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Tropical Storm ULIKA Forecast Discussion


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000
WTPZ44 KNHC 272033
TCDEP4

TROPICAL STORM ULIKA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192016
200 PM PDT TUE SEP 27 2016

Ulika has become a little better organized during the past several
hours with the formation of a ragged central dense overcast in
visible imagery and the continued presence of an eye in GPM data
near 1530 UTC.  Satellite intensity estimates from TAFB and SAB are
55 kt and 45 kt respectively, and based on these data the initial
intensity is raised to 50 kt.

The initial motion is 045/4.  Ulika is currently being steered by a
mid- to upper-level low seen in water vapor imagery near 18N 143W.
The dynamical models forecast this feature to move westward to
northwestward during the next 48 hours or so.  This should allow
the subtropical ridge to rebuild east and north of Ulika, which in
turn should cause the tropical cyclone to turn northward and
northwestward.  After that time, Ulika should be steered more
westward by the low-level trade winds as it weakens.  The new
forecast track is similar to the previous track and lies near the
center of the track guidance envelope.

Ulika is currently experiencing 15-20 kt of northwesterly vertical
wind shear.  This shear should abate somewhat during the next 24
hours or so while the cyclone remains over warm sea surface
temperatures.  Based on these expected conditions, the intensity
forecast calls for continued slow strengthening. Subsequently, Ulika
is forecast to encounter stronger westerly shear which should
persist through the end of the forecast period.  All of the guidance
forecast weakening with dissipation near or just after 120 hours,
and the intensity forecast follows this scenario.  The new intensity
forecast is an update of the previous forecast with a slightly
higher peak intensity, and overall it is in best agreement with the
intensity consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 12.7N 139.6W   50 KT  60 MPH
 12H  28/0600Z 13.5N 139.3W   55 KT  65 MPH
 24H  28/1800Z 14.5N 139.0W   60 KT  70 MPH
 36H  29/0600Z 15.4N 139.0W   55 KT  65 MPH
 48H  29/1800Z 16.1N 139.7W   45 KT  50 MPH
 72H  30/1800Z 17.0N 142.0W   35 KT  40 MPH
 96H  01/1800Z 17.5N 145.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  02/1800Z 17.5N 149.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven