[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 141457
TCDAT4

Hurricane Margot Discussion Number  29
NWS National Hurricane Center Miami FL       AL142023
Issued by the NWS Weather Prediction Center College Park MD
300 PM GMT Thu Sep 14 2023

The double-eyewall structure of Margot has changed this morning,
with the inner-eye almost completely dissipated, and the outer
eyewall has taken over as the dominant feature.  This is confirmed
by scatterometer data from ASCAT-B and a SAR pass around 9 UTC.  The
initial wind speed is set to 70 kt, a compromise between higher SAR
estimates and Dvorak values closer to 65 kt.  Note that the
hurricane- and storm-force wind radii have been changed/expanded
significantly due to the SAR/scatterometer data.

Margot has turned further to the right, or 030/5.  A blocking ridge
over the north-central Atlantic should force Margot to slow down
and execute a clockwise loop during the next few days.  After the
ridge shifts eastward, the hurricane could gain some latitude and
begin to move more to the northeast at the end of the forecast
period.  Model guidance is coming into better agreement on this
solution, although there is considerable spread at long range with
the GFS faster and more to the northeast than the ECMWF-based
guidance.  The new NHC forecast is shifted southward in the near
term with the GFS coming more into line with the other guidance,
and ends up in almost the same spot as the last forecast by day 5.

The hurricane should gradually weaken as the large system slows
down and upwells cooler water, along with Margot crossing over its
own path.  Additionally, there is plenty of mid-level dry air in
the surrounding environment that could be mixed in the core
eventually. The updated forecast is adjusted higher initially
because of the current intensity, but is blended back with the
previous forecast and consensus aids at longer term.  Margot could
become a post-tropical cyclone without deep convection early next
week, but it really depends on how it handles the more hostile
conditions.  Given how resilient this season's tropical cyclones
have been, it could be optimistic that Margot is post-tropical on
day 5.


FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 36.5N  39.8W   70 KT  80 MPH
 12H  15/0000Z 36.8N  39.3W   65 KT  75 MPH
 24H  15/1200Z 36.7N  38.9W   65 KT  75 MPH
 36H  16/0000Z 36.2N  38.8W   60 KT  70 MPH
 48H  16/1200Z 35.5N  39.5W   55 KT  65 MPH
 60H  17/0000Z 35.0N  41.0W   50 KT  60 MPH
 72H  17/1200Z 35.1N  42.3W   45 KT  50 MPH
 96H  18/1200Z 37.5N  43.3W   45 KT  50 MPH
120H  19/1200Z 40.0N  39.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Fracasso/Blake
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