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TROPICAL STORM FRED DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015
500 PM AST TUE SEP 01 2015
Fred's weakening appears to have ceased for the moment. Deep
convection developed just north of the center since the previous
advisory and the overall organization of the tropical cyclone has
changed little during the day. A blend of the various Dvorak
T-numbers and the earlier ASCAT data support maintaining an initial
intensity of 45 kt. The intensity forecast reasoning remains
unchanged from the previous forecast. Fred will be moving into an
area of increasing southwesterly shear and a less conducive
thermodynamic environment. This should cause the tropical cyclone
to gradually weaken during the next several days, and Fred is
expected to become a tropical depression in about 36 hours and
degenerate to a remnant low in 2 to 3 days.
The initial motion estimate is 300/10 kt. Fred should continue
moving west-northwestward to the south of a deep-layer ridge over
the eastern Atlantic during the next 2 to 3 days. The global
models predict that the western portion of the ridge will weaken
after 72 hours when a trough deepens over the central Atlantic.
After this occurs, the remnant low should turn northwestward and
northward in the low-level southeasterly flow. The model guidance
has shifted significantly westward this cycle, with most of the
models showing a weaker Fred moving more westward. The NHC forecast
has been adjusted accordingly, however it lies to the north of the
model consensus after 36 hours to maintain some continuity from
the previous advisory.
FORECAST POSITIONS AND MAX WINDS
INIT 01/2100Z 18.8N 28.1W 45 KT 50 MPH
12H 02/0600Z 19.4N 29.4W 40 KT 45 MPH
24H 02/1800Z 20.0N 31.0W 35 KT 40 MPH
36H 03/0600Z 20.6N 32.5W 30 KT 35 MPH
48H 03/1800Z 21.3N 34.1W 30 KT 35 MPH
72H 04/1800Z 22.0N 37.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 05/1800Z 23.0N 40.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 06/1800Z 25.0N 42.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
$$
Forecaster Brown
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