WTPZ42 KNHC 272032
TROPICAL STORM FRANK DISCUSSION NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL EP072016
200 PM PDT WED JUL 27 2016
Frank has continued its weakening trend with only a small area of
convection now displaced to the northwest of the low-level center.
Although subjective and objective satellite intensity estimates
support an intensity of about 60 kt, the initial intensity has been
lowered to 50 kt based on a partial ASCAT-B scatterometer pass
that showed winds of only about 40 kt in the eastern semicircle.
Even though the western half of the cyclone was not sampled, it is
assumed that some stronger winds exist in that part of the
circulation, but not as strong as the satellite estimates due to the
cooler waters creating a more stable boundary layer.
The initial motion estimate is now 295/09 kt. Frank should move
west-northwestward for the next 24 hours or so before turning
westward by 36 hours after the cyclone degenerates into a shallow
remnant low, which will be steered by the low-level easterly trade
wind flow. The new NHC model guidance is in good agreement on this
track scenario, although there is significant cross-track spread in
the models after 48 hours. The official forecast track is similar
to the previous advisory track and lies a little south of the
consensus track model TVCN.
Microwave imagery indicates that Frank's circulation has a
northwestward tilt due to some southeasterly mid-level wind shear.
The cyclone is also moving over sub-24C SSTs at this time, and
cooler waters lie ahead of Frank. The combination of increasing
shear, decreasing water temperatures, and a drier and more stable
airmass should result in rapid weakening during the next 24 hours.
Therefore, Frank is forecast to degenerate into a remnant low on
Thursday and dissipate on Saturday. The official intensity forecast
follows the intensity consensus model IVCN.
FORECAST POSITIONS AND MAX WINDS
INIT 27/2100Z 23.1N 121.8W 50 KT 60 MPH
12H 28/0600Z 23.8N 122.9W 40 KT 45 MPH
24H 28/1800Z 24.5N 124.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 29/0600Z 24.9N 125.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 29/1800Z 24.9N 126.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 30/1800Z 24.4N 128.0W 15 KT 15 MPH...POST-TROP/REMNT LOW