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KF5JRV > WX 13.09.18 12:46l 286 Lines 12205 Bytes #999 (0) @ NA
BID : 21195_KF5JRV
Read: GUEST
Subj: NWS NHC Atlantic WX - Sept 13
Path: IW8PGT<CX2SA<EA2RCF<LU9DCE<XE1FH<VE3UIL<AB0AF<KF5JRV
Sent: 180913/1115Z 21195@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.16
440
WTNT41 KNHC 130856
TCDAT1
Hurricane Florence Discussion Number 56
NWS National Hurricane Center Miami FL AL062018
500 AM EDT Thu Sep 13 2018
The satellite presentation of Florence has changed little overnight
with the eye waxing and waning in infrared imagery. The eye has
moved into NWS radar range and can be seen in radar data from
Morehead City and Wilmington NWS 88-D imagery. An 0616 UTC
AMSR2 microwave overpass indicated that the convection over the
southern and southeastern portions of the storm is still disrupted,
and that the eyewall was open to the southeast. An Air Force
Hurricane Hunter aircraft also reported that the eyewall was not
fully intact on its last pass through the storm just after that
time. The Air Force plane measured a peak 700-mb flight level wind
of 102 kt and peak SFMR winds of 85 kt during the mission. These
data suggest that the intensity may be slightly lower, but the
initial intensity has been maintained at 95 kt, since the plane
may not have sampled the strongest winds. Another Air Force
plane will be in Florence shortly, and should provide a better
assessment of the intensity of the hurricane. As mentioned in
the previous discussion, it appears that some southern shear has
caused the degradation of the inner core. The global models suggest
that this shear will relax today while Florence moves over warm
waters, however, given the current storm structure, little overall
change in strength is anticipated as Florence approaches the coast.
Gradual weakening should occur as the hurricane interacts with land
in 24-36 h, with a faster rate of weakening predicted once Florence
moves farther inland.
Florence is moving northwestward or 315 degrees at 13 kt. A
developing mid-level ridge over the north-central United States
should cause the forward speed of the hurricane to decrease today.
As the steering currents collapse tonight and Friday, Florence is
forecast to drift westward or west-southwestward and continue that
slow motion into the weekend. The global models predict that the
ridge will slide eastward over the weekend, which should allow
Florence to turn northwestward and northward by the end of the
forecast period. Although there is still some spread in the
guidance by 48 hours, with the GFS along the northern side of the
guidance envelope, and the ECWMF along the southern edge, the
various consensus aids have moved little. As a result, the new NHC
forecast track is very similar to the previous advisory.
Aircraft and satellite wind data show that Florence is a large
hurricane. Life-threatening storm surge, heavy rainfall, and
damaging wind will cover a large area regardless of exactly where
the center of Florence moves.
Key Messages:
1. A life-threatening storm surge is now highly likely along
portions of the coastlines of South Carolina and North Carolina, and
a Storm Surge Warning is in effect for a portion of this area. All
interests in these areas should complete preparations and follow any
advice given by local officials.
2. Life-threatening, catastrophic flash flooding and prolonged
significant river flooding are likely over portions of the Carolinas
and the southern and central Appalachians late this week into early
next week, as Florence is expected to slow down as it approaches the
coast and moves inland.
3. Damaging hurricane-force winds are likely along portions of the
coasts of South Carolina and North Carolina, and a Hurricane Warning
is in effect. Strong winds could also spread inland into portions
of the Carolinas.
4. Large swells affecting Bermuda, portions of the U.S. East
Coast, and the northwestern and central Bahamas will continue this
week, resulting in life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0900Z 32.8N 74.7W 95 KT 110 MPH
12H 13/1800Z 33.7N 76.1W 95 KT 110 MPH
24H 14/0600Z 34.2N 77.4W 90 KT 105 MPH
36H 14/1800Z 34.3N 78.4W 70 KT 80 MPH...INLAND
48H 15/0600Z 34.1N 79.2W 50 KT 60 MPH...INLAND
72H 16/0600Z 33.9N 81.2W 30 KT 35 MPH...INLAND
96H 17/0600Z 35.4N 83.3W 25 KT 30 MPH...INLAND
120H 18/0600Z 39.5N 81.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
$$
Forecaster Brown
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-TROPTRATROP
120H 18/0600Z 51.1N 10.8W 45 KT 50 MPH...POST-TROPTRATROP
$$
Forecaster Roberts
142
WTNT44 KNHC 130859
TCDAT4
Tropical Storm Isaac Discussion Number 23
NWS National Hurricane Center Miami FL AL092018
500 AM AST Thu Sep 13 2018
Data from a NOAA P-3 Hurricane Hunter aircraft that departed the
storm shortly before 0600 UTC indicated that the tropical storm has
weakened a little more. Maximum flight-level winds were around 51
kt, while maximum SFMR winds were only 41 kt. Both of these
support an initial intensity of 40 kt. Wind measurements from the
plane also suggested that Isaac is close to opening up into a
tropical wave and its circulation is likely barely closed at the
surface. Another P-3 mission is scheduled for this morning.
Isaac is nearly completely devoid of deep convection at the moment,
and is not trackable in radar data from Guadeloupe and Martinique.
Given the lack of deep convection to sustain the cyclone, continued
gradual weakening is expected. However, given the extent of
40 mph winds observed by the NOAA plane, Isaac is still likely to
bring gusty conditions to many of the Leeward Islands through
this afternoon. The dynamical guidance is now in fairly good
agreement on the intensity of Isaac for the next few days, and
nearly all of the models depict Isaac opening into a trough between
48 and 96 h. The NHC forecast conservatively maintains Isaac
through day 4 in an attempt to maintain some continuity, but it
is very possible that Isaac will open into a trough sooner than
indicated. Some of the dynamical models suggest that regeneration
could occur in the western Caribbean, however the predictability of
such an event is too low to explicitly show in the forecast at this
point.
Isaac is still moving quickly westward, with an initial motion of
275/15 kt. Confidence in the track forecast remains high, and the
track guidance is tightly clustered through the forecast period.
Very little change was made to the track forecast, which continues
to closely follow the HCCA model. As long as Isaac remains a
shallow cyclone, it should continue to be steered westward by the
low-level tradewind flow, even if, or when, it opens up into a
trough.
Key Messages:
1. Isaac is expected to produce tropical-storm-force winds across
portions of the Lesser Antilles this morning and afternoon, and
tropical storm warnings are in effect for Martinique, Dominica, and
Guadeloupe.
2. Tropical storm watches are in effect for Montserrat, St. Kitts
and Nevis, Antigua, Barbuda, Saba and St. Eustatius, St. Maarten,
and St. Martin. Tropical storm conditions are possible on these
islands today and interests on those islands should follow any
advice given by their local officials.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0900Z 15.4N 59.7W 40 KT 45 MPH
12H 13/1800Z 15.5N 61.8W 35 KT 40 MPH
24H 14/0600Z 15.5N 64.8W 35 KT 40 MPH
36H 14/1800Z 15.5N 67.8W 35 KT 40 MPH
48H 15/0600Z 15.4N 70.4W 35 KT 40 MPH
72H 16/0600Z 15.6N 74.8W 35 KT 40 MPH
96H 17/0600Z 16.9N 78.5W 30 KT 35 MPH
120H 18/0600Z...DISSIPATED
$$
Forecaster Zelinsky
024
WTNT45 KNHC 130858
TCDAT5
Subtropical Storm Joyce Discussion Number 3
NWS National Hurricane Center Miami FL AL102018
500 AM AST Thu Sep 13 2018
Joyce is still co-located with an upper-level low, and the most
recent TAFB intensity classification was still a subtropical type.
Furthermore, there has been no discernible increase of convection
near the center of the cyclone, and cloud tops have actually warmed
over the past few hours. Therefore, Joyce is still classified as
subtropical for this advisory. Since the cyclone hasn't changed
much in organization, the initial intensity has been held at 40 kt
based on the TAFB subtropical intensity estimate, but this is still
possibly generous.
Joyce's struggle to maintain deep convection bodes poorly for its
intensification prospects, considering that the shear is forecast
by the global models to increase considerably over the next few
days. SHIPS, LGEM, and the global models continue to show Joyce
changing little in strength over the next few days until the
system dissipates by early next week. The HWRF and HMON models are
still outliers in showing substantial intensification, but even
these models aren't quite as aggressive in strengthening Joyce as
they were previously. The NHC forecast continues to favor the
statistical guidance and is just below the intensity consensus at
most forecast hours because it is frankly hard to believe that Joyce
will become a hurricane in 48 h based on its current appearance.
Joyce is still moving slowly southwestward with an initial motion
of 220/5 kt. The global models remain in fairly good agreement
that Joyce will move slowly southwestward for the next day or
so as the storm remains in light steering flow. A turn toward the
south will likely occur as Helene approaches from the southeast,
followed by a quick turn northeastward once the larger tropical
cyclone passes by. Joyce should then accelerate quickly
northeastward ahead of a mid-latitude trough before dissipating
southwest of the Azores. Little change was made to the official
track forecast which is near the middle of the various consensus
aids.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0900Z 33.8N 43.1W 40 KT 45 MPH
12H 13/1800Z 33.3N 43.8W 40 KT 45 MPH
24H 14/0600Z 32.6N 44.2W 45 KT 50 MPH
36H 14/1800Z 32.0N 44.0W 45 KT 50 MPH
48H 15/0600Z 32.1N 43.2W 45 KT 50 MPH
72H 16/0600Z 34.6N 39.4W 40 KT 45 MPH
96H 17/0600Z 37.0N 32.5W 40 KT 45 MPH
120H 18/0600Z...DISSIPATED
$$
Forecaster Zelinsky
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
email: KF5JRV@ICLOUD.COM
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