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Tropical Storm ALETTA


ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Storm Aletta Discussion Number  18
NWS National Hurricane Center Miami FL       EP022018
900 PM MDT Sat Jun 09 2018

Aletta's downfall has been remarkable.  All associated deep
convection has dissipated due to 25 kt of southerly shear and
marginally warm sea surface temperatures, leaving a swirl of low-
to mid-level clouds.  Dvorak estimates are falling as fast as they
can based on rules, and the advisory intensity is being set at 50
kt.  The latest SATCON numbers support this estimate.

Aletta has been losing latitude through the day, moving
west-southwestward since this morning.  Recent satellite images
seem to suggest that the cyclone is now moving westward, and the
motion estimate is 270/6 kt.  The dynamical and simpler Trajectory
and Beta Models (TAB) have been insisting that Aletta will turn
generally northwestward, but that obviously hasn't happened.  The
models seem to be assuming that Aletta is still producing
convection, with the deeper modeled vortex being steered toward the
northwest.  With no deep convection, the shallow circulation is
likely to continue generally westward or south of due west, and the
NHC forecast is along the southern edge of the guidance, roughly
between the ECMWF model and the skill-baseline Trajectory-CLIPER
(TCLP) model.

The new NHC intensity forecast now makes Aletta a remnant low in 36
hours, but if deep convection doesn't redevelop, that transition
will occur on Sunday.  Fast weakening is expected to continue, and
the official forecast closely follows the HCCA model and the
intensity consensus during the first 24-36 hours.  After that, the
remnant low's winds are based on the GFS and ECMWF forecast wind
fields.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 15.9N 114.3W   50 KT  60 MPH
 12H  10/1200Z 15.9N 115.2W   35 KT  40 MPH
 24H  11/0000Z 15.9N 116.4W   30 KT  35 MPH
 36H  11/1200Z 15.8N 117.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  12/0000Z 15.8N 118.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  13/0000Z 15.8N 120.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  14/0000Z 15.5N 121.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  15/0000Z 15.0N 121.5W   15 KT  15 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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