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Tropical Storm FRANK Forecast Discussion


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000
WTPZ42 KNHC 250832
TCDEP2

TROPICAL STORM FRANK DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072016
300 AM MDT MON JUL 25 2016

Deep convection associated with Frank has diminished considerably
since Sunday.  Since the vertical shear over the storm is weak, the
likely cause for this decrease is the upwelling of cooler ocean
waters beneath the slow-moving cyclone.  The current intensity
estimate is reduced to 55 kt in accordance with a Dvorak estimate
from SAB, and this may be generous.  Since the storm is expected to
begin moving west-northwestward at a faster forward speed soon, it
should temporarily pass over a warmer ocean.  Thus some slight
restrengthening is forecast within the next 24 hours.  After that,
decreasing SSTs should induce gradual weakening.  Frank is likely
to be reduced to a remnant low pressure system in 4 days or so, and
this could occur sooner than that.  The official intensity forecast
is a blend of the latest SHIPS and LGEM guidance.

Frank had been quasi-stationary over the past several hours,
although recent images suggest a slightly north-of-west drift
at about 280/3 kt.  The mid-level subtropical ridge to the north of
the tropical cyclone collapsed, causing a very weak steering
current.  However, the global models predict that the ridge to the
north of Frank will rebuild over the next several days and this
should produce a west-northwestward motion with some acceleration.
Late in the forecast period, the shallow remnant low is likely to
move mostly westward in the low-level flow.  The official forecast
is a little faster than the previous one and close to the model
consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  25/0900Z 20.1N 113.2W   55 KT  65 MPH
 12H  25/1800Z 20.3N 114.0W   55 KT  65 MPH
 24H  26/0600Z 20.6N 115.3W   60 KT  70 MPH
 36H  26/1800Z 21.0N 117.0W   55 KT  65 MPH
 48H  27/0600Z 21.6N 118.7W   45 KT  50 MPH
 72H  28/0600Z 23.1N 122.2W   35 KT  40 MPH
 96H  29/0600Z 24.0N 125.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  30/0600Z 24.5N 128.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Pasch