|#892633 (Received by flhurricane at: 11:10 AM 19.Jun.2017)|
Potential Tropical Cyclone Two Discussion Number 4
NWS National Hurricane Center Miami FL AL022017
1100 AM AST Mon Jun 19 2017
The convective pattern of the disturbance has become better
organized this morning with a ragged band that wraps more than half
way around its center. The intensity is assessed at 35 kt based
upon the Dvorak 2.5 CI number from TAFB. These winds are likely
only occurring in the northern semicircle due to the very quick
translational velocity of the system.
Intensity model guidance is in good agreement that the
environmental conditions may allow for some slight intensification
in the next day or so with the system embedded within low vertical
shear and an atmosphere that is marginally moist and unstable.
Beginning in about 36 hours, however, the shear should go up to
either moderate (if the GFS is correct) or high (if the ECMWF is
correct) levels because of an approaching tropical upper-
tropospheric trough. Because of this increasing shear, all guidance
shows the system dissipating before 72 hr and so does the official
forecast. An alternative scenario - given that the disturbance has
tracked left, or equatorward, of the guidance thus far - is that
it could remain south of guidance and dissipate over Venezuela and
never reach the Caribbean Sea.
The quick motion also makes it ambiguous as to whether the system
has a closed, earth-relative circulation center. An Air Force
Hurricane Hunter plane is scheduled to investigate the system later
today to help in this determination. It is still anticipated that
the system will become a tropical storm, but it may be running out
of time if it interacts significantly with Venezuela.
The system is moving toward the west at a very rapid 22 kt due to
the fast low to mid-level tradewinds south of a strong Bermuda
high. It is likely that a rapid motion toward the west
or west-northwest will continue until dissipation. The official
track forecast is based upon the HCCA corrected consensus technique
and is slightly south compared with the previous advisory.
FORECAST POSITIONS AND MAX WINDS
INIT 19/1500Z 8.8N 56.8W 35 KT 40 MPH...POTENTIAL TROP CYCLONE
12H 20/0000Z 9.5N 59.7W 40 KT 45 MPH...TROPICAL CYCLONE
24H 20/1200Z 10.6N 63.1W 40 KT 45 MPH
36H 21/0000Z 11.7N 66.6W 35 KT 40 MPH
48H 21/1200Z 12.6N 70.6W 35 KT 40 MPH