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Tropical Storm OSCAR


Tropical Storm Oscar Discussion Number   7
NWS National Hurricane Center Miami FL       AL162018
1100 AM AST Sun Oct 28 2018

Deep convection has redeveloped near the center of Oscar since early
this morning and its low-level center is no longer exposed.
Satellite intensity estimates have not changed since last night and
the estimated intensity of 60 kt is above the various techniques.
The initial intensity estimate is based primarily on the latest
available ASCAT data from last night around 0100 UTC that showed
maximum winds of 55-60 kt. Given the recent increase in convection
observed near the center of Oscar, it seems unlikely that the winds
have decreased since that time.  It is worth noting that the small
inner-core of Oscar increases the uncertainty of the intensity
estimate, and could make the cyclone susceptible to short term
intensity fluctuations that are nearly impossible to forecast or
precisely detect.

Virtually no change has been made to the intensity forecast. The
tropical storm is moving over sufficiently warm water to support
intensification and it is located within a light to moderate shear
environment. All the intensity models forecast at least some
strengthening, and Oscar is expected to become a hurricane later
today or tonight, with some additional strengthening possible
through Wednesday. Extratropical transition is forecast to begin
soon thereafter, which will likely result in a decrease in the
maximum winds, even as the extent of tropical-storm-force winds
rapidly increases. This process is expected to be complete by 120 h.
The new NHC intensity forecast is very close to the intensity
consensus IVCN at all forecast hours.

Oscar turned abruptly westward earlier this morning, and the initial
motion estimate is now 270/10 kt. The tropical cyclone is forecast
to continue moving generally westward for another 12 to 24 h on the
south side of a mid-layer ridge over the northern central Atlantic.
Oscar should then turn toward the north between the ridge and a
mid-latitude trough approaching from the west.  By Wednesday, the
cyclone is expected to accelerate north-northeastward or
northeastward as it becomes embedded in deep-layer southwesterly
flow ahead of the aforementioned trough. All of the global models
agree on this general scenario, though there are differences
regarding the exact timing that Oscar will begin its recurvature
and how quickly it will accelerate across the northern Atlantic.
That said, the track consensus aids have changed very little, and no
significant changes were made to the previous track forecast.


INIT  28/1500Z 25.5N  53.8W   60 KT  70 MPH
 12H  29/0000Z 25.6N  55.8W   65 KT  75 MPH
 24H  29/1200Z 26.2N  57.8W   65 KT  75 MPH
 36H  30/0000Z 27.3N  58.4W   70 KT  80 MPH
 48H  30/1200Z 29.3N  57.8W   75 KT  85 MPH
 72H  31/1200Z 37.1N  51.3W   80 KT  90 MPH
 96H  01/1200Z 45.5N  40.0W   65 KT  75 MPH
120H  02/1200Z 53.0N  22.0W   55 KT  65 MPH...POST-TROP/EXTRATROP

Forecaster Zelinsky