[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 142033
TCDAT5

TROPICAL STORM IAN DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102016
500 PM AST WED SEP 14 2016

Ian does not look much like a tropical storm this afternoon with all
of its convection well removed from a rather broad and disorganized
low-level circulation.  In fact, Ian has some subtropical
characteristics, including its collocation with an upper-level low
and a large radius of maximum wind.  However, these features could
be temporary. The initial wind speed remains 45 kt based on
continuity.

An uncertain estimate of the initial motion is 350/15.  Ian should
be steered northward and northeastward during the next day or so as
it moves around the subtropical ridge.  The cyclone is expected to
accelerate quickly toward the northeast as it gets picked up by a
mid-latitude trough moving eastward from Atlantic Canada. Similar to
the previous advisory, a slight westward shift in the official track
forecast was required mostly due to the updated initial position.
Otherwise, the forecast is a bit faster than the model consensus.

Ian does not have much time left to intensify as a tropical cyclone
since it should move over colder waters by tomorrow evening. It does
have a narrow window of lower shear during the next day, although
given its current poor organization and structure, no significant
intensification is forecast during that time.  Ian is then expected
to lose its tropical characteristics by 36 hours and be absorbed by
another extratropical low by 72 hours.  The only significant change
to the intensity forecast is for a stronger extratropical phase, but
not quite as strong as the 12 UTC GFS solution.

FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 32.9N  53.6W   45 KT  50 MPH
 12H  15/0600Z 34.8N  53.0W   50 KT  60 MPH
 24H  15/1800Z 38.0N  50.0W   50 KT  60 MPH
 36H  16/0600Z 42.7N  44.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  16/1800Z 49.0N  35.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  17/1800Z...DISSIPATED

$$
Forecaster Blake
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