[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 230855
TCDAT3

TROPICAL STORM LISA DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016
500 AM AST FRI SEP 23 2016

The center of Lisa has become fully exposed due to strong shear,
like so many Atlantic tropical cyclones in 2016.  Some convection
remains, although well away from the center, in the northern
semicircle.  The initial wind speed is reduced to 35 kt, which is on
the high side of the latest Dvorak estimates.  Very strong shear
should cause further weakening, along with marginal SSTS and
increasingly dry air aloft.  Deep convection will likely be
struggling in that environment within 24 hours, and the new forecast
has Lisa becoming a remnant low in 36 hours.  Most of the global
models now show Lisa decaying to a trough in 3 to 4 days before it
gets absorbed by a cold front, but either way it should be a weak
system by then.

Lisa continues moving northwestward at about 8 kt.  A track toward
the west-northwest or northwest is expected for the next couple of
days while the system moves around the subtropical ridge. Afterward
the post-tropical cyclone should turn northward as it gets caught up
in southerly flow ahead of Karl.  The guidance has shifted westward
on this cycle, possibly due to a weaker Lisa being steered more by
the low-level subtropical ridge.  Thus, the official forecast
is moved westward as well, near or just west of the model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  23/0900Z 21.8N  35.7W   35 KT  40 MPH
 12H  23/1800Z 22.7N  36.8W   30 KT  35 MPH
 24H  24/0600Z 23.6N  38.3W   30 KT  35 MPH
 36H  24/1800Z 24.6N  40.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  25/0600Z 26.1N  41.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  26/0600Z 30.5N  42.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  27/0600Z...DISSIPATED

$$
Forecaster Blake
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