ATL: DANIELLE - Advisories

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Re: ATL: DANIELLE - Advisories

#21 Postby cycloneye » Mon Sep 05, 2022 9:37 am

Hurricane Danielle Discussion Number 18
NWS National Hurricane Center Miami FL AL052022
300 PM GMT Mon Sep 05 2022

Danielle's satellite presentation has degraded since this morning.
Cloud tops have warmed and its eye-like feature is not very well
defined anymore. The hurricane has reached a relatively cool part
of the Gulf Stream, which could be a main factor in its apparent
weakening. Satellite intensity estimates from TAFB, SAB, and
UW-CIMSS (both ADT and SATCON) have decreased, so the initial
intensity has been lowered conservatively to 75 kt, which is at the
high end of the estimates.

The lower initial intensity has also contributed to a lower
intensity forecast, but the idea is generally the same. Danielle
should slowly weaken during the next few days as it continues
northeastward over marginally warm waters. The exact timing of the
cyclone's upcoming extratropical transition is still uncertain, but
most models indicate it should complete the process on or by
Thursday. Further weakening is expected by all global models after
that time, which continues to be reflected in the NHC forecast.

Negligible change was made to the portion of the track forecast when
Danielle is expected to be a tropical cyclone. The hurricane is
forecast to move generally northeastward today and
east-northeastward through the middle of the week, steered by a
mid-latitude system approaching from the northwest. At the end of
the forecast period, most global models now suggest Danielle could
make a sharp northward turn as an extratropical cyclone. This would
represent a significant change to the day 4-5 forecast, so I would
prefer to see if that stays consistent for another cycle of model
runs before making too big of a change. The official track forecast
is therefore very close to the multi-model consensus through 72 h,
but is notably to the south and east of the consensus at days 4 and
5, That said, it has still been adjusted to the northwest of the
previous forecast at those times.


FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 40.2N 43.9W 75 KT 85 MPH
12H 06/0000Z 41.1N 43.0W 70 KT 80 MPH
24H 06/1200Z 41.9N 41.5W 70 KT 80 MPH
36H 07/0000Z 42.5N 39.4W 65 KT 75 MPH
48H 07/1200Z 43.4N 36.7W 65 KT 75 MPH
60H 08/0000Z 44.7N 33.9W 60 KT 70 MPH
72H 08/1200Z 46.3N 30.9W 55 KT 65 MPH...POST-TROP/EXTRATROP
96H 09/1200Z 49.5N 25.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 10/1200Z 52.0N 21.5W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster D. Zelinsky
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Re: ATL: DANIELLE - Advisories

#22 Postby cycloneye » Mon Sep 05, 2022 3:36 pm

Hurricane Danielle Discussion Number 19
NWS National Hurricane Center Miami FL AL052022
900 PM GMT Mon Sep 05 2022

After a large degradation in Danielle's appearance earlier this
afternoon, the hurricane appears to be holding more steady now with
colder cloud tops wrapping further around its center than were noted
6 hours ago. Dvorak-based intensity estimates still support an
intensity near 75 kt. The hurricane has moved a little
faster north-northeastward than anticipated during the last few
hours, with an initial motion estimate of 030/kt.

A significant adjustment was made to the track forecast at days 4
and 5, at which time Danielle is forecast to be an extratropical
cyclone. For the first 3 days of the forecast period, Danielle is
still forecast to move generally northeastward in the mid-latitude
flow. After that, it looks like Danielle could occlude and "cut-off"
from that steering flow, which may cause it to turn abruptly
northward and then southeastward at days 4-5. This scenario has been
consistently forecast for a few model cycles of the GFS and other
global models, so large changes were made to the NHC track forecast
to bring it closer to the model consensus. Other than a slight
adjustment northward and faster, no important changes were made to
the NHC track forecast for the first 72 h. Given the uncertainty at
the extended portion of the forecast, it should be noted that
confidence in the track forecast is substantially higher for the
first 72 h than the later hours. It is worth noting that Danielle
is forecast to be post-tropical by 96 h, so users should not focus
on the exact track of the cyclone since the largest impacts could
be felt far from its center.

Danielle should slowly weaken during the next few days as it moves
over marginally cool water, but most dynamical guidance suggests it
will still maintain its tropical characteristics for at least a
couple more days. Around day 3, SHIPS diagnostics indicate the
waters below the cyclone will be less than 20 deg C, and it will
likely complete its extratropical transition around that time.
The NHC forecast follows accordingly, but it should be noted this
suggests a slightly later completion to the transition than
previously forecast. The NHC intensity forecast is near the middle
of the relatively low-spread intensity guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 41.1N 43.2W 75 KT 85 MPH
12H 06/0600Z 41.9N 42.2W 70 KT 80 MPH
24H 06/1800Z 42.6N 40.4W 70 KT 80 MPH
36H 07/0600Z 43.4N 38.1W 65 KT 75 MPH
48H 07/1800Z 44.6N 35.3W 65 KT 75 MPH
60H 08/0600Z 46.2N 32.4W 60 KT 70 MPH
72H 08/1800Z 48.2N 29.7W 55 KT 65 MPH...POST-TROP/EXTRATROP
96H 09/1800Z 50.0N 29.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 10/1800Z 47.5N 25.5W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster D. Zelinsky
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Re: ATL: DANIELLE - Advisories

#23 Postby cycloneye » Mon Sep 05, 2022 9:37 pm

WTNT45 KNHC 060236
TCDAT5

Hurricane Danielle Discussion Number 20
NWS National Hurricane Center Miami FL AL052022
300 AM GMT Tue Sep 06 2022

Danielle's cloud pattern has deteriorated during the past
several hours. The outer curved band cloud tops have warmed while
becoming ragged, and the eye temperature has cooled while becoming
partially obscured. A recent microwave image, however, indicated
very little vertical tilt while maintaining a symmetric structure.
A blend of the subjective satellite intensity estimates from TAFB
and SAB along with the AI-enhanced Advanced Dvorak Technique (AiDT)
from UW-CIMSS yields an initial intensity of 70 kt for this
advisory. Danielle's wind radii profile was expanded a bit in the
east semicircle based on recent METOP-B/C scatterometer data.

The cyclone should gradually spin down as it traverses cooler SSTs
of less than 22C by mid-period. The GFS/ECMWF/UKMET continue to be
in agreement that Danielle will complete its extratropical
transition on Thursday, although the vertical thermal structure
shows the system maintaining a warm core above 600 mb. Over the
weekend, Global model simulated IR imagery, and the Cyclone Phase
Analysis show Danielle merging with a baroclinic system approaching
from the west and developing a warm seclusion structure (shallow
warm core with a cold core upper troposphere). Although not
explicitly indicated in the official forecast, Danielle could
maintain its intensity during this evolution is due to dynamic
forcing/favorable jet finger support while it tracks cyclonically
over the central-north Atlantic. The NHC intensity forecast
resembles the IVCN intensity consensus which has performed well so
far on the system.

Danielle should still move generally northeastward in the
deep-layer mid-latitude steering flow through the afternoon hours.
Danielle is forecast to turn east-northeast on Wednesday while
accelerating. Toward the end of the week, as mentioned above, the
cyclone is expected to interact with a baroclinic system, while
rotating cyclonically north of the westerlies, then turn toward the
southeast. The only significant change in the official forecast
track is the implementation of the cyclonic turn around day 3-4,
which is based on the majority of the global models.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 41.6N 42.6W 70 KT 80 MPH
12H 06/1200Z 42.2N 41.6W 65 KT 75 MPH
24H 07/0000Z 42.8N 39.5W 65 KT 75 MPH
36H 07/1200Z 43.9N 36.9W 65 KT 75 MPH
48H 08/0000Z 45.5N 34.1W 60 KT 70 MPH
60H 08/1200Z 47.4N 31.6W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 09/0000Z 49.2N 30.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 10/0000Z 49.8N 31.6W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 11/0000Z 46.8N 26.1W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: DANIELLE - Advisories

#24 Postby cycloneye » Tue Sep 06, 2022 4:14 am

Hurricane Danielle Discussion Number 21
NWS National Hurricane Center Miami FL AL052022
900 AM GMT Tue Sep 06 2022

Danielle's cloud pattern has degraded further this morning by
shedding its curved bands in the eastern semicircle. The remaining
outer bands have become more fragmented with cloud top
temperatures of only -47C. Dvorak final-T numbers are on the
decline, and a compromise of both TAFB's and SAB's intensity
estimates, along with the UW-CIMSS objective assessment, supports
lowering the initial intensity to 65 kt for this advisory.

Although Danielle is currently moving over relatively warm (25C)
oceanic surface temperatures, the cyclone should begin to lose its
tropical characteristics soon as it traverses cooler SSTs of less
than 22C during the next day or two. Guidance continues to
indicate that Danielle will complete its extratropical transition
on Thursday, although the vertical thermal structure shows the
system sustaining its warm core above 600 mb. Over the
weekend, deterministic cyclone phase analyses, and simulated IR
predictions show Danielle, as the dominant system, merging with a
baroclinic system approaching from the west. A warm seclusion
structure develops while the system occludes, or is cut-off north
of the mid-latitude westerlies. The NHC intensity forecast is
similar to the previous advisory and continues to lean toward the
IVCN intensity consensus model.

The initial motion is estimated to be northeastward at 7 kt, and
Danielle should continue moving in this heading through this
evening. Afterward, a turn toward the east-northeast by early
Wednesday, while accelerating, is anticipated. By the early
weekend, the cyclone is expected to interact with a baroclinic
system by rotating cyclonically north of the westerlies and
becoming a vastly larger extratropical low well west of the British
Isles. Once merged into one large, storm-force extratropical low,
the system should commence a general motion toward the
east-southeast on Sunday.

Danielle is producing huge seas over the central-north Atlantic.
Complete information on the High Seas Forecasts can be found at the
Ocean Prediction Center under AWIPS header NFDHSFAT1, WMO header
FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 42.1N 41.9W 65 KT 75 MPH
12H 06/1800Z 42.5N 40.7W 65 KT 75 MPH
24H 07/0600Z 43.3N 38.4W 65 KT 75 MPH
36H 07/1800Z 44.7N 35.6W 60 KT 70 MPH
48H 08/0600Z 46.5N 32.9W 60 KT 70 MPH
60H 08/1800Z 48.6N 31.4W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 09/0600Z 50.3N 31.6W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 10/0600Z 49.1N 32.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 11/0600Z 46.5N 25.4W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: DANIELLE - Advisories

#25 Postby cycloneye » Tue Sep 06, 2022 9:34 am

Hurricane Danielle Discussion Number 22
NWS National Hurricane Center Miami FL AL052022
300 PM GMT Tue Sep 06 2022

Danielle's overall appearance has changed little this morning. The
system remains characterized by fragmented deep convection within a
symmetrical and vertically stacked circulation. In addition, an eye
feature has remained generally identifiable in visible satellite
imagery. The latest Dvorak CI values of 4.0 from TAFB and SAB also
suggest little change in intensity, and thus the system will be kept
as a 65-kt hurricane for this advisory.

The hurricane has slowed its forward motion, and over the past 12-h
the system has been moving east-northeastward at around 5 kt.
Danielle is expected to accelerate east-northeastward tonight in the
increasing flow ahead of a digging upper-trough. This trough is
forecast to spawn a baroclinic system west of Danielle by late this
week, forcing it to make a cyclonic loop while the two systems merge
into a larger extratropical low. The merged system is then forecast
to move east-southeastward to southeastward over the weekend. There
was little change to the NHC track forecast compared to the previous
advisory.

Danielle is forecast to continue over SSTs of about 25 degrees C
over the next 12-24 h, so little change in strength is indicated
during that time. However, on Wednesday the cyclone should cross a
tight SST gradient and begin traversing over waters of 20 degrees C
or less for the remainder of the forecast period. The combination of
these cooler waters and the interaction with the baroclinic system
should cause extratropical transition to complete by Thursday. The
latest NHC intensity forecast is unchanged from the previous one,
and is close to the various multi-model consensus and SHIPS values.

Danielle is producing a large area of very rough seas over the
central-north Atlantic. Complete information on the High Seas
Forecasts can be found at the Ocean Prediction Center under AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php.


FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 42.2N 41.2W 65 KT 75 MPH
12H 07/0000Z 42.6N 39.8W 65 KT 75 MPH
24H 07/1200Z 43.7N 37.2W 65 KT 75 MPH
36H 08/0000Z 45.4N 34.5W 60 KT 70 MPH
48H 08/1200Z 47.5N 32.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
60H 09/0000Z 49.5N 32.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 09/1200Z 50.1N 32.8W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 10/1200Z 48.2N 30.7W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 11/1200Z 45.5N 24.2W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto
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Re: ATL: DANIELLE - Advisories

#26 Postby cycloneye » Tue Sep 06, 2022 4:07 pm


Hurricane Danielle Discussion Number 23
NWS National Hurricane Center Miami FL AL052022
900 PM GMT Tue Sep 06 2022

Danielle is holding its own over the north-central Atlantic. The
cyclone's structure has stabilized since early this morning and the
cloud tops have been cooling slightly over the past several hours,
suggesting that any weakening that had been occurring overnight has
temporarily ended. The initial intensity is being held at 65 kt for
this advisory, which is based on the latest subjective Dvorak
intensity estimate from SAB, and objective data from UW-CIMSS.

The hurricane continues to move slowly east-northeastward, or 070/6
kt. There is no change to the forecast track reasoning. Danielle is
expected to accelerate east-northeastward tonight in the increasing
flow ahead of a digging upper-level trough. This trough is forecast
to spawn a baroclinic system west of Danielle by late this week,
forcing it to make a cyclonic loop while the two systems merge into
a larger extratropical low. The merged system is then forecast to
move east-southeastward to southeastward over the weekend. There
were no significant changes to the NHC track forecast compared to
the previous advisory, as model guidance remains in good agreement.

Danielle is forecast to continue over SSTs of about 25 degrees C
over the next 18-24 h, so only minor fluctuations in strength is
indicated during that time. However, by late Wednesday the cyclone
should cross a tight SST gradient and begin traversing over waters
of 20 degrees C or less for the remainder of the forecast period.
The combination of these cooler waters and the interaction with the
baroclinic system should cause extratropical transition to complete
by Thursday. The latest NHC intensity forecast closely follows the
latest multi-model consensus.

Danielle is producing a large area of very rough seas over the
central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php.


FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 42.5N 40.3W 65 KT 75 MPH
12H 07/0600Z 43.1N 38.6W 65 KT 75 MPH
24H 07/1800Z 44.6N 35.9W 65 KT 75 MPH
36H 08/0600Z 46.5N 33.2W 60 KT 70 MPH
48H 08/1800Z 48.8N 31.9W 55 KT 65 MPH...POST-TROP/EXTRATROP
60H 09/0600Z 50.3N 32.6W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 09/1800Z 50.0N 33.6W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 10/1800Z 47.1N 29.4W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 11/1800Z 44.1N 22.0W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto
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Re: ATL: DANIELLE - Advisories

#27 Postby cycloneye » Tue Sep 06, 2022 9:34 pm

Hurricane Danielle Discussion Number 24
NWS National Hurricane Center Miami FL AL052022
300 AM GMT Wed Sep 07 2022

This morning's conventional satellite presentation indicates
little change in Danielle's cloud pattern since yesterday morning.
However, a recent SSMI/S microwave image shows a subtle vertical
tilt toward the east. The initial intensity is held at 65 kt for
this advisory and is based on a blend of the subjective and AiDT
objective satellite intensity estimates and an earlier STAR SAR/S1
surface wind retrieval that indicated winds of 70 kt.

Danielle should remain over marginally warm waters for the next
12-18 hours. Subsequently, little change in strength is expected
during that time. By early Thursday, Danielle will move over a
sharp surface temperature gradient of 22C or less. This negative
oceanic contribution, combined with the loss of dynamic forcing
after the cyclone merges with the approaching baroclinic system,
should induce a slow weakening trend through the end of the period.

Danielle's initial motion is estimated to be east-northeastward, or
060/11 kt. There is no significant change to the NHC forecast
philosophy. Danielle should continue accelerating in response to a
vigorous baroclinic system approaching from the northwest Atlantic
east of the Newfoundland coast. Danielle is forecast to interact
with the system mentioned above late Thursday night. On Friday, the
two systems are predicted to merge and become a larger and strong
extratropical low with asymmetric deep warm core characteristics
typical of warm seclusions. Over the weekend, the large
post-tropical low is expected to turn east-southeastward and
maintain this general motion through early next week.

Danielle is producing a vast area of very rough seas over the
central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php.
The UK Met Office also has information in High Seas Forecasts for
the west Central and east Central sections issued under WMO header
FQNT21 EGRR and on the web at
metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast


FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 42.7N 39.3W 65 KT 75 MPH
12H 07/1200Z 43.6N 37.4W 65 KT 75 MPH
24H 08/0000Z 45.4N 34.5W 60 KT 70 MPH
36H 08/1200Z 47.6N 32.6W 55 KT 65 MPH...POST-TROP/EXTRATROP
48H 09/0000Z 50.0N 32.7W 55 KT 65 MPH...POST-TROP/EXTRATROP
60H 09/1200Z 50.9N 34.7W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 10/0000Z 48.9N 34.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 11/0000Z 45.3N 26.6W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 12/0000Z 43.1N 18.1W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: DANIELLE - Advisories

#28 Postby cycloneye » Wed Sep 07, 2022 3:44 am

Hurricane Danielle Discussion Number 25
NWS National Hurricane Center Miami FL AL052022
900 AM GMT Wed Sep 07 2022

Danielle's cloud pattern has significantly improved over the past 6
hours. The banding eye feature has warmed back up and cleared out,
and the cloud tops are cooling in two prominent curved bands located
in the north and south semicircles. The subjective Dvorak T-numbers
from TAFB and SAB have increased, and a UW-CIMSS OPEN-AIIR satellite
intensity analysis yields 70-75 kt. These data and the earlier
SAROPS surface wind retrieval support raising the initial intensity
to 70 kt for this advisory.

Danielle should continue moving over marginally warm waters for
just a few more hours, so some fluctuations in strength, similar to
what the cyclone has just undergone, are still possible.
Satellite imagery and global model data indicate that a
favorable position of a polar jet finger associated with the
approaching baroclinic zone may be dynamically influencing
Danielle's short-term intensification. By early Thursday, the
cyclone is expected to traverse a sharp sea surface temperature
gradient of 20C or less. These cooler waters, along with the
eventual loss of dynamic forcing should cause a gradual weakening
trend through the early next week.

Danielle's initial motion is estimated to be northeastward, or
050/12 kt. Once again, there is no significant change to the NHC
forecast philosophy. The hurricane should continue accelerating in
response to a vigorous baroclinic system approaching from the
northwest midway between Newfoundland and Danielle. Danielle
is forecast to interact and merge with the system mentioned above
late Thursday night into Friday. Over the weekend, the large
post-tropical storm-force low is expected to slip south back into
the deep-layer mid-latitude westerlies, turn south-southeastward to
southeastward, and continue in this general heading through early
next week. The NHC forecast is similar to the previous one and is
close to the various multi-model consensus aids.

Danielle is producing a vast area of very rough seas over the
central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php. The UK Met Office also has
information in High Seas Forecasts for the west Central and east
Central sections issued under WMO header FQNT21 EGRR and on the web
at metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast


FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 43.4N 38.1W 70 KT 80 MPH
12H 07/1800Z 44.4N 35.9W 70 KT 80 MPH
24H 08/0600Z 46.3N 33.4W 65 KT 75 MPH
36H 08/1800Z 48.6N 32.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 09/0600Z 50.5N 32.7W 55 KT 65 MPH...POST-TROP/EXTRATROP
60H 09/1800Z 50.0N 34.7W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 10/0600Z 48.6N 33.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 11/0600Z 43.9N 23.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 12/0600Z 42.2N 15.1W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: DANIELLE - Advisories

#29 Postby cycloneye » Wed Sep 07, 2022 9:39 am

Hurricane Danielle Discussion Number 25
NWS National Hurricane Center Miami FL AL052022
900 AM GMT Wed Sep 07 2022

Danielle's cloud pattern has significantly improved over the past 6
hours. The banding eye feature has warmed back up and cleared out,
and the cloud tops are cooling in two prominent curved bands located
in the north and south semicircles. The subjective Dvorak T-numbers
from TAFB and SAB have increased, and a UW-CIMSS OPEN-AIIR satellite
intensity analysis yields 70-75 kt. These data and the earlier
SAROPS surface wind retrieval support raising the initial intensity
to 70 kt for this advisory.

Danielle should continue moving over marginally warm waters for
just a few more hours, so some fluctuations in strength, similar to
what the cyclone has just undergone, are still possible.
Satellite imagery and global model data indicate that a
favorable position of a polar jet finger associated with the
approaching baroclinic zone may be dynamically influencing
Danielle's short-term intensification. By early Thursday, the
cyclone is expected to traverse a sharp sea surface temperature
gradient of 20C or less. These cooler waters, along with the
eventual loss of dynamic forcing should cause a gradual weakening
trend through the early next week.

Danielle's initial motion is estimated to be northeastward, or
050/12 kt. Once again, there is no significant change to the NHC
forecast philosophy. The hurricane should continue accelerating in
response to a vigorous baroclinic system approaching from the
northwest midway between Newfoundland and Danielle. Danielle
is forecast to interact and merge with the system mentioned above
late Thursday night into Friday. Over the weekend, the large
post-tropical storm-force low is expected to slip south back into
the deep-layer mid-latitude westerlies, turn south-southeastward to
southeastward, and continue in this general heading through early
next week. The NHC forecast is similar to the previous one and is
close to the various multi-model consensus aids.

Danielle is producing a vast area of very rough seas over the
central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php. The UK Met Office also has
information in High Seas Forecasts for the west Central and east
Central sections issued under WMO header FQNT21 EGRR and on the web
at metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast


FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 43.4N 38.1W 70 KT 80 MPH
12H 07/1800Z 44.4N 35.9W 70 KT 80 MPH
24H 08/0600Z 46.3N 33.4W 65 KT 75 MPH
36H 08/1800Z 48.6N 32.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 09/0600Z 50.5N 32.7W 55 KT 65 MPH...POST-TROP/EXTRATROP
60H 09/1800Z 50.0N 34.7W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 10/0600Z 48.6N 33.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 11/0600Z 43.9N 23.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 12/0600Z 42.2N 15.1W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: DANIELLE - Advisories

#30 Postby cycloneye » Wed Sep 07, 2022 3:45 pm

Hurricane Danielle Discussion Number 27
NWS National Hurricane Center Miami FL AL052022
900 PM GMT Wed Sep 07 2022

Danielle has generally changed little since this morning and it
remains an impressive hurricane for being at a relatively
high latitude of around 45 N. The system continues to have a
large eye with a fairly symmetric convective pattern surrounding it.
The Dvorak estimates at 18Z range from 65 to 77 kt, and on this
basis, the initial intensity is held at 70 kt.

A mid-to upper-level trough is quickly approaching Danielle, and
it should cause an increase in shear soon. The higher shear,
interaction with the trough, and sharply cooler SSTs along the
predicted track should cause Danielle to complete extratropical
transition on Thursday and cause the cyclone to gradually decay.
The intensity models are in good agreement, and the NHC intensity
forecast is just an update of the previous one.

Danielle is moving northeastward at 14 kt, which is the fastest this
system has moved in quite some time. This general motion should
continue through tonight, however, a slow down and counterclockwise
loop is expected to occur on Thursday and Friday when Danielle
interacts with the trough that is expected to cut off. After that
time, a faster motion to the southeast is forecast, which should
take the extratropical cyclone toward western Europe by the end of
the period. The NHC track forecast is a little faster than the
previous one, trending toward the latest consensus aids.

Danielle continues to produce a large area of very rough seas over
the central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php. The UK Met Office also has
information in High Seas Forecasts for the west Central and east
Central sections issued under WMO header FQNT21 EGRR and on the web
at metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast


FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 44.9N 34.9W 70 KT 80 MPH
12H 08/0600Z 46.4N 32.6W 65 KT 75 MPH
24H 08/1800Z 48.7N 31.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 09/0600Z 50.4N 31.9W 55 KT 65 MPH...POST-TROP/EXTRATROP
48H 09/1800Z 49.7N 33.7W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 10/0600Z 47.3N 31.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 10/1800Z 45.3N 27.1W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 11/1800Z 42.1N 17.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 12/1800Z 42.3N 10.0W 30 KT 35 MPH...POST-TROP/EXTRATROP

$$
Forecaster Cangialosi
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Re: ATL: DANIELLE - Advisories

#31 Postby cycloneye » Wed Sep 07, 2022 9:36 pm

Hurricane Danielle Discussion Number 28
NWS National Hurricane Center Miami FL AL052022
300 AM GMT Thu Sep 08 2022

Danielle is beginning to feel the effects of an approaching mid-to
upper-level trough just to its west. There has been some erosion of
the deep convection over the southern portion of the circulation,
likely due to increasing southwesterly shear, while the eye has
filled with cloud cover. The latest Dvorak intensity estimates have
overall lowered since the previous advisory, and a blend of these
values suggest the cyclone's initial intensity has decreased to 65
kt.

The cyclone is expected to undergo extratropical transition through
Thursday morning due to the higher shear, interaction with the
trough, and sharply cooler SSTs along its forecast track. These
conditions are also expected to cause Danielle to gradually weaken.
The latest NHC intensity forecast was tweaked slightly lower than
the previous one, and closely follows the various multi-model
consensus values.

Danielle is moving northeastward at 15 kt, and this general motion
should continue through tonight. A slow down and counterclockwise
loop is expected to occur on Thursday and Friday when the cyclone
interacts with the trough that is expected to cut off. After that
time, a faster motion to the southeast is forecast, which should
take the extratropical cyclone toward western Europe by the end of
the period. The NHC track forecast is little changed from the
previous one, and is near the latest consensus aids.

Danielle continues to produce a large area of very rough seas over
the central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php. The UK Met Office also has
information in High Seas Forecasts for the west Central and east
Central sections issued under WMO header FQNT21 EGRR and on the web
at metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast


FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 45.6N 32.9W 65 KT 75 MPH
12H 08/1200Z 47.2N 30.9W 60 KT 70 MPH
24H 09/0000Z 49.3N 30.6W 55 KT 65 MPH...POST-TROP/EXTRATROP
36H 09/1200Z 50.0N 32.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 10/0000Z 48.6N 32.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
60H 10/1200Z 45.8N 28.8W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 11/0000Z 44.0N 24.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 12/0000Z 41.6N 15.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 13/0000Z 42.9N 9.5W 30 KT 35 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto
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Re: ATL: DANIELLE - Advisories

#32 Postby cycloneye » Thu Sep 08, 2022 3:46 am

Tropical Storm Danielle Discussion Number 29
NWS National Hurricane Center Miami FL AL052022
900 AM GMT Thu Sep 08 2022

Danielle is losing its tropical characteristics. The deep convection
has completely eroded across the southwestern portion of the
circulation. There is no longer an eye-like feature as seen
yesterday, and the system is taking on characteristics more similar
to the comma-shaped cloud shield of a mid-latitude cyclone. The
latest Dvorak intensity estimates suggest that Danielle is no longer
a hurricane, and the initial intensity has been decreased to 60 kt
for this advisory.

The cyclone is expected to quickly complete extratropical transition
through this morning due to higher shear, interaction with a mid- to
upper-level trough just to its west, and cool SSTs along its
forecast track. These conditions are also expected to cause Danielle
to continue weakening through the remainder of the forecast period.
The latest NHC intensity forecast was once again tweaked slightly
lower than the previous one, mainly to adjust for the lower initial
intensity.

Danielle is moving northeastward at 14 kt, and this general motion
should continue for the next few hours. A slow down and
counterclockwise loop is expected to occur later today and Friday
when the cyclone interacts with the trough that is expected to cut
off. After that time, a faster motion to the southeast is forecast,
which should take the extratropical cyclone toward western Europe by
the end of the period. The NHC track forecast was adjusted a little
to the right after the counterclockwise loop due to an overall shift
in the model guidance.

Danielle continues to produce a large area of very rough seas over
the central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php. The UK Met Office also has
information in High Seas Forecasts for the west Central and east
Central sections issued under WMO header FQNT21 EGRR and on the web
at metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast. Meteo France's High Seas Forecast also includes
information regarding Danielle at http://weather.gmdss.org/II.html.


FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 46.8N 32.0W 60 KT 70 MPH
12H 08/1800Z 48.5N 30.9W 55 KT 65 MPH...POST-TROP/EXTRATROP
24H 09/0600Z 49.9N 31.6W 50 KT 60 MPH...POST-TROP/EXTRATROP
36H 09/1800Z 49.5N 33.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 10/0600Z 47.2N 31.7W 40 KT 45 MPH...POST-TROP/EXTRATROP
60H 10/1800Z 44.4N 26.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 11/0600Z 42.8N 21.4W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 12/0600Z 41.5N 14.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 13/0600Z 43.3N 9.3W 30 KT 35 MPH...POST-TROP/EXTRATROP

$$
Forecaster Latto
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Re: ATL: DANIELLE - Advisories

#33 Postby cycloneye » Thu Sep 08, 2022 9:40 am

BULLETIN
Post-Tropical Cyclone Danielle Advisory Number 30
NWS National Hurricane Center Miami FL AL052022
300 PM GMT Thu Sep 08 2022

...DANIELLE NOW POST-TROPICAL...
...THIS IS THE LAST NHC ADVISORY...



Post-Tropical Cyclone Danielle Discussion Number 30
NWS National Hurricane Center Miami FL AL052022
300 PM GMT Thu Sep 08 2022

Satellite imagery this afternoon has shown Danielle develop a clear
comma-shaped cloud shield, a hallmark of an extratropical cyclone.
In addition, an ASCAT-B pass near 12Z showed a wind shift,
indicative of a front, that extended from the center of the cyclone
northeastward. Based on these data, Danielle has been classified as
post-tropical and this is the last NHC advisory. Peak winds in the
ASCAT pass were just above 50 kt, so the intensity of Danielle was
lowered slightly to 55 kt. It is worth noting that the peak winds
are generally not representative of the impacts associated with
extratropical cyclones and gale- to storm-force winds extend well
from the center of Danielle.

Danielle has begun its long-awaited counterclockwise loop, which
should take another 36 to 48 h to complete. After that, the
post-tropical cyclone is forecast to move initially southeastward,
then eastward as it is caught within the flow of a broader
mid-latitude trough moving eastward over the northeastern Atlantic.
The track forecast for the post-tropical cyclone is based heavily on
the multi-model consensus TVCN. All guidance indicates the cyclone
will gradually weaken, both in terms of maximum winds and size
through the end of the forecast period.

Danielle continues to produce a large area of very rough seas over
the central-north Atlantic. More information about the
post-tropical cyclone can be found in High Seas Forecasts issued by
the UKMET office under WMO header FQNT21 EGRR and on the web at
metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast. Information can also be found in Meteo France's High
Seas Forecast at weather.gmdss.org/II.html.


FORECAST POSITIONS AND MAX WINDS

INIT 08/1500Z 47.9N 31.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
12H 09/0000Z 49.5N 31.2W 55 KT 65 MPH...POST-TROP/EXTRATROP
24H 09/1200Z 49.9N 33.1W 50 KT 60 MPH...POST-TROP/EXTRATROP
36H 10/0000Z 48.3N 33.5W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 10/1200Z 45.2N 29.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
60H 11/0000Z 43.4N 23.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 11/1200Z 41.5N 19.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 12/1200Z 41.0N 13.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 13/1200Z 43.0N 9.4W 30 KT 35 MPH...POST-TROP/EXTRATROP

$$
Forecaster D. Zelinsky
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