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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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