Post-Tropical Cyclone Nestor Discussion Number 10
NWS National Hurricane Center Miami FL AL162019
500 PM EDT Sat Oct 19 2019
The center of Post-Tropical Cyclone Nestor made landfall along on
St. Vincent Island, Florida, around 1730 UTC. Since then, that
center has moved inland over the Florida Panhandle between
Apalachicola and Tallahassee. However, during the past hour, a new
center appears to have formed farther west along a quasi-occluded
frontal boundary. The earlier 40-45 kt winds over water have moved
inland and weakened, and the initial intensity of 35 kt is based on
a recent wind report of a sustained wind of 33 kt at 5-meters
elevation from NOAA buoy 41008/Gray's Reef, Georgia.
The initial motion estimate is now northeastward or 055/20 kt.
Nestor is forecast to move northeastward over the next 36 hours or
so, followed by a turn toward the east once the cyclone reaches the
North Carolina Outer Banks. On days 2 an 3, upper-level support is
expected to weaken and lift out to the northeast, leaving a
weakening extratropical cyclone Nestor behind. The cyclone should
then dissipate or merge with another frontal system by 96 h offshore
of the U.S. east coast. The new official forecast track is similar
to the previous advisory, and lies close to the center of the
tightly packed model guidance envelope.
Some slight strengthening is expected on Sunday, mainly due to the
robust circulation moving out over the warm waters of the far
western Atlantic where less friction will affect the cyclone. The
official intensity foreast closely follows an average of the 1200
UTC GFS, UKMET, and ECMWF global model intensity forecasts.
This is the last advisory issued by the National Hurricane Center on
Nestor. Additional information on this system can be found in High
Seas Forecasts issued by the National Weather Service...under AWIPS
header NFDHSFAT1 and WMO header FZNT01 KWBC.
Key Messages:
1. Gale-force winds will gradually develop over the Atlantic waters
and along the coasts northeastern Florida and Georgia tonight, and
spread northward to the Carolinas on Sunday.
2. Isolated flash flooding is possible across the southeastern
United States into Sunday.
3. Wind and coastal flooding hazards along the U.S. East Coast will
be covered by non-tropical watches and warnings issued by local NWS
offices, since the system is expected to lose its tropical
characteristics after it moves inland along the Gulf Coast.
Tropical Storm Nestor Discussion Number 6
NWS National Hurricane Center Miami FL AL162019
400 PM CDT Fri Oct 18 2019
Nestor's structure has evolved quite a bit today. Since the release
of the previous advisory, the center has become better defined based
on data from aircraft, satellite, and surface observations, and on
that basis, the system was classified as a tropical cyclone around
1800 UTC. Since that time, the center has become more separated from
the area of deep convection to the east, consistent with 30-40 kt of
deep-layer westerly shear analyzed by the SHIPS model and UW-CIMSS.
The initial intensity remains 50 kt based on aircraft data and
earlier ASCAT data.
The mid/upper-level trough seen in water vapor imagery over
southeastern Louisiana is beginning to impinge on Nestor, and the
cloud pattern has become more lopsided. It would not be surprising
to see Nestor take on a more subtropical appearance overnight, as
the GFS and ECMWF show the upper trough becoming superimposed on the
low-level circulation, with the pressure continuing to deepen and
some increase in the peak winds noted in both those models. This is
reflected in the 12-h intensity forecast of 55 kt. After that time,
the upper-level pattern becomes less favorable and Nestor should
weaken while it moves inland over the southeastern United States
and becomes post-tropical. Gale-force winds are shown over the
western Atlantic waters, but are not expected over land areas from
24 h onward. The global models show Nestor's circulation dissipating
by 96 hours, and that is reflected in the NHC forecast.
The initial motion estimate is 050/19, but remains somewhat
uncertain given the recent formation of a better defined center.
The track forecast reasoning remains unchanged, with Nestor
expected to move quickly northeastward ahead of the approaching
upper trough and moving inland over the Florida Panhandle early
Saturday. The circulation center will move across the southeastern
United States before moving back offshore after 48 hours with a
slower east-northeastward to eastward motion shown late in the
period before dissipation. The new NHC track forecast lies a little
to the right of the previous and is close to the middle of the
guidance envelope. It should be noted that dangerous storm surge
and tropical storm force winds will occur along a large portion of
the Gulf Coast well east of the track of Nestor's center.
Key Messages:
1. There is a danger of life-threatening storm surge inundation of
up to 5 feet above ground level beginning this evening along the
Florida Gulf Coast from Indian Pass to Clearwater Beach, where a
Storm Surge Warning is in effect. Residents in these areas should
follow advice given by local officials.
2. Tropical storm force winds are likely later today and tonight
along portions of the Florida Gulf Coast, where tropical storm
warnings are in effect. Regardless of the exact track and intensity
of the system, these winds will cover a large area, especially east
of the center.
3. Isolated flash flooding is possible along the central and eastern
Gulf Coast and Southeast United States coast from late tonight
through Sunday.
4. Wind and coastal flooding hazards along the U.S. East Coast will
be covered by non-tropical watches and warnings issued by local NWS
offices, since the system is expected to lose its tropical
characteristics after it moves inland along the Gulf Coast.
Potential Tropical Cyclone Sixteen Discussion Number 5
NWS National Hurricane Center Miami FL AL162019
1000 AM CDT Fri Oct 18 2019
The satellite presentation of the system features an area of very
deep convection with cloud tops colder than -80C within the eastern
part of a rather broad and elongated surface circulation seen in
visible satellite imagery and data from an Air Force Reserve
Hurricane Hunter aircraft. A NOAA Hurricane Hunter aircraft found
flight-level winds as high as 72 kt and SFMR winds of 45-50 kt
southeast of the ill-defined center, and based on these data the
initial intensity is set to 50 kt. The NOAA aircraft also measured a
pressure of around 1001 mb. While the cyclone has deepened, the
circulation is still quite elongated and not well defined, so the
system is maintained as a Potential Tropical Cyclone for now.
The global models continue to indicate that the circulation will
consolidate and the system will strengthen some during the next 12
hours or so, as the low-level circulation will be overtaken by an
upper-level trough currently situated over southwest Louisiana. The
system is still expected to become a tropical or subtropical storm
later today, with the exact phase dependent on the timing of the
circulation improving and the interaction with the upper trough.
Once the system moves inland, it should become extratropical by 36
hours and slowly weaken once it moves offshore of the Carolinas by
72-96 hours before dissipating by day 5. The new NHC intensity
forecast is adjusted upward from the previous one through 24 hours
based on the initial intensity and allows for the possibility of at
least some additional strengthening later today.
The initial motion is a somewhat uncertain 055/19 given the lack of
a well-defined center. The track model guidance remains in good
agreement on the system moving quickly northeastward toward the
northeastern Gulf Coast during the next 24 hours as it interacts
with the upper trough. After moving inland, a northeastward motion
is forecast to continue until after 48 hours, when an east-
northeastward motion is expected, which will take the circulation
offshore over the Atlantic by 72 hours. The new NHC track forecast
is similar to, but a bit to the south of the previous one and is
close to the various track consensus aids.
Regardless of the exact evolution of the system, portions of the
northeastern coast of the Gulf of Mexico will experience strong
winds, locally heavy rains, and storm surge later today and
Saturday. Similar impacts are expected across portions of the
Atlantic coast of the southeastern United States Saturday and
Sunday.
Key Messages:
1. There is a danger of life-threatening storm surge inundation of
up to 5 feet above ground level beginning later today along the
Florida Gulf Coast from Indian Pass to Clearwater Beach, where a
Storm Surge Warning is in effect. Residents in these areas should
follow advice given by local officials.
2. Tropical storm force winds are likely later today and tonight
along portions of the central and eastern Gulf Coast, where tropical
storm warnings are in effect. Regardless of the exact track and
intensity of the system, these winds will cover a large area,
especially east of the center.
3. Isolated flash flooding is possible along the central and
eastern Gulf Coast and the southeast United States coast through
Saturday night.
4. Wind and coastal flooding hazards along the U.S. East Coast will
be covered by non-tropical watches and warnings issued by local NWS
offices, since the system is expected to lose any tropical
characteristics after it moves inland along the Gulf Coast.
Potential Tropical Cyclone Sixteen Discussion Number 1
NWS National Hurricane Center Miami FL AL162019
1000 AM CDT Thu Oct 17 2019
A complicated weather situation is evolving in the Gulf of Mexico.
The circulation associated with the tropical disturbance over the
southwestern Gulf of Mexico is getting better defined, and the
associated convection is getting better organized. However, a
strong mid- to upper-level trough is moving eastward across
southern Texas and northern Mexico, and a frontal system is present
over the northern and northwestern Gulf of Mexico. The ECMWF and
GFS models suggest that the trough will spawn a low along the
front, with the tropical disturbance merging with that low. On the
other hand, the UKMET suggests the tropical disturbance will become
the primary low pressure system. Either way, it is likely that a
low pressure area with gale-force winds and at least some tropical
cyclone characteristics will move northeastward and affect
portions of the northern Gulf coast during the next 36-48 h. Based
on this, advisories are initiated on Potential Tropical cyclone
Sixteen, and coastal tropical cyclone and storm surge
watches/warnings are being issued.
The system should track generally northeastward in the southern
portion of the mid-latitude westerlies, and the track model
guidance is in reasonably good agreement through 96 h. The forecast
track lies a little to the south of the model consensus, as the
UKMET has a somewhat more southerly track. The forecast track
brings the system across the southeastern United States between
48-72 h, and then has it moving into the Atlantic east of the
mid-Atlantic States.
Gradual strengthening is expected as strong upper-level
divergence caused by the trough partly prevails over strong
vertical shear. Thus, the intensity forecast calls for gradual
strengthening along the lines of that in the global models. It is
unlikely, though, that the system will develop into a classical
tropical cyclone. The system is expected to be fully extratropical
by 48 h, with gradual weakening expected after that time.
Regardless of the exact evolution of this weather system, portions
of the northern coast of the Gulf of Mexico will experience strong
winds, locally heavy rains, and storm surge Friday and Saturday.
Similar impacts are expected across portions of the Atlantic coast
of the southeastern United States Saturday and Sunday.
KEY MESSAGES:
1. Dangerous storm surge inundation of up to 5 feet above ground
level is possible along the Florida Gulf Coast from Indian Pass to
Clearwater, where a Storm Surge Watch is in effect. Residents in
these areas should follow advice given by local officials.
2. Tropical storm force winds are likely along portions of the
north-central and northeastern Gulf Coast where tropical storm
watches and warnings are in effect. Regardless of the exact track
and intensity of the system, these winds will cover a large area,
especially east of the center, and begin well in advance of the
arrival of the center.
3. Wind and coastal flooding hazards along the U.S. East Coast will
be covered by non-tropical watches and warnings issued by local NWS
offices, since the system is expected to lose any tropical
characteristics after it moves inland along the Gulf Coast.
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