ATL: HELENE - Post-Tropical - Discussion

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Re: ATL: HELENE - Hurricane - Discussion

#101 Postby chaser1 » Mon Sep 10, 2018 11:47 am

supercane4867 wrote:11AM advisory now forecasts Helene to become a major. I'm actually a bit disappoint that Isaac is struggling right now which we may not see three simultaneous major hurricanes, but that's good news for the islands :P


Isaac really is struggling at the moment but it's a really small storm that progressing closer to the Islands might well shed the present undercutting low level easterly shear and possibly undergo significant strengthening that NHC has been anticipating. My guess is that Isaac will begin to look even more raged as the day goes on but then move into an area by late tomorrow where conditions will become more conducive for increased organization and become stronger.
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Re: ATL: HELENE - Advisories

#102 Postby cycloneye » Mon Sep 10, 2018 3:44 pm

Hurricane Helene Discussion Number 14
NWS National Hurricane Center Miami FL AL082018
500 PM AST Mon Sep 10 2018

Helene's cloud pattern continues to be well organized with a large
eye of about 20 nm in diameter, surrounded by a ring of deep
convection. The cyclone's circulation is large with numerous
cyclonically curved convective bands, and the outflow is fair in all
quadrants. Dvorak classifications have not changed much, and support
an initial intensity of 90 kt.

Helene has the opportunity to strengthen some during the next 24
hours or so, while the shear is low and the ocean is still
relatively warm. After that time, both shear and SSTs will become
less favorable and gradual weakening should then begin. The NHC
intensity forecast is similar to the previous one, and follows
closely the intensity consensus aids.

Helene is moving toward the west-northwest or 290 degrees at 15 kt.
Soon, the hurricane will encounter a mid-level trough which the most
reliable global models are forming in the eastern Atlantic.
This new flow pattern will force Helene to turn to the northwest
and north ahead of the developing trough. Track models are quite
consistent with this solution and the the spread of the guidance
envelope is small through the forecast period. This increases the
confidence in the Helene's northward turn, followed by recurvature
over the eastern Atlantic.

FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 14.9N 31.5W 90 KT 105 MPH
12H 11/0600Z 15.5N 33.3W 100 KT 115 MPH
24H 11/1800Z 16.4N 35.3W 100 KT 115 MPH
36H 12/0600Z 17.5N 37.0W 85 KT 100 MPH
48H 12/1800Z 19.0N 38.0W 75 KT 85 MPH
72H 13/1800Z 23.0N 39.5W 60 KT 70 MPH
96H 14/1800Z 28.5N 40.0W 50 KT 60 MPH
120H 15/1800Z 34.0N 37.0W 50 KT 60 MPH

$$
Forecaster Avila
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Re: ATL: HELENE - Advisories

#103 Postby cycloneye » Mon Sep 10, 2018 9:47 pm

Hurricane Helene Discussion Number 15
NWS National Hurricane Center Miami FL AL082018
1100 PM AST Mon Sep 10 2018

Helene remains a well organized hurricane with a fairly large 25 n
mi diameter eye and ring of cold cloud tops surrounding that
feature. There are a few dry slots beyond the inner core, however,
which have prevented some of the Dvorak estimates from increasing
this cycle. A blend of the latest subjective and objective
satellite intensity estimates supports raising the initial intensity
slightly to 95 kt.

The hurricane has a limited amount of time to strengthen as the
current environment of low wind shear and relatively warm SSTs will
be changing soon. Helene is expected to cross the 26 deg C isotherm
within 24 hours and it will enter an environment of increasing
south-southwesterly shear just beyond that time period. These
conditions should promote a steady weakening trend beginning late
Tuesday. By the end of the forecast period, however, SSTs increase
along the forecast track, and there could be some baroclinic
enhancements to end the weakening trend and perhaps even cause some
strengthening. This scenario is supported by the HWRF/HMON regional
models and the GFS/ECMWF global models. The NHC intensity forecast
is largely an update of the previous one, except it is slightly
higher at the end of the period.

The hurricane is gradually turning to the right, with the latest
initial motion estimate being 295/13 kt. A large mid- to
upper-level trough over the north Atlantic is expected to dig
southward causing a significant weakness in the subtropical ridge.
In response to this change in the steering pattern, Helene is
forecast to gradually turn northward and then north-northeastward
during the next several days. The track models are in fairly good
agreement, and the NHC track forecast lies near the middle of the
guidance envelope. This forecast is only a little to the right of
the previous track.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 15.5N 32.4W 95 KT 110 MPH
12H 11/1200Z 16.2N 34.0W 95 KT 110 MPH
24H 12/0000Z 17.2N 35.7W 85 KT 100 MPH
36H 12/1200Z 18.6N 37.2W 75 KT 85 MPH
48H 13/0000Z 20.1N 38.0W 65 KT 75 MPH
72H 14/0000Z 24.6N 39.0W 60 KT 70 MPH
96H 15/0000Z 30.0N 38.0W 50 KT 60 MPH
120H 16/0000Z 36.2N 34.0W 55 KT 65 MPH

$$
Forecaster Cangialosi
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Re: ATL: HELENE - Hurricane - Discussion

#104 Postby CyclonicFury » Mon Sep 10, 2018 9:57 pm

Up to 95 kts. Will be interesting to see if it can reach major status overnight.
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Re: ATL: HELENE - Hurricane - Discussion

#105 Postby supercane4867 » Mon Sep 10, 2018 10:22 pm

Satellite presentation does support a marginal CAT3. However, dvorak tends to overestimate TCs with large ragged eye

Image
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Re: ATL: HELENE - Hurricane - Discussion

#106 Postby EquusStorm » Mon Sep 10, 2018 10:49 pm

If the eyewall can consistently close off to the north and west and dry air can be locked out, it certainly has a little time left to get bumped to 100kts
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...but still, though, a lot more interesting than the 2013 season.

Not a meteorologist, in fact more of an idiot than anything. You should probably check with the NHC or a local NWS office for official information.

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Re: ATL: HELENE - Hurricane - Discussion

#107 Postby 1900hurricane » Tue Sep 11, 2018 3:48 am

SATCON is up to 102 kt, although there is a little bit of a larger spread in members than usual. If things at least hold steady until 12Z, I'd probably go 100 kt then.
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Re: ATL: HELENE - Advisories

#108 Postby cycloneye » Tue Sep 11, 2018 4:53 am

Hurricane Helene Discussion Number 16
NWS National Hurricane Center Miami FL AL082018
500 AM AST Tue Sep 11 2018

An Advanced Microwave Technology Sounder (ATMS) 165GHZ overpass on
Helene indicated a well-developed closed eyewall and a deep
convective outer band with associated cold cloud tops of -76C
wrapping around the south through east quadrants of the cyclone.
The initial intensity is held at 95 kt for this advisory and is
based on a blend of the subjective and objective T-numbers.

There still appears to be a small window of opportunity for Helene
to strengthen, during the next 12 hours or so, before the ocean and
the upper wind environment become less conducive. Afterward, the
SSTs decrease significantly and the vertical shear increases, which
should induce gradual weakening. By day 3, the sea surface
temperatures increase, however, the southwesterly shear persists and
the mid-level atmospheric moisture decreases. Interestingly
enough, the global models show Helene either maintaining tropical
storm strength or even intensifying by the end of the period,
possibly due to some mid-latitude dynamic forcing influences. It's
also worth noting that the Florida State Cyclone Phase Evolution
analysis and forecast product shows the system retaining a
relatively symmetric warm core through the entire forecast.

The initial motion is estimated to be west-northwestward, or 300/12
kt. A turn more toward the northwest is forecast early on
Wednesday. Beyond mid-period, the large-scale models agree that a
mid- to upper tropospheric trough over the northeast Atlantic will
dig southward inducing a weakness in the eastern portion of the
subtropical ridge. In response to this change in the synoptic
steering pattern, Helene should slowly turn northward and then
north-northeastward during the next 72 to 96 hours, followed by a
turn toward the northeast on day 5. The official forecast is close
to the previous one, and lies near the TVCN consensus model and the
GFS ensemble mean.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 16.0N 33.6W 95 KT 110 MPH
12H 11/1800Z 16.8N 35.0W 100 KT 115 MPH
24H 12/0600Z 18.0N 36.5W 85 KT 100 MPH
36H 12/1800Z 19.5N 37.6W 75 KT 85 MPH
48H 13/0600Z 21.4N 38.3W 65 KT 75 MPH
72H 14/0600Z 25.7N 38.8W 55 KT 65 MPH
96H 15/0600Z 31.4N 36.6W 50 KT 60 MPH
120H 16/0600Z 37.3N 31.2W 50 KT 60 MPH

$$
Forecaster Roberts
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Re: ATL: HELENE - Advisories

#109 Postby cycloneye » Tue Sep 11, 2018 9:42 am

Hurricane Helene Discussion Number 17
NWS National Hurricane Center Miami FL AL082018
1100 AM AST Tue Sep 11 2018

It appears that Helene already peaked in intensity earlier this
morning with 95 kt. The cloud pattern has not changed much, and
still consists of a large eye surrounded by deep convection.
However, these convective tops have warmed a little, and
consequently Dvorak numbers have remained steady. From now on,
Helene will begin to move over increasingly cooler waters, and
become embedded within higher shear in about a day. These
environmental conditions should result in weakening, and the NHC
forecast calls for a decrease in the winds at the same rate as the
intensity consensus aids.

Helene has turned toward the northwest or 310 degrees at 10 kt.
Models continue to erode the ridge to the north of the cyclone, and
are also developing a large mid-level trough over eastern Atlantic.
This forecast flow pattern will force Helene to turn more toward the
north-northwest and north ahead of the trough for the next 2 to 3
days. After that time, the cyclone will recurve in the mid-
latitude westerlies, and will begin to lose tropical characteristics
at the very long ranges. Track models are in very good agreement
with this solution. The NHC forecast is in the middle of the
guidance envelope and in between HCCA and the multi-model consensus
aids.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 16.5N 34.3W 95 KT 110 MPH
12H 12/0000Z 17.5N 35.5W 90 KT 105 MPH
24H 12/1200Z 18.9N 36.9W 80 KT 90 MPH
36H 13/0000Z 20.7N 37.8W 70 KT 80 MPH
48H 13/1200Z 22.5N 38.2W 60 KT 70 MPH
72H 14/1200Z 27.5N 38.0W 50 KT 60 MPH
96H 15/1200Z 35.0N 35.0W 50 KT 60 MPH
120H 16/1200Z 40.0N 30.0W 50 KT 60 MPH

$$
Forecaster Avila
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Re: ATL: HELENE - Advisories

#110 Postby cycloneye » Tue Sep 11, 2018 3:53 pm

Hurricane Helene Discussion Number 18
NWS National Hurricane Center Miami FL AL082018
500 PM AST Tue Sep 11 2018

Helene is feeling the effects of cooler waters, and the convection
surrounding the distinct eye is weaker that earlier today. Dvorak
numbers are decreasing, and only support an initial intensity of 90
kt. Both cooler waters and high shear will continue to impact the
hurricane, and Helene will probably weaken to a tropical storm
in about 36 hours or so. The NHC forecast calls for a decrease in
the winds at the same rate as the intensity consensus aids.

Helene is already on the southwestern side of the subtropical
ridge, and it is now moving toward the northwest or 320 degrees at
10 kt. Global models continue to develop a large mid-level trough
over eastern Atlantic, and the flow associated with this trough
should steer Helene north-northwestward and northward during the
next day to so. The cyclone should then recurve northeastward with
an increase in forward speed and by Friday, a weakened Helene
should be approaching the Azores. At the very long range, the
cyclone will begin to lose tropical characteristics over the even
colder waters of the north Atlantic. There has been little change in
the track forecast since models have been very consistent with the
current solution.

FORECAST POSITIONS AND MAX WINDS

INIT 11/2100Z 17.2N 34.9W 90 KT 105 MPH
12H 12/0600Z 18.3N 36.0W 80 KT 90 MPH
24H 12/1800Z 20.2N 37.2W 70 KT 80 MPH
36H 13/0600Z 22.3N 37.8W 60 KT 70 MPH
48H 13/1800Z 25.0N 38.0W 50 KT 60 MPH
72H 14/1800Z 31.5N 37.0W 45 KT 50 MPH
96H 15/1800Z 39.0N 32.5W 45 KT 50 MPH
120H 16/1800Z 43.5N 25.0W 45 KT 50 MPH

$$
Forecaster Avila
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Re: ATL: HELENE - Advisories

#111 Postby cycloneye » Tue Sep 11, 2018 9:39 pm

Hurricane Helene Discussion Number 19
NWS National Hurricane Center Miami FL AL082018
1100 PM AST Tue Sep 11 2018

Satellite imagery indicates that Helene is gradually weakening,
likely due to cool SSTs of around 25.5 deg C beneath the cyclone.
The eye has become a little less distinct and cloud tops associated
with the inner-core convection have warmed. The initial intensity
has been lowered to 85 kt, based on a blend of Final-T and CI
numbers from TAFB. Continued weakening is likely for the next 36 to
48 h since Helene will remain over marginal SSTs, and the intensity
guidance is in good agreement. After that time, the cyclone will
reach somewhat warmer waters and will begin to interact with an
upper-level trough to the northwest. While this interaction will
cause an increase of shear over Helene, it could also provide some
baroclinic support to help maintain Helene's intensity before it
undergoes extratropical transition. Some of the dynamical models
suggest that reintensification is possible through this period,
while the statistical models quickly weaken the cyclone. For now the
official intensity forecast continues to show little change in
intensity from 72-120 h and remains close to the various intensity
consensus aids, but confidence in this portion of the forecast is
lower.

Virtually no change has been made to the official track forecast.
Helene is currently moving northwestward, and a steady turn
northward, and eventually northeastward is expected as the cyclone
is steered between a mid-level ridge to the east and a trough to
west. All of the global models are in good agreement, with the
forward speed of the cyclone being the only notable difference from
model to model. Since I have no reason to depart from the consensus
at this point, the NHC forecast remains very close to HCCA through
day 5.

FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 18.0N 35.4W 85 KT 100 MPH
12H 12/1200Z 19.3N 36.3W 75 KT 85 MPH
24H 13/0000Z 21.2N 37.3W 65 KT 75 MPH
36H 13/1200Z 23.6N 37.7W 60 KT 70 MPH
48H 14/0000Z 26.6N 37.7W 55 KT 65 MPH
72H 15/0000Z 33.7N 35.9W 50 KT 60 MPH
96H 16/0000Z 40.5N 31.0W 50 KT 60 MPH
120H 17/0000Z 45.0N 23.0W 50 KT 60 MPH

$$
Forecaster Zelinsky
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Re: ATL: HELENE - Hurricane - Discussion

#112 Postby HurricaneRyan » Tue Sep 11, 2018 10:05 pm

Helene and Isaac are definitely on the backburner as Florence is stealing the show.
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Re: ATL: HELENE - Advisories

#113 Postby southerngale » Wed Sep 12, 2018 3:51 am

ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM

Hurricane Helene Discussion Number 20
NWS National Hurricane Center Miami FL AL082018
500 AM AST Wed Sep 12 2018

Earlier this morning, Helene looked quite ragged in IR imagery. The
eye became poorly defined and cloud tops were steadily warming.
However, beginning around 0500 UTC, a new burst of convection began
wrapping around the previously open western portion of Helene's
inner core. Objective and subjective Dvorak current intensity
estimates range from 77 to 91 kt, and the initial intensity is
therefore set at 80 kt as a blend of all of these data.

Despite the fact that Helene appears to be on the upswing at the
moment, the cyclone is still passing over sub-26 deg C waters and
all of the intensity guidance shows weakening for the next 24 h.
Beyond that time, there is still some spread among the intensity
models, though it has decreased since the last advisory. Helene will
begin interacting with a mid-latitude trough over the north-central
Atlantic, which will result in an increase in shear over the
hurricane. However, Helene will also begin to move over warmer
waters and could get some baroclinic support from the upper-level
trough. Overall the intensity guidance is a little lower than
before, and now the NHC intensity forecast is near the middle of the
intensity guidance envelope.

Once again, no meaningful change has been made to the NHC track
forecast which continues to closely follow the HFIP Corrected
Consensus. Helene is moving north-northwestward, and should
gradually turn northward, and eventually northeastward, as the
cyclone is steered between a mid-level ridge to the east and the
aforementioned mid-latitude trough to northwest. The global models
remain in fairly good agreement on the track of Helene, especially
through 72-96 h, when Helene is forecast to pass near the Azores,
and interests in those islands should closely monitor the progress
of Helene over the next several days.

FORECAST POSITIONS AND MAX WINDS

INIT 12/0900Z 19.2N 35.7W 80 KT 90 MPH
12H 12/1800Z 20.7N 36.6W 75 KT 85 MPH
24H 13/0600Z 22.9N 37.2W 65 KT 75 MPH
36H 13/1800Z 25.5N 37.3W 55 KT 65 MPH
48H 14/0600Z 28.9N 36.9W 55 KT 65 MPH
72H 15/0600Z 36.0N 34.3W 50 KT 60 MPH
96H 16/0600Z 41.0N 28.5W 50 KT 60 MPH
120H 17/0600Z 45.5N 19.0W 50 KT 60 MPH

$$
Forecaster Zelinsky
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Re: ATL: HELENE - Advisories

#114 Postby southerngale » Wed Sep 12, 2018 3:52 am

358
WTNT33 KNHC 120834
TCPAT3

BULLETIN
Hurricane Helene Advisory Number 20
NWS National Hurricane Center Miami FL AL082018
500 AM AST Wed Sep 12 2018

...HELENE CONTINUES TO WEAKEN...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...19.2N 35.7W
ABOUT 800 MI...1290 KM WNW OF THE CABO VERDE ISLANDS
ABOUT 1400 MI...2250 KM SSW OF THE AZORES
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H
PRESENT MOVEMENT...NNW OR 335 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...977 MB...28.85 INCHES


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

Interests in the Azores should monitor the progress of Helene.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the center of Hurricane Helene was located
near latitude 19.2 North, longitude 35.7 West. Helene is moving
toward the north-northwest near 13 mph (20 km/h), and a turn
toward the north is expected later today. A turn toward the
northeast with an increase in forward speed is likely by the end of
the week.

Maximum sustained winds are near 90 mph (150 km/h) with higher
gusts. Gradual weakening is forecast over the next couple of days,
and Helene is expected to become a tropical storm on Thursday.

Hurricane-force winds extend outward up to 45 miles (75 km) from the
center and tropical-storm-force winds extend outward up to 175 miles
(280 km).

The estimated minimum central pressure is 977 mb (28.85 inches).


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


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Zelinsky
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Re: ATL: HELENE - Advisories

#115 Postby cycloneye » Wed Sep 12, 2018 3:47 pm

BULLETIN
Hurricane Helene Advisory Number 22
NWS National Hurricane Center Miami FL AL082018
500 PM AST Wed Sep 12 2018

...HELENE HEADING NORTHWARD ACROSS THE EASTERN ATLANTIC...
...INTERESTS IN THE AZORES SHOULD MONITOR THE PROGRESS OF HELENE...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...21.4N 36.7W
ABOUT 910 MI...1465 KM WNW OF THE CABO VERDE ISLANDS
ABOUT 1285 MI...2065 KM SSW OF THE AZORES
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...N OR 350 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...980 MB...28.94 INCHES



Hurricane Helene Discussion Number 22
NWS National Hurricane Center Miami FL AL082018
500 PM AST Wed Sep 12 2018

The eye has continued to become less distinct in conventional
imagery, but the overall convective pattern remains well organized
and symmetric. Based on the latest Dvorak estimates, the initial
intensity is lowered to 75 kt. Most of the guidance show a
significant increase in the shear in 24 hours, but the SSTs are not
changing much for the next 2 days or so, thus gradual weakening is
forecast. After that time, both shear and SSTs will become
highly unfavorable, resulting in additional weakening. By the end of
the forecast period, Helene should have acquired extratropical
characteristics.

The hurricane is moving toward the north or 350 degrees at 12 kt,
embedded in the southerly flow to the east of the digging trough
over the central Atlantic. Since the trough is forecast to amplify,
Helene will be forced to turn to the north-northeast and northeast
with an increase in forward speed. The global models remain in
fairly good agreement on the current forecast track of Helene, and
they all bring the cyclone near the Azores in about 3 days.
Interests in those islands should closely monitor the progress of
Helene over the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT 12/2100Z 21.4N 36.7W 75 KT 85 MPH
12H 13/0600Z 23.1N 37.1W 70 KT 80 MPH
24H 13/1800Z 26.0N 37.2W 60 KT 70 MPH
36H 14/0600Z 29.0N 36.5W 55 KT 65 MPH
48H 14/1800Z 32.5N 35.5W 55 KT 65 MPH
72H 15/1800Z 39.0N 32.0W 50 KT 60 MPH
96H 16/1800Z 43.0N 24.0W 45 KT 50 MPH
120H 17/1800Z 47.5N 14.5W 40 KT 45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Avila
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Re: ATL: HELENE - Hurricane - Discussion

#116 Postby supercane4867 » Wed Sep 12, 2018 3:57 pm

Saved images of 4 simultaneous named storms in the Atlantic. Perhaps soon to be 5

Image

Image

Image
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Re: ATL: HELENE - Advisories

#117 Postby cycloneye » Wed Sep 12, 2018 9:46 pm

BULLETIN
Hurricane Helene Advisory Number 23
NWS National Hurricane Center Miami FL AL082018
1100 PM AST Wed Sep 12 2018

...HELENE WEAKENS SOME MORE...
...INTERESTS IN THE AZORES SHOULD MONITOR THE PROGRESS OF HELENE...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.4N 36.9W
ABOUT 1270 MI...2045 KM SSW OF LAJES AIR BASE IN THE AZORES
ABOUT 1225 MI...1975 KM SSW OF THE AZORES
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...N OR 350 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...983 MB...29.03 INCHES


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

Interests in the Azores should monitor the progress of Helene.


Hurricane Helene Discussion Number 23
NWS National Hurricane Center Miami FL AL082018
1100 PM AST Wed Sep 12 2018

Helene's surface circulation has become rather difficult to find
this evening in shortwave and enhanced infrared satellite imagery.
Based on an earlier SSMI/S microwave pass, the center was removed
well to the south of the convective mass. A blend of the Dvorak
intensity estimates from TAFB and SAB, as well as a SATCON analysis
of 72 kt, yields an initial intensity of 70 kt for this advisory.

Global models and the ECMWF/GFS Decay SHIPS models show the
southwesterly shear increasing significantly in 24 hours, however,
the warm sea surface temperatures are expected to limit the
weakening trend some. Beyond the 48 hour period, Helene is expected
to traverse cooler waters while the harsh upper wind environment
persists. Therefore, additional weakening is forecast at a
faster rate. Toward the end of the period, the global models, as
well as the Florida State Cyclone Phase Evolution analysis and
forecast product, show Helene transitioning to a post-tropical
extratropical cyclone as it moves toward Ireland and the United
Kingdom.

Helene is estimated to be moving northward, or 350/11 kt, within the
mid-tropospheric southerly flow produced by an amplifying deep-layer
trough over the central Atlantic. At the 48 hour period, the
cyclone should turn to the north-northeast followed by a
northeastward turn with an increase in forward motion toward the
end of the forecast period. The large-scale models, and the
HWRF hurricane model, are clustered fairly close together and
indicate that Helene will pass near the Azores in about 72 hours.
Interests in those islands should closely monitor the progress of
Helene over the next several days. The NHC forecast lies in the
middle of the guidance envelope and is nudged toward the TVCN
multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 13/0300Z 22.4N 36.9W 70 KT 80 MPH
12H 13/1200Z 24.4N 37.1W 60 KT 70 MPH
24H 14/0000Z 27.3N 37.0W 55 KT 65 MPH
36H 14/1200Z 30.7N 36.4W 55 KT 65 MPH
48H 15/0000Z 34.3N 35.3W 55 KT 65 MPH
72H 16/0000Z 40.1N 30.5W 50 KT 60 MPH
96H 17/0000Z 43.4N 22.4W 50 KT 60 MPH
120H 18/0000Z 48.7N 12.9W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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Re: ATL: HELENE - Advisories

#118 Postby southerngale » Thu Sep 13, 2018 3:55 am

329
WTNT33 KNHC 130847
TCPAT3

BULLETIN
Hurricane Helene Advisory Number 24
NWS National Hurricane Center Miami FL AL082018
500 AM AST Thu Sep 13 2018

...HELENE WEAKENING WHILE MOVING NORTHWARD OVER THE EASTERN
ATLANTIC...
...INTERESTS IN THE AZORES SHOULD MONITOR THE PROGRESS OF HELENE...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...23.5N 37.3W
ABOUT 1215 MI...1955 KM SSW OF LAJES AIR BASE IN THE AZORES
ABOUT 1170 MI...1885 KM SW OF THE AZORES
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...N OR 355 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES


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

Interests in the Azores should monitor the progress of Helene.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the center of Hurricane Helene was located
near latitude 23.5 North, longitude 37.3 West. Helene is moving
toward the north near 14 mph (22 km/h). A turn toward the
north-northeast with an increase in forward speed is expected
tonight followed by a turn toward the northeast over the
weekend.

Maximum sustained winds have decreased to near 75 mph (120 km/h)
with higher gusts. Continued weakening is forecast over the next
couple of days, and Helene is expected to become a tropical storm
by tonight.

Hurricane-force winds extend outward up to 45 miles (75 km) from the
center and tropical-storm-force winds extend outward up to 175 miles
(280 km).

The estimated minimum central pressure is 986 mb (29.12 inches).


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


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Roberts

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Re: ATL: HELENE - Advisories

#119 Postby southerngale » Thu Sep 13, 2018 3:56 am

082
WTNT43 KNHC 130848
TCDAT3

Hurricane Helene Discussion Number 24
NWS National Hurricane Center Miami FL AL082018
500 AM AST Thu Sep 13 2018

Helene's surface circulation has become fully exposed this morning
with the center decoupled about 110 miles south of edge of the
remaining deep convection. Subjective and objective satellite
intensity estimates have decreased and support lowering the initial
intensity to 65 kt.

Statistical and global model guidance show the southwesterly shear
increasing significantly in 12 hours or so, however, the 26 to
27C sea surface temperatures should govern the weakening trend a
little. In 3 days, Helene is forecast to move over much cooler
waters while the cyclone becomes embedded in the hostile
mid-latitude upper-level westerlies. Subsequently, further
weakening is expected at a faster pace. By day 4, the large-scale
models all show Helene acquiring extratropical cyclone
characteristics as it moves toward Ireland and the United
Kingdom. The NHC intensity forecast is similar to the previous
advisory, and is based primarily on the NOAA-HCCA and the IVCN
consensus models.

Helene is still moving northward, or 355/12 kt, within the
deep-layer southerly flow produced by an amplifying mid-Atlantic
trough to the west of the cyclone. In 48 hours, Helene is forecast
to turn north-northeastward followed by a turn toward the northeast
with an increase in forward motion at the 72 hour period. The
guidance suite remains tightly clustered through day 4, with some
slight spread at day 5, and indicates that Helene will pass near the
Azores in about 3 days. Interests in those islands should closely
monitor the progress of Helene over the next few days. The official
forecast is basically an update of the previous one, and lies close
to the TVCN multi-model consensus through the entire forecast
period.


FORECAST POSITIONS AND MAX WINDS

INIT 13/0900Z 23.5N 37.3W 65 KT 75 MPH
12H 13/1800Z 25.7N 37.4W 60 KT 70 MPH
24H 14/0600Z 29.1N 36.9W 55 KT 65 MPH
36H 14/1800Z 32.5N 36.2W 55 KT 65 MPH
48H 15/0600Z 35.8N 34.7W 55 KT 65 MPH
72H 16/0600Z 40.7N 28.2W 50 KT 60 MPH
96H 17/0600Z 44.6N 19.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 18/0600Z 51.1N 10.8W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts

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Re: ATL: HELENE - Hurricane - Discussion

#120 Postby Bunkertor » Thu Sep 13, 2018 8:34 am

Summer will bounce back next week here. I think Helene will provide some extra fuel.
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