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Tropical Storm Aletta Discussion Number  20
NWS National Hurricane Center Miami FL       EP022018
800 AM PDT Sun Jun 10 2018

Shortly after 0600Z, a strong burst of deep convection, containing
very cold cloud top temperatures of -90C and significant lightning
activity, developed northwest of the previously exposed low-level
circulation center. The center has since made a jog toward the
northwest closer to the strongest convection. The initial intensity
has been decreased to 40 kt, based on average of TAFB current
intensity (CI) and the current T-number estimates. Although the
general trend for the next 24 h or so should be a gradual erosion of
the deep convection due to the entrainment of drier and more stable
air and the cyclone moving over SSTs less than 26C. However, there
will likely be intermittent bursts of convection that will slow the
weakening rate and maintain Aletta as a tropical cyclone. By 36 h
and beyond, increasing southwesterly vertical wind shear of 15-20
kt, coupled with the aforementioned stabilizing environment, should
cause all convection to dissipate, resulting in Aletta becoming a
shallow remnant low pressure system. The new NHC intensity forecast
is similar to the previous advisory, and closely follows the HCCA
and IVCN consensus intensity models.

Despite the recent northwestward jog, the average motion over the
last 36 h yields a motion of 280/05 kt, similar to the previous
advisory motion.  Aletta is forecast by most of the model guidance
to move westward to west-northwestward, or around 280/05 kt for the
next 24 h or so. After that, a weak low- to mid-level ridge to the
north of the cyclone is expected to build southward slightly,
forcing the weak and shallow cyclone toward the west-southwest. By
days 4 and 5, the system could stall as it comes under the
increasing influence of strengthening Tropical Storm Bud, currently
located about 700 nmi to the east-southeast. The official forecast
track is similar to the previous advisory and is in the middle of
the track model guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 16.5N 115.1W   40 KT  45 MPH
 12H  11/0000Z 16.6N 116.0W   35 KT  40 MPH
 24H  11/1200Z 16.7N 117.2W   30 KT  35 MPH
 36H  12/0000Z 16.6N 118.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  12/1200Z 16.4N 119.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  13/1200Z 16.2N 120.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  14/1200Z 16.0N 120.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  15/1200Z 15.8N 121.0W   15 KT  15 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart

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