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Tropical Storm ULIKA Forecast Discussion

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WTPZ44 KNHC 281444

800 AM PDT WED SEP 28 2016

Ulika was maintaining a small central dense overcast (CDO), with the
center well embedded within this convective mass overnight.  Since
then, the cloud pattern has undergone considerable degradation.  The
CDO has become much less distinct, to the point that it has no
longer become discernible.  The deep convection in the former CDO
has also decreased in coverage and cloud top temperatures have
warmed substantially.  TAFB and SAB provided a satellite
classifications of T4.0 and T2.5 at 1200 UTC, respectively.  Since
that time, the cyclone's cloud pattern has further degraded, and the
initial intensity is lowered to a possibly generous 60 kt.

Ulika's environment already appears to have become much less
favorable.  West-southwesterly to southwesterly shear is only likely
to increase as the cyclone gains latitude during the next couple of
days.  In fact, the SHIPS model output indicates more than 30 kt of
shear by 36 hours.  This, combined with a marginally moist
environment and an increasingly convergent flow aloft, means that
steady weakening is most likely.  Global models show Ulika being
sheared apart in about 2 days, with the mid-level center racing
northeastward away from the low-level center.  Rapid weakening
should occur by then, if it has not begun already, and remnant low
status is forecast in 72 hours.  The new intensity forecast is
lowered relative to the previous one, and is near or below the
multi-model consensus.

The initial motion is 030/06.  Ulika should turn northward soon,
as it rotates around a nearly stationary mid-tropospheric low seen
in water vapor imagery around 17N 143W.  Once the system decouples
fully, the shallower cyclone's motion will be governed by the
low-level trade wind flow and turn westward with an increase in
forward speed.  The new track forecast is a little to the right of
the previous one through 24 hours and then is very similar, with
the new forecast close to the multi-model consensus.


INIT  28/1500Z 14.5N 138.7W   60 KT  70 MPH
 12H  29/0000Z 15.3N 138.6W   55 KT  65 MPH
 24H  29/1200Z 16.0N 139.2W   50 KT  60 MPH
 36H  30/0000Z 16.7N 140.1W   45 KT  50 MPH
 48H  30/1200Z 17.3N 141.2W   35 KT  40 MPH
 72H  01/1200Z 17.5N 144.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 17.5N 148.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/1200Z...DISSIPATED

Forecaster Kimberlain