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Tropical Storm Carlotta Discussion Number   7
NWS National Hurricane Center Miami FL       EP042018
400 AM CDT Sat Jun 16 2018

A surprise during the midnight shift. Tiny Carlotta is stronger and
is not moving as anticipated.

Satellite images indicate that the cloud pattern is better organized
with a well defined cyclonically curved band wrapping around a
small area of convection near the center. T-numbers from TAFB,
SAB and UW/CIMSS are unanimously 3.0 on the Dvorak scale. On this
basis, the initial intensity has been adjusted upward to 45 kt.
ASCAT missed it this time.  Depending how long Carlotta remains
nearly stationary over water, some additional strengthening could
occur. Once it moves inland, if at all, rapid weakening is
anticipated.

The center is difficult to locate, but it has to be very
near the given position, since the cyclone has been meandering
during the past several hours. The track forecast is highly
uncertain and I mean highly uncertain. Deterministic runs of the
global models have failed miserably in forecasting the track of
Carlotta, at least in the very short term. In the earlier 00 UTC
guidance, most of the NHC trackers moved the cyclone northeastward.
However, at 06 UTC, most of the available trackers changed and now
move the cyclone toward the west-northwest along the coast of
Mexico. This shift in track also includes HCCA and HWRF models. The
GFS, ECMWF and UK models quickly dissipate Carlotta, so most of the
consensus are not available at 06 UTC.  Given the uncertainty in the
forecast, the NHC forecast calls for little motion in the next 12
hours, and then a gradual northward track toward the coast within
the warning area. Although this is a change from the previous NHC
forecast, it is not necessary a change in the warnings.

Despite the changes in track tonight, the impacts have not changed.
The main threat from Carlotta continues to be the heavy rainfall and
the associated risk of life-threatening flash floods and mudslides
over the southern parts of Guerrero and Oaxaca.  The significant
rainfall threat is enhanced by moist southwesterly flow intersecting
the southern Sierra Madre mountains.  For details, please see
products issued by your local weather office.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 15.8N  99.5W   45 KT  50 MPH
 12H  16/1800Z 16.0N  99.5W   45 KT  50 MPH
 24H  17/0600Z 16.7N  99.5W   40 KT  45 MPH
 36H  17/1800Z 17.5N  99.5W   20 KT  25 MPH...POST-TROP/INLAND
 48H  18/0600Z...DISSIPATED

$$
Forecaster Avila

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