamorphosis, with to development of frontal features as the wind
field becomes quite asymmetric. In fact, the maximum sustained winds
in 24-36 h are likely related to a sting jet that curves
cyclonically around the cyclone's western flank during this time
frame. The hurricane-regional models, and even the most recent 12
UTC ECMWF run show winds up to hurricane-force in the southwest
quadrant. Thus, the latest NHC intensity forecast will now
explicitly show a 65-kt extratropical cyclone in 36 h. After
occlusion, the low will slowly weaken through the remainder of the
forecast period, ultimately dissipating by early next week in the
far northeastern Atlantic.


FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 40.0N 56.3W 45 KT 50 MPH
12H 07/0600Z 40.6N 53.5W 50 KT 60 MPH
24H 07/1800Z 41.9N 49.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 08/0600Z 43.5N 45.3W 65 KT 75 MPH...POST-TROP/EXTRATROP
48H 08/1800Z 44.8N 41.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 09/0600Z 45.5N 37.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 09/1800Z 46.0N 32.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 10/1800Z 47.0N 24.5W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 11/1800Z...DISSIPATED

$$
Forecaster Papin

[cycloneye]

Tropical Storm Dexter Discussion Number 13
NWS National Hurricane Center Miami FL AL042025
1100 PM AST Wed Aug 06 2025

Dexter is very close to being an extratropical cyclone. Satellite
images suggest that frontal features are forming both to the east
and south of the center, and the overall cloud pattern is beginning
to take on an extratropical appearance. Strong westerly vertical
wind shear has caused the low-level center to become completely
exposed with disorganized convection limited to the northeast
quadrant. The initial intensity is held at 45 kt, which is in line
with the latest satellite intensity estimates and recent ASCAT data.

A mid- to upper-level trough currently over the Canadian Maritimes
is expected to merge with the system early Thursday, which should
complete Dexter's extratropical transition. This will also likely
cause strengthening due to baroclinic forcing, and Dexter could
become a hurricane-force extratropical low in about 24 hours.
Gradual weakening is expected after that time as the upper-level
trough dampens out. The NHC intensity forecast is slightly above
the guidance in the short term, but in line with the bulk of the
models from 48 to 96 hours.

Dexter is moving a little faster to the east now, with the latest
initial motion estimated to be 085/14 kt. A northeastward motion is
expected during the next day or two as Dexter interacts and merges
with the aforementioned trough. After that time, a turn back to
the east-northeast or east is predicted in the mid-latitude
westerly flow. The NHC track forecast lies fairly close to the
various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 40.2N 54.2W 45 KT 50 MPH
12H 07/1200Z 40.9N 51.1W 55 KT 65 MPH...POST-TROP/EXTRATROP
24H 08/0000Z 42.6N 46.7W 65 KT 75 MPH...POST-TROP/EXTRATROP
36H 08/1200Z 44.3N 43.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 09/0000Z 45.3N 38.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 09/1200Z 46.0N 34.4W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 10/0000Z 46.7N 29.7W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 11/0000Z 47.4N 22.0W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 12/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Tropical Storm Dexter Discussion Number 14
NWS National Hurricane Center Miami FL AL042025
500 AM AST Thu Aug 07 2025

Dexter is on the edge of being extratropical. An earlier
scatterometer overpass showed what is likely a warm front extending
from the east into or near the center. In addition, a cloud band in
the southeastern semicircle appears to be a developing cold front.
However, a strong convective burst is currently occurring a little
east of the center, and based on this Dexter as maintained as a
tropical storm at this time. Satellite intensity estimates have
changed little since the last advisory, so the initial intensity is
held at 45 kt.

Dexter should complete extratropical transition during the next
6-12 h as it merges with a mid- to upper-level trough approaching
from the northwest. Global model show strengthening due to
baroclinic forcing as this happens, and Dexter is forecast to
become a hurricane-force extratropical low in about 24 hours.
Gradual weakening is expected after that time as the upper-level
trough dampens out. The NHC intensity forecast remains above the
guidance in the short term, but in line with the bulk of the models
from 48 to 96 hours. The cyclone is forecast to weaken to a trough
by 120 h.

The initial motion is now 070/16. A northeastward motion is expected
during the next day or two as Dexter interacts and merges with the
aforementioned trough. After that time, a turn back to the
east-northeast or east is likely as the cyclone is steered by the
mid-latitude westerly flow. The guidance nudged slightly northward
between 24-60 h, and the new track forecast has a similar small
nudge. It is otherwise similar to the previous forecast and close to
the various consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 40.6N 52.1W 45 KT 50 MPH
12H 07/1800Z 41.7N 49.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
24H 08/0600Z 43.4N 45.3W 65 KT 75 MPH...POST-TROP/EXTRATROP
36H 08/1800Z 44.8N 41.2W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 09/0600Z 45.7N 36.8W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 09/1800Z 46.3N 32.4W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 10/0600Z 46.7N 28.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 11/0600Z 47.6N 20.7W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 12/0600Z...DISSIPATED

$$
Forecaster Beven

[cycloneye]

Post-Tropical Cyclone Dexter Advisory Number 15
NWS National Hurricane Center Miami FL AL042025
1100 AM AST Thu Aug 07 2025

...DEXTER BECOMES A STORM-FORCE EXTRATROPICAL LOW OVER THE NORTH
ATLANTIC...
...THIS IS THE FINAL NHC ADVISORY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...41.4N 50.4W
ABOUT 390 MI...625 KM SSE OF CAPE RACE NEWFOUNDLAND
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...ENE OR 70 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES

Post-Tropical Cyclone Dexter Discussion Number 15
NWS National Hurricane Center Miami FL AL042025
1100 AM AST Thu Aug 07 2025

Satellite imagery and surface observations indicate that Dexter has
completed its transition to an extratropical cyclone. Strong
westerly wind shear is leaving an exposed, elongated center with all
convection in the eastern semicircle. The convection is decreasing
in strength and areal coverage, and it is also becoming more
asymmetric. A warm front clearly extends east-northeastward from
Dexter, and there also appears to be a developing cold front
extending towards the southwest, as noted in an earlier AMSR2
microwave pass. Surface marine observations show temperatures in
the upper 50s and lower 60s just a couple hundred n mi northwest of
Dexter's center. A recent partial ASCAT pass showed winds up to 45
kt, but this pass did not sample the entire circulation. The
initial intensity of the extratropical cyclone is increased to 50 kt
based on the ASCAT data as well as global model analyses, which
suggest the winds have likely reached 50 kt.

Dexter is merging with an approaching mid- to upper-level trough.
Global models show strengthening over the next 12-24 h due to
baroclinic forcing due to the trough interaction. Thereafter, the
cyclone will begin to steadily weaken late Friday into the weekend
as the upper-level trough dampens out. The NHC intensity forecast is
near the high end of the guidance during the first 24 hours of the
forecast, and near the middle of the guidance envelope thereafter.
The cyclone is forecast to weaken to a trough in 4 to 5 days.

The initial motion is 070/15. A motion between northeast and
east-northeast is expected during the next 24-36 hours as Dexter
interacts with the aforementioned trough. After that time, a slight
bend more toward the east is expected as the cyclone is steered by
the mid-latitude flow. The new NHC forecast is a bit slower than
the previous one, and lies in between the simple and corrected
consensus aids.

This is the final NHC advisory on Dexter. Additional information on
this system can be found in 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 07/1500Z 41.4N 50.4W 50 KT 60 MPH...POST-TROP/EXTRATROP
12H 08/0000Z 42.6N 47.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
24H 08/1200Z 44.2N 43.8W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 09/0000Z 45.2N 39.9W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 09/1200Z 45.9N 35.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
60H 10/0000Z 46.5N 30.9W 35 KT 40 MPH...POST-TROP/EXTRATROP
72H 10/1200Z 47.1N 26.8W 30 KT 35 MPH...POST-TROP/EXTRATROP
96H 11/1200Z 48.0N 20.0W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 12/1200Z...DISSIPATED