POTENTIAL TROPICAL CYCLONE NINE
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<span-size:10.5pt;font-family:"Courier New";color:black">WTNT44 KNHC 130858
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<span-size:10.5pt;font-family:"Courier New";color:black">Potential Tropical Cyclone Nine Discussion Number 3
<span-size:10.5pt;font-family:"Courier New";color:black">NWS National Hurricane Center Miami FL AL092019
<span-size:10.5pt;font-family:"Courier New";color:black">500 AM EDT Fri Sep 13 2019
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<span-size:10.5pt;font-family:"Courier New";color:black">Satellite imagery and surface observations indicate that the
<span-size:10.5pt;font-family:"Courier New";color:black">tropical disturbance is currently comprised of a trough elongated
<span-size:10.5pt;font-family:"Courier New";color:black">from west-southwest to east-northeast, with a vorticity center near
<span-size:10.5pt;font-family:"Courier New";color:black">a loosely curved convective band at the eastern end of the trough.
<span-size:10.5pt;font-family:"Courier New";color:black">While the system has become a little better organized since the
<span-size:10.5pt;font-family:"Courier New";color:black">last advisory, it does not yet have a well-defined circulation
<span-size:10.5pt;font-family:"Courier New";color:black">center. The initial intensity remains 25 kt based on satellite
<span-size:10.5pt;font-family:"Courier New";color:black">intensity estimates and earlier scatterometer data.
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<span-size:10.5pt;font-family:"Courier New";color:black">The disturbance is now moving a little faster, with the initial
<span-size:10.5pt;font-family:"Courier New";color:black">motion of 315/5. The system is to the south of a low- to mid-level
<span-size:10.5pt;font-family:"Courier New";color:black">ridge over the southeastern United States, and it is to the east of
<span-size:10.5pt;font-family:"Courier New";color:black">a mid- to upper-level low over the central Gulf of Mexico. The
<span-size:10.5pt;font-family:"Courier New";color:black">large-scale models forecast the ridge to shift eastward into the
<span-size:10.5pt;font-family:"Courier New";color:black">Atlantic during the next 24-48 h, with a weakness developing near
<span-size:10.5pt;font-family:"Courier New";color:black">the southeastern coast of the United States and the east coast of
<span-size:10.5pt;font-family:"Courier New";color:black">the Florida peninsula. The track guidance indicates that the
<span-size:10.5pt;font-family:"Courier New";color:black">disturbance will move generally northwestward for 48 h or so,
<span-size:10.5pt;font-family:"Courier New";color:black">followed by a turn to the north and eventually to the northeast as
<span-size:10.5pt;font-family:"Courier New";color:black">the system moves through the weakness in the ridge. There is some
<span-size:10.5pt;font-family:"Courier New";color:black">spread in the guidance, with the GFS model taking a weaker system
<span-size:10.5pt;font-family:"Courier New";color:black">into the Florida peninsula while the UKMET and ECMWF models show a
<span-size:10.5pt;font-family:"Courier New";color:black">stronger cyclone farther offshore. Overall, there has been an
<span-size:10.5pt;font-family:"Courier New";color:black">eastward shift of the guidance since the previous advisory,
<span-size:10.5pt;font-family:"Courier New";color:black">especially after 72 h. The new forecast track is thus also nudged
<span-size:10.5pt;font-family:"Courier New";color:black">a little to the east and now calls for the system to spend less
<span-size:10.5pt;font-family:"Courier New";color:black">time over the Florida peninsula than previously forecast. The new
<span-size:10.5pt;font-family:"Courier New";color:black">forecast track is to the left of the center of the guidance
<span-size:10.5pt;font-family:"Courier New";color:black">envelope and the consensus models, and additional adjustments may
<span-size:10.5pt;font-family:"Courier New";color:black">be necessary once the circulation center becomes better defined.
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<span-size:10.5pt;font-family:"Courier New";color:black">The disturbance is currently in an environment of moderate
<span-size:10.5pt;font-family:"Courier New";color:black">southwesterly shear and upper-level divergence caused by the
<span-size:10.5pt;font-family:"Courier New";color:black">upper-level low and a shortwave trough extending from the low
<span-size:10.5pt;font-family:"Courier New";color:black">eastward to the southeastern Bahamas. The shear should gradually
<span-size:10.5pt;font-family:"Courier New";color:black">diminish during the next couple of days, which should allow the
<span-size:10.5pt;font-family:"Courier New";color:black">disturbance to develop into a tropical cyclone and intensify. The
<span-size:10.5pt;font-family:"Courier New";color:black">large-scale models forecast the shear to increase after 72 h as a
<span-size:10.5pt;font-family:"Courier New";color:black">mid-latitude westerly trough moves through the southeastern United
<span-size:10.5pt;font-family:"Courier New";color:black">States and approaches the system. The new intensity forecast is
<span-size:10.5pt;font-family:"Courier New";color:black">similar to the previous forecast through 72 h, then it is stronger
<span-size:10.5pt;font-family:"Courier New";color:black">than the previous forecast due to the forecast track keeping the
<span-size:10.5pt;font-family:"Courier New";color:black">system more over water.
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<span-size:10.5pt;font-family:"Courier New";color:black">Key Messages:
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<span-size:10.5pt;font-family:"Courier New";color:black">1. The system is expected to become a tropical storm and bring
<span-size:10.5pt;font-family:"Courier New";color:black">tropical-storm-force winds and heavy rainfall to portions of the
<span-size:10.5pt;font-family:"Courier New";color:black">northwestern Bahamas today and Saturday. Significant storm surge is
<span-size:10.5pt;font-family:"Courier New";color:black">not expected in the northwest Bahamas from this system. Residents
<span-size:10.5pt;font-family:"Courier New";color:black">there should follow any advice given by local officials.
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<span-size:10.5pt;font-family:"Courier New";color:black">2. The system could bring tropical-storm-force winds to portions of
<span-size:10.5pt;font-family:"Courier New";color:black">the Florida east coast over the weekend. Residents there should
<span-size:10.5pt;font-family:"Courier New";color:black">monitor the progress of this system and follow any advice given by
<span-size:10.5pt;font-family:"Courier New";color:black">local officials.
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<span-size:10.5pt;font-family:"Courier New";color:black">3. Heavy rainfall is possible from Potential Tropical Cyclone Nine
<span-size:10.5pt;font-family:"Courier New";color:black">across portions of eastern Florida into this weekend, which could
<span-size:10.5pt;font-family:"Courier New";color:black">produce flash flooding. There is greater uncertainty than usual in
<span-size:10.5pt;font-family:"Courier New";color:black">heavy rainfall prospects farther north across the Carolinas.
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<span-size:10.5pt;font-family:"Courier New";color:black">4. Note that forecast uncertainty for these disturbances is
<span-size:10.5pt;font-family:"Courier New";color:black">generally larger than for tropical cyclones, especially beyond 48-72
<span-size:10.5pt;font-family:"Courier New";color:black">hours.
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<span-size:10.5pt;font-family:"Courier New";color:black">FORECAST POSITIONS AND MAX WINDS
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<span-size:10.5pt;font-family:"Courier New";color:black">INIT 13/0900Z 24.6N 75.2W 25 KT 30 MPH...POTENTIAL TROP CYCLONE
<span-size:10.5pt;font-family:"Courier New";color:black">12H 13/1800Z 25.1N 76.2W 30 KT 35 MPH...TROPICAL DEPRESSION
<span-size:10.5pt;font-family:"Courier New";color:black">24H 14/0600Z 26.0N 77.8W 35 KT 40 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">36H 14/1800Z 27.0N 79.3W 40 KT 45 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">48H 15/0600Z 28.2N 80.4W 45 KT 50 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">72H 16/0600Z 30.3N 81.1W 50 KT 60 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">96H 17/0600Z 31.0N 80.5W 50 KT 60 MPH
<span-size:10.5pt;font-family:"Courier New";color:black">120H 18/0600Z 32.0N 78.5W 55 KT 65 MPH
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<span-size:10.5pt;font-family:"Courier New";color:black">$$
<span-size:10.5pt;font-family:"Courier New";color:black">Forecaster Beven