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Tropical Storm Selma Discussion Number   2
NWS National Hurricane Center Miami FL       EP202017
1000 AM CDT Fri Oct 27 2017

Selma is a sheared tropical cyclone. Early morning visible
satellite images and recent microwave imagery show that the center
is located near the northeastern edge of a small, but persistent
cluster of deep convection.  The latest subjective Dvorak intensity
estimates are still below tropical storm strength, but the initial
intensity remains at 35 kt, in agreement with the earlier
scatterometer data.

Recent satellite and microwave fixes indicate that Selma is moving
northwestward at about 4 kt.  A weak ridge to the north of the
tropical cyclone is forecast to weaken today as a large mid-latitude
trough moves into the Gulf of Mexico.  This pattern should cause
Selma to turn northward toward the Pacific coast of Central America
tonight and early Saturday.  However, there is a large spread in the
guidance regarding the sharpness of the turn.  The UKMET shows an
immediate northward or northeastward motion and is along the right
side of the guidance envelope.  On the opposite side of the envelope
are the GFS, HWRF, and HMON, which depict a longer north-
northwestward motion and bring Selma inland near western Guatemala.
The NHC forecast is closest to the ECMWF and HFIP corrected
consensus models, which are a little to the right of the multi-model
consensus.   Given the large uncertainty in the track forecast, the
government of Guatemala has issued a tropical storm watch for the
entire Pacific coast of Guatemala.

The shear over Selma appears to be a little stronger than initially
expected, and the SHIPS guidance does not show any decrease in this
shear during the next day or so.  As a result, only slight
strengthening is indicted before landfall, and the NHC forecast is
close to the various consensus models.  Since the system is small,
it is expected to weaken and dissipate very quickly after it moves
inland over the high terrain of Central America.

It should be noted that the primary threat associated with Selma
is heavy rainfall, with totals possibly as high as 10 inches
over portions of El Salvador and Guatemala.  This rainfall could
cause life-threatening flash floods and mudslides.


FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 11.1N  89.5W   35 KT  40 MPH
 12H  28/0000Z 11.8N  89.9W   40 KT  45 MPH
 24H  28/1200Z 13.0N  90.0W   40 KT  45 MPH
 36H  29/0000Z 14.2N  89.8W   35 KT  40 MPH...INLAND
 48H  29/1200Z...DISSIPATED

$$
Forecaster Brown

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