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Tropical Depression Twelve-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP122019
500 AM HST Wed Sep 04 2019

A small well-defined low pressure system quickly developed late
yesterday and early this morning over the far western portion of the
eastern North Pacific. Beginning around 0600 UTC, a large increase
in convection was noted with the low, and convection has continued
to increase since then. AMSR-2 imagery at 1030 UTC showed that the
convection is fairly well organized in bands, enough to designate
the system as a tropical cyclone. Advisories have therefore been
initiated on Tropical Depression Twelve-E. The initial intensity of
the depression is 25 kt, based on ASCAT data from early this
morning.

The track forecast is based on a blend of the explicit low positions
in the GFS, ECMWF, and UKMET global models. All of these models
forecast that the depression will move generally westward for the
next 3 days, followed by a turn toward the west-northwest, steered
primarily by a low- to mid-level ridge located to the north of the
depression. There is a fair amount of difference in those models
regarding the speed at which the depression will move west, and this
appears to be the largest source of uncertainty in the forecast.
The confidence in the track forecast is quite low for this initial
advisory, but hopefully will increase with subsequent forecasts.

The depression appears to be located within an environment that will
support at least slow strengthening. In fact, the GFS, SHIPS and
ECMWF-based SHIPS models all call for strengthening at varying
rates. Strong shear to the north and northwest of the depression
could be a limiting factor in a few days, especially if the
depression moves farther north than currently expected. The NHC
forecast accordingly calls for slow strengthening through 96 h. More
intensity guidance will be available with the next advisory, and
users should keep in mind that large changes may be required to the
intensity forecast based on that guidance. Confidence in this
aspect of the forecast is also lower than usual.

This system has moved into the Central Pacific basin and subsequent
advisories will be issued by the Central Pacific Hurricane Center.
Products will continue to be available on the web at hurricanes.gov

FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 13.2N 140.5W   25 KT  30 MPH
 12H  05/0000Z 12.8N 141.8W   30 KT  35 MPH
 24H  05/1200Z 12.6N 143.1W   30 KT  35 MPH
 36H  06/0000Z 12.6N 144.2W   35 KT  40 MPH
 48H  06/1200Z 12.6N 145.4W   40 KT  45 MPH
 72H  07/1200Z 13.2N 148.8W   50 KT  60 MPH
 96H  08/1200Z 14.5N 154.0W   60 KT  70 MPH
120H  09/1200Z 16.0N 161.0W   60 KT  70 MPH

$$
Forecaster Zelinsky

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