[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 212043
TCDAT2

TROPICAL DEPRESSION KARL DISCUSSION NUMBER  30
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM AST WED SEP 21 2016

The low-level center of Karl appears to have turned toward the
northwest with a motion of 305/10 kt based on GOES-East visible
imagery, recently tucking underneath the cirrus canopy of developing
convection.  Though strong at the moment, the deep convection
continues to be inconsistent, making the intensity determination a
bit muddled.  Proximity to NOAA buoy 41044 indicates the circulation
appears closed with winds backing from east-northeast to northwest
during the past few hours, but there have been no significant
pressure falls.  ASCAT passes from this morning indicated a broad
area of 30-kt winds about 150 n mi to the northeast and east of the
center.  As such, the initial intensity remains 30 kts at this
time.

Karl has turned toward northwest as it is being funneled between the
southwestern periphery of subtropical ridge and the upper- to
mid-level low located north of Puerto Rico and the Virgin Islands.
This northwest track should continue through Friday until Karl turns
north and rapidly accelerates northeastward, becoming embedded in
mid-latitude westerlies.  There has been little change in the
track guidance, which remains in fairly good agreement through 48
hours.   However, differences begin to appear toward the end of the
forecast period as the ECMWF continues to be a bit slower. The
official forecast remains close to a blend of the GFS and ECMWF but
hedges toward the faster GFS solution.  This is also in close
proximity to the HWRF.

Karl's environment continues to gradually improve as the upper low
moves westward, reducing vertical wind shear as well supporting a
more diffluent upper-level pattern for increased thunderstorm
development.  However, mid-level moisture values are marginal and
may remain as a limiting factor for intensification during the
next day or so.  Based on the latest intensity guidance, the
official forecast now brings Karl back to tropical storm strength
over the next day, with intensification continuing through day 4
after the cyclone recurves into the mid-latitude westerlies.  Some
weakening is possible by the end of the forecast period after Karl's
transition to an extratropical cyclone.

FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 21.9N  58.7W   30 KT  35 MPH
 12H  22/0600Z 23.3N  60.7W   35 KT  40 MPH
 24H  22/1800Z 24.9N  63.0W   40 KT  45 MPH
 36H  23/0600Z 26.5N  64.4W   45 KT  50 MPH
 48H  23/1800Z 28.2N  65.0W   50 KT  60 MPH
 72H  24/1800Z 31.5N  61.8W   65 KT  75 MPH
 96H  25/1800Z 36.6N  51.5W   70 KT  80 MPH
120H  26/1800Z 44.5N  38.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Gallina/Berg
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