[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 300242
TCDAT1

Hurricane Oscar Discussion Number  13
NWS National Hurricane Center Miami FL       AL162018
1100 PM AST Mon Oct 29 2018

The satellite presentation of Oscar continued to improved after
the release of the previous advisory, with the small eye becoming
a little more distinct around 0000 UTC, but it has again become
cloud filled within the past hour or so.  Recent microwave imagery
continues to depict a tiny eye with a solid ring of deep convection
surrounding it, but there is little outer banding over the
southwestern portion of the circulation likely due to shear and
dry air.  Objective satellite intensity estimates which may be
having trouble discerning the small eye are around 80 kt, while
subjective T-numbers range from T5.0 from SAB to T5.5 from TAFB.
As a result, the initial intensity has been increased to 90 kt
for this advisory.

Although the NHC intensity forecast does not explicitly show
additional strengthening, Oscar has another 12 hours or so over
SSTs of 26-26.5 deg C in which some slight intensification could
occur.  After that time, increasing southwesterly shear and cooler
waters along the forecast track should cause the hurricane to weaken
gradually as extratropical transition begins.  Oscar is forecast to
complete extratropical transition in about 48 hours, and remain a
powerful post-tropical cyclone over the north Atlantic for much of
the forecast period.  The global models indicate that Oscar's wind
field will quickly expand during its transition to a post-tropical
cyclone, and this is reflected in the NHC wind radii forecast.

The hurricane has been moving slightly east of due north or 010/8
kt.  Oscar is forecast to begin to accelerate north-northeastward or
northeastward ahead of a deep-layer trough that will be moving over
the western Atlantic on Tuesday.  The hurricane should be well
embedded within the deep-layer southwesterly flow ahead of the
trough by Tuesday night or Wednesday, and the cyclone is expected to
move rapidly northeastward across the north-central and northeastern
Atlantic later this week.  There has been little change to the
guidance envelope, and the new NHC track forecast is essentially
an update of the previous advisory.  The official forecast again
lies near the various consensus aids and is near the middle of the
tightly clustered model guidance.

Although Oscar is not expected to directly affect any land areas,
large swells from Oscar will affect Bermuda through Wednesday.
Please consult products from your local weather office as these
conditions could cause life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 27.4N  58.3W   90 KT 105 MPH
 12H  30/1200Z 28.8N  57.7W   90 KT 105 MPH
 24H  31/0000Z 31.5N  55.6W   85 KT 100 MPH
 36H  31/1200Z 35.3N  52.1W   80 KT  90 MPH
 48H  01/0000Z 40.1N  47.8W   70 KT  80 MPH...POST-TROP/EXTRATROP
 72H  02/0000Z 49.1N  36.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  03/0000Z 56.2N  22.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  04/0000Z 62.5N   9.5W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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