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KF5JRV > WX 14.09.18 12:46l 245 Lines 10094 Bytes #999 (0) @ NA
BID : 21259_KF5JRV
Read: GUEST
Subj: NWS NHC Atlantic WX - Sept 14
Path: IW8PGT<CX2SA<HG8LXL<XE1FH<W9ABA<N9LYA<KF5JRV
Sent: 180914/1115Z 21259@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.16
755
WTNT41 KNHC 140842
TCDAT1
Hurricane Florence Discussion Number 60
NWS National Hurricane Center Miami FL AL062018
500 AM EDT Fri Sep 14 2018
An Air Force Hurricane Hunter aircraft has been investigating
Florence over the past few hours. Data from the aircraft indicate
little change in the intensity with the central pressure holding
fairly steady. The current intensity estimate is kept at 80 kt for
this advisory. There were a couple of SFMR-observed surface winds
that were a little higher than that value, however these
observations were very near Cape Lookout North Carolina, where
shoaling likely caused some inflated wind speeds. The current
intensity estimate is also consistent with peak WSR-88D Doppler
radar velocities. The center of Florence will be moving inland very
soon, but is expected to slow down even more today and tonight. As
a result, it will remain fairly close to the coast today, with much
of the circulation still over water. Therefore only a gradual
decrease in intensity is called for through tonight. Over the
weekend, a faster rate of weakening is likely while the center moves
at a faster pace and goes farther inland.
The hurricane is turning westward as it continues a slow forward
motion of about 285/5 kt. Florence is currently in a region of weak
steering currents associated with a col between two mid-level
anticyclones. Over the next few days, a high pressure area is
forecast to build to the east-northeast of the tropical cyclone.
As a result, the system should gradually turn northwestward and
northward in 2-3 days. Later in the forecast period, Florence
should turn northeastward as it approaches the mid-latitude
westerlies. The official track forecast is similar to the
previous one and about in the middle of the dynamical guidance
suite.
It cannot be emphasized enough that the most serious hazard
associated with slow-moving Florence is extremely heavy rainfall,
which will cause disastrous flooding that will be spreading inland
through the weekend.
Key Messages:
1. A life-threatening storm surge is already occurring along
portions of the North Carolina coast and will continue through
today and tonight. This surge is also likely along portions of the
South Carolina coast. The greatest storm surge inundation is
expected between Cape Fear and Cape Hatteras, including the Neuse
and Pamlico Rivers and western Pamlico Sound.
2. Life-threatening, catastrophic flash flooding and prolonged
significant river flooding are likely over portions of the Carolinas
and the southern and central Appalachians through early next week,
as Florence is expected to slow down while it moves inland.
3. Damaging hurricane-force winds are occurring along portions of
the North Carolina coast and are expected to spread to portions of
the South Carolina coast later today. Strong winds could
also spread inland into portions of the Carolinas over the next
couple of days.
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 14/0900Z 34.2N 77.4W 80 KT 90 MPH
12H 14/1800Z 34.1N 78.3W 75 KT 85 MPH...INLAND
24H 15/0600Z 33.9N 79.1W 65 KT 75 MPH...INLAND
36H 15/1800Z 33.8N 79.9W 45 KT 50 MPH...INLAND
48H 16/0600Z 34.1N 81.1W 35 KT 40 MPH...INLAND
72H 17/0600Z 36.6N 83.2W 25 KT 30 MPH...INLAND
96H 18/0600Z 40.5N 80.5W 25 KT 30 MPH...POST-TROP/INLAND
120H 19/0600Z 43.5N 72.0W 25 KT 30 MPH...POST-TROP/INLAND
$$
Forecaster Pasch
163
WTNT43 KNHC 140852
TCDAT3
Tropical Storm Helene Discussion Number 28
NWS National Hurricane Center Miami FL AL082018
500 AM AST Fri Sep 14 2018
Helene is looking increasingly like an extratropical cyclone, with
a rain shield extending from its northwest quadrant and a line of
clouds to the southeast, probably associated with a convergence
zone, that looks like a developing a front. However, earlier ASCAT
data suggested that the cyclone still had a compact wind field with
maximum winds of around 55 kt on the west side, and the most recent
available AMSU data still showed a distinct warm core.
The extratropical transition (ET) process will likely be completed
within the next 48 h, around the time that Helene will likely pass
near or over the Azores. While this process occurs, little weakening
is forecast by the various dynamical models, but gradual weakening
should occur once ET is completed. By the end of the forecast
period, nearly all of the global models depict the cyclone being
absorbed into a larger mid-latitude low pressure system over the far
northeast Atlantic.
Helene continues to accelerate northward, and the initial motion is
010/20 kt. Almost no change has been made to the track forecast.
Helene is still forecast to move quickly northward to
north-northeastward between a mid-level ridge to its east and a
sharp mid-latitude trough to its west. A northeastward turn should
occur over the weekend as Helene reaches the northern extent of the
ridge and becomes embedded within the mid-latitude westerlies. The
official track forecast remains near the various consensus aids.
The government of Portugal has issued an orange wind warning for
the Azores, equivalent to a tropical storm warning. Tropical Storm
conditions with gusty winds and heavy rains are likely over the
weekend as Helene passes the islands, regardless of whether the
cyclone is a tropical storm or post-tropical.
Helene is expected to be a post-tropical cyclone when it approaches
Ireland and the United Kingdom in a few days. Interests in those
locations should consult products from their local meteorological
service for information about potential impacts from Helene. Local
forecasts and warnings for the UK can be found on the website of the
UK Met Office at https://www.metoffice.gov.uk/. Local forecasts and
warnings for Ireland can be found on the website of Met Eireann at
https://www.met.ie/.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0900Z 30.6N 36.0W 55 KT 65 MPH
12H 14/1800Z 33.4N 35.3W 55 KT 65 MPH
24H 15/0600Z 36.7N 33.8W 55 KT 65 MPH
36H 15/1800Z 39.3N 30.8W 55 KT 65 MPH
48H 16/0600Z 41.3N 26.9W 50 KT 60 MPH...POST-TROPTRATROP
72H 17/0600Z 45.5N 17.7W 50 KT 60 MPH...POST-TROPTRATROP
96H 18/0600Z 51.5N 8.0W 45 KT 50 MPH...POST-TROPTRATROP
120H 19/0600Z...DISSIPATED
$$
Forecaster Zelinsky
207
WTNT44 KNHC 140832
TCDAT4
Tropical Depression Isaac Discussion Number 27
NWS National Hurricane Center Miami FL AL092018
500 AM AST Fri Sep 14 2018
Northwesterly shear continues to take a toll on Isaac. Although the
system is still producing areas of deep convection, an ASCAT
overpass that arrived shortly after the release of the previous
advisory, indicated that the circulation had become even less
defined. The ASCAT data also showed that the winds are below
tropical storm strength, therefore the initial intensity has been
reduced to 30 kt.
Moderate to strong northwesterly shear and dry mid-level air are
likely to cause additional weakening, and Isaac is forecast to
degenerate into an open wave within the next several days, but this
could occur much sooner if the current trends continue.
When the system reaches the western Caribbean Sea the shear may
relax somewhat and moisture levels are expected to be higher. These
conditions could allow for regeneration of the system, but the ECMWF
and GFS both show Issac weakening and moving over the western
Caribbean as an open wave, and the NHC forecast follows this
scenario.
A low- to mid-level ridge over the southwestern Atlantic continues
to steer Isaac westward, and this general motion should continue
until dissipation occur. The new track forecast is once again
essentially an update of the previous advisory.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0900Z 15.0N 65.5W 30 KT 35 MPH
12H 14/1800Z 15.1N 67.3W 30 KT 35 MPH
24H 15/0600Z 15.2N 69.7W 30 KT 35 MPH
36H 15/1800Z 15.2N 72.0W 25 KT 30 MPH
48H 16/0600Z 15.4N 73.8W 25 KT 30 MPH
72H 17/0600Z 16.4N 77.7W 25 KT 30 MPH
96H 18/0600Z...DISSIPATED
$$
Forecaster Brown
373
WTNT45 KNHC 140833
TCDAT5
Tropical Storm Joyce Discussion Number 7
NWS National Hurricane Center Miami FL AL102018
500 AM AST Fri Sep 14 2018
There has been little change in the convective organization of
Joyce overnight. The system continues to produce bands of
convection over the northeastern portion of the circulation, but
the center remains exposed due to shear. The initial intensity is
held at 35 kt, in agreement with the earlier ASCAT data and recent
TAFB satellite estimate.
Joyce is still moving southwestward or 210 degrees at 7 kt. Joyce
is being steered in that direction around the larger circulation of
Helene to its east-southeast. Once Helene passes east-northeast of
Joyce later today, Joyce should turn eastward, then begin to
accelerate northeastward ahead of a mid-latitude trough over the
weekend. The global models have trended toward a faster
northeastward motion after 24 h, and the NHC track forecast has been
adjusted in that direction as well.
Southwesterly upper-level winds are forecast to increase over the
cyclone within the next day or two, which should prevent Joyce from
strengthening. The NHC forecast calls for little change in
wind speed over the next 36 h, then shows weakening as the shear
increases further. Both the GFS and ECMWF dissipate Joyce by day 4,
but the system could lose its deep convection and become
post-tropical before that time.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0900Z 32.1N 44.9W 35 KT 40 MPH
12H 14/1800Z 31.7N 44.7W 35 KT 40 MPH
24H 15/0600Z 31.8N 43.7W 35 KT 40 MPH
36H 15/1800Z 32.7N 42.5W 35 KT 40 MPH
48H 16/0600Z 34.0N 40.7W 30 KT 35 MPH
72H 17/0600Z 36.5N 34.5W 30 KT 35 MPH
96H 18/0600Z...DISSIPATED
$$
Forecaster Brown
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
email: KF5JRV@ICLOUD.COM
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