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TROPICAL STORM CARLOS DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032015
1000 AM CDT MON JUN 15 2015

First-light visible satellite imagery indicates Carlos remains a
very small tropical cyclone. An earlier GCOM-AMSR microwave pass
also indicated the compact nature of the system, including a closed
5-10 nmi diameter eye. The consensus of satellite intensity
estimates is 55 kt, but we'll hold the initial intensity at 60 kt
pending the arrival of a United States Air Force Reserve hurricane
hunter aircraft.

The initial motion estimate is 290/05 kt.  Carlos is expected
to maintain a slow west-northwestward motion and move essentially
parallel to the south-central coast of Mexico for the next 24-36
hours. After that time, there is a distinct bifurcation in the model
guidance with how strong the mid-level ridge across northern Mexico
and Texas is forecast to be. The GFS, UKMET, NAVGEM, HWRF, and the
BAM models keep the ridge stronger and also weaken Carlos, resulting
in the cyclone moving westward at 48 hours and beyond. In contrast,
the ECMWF and GFDL models weaken the ridge and keep Carlos stronger,
and gradually move the cyclone northwestward and then northward near
the southwestern coast of Mexico during that time. Given that the
large low pressure system currently located over the central Gulf of
Mexico is forecast to move inland over Texas by 48 hours, which
should act to weaken the mid-level ridge to the north and northeast
of Carlos, the ECMWF-GFDL solution is preferred at this time. The
NHC official track forecast is essentially just an update of the
previous advisory, and lies close to a blend of the ECMWF, FSSE, and
GFDL forecast tracks. However, only a slight deviation to the right
of the forecast track would bring Carlos inland along the
southwestern coast of Mexico.

The very small size of Carlos makes the cyclone susceptible to small
fluctuations in the vertical wind shear. However, the general trend
in the GFS-based SHIPS intensity model is calling for the shear to
decrease to less than 5 kt by 48 hours and beyond, which should
allow for some strengthening to occur over 29C SSTs . Carlos is
expected to weaken into a depression by 72 hours due to
land interaction and an unfavorable thermodynamic environment,
becoming a remnant low by 96 hrs, and dissipating by 120 hrs. The
intensity forecast is similar to the previous advisory and closely
follows the LGEM model.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 17.0N 102.5W   60 KT  70 MPH
 12H  16/0000Z 17.3N 103.3W   60 KT  70 MPH
 24H  16/1200Z 17.8N 104.2W   65 KT  75 MPH
 36H  17/0000Z 18.4N 105.0W   60 KT  70 MPH
 48H  17/1200Z 19.4N 105.6W   50 KT  60 MPH
 72H  18/1200Z 21.2N 106.1W   30 KT  35 MPH
 96H  19/1200Z 22.8N 106.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  20/1200Z...DISSIPATED

$$
Forecaster Stewart

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