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TROPICAL DEPRESSION TWENTY-E DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202015
400 PM CDT TUE OCT 20 2015

The convective pattern associated with Tropical Depression Twenty-E
is gradually becoming better organized, with a large band now
developing over the southeastern semicircle and a smaller band west
of the center.  In addition, while the circulation continues to be
elongated north-northeast to south-southwest, microwave imagery
suggests a small inner core is developing under the main convection.
A recent Rapidscat overpass shows gale-force winds over the Gulf of
Tehuantepec.  However, these winds appear to be more related to flow
from the Gulf of Mexico through the Isthmus of Tehuantepec than to
the tropical cyclone.  Thus, the initial intensity remains 30 kt in
agreement with a satellite intensity estimate from TAFB.

The initial motion is 265/3.  A mid-level ridge over the Gulf of
Mexico should steer the tropical cyclone west-southwestward to
westward for the next 24 hours or so.  After that time, the ridge is
forecast to move eastward, with the cyclone being steered between
the ridge and a deep-layer trough over the southwestern U. S. and
northwestern Mexico.  While there is some spread due to differences
in how the dynamical models forecast the ridge and trough to evolve,
the guidance is in good agreement that the cyclone should turn
northwestward by about 48 hours and northward after 72 hours, making
landfall in western Mexico between 72-96 hours. The new forecast
track is nudged a little to the east of the previous track between
48-72 hours, but at other times is little changed from the previous
track.  The new track lies close to the various consensus models.

The large-scale environment around the cyclone is forecast to be
quite conducive for intensification through about 72 hours, with
SSTs to above 30 deg C, a generally rich moisture supply in the
lower to middle troposphere, and light vertical shear.  The two main
limiting factors are whether the current inner core will develop
further, and whether the flow through the Isthmus of Tehuantepec
will entrain a tongue of drier low-level air into the cyclone. Based
on the premise that the positive factors will outweigh the
negatives, the intensity forecast is unchanged from that of the
previous advisory and calls for the cyclone to become a tropical
storm in 12 hours and a hurricane before landfall in Mexico.  After
landfall, the cyclone should quickly weaken and dissipate over the
mountains of Mexico.

FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 13.2N  94.8W   30 KT  35 MPH
 12H  21/0600Z 12.9N  95.8W   35 KT  40 MPH
 24H  21/1800Z 12.9N  97.5W   45 KT  50 MPH
 36H  22/0600Z 13.4N  99.4W   55 KT  65 MPH
 48H  22/1800Z 14.5N 101.3W   70 KT  80 MPH
 72H  23/1800Z 17.5N 103.5W   85 KT 100 MPH
 96H  24/1800Z 21.5N 104.5W   45 KT  50 MPH...INLAND
120H  25/1800Z...DISSIPATED

$$
Forecaster Beven

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