[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 091503
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
1100 AM AST SUN OCT 09 2016

Overnight microwave data indicated that Nicole had formed a
well-defined low- to mid-level eye, embedded within a significant
convective burst. Since then, the shear has caused the new
convective growth to diminish and pushed the coldest cloud tops
south of the low-level center. Satellite classifications are T3.0
and T3.5 from SAB and TAFB, respectively. A blend of these is used
to set the initial intensity estimate to 50 kt.

Nicole appears to have drifted southeastward during the last
several hours, but is now essentially stationary.  The blocking
ridge north of Nicole has begun to shift eastward, which should
cause the cyclone to begin a slow motion, generally toward the
north. Variations in the orientation and strength of this ridge in
the GFS and ECMWF solutions result in either a north-northeastward
or north-northwestward motion, respectively, during the next couple
of days, and these differences could have implications on Nicole's
track longer term. A turn toward the northeast is expected late in
the period when Nicole reaches the mid-latitude westerly flow. The
split in the track guidance over the forecast period is notable
this cycle, with the ECMWF and all but a few of its 0000 UTC
ensemble members even or left of the previous forecast track. All of
the other track guidance is to the east, including the GFS which is
the rightmost of the members in this camp.  The new forecast track
is very near the previous one in deference to the ECMWF and its
ensemble output even though the model consensus aids are to the
east through 96 hours.

The strong northerly shear over Nicole has marginally decreased
since yesterday, but is forecast to remain at about the same
magnitude for another 24 hours. The shear should then gradually
diminish until about day 3, and Nicole is likely to find itself in
the lowest-shear environment it has seen in several days.  Since
the cyclone will be over anomalously warm waters at that time, in a
moist environment and under a somewhat diffluent flow aloft,
intensification seems likely.  The intensity forecast is increased
over the previous one and is slightly above the multi-model
consensus.  It should be noted that the global models show
significant deepening of Nicole starting around this time,
potentially much more than what is indicated in this forecast.
Southwesterly shear should greatly increase by day 4, which could
curb any additional intensification after that time unless the
cyclone's intensification is being driven by baroclinic forcing.


FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 24.0N  65.4W   50 KT  60 MPH
 12H  10/0000Z 24.4N  65.3W   55 KT  65 MPH
 24H  10/1200Z 25.2N  65.3W   55 KT  65 MPH
 36H  11/0000Z 26.1N  65.3W   55 KT  65 MPH
 48H  11/1200Z 27.0N  65.6W   60 KT  70 MPH
 72H  12/1200Z 28.6N  65.9W   65 KT  75 MPH
 96H  13/1200Z 31.8N  64.2W   70 KT  80 MPH
120H  14/1200Z 34.9N  59.4W   70 KT  80 MPH

$$
Forecaster Kimberlain
This weather bulletin was brought to you by:
www.nashvilleweather.net