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000
WTPZ42 KNHC 210243
TCDEP2

TROPICAL STORM LOWELL DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP122014
800 PM PDT WED AUG 20 2014

Microwave imagery shows that Lowell has formed a ragged eye with a
diameter of about 90 n mi, with conventional satellite imagery
continuing to show a complex of convective bands wrapped around the
eye.  Satellite intensity estimates from TAFB and SAB remain 55 kt,
and there was a recent CIMSS AMSU estimate of 64 kt.  The initial
intensity remains 55 kt, although this could be a little
conservative.  The cirrus outflow remains good to excellent in all
directions.

The initial motion is now 320/3.  Water vapor imagery shows a
mid/upper-level trough extending from a low over southern California
south-southwestward into the Pacific.  This trough has weakened the
subtropical ridge north of Lowell and left the cyclone in an area of
weak steering currents.  After 12 hours, the ridge is forecast to
re-build as the trough moves eastward.  This should allow Lowell to
move somewhat faster toward the northwest.  Later in the forecast
period, a weakening Lowell should turn west-northwestward as it
comes under the influence of a low-level ridge over the north
Pacific.  There is no significant change to the guidance since the
last advisory, so the new forecast track lies close to the previous
track and in the center of the guidance envelope.

A little strengthening is possible before Lowell crosses the 26C
isotherm in about 24 hours, and there is a chance Lowell could
briefly become a hurricane during this time.  Thereafter, the
cyclone should gradually weaken as it encounters colder water along
the forecast track.  The new intensity forecast is an update of the
previous forecast, and it is in best agreement with the LGEM model.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 19.6N 121.6W   55 KT  65 MPH
 12H  21/1200Z 20.0N 122.0W   60 KT  70 MPH
 24H  22/0000Z 21.0N 122.9W   60 KT  70 MPH
 36H  22/1200Z 22.0N 124.0W   55 KT  65 MPH
 48H  23/0000Z 23.2N 125.4W   45 KT  50 MPH
 72H  24/0000Z 25.0N 128.0W   35 KT  40 MPH
 96H  25/0000Z 26.5N 130.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  26/0000Z 28.0N 133.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven




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