565 
WTPZ45 KNHC 261438
TCDEP5

Tropical Storm Miriam Discussion Number   2
NWS National Hurricane Center Miami FL       EP152018
800 AM PDT Sun Aug 26 2018

Deep convection associated with the tropical cyclone has continued
to become better organized this morning, with a significant increase
in banding noted in conventional satellite imagery.  An earlier
AMSR2 microwave overpass also revealed the increase in banding, but
the low-level center was located near the northeastern portion of
the main convective mass.  A Dvorak satellite intensity estimate of
T2.5 (35 k) was the basis for the 1200 UTC synoptic intensity, but
with the continued increase in organization, the initial wind speed
for this advisory has been set to 40 kt.

Miriam is moving westward or 275/11 kt. The tropical storm should
remain on a general westward heading during the next few days while
it remains to the south of a deep-layer ridge.  The orientation of
the ridge may shift more west-southwestward within the next day or
so, which could steer the tropical storm on a track slightly south
of due west.  The bulk of the dynamical model guidance has shifted
southward, so the NHC forecast track has been adjusted accordingly
through the first 3 days.  After that time, a weakness in the
subtropical ridge between 140W-145W longitude is expected to cause
Miriam to turn northwestward, then north-northwestward by the end
of the forecast period.  The latter portion of the official forecast
is similar to the previous advisory and is in best agreement with
the HFIP corrected consensus model.

The environment ahead of Miriam is expected to remain favorable for
strengthening.  The tropical storm will be traversing SSTs of 27-28C
and within low vertical wind shear conditions.   The NHC intensity
forecast calls for steady intensification during the next few days
and is at the upper-end of the intensity guidance.  Although the
various rapid intensification prediction techniques are not
particularly bullish, perhaps due to the low initial intensity of
the cyclone, it would not be surprising if the tropical storm went
through a period of rapid intensification within the next couple of
days.  The NHC intensity forecast is closest to the more aggressive
HWRF and HMON dynamical models.


FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 13.2N 125.3W   40 KT  45 MPH
 12H  27/0000Z 13.3N 127.1W   50 KT  60 MPH
 24H  27/1200Z 13.5N 129.4W   60 KT  70 MPH
 36H  28/0000Z 13.5N 131.5W   70 KT  80 MPH
 48H  28/1200Z 13.5N 133.6W   80 KT  90 MPH
 72H  29/1200Z 13.5N 137.6W   85 KT 100 MPH
 96H  30/1200Z 14.9N 140.5W   90 KT 105 MPH
120H  31/1200Z 18.5N 142.0W   85 KT 100 MPH

$$
Forecaster Brown