[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 130854
TCDAT4

Hurricane Margot Discussion Number  24
NWS National Hurricane Center Miami FL       AL142023
900 AM GMT Wed Sep 13 2023

The eye of Margot has been obscured by clouds to varying degrees
overnight, but has begun to warm in the latest infrared satellite
images this morning. Recent AMSR2 microwave images reveal the
hurricane has a compact inner core, with a concentric outer ring of
convection that is broken to the northwest. Earlier scatterometer
data indicated a secondary wind maximum exists within this outer
band. The vortex is slightly tilted with height, as the mid-level
89-GHz eye lies to the southwest of the 37-GHz center. The
intensity for this advisory remains 75 kt based on consensus T4.5
Dvorak classifications from TAFB and SAB.

Margot has begun to slow down while moving northward (350/10 kt)
within the flow between a deep-layer ridge over the eastern Atlantic
and a narrow upper trough to its west. A general northward motion
should continue over the next day or so before the track forecast
becomes very challenging. Margot is forecast to become caught in
weak steering currents, with the global models showing a blocking
ridge developing to the north of the cyclone by late week into the
weekend. There are significant differences between the GFS and ECMWF
with regards to the strength and position of this ridge, which has
large implications in the longer-range track of Margot. Based on the
overall shift in the guidance suite this cycle, the latest NHC
forecast shows little net motion between 36-72 h as Margot meanders
over the central Atlantic. This is a fairly large departure from the
previous advisory, but better represents the latest consensus track
solutions. At days 4-5, most models (except for the ECMWF) show the
ridge sliding eastward, but overall track forecast confidence is
very low and larger future adjustments could be necessary.

It is possible that Margot is at or near its peak intensity. The
deep-layer shear is forecast to increase during the next 24 h, and
thereafter the coupled atmosphere-ocean models indicate the slow
motion of the storm is likely to result in upwelling of cooler
waters. In addition, the surrounding environment is expected to
become drier and more subsident by this weekend. The NHC intensity
forecast has been lowered from the previous one and shows steady
weakening beyond 36 h, in good agreement with the latest HCCA and
IVCN aids. Although this forecast keeps Margot a tropical cyclone
through day 5, simulated satellite imagery from the global models
suggests these environmental factors could cause the system to lose
organized convection and become post-tropical early next week.


FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 33.6N  40.0W   75 KT  85 MPH
 12H  13/1800Z 34.5N  40.5W   75 KT  85 MPH
 24H  14/0600Z 35.6N  40.5W   70 KT  80 MPH
 36H  14/1800Z 36.5N  39.9W   70 KT  80 MPH
 48H  15/0600Z 36.9N  39.5W   65 KT  75 MPH
 60H  15/1800Z 36.7N  39.4W   60 KT  70 MPH
 72H  16/0600Z 36.5N  39.7W   55 KT  65 MPH
 96H  17/0600Z 36.5N  42.5W   45 KT  50 MPH
120H  18/0600Z 38.0N  43.0W   40 KT  45 MPH

$$
Forecaster Reinhart
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